Internet DRAFT - draft-ietf-trill-oam-fm
draft-ietf-trill-oam-fm
TRILL Working group Tissa Senevirathne
Internet Draft Norman Finn
Intended status: Standard Track Samer Salam
Updates: 6325 Deepak Kumar
CISCO
Donald Eastlake
Sam Aldrin
Yizhou Li
Huawei
October 24, 2014
Expires: April 2015
TRILL Fault Management
draft-ietf-trill-oam-fm-11.txt
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Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Abstract
This document specifies TRILL OAM Fault Management. Methods in
this document follow the IEEE 802.1 CFM (Continuity Fault
Management) framework and reuse OAM tools where possible.
Additional messages and TLVs are defined for TRILL specific
applications or where a different set of information is required
other than IEEE 802.1 CFM. This document updates RFC 6325.
Table of Contents
1. Introduction ............................................... 4
2. Conventions used in this document .......................... 4
3. General Format of TRILL OAM Packets ........................ 5
3.1. Identification of TRILL OAM frames .................... 7
3.2. Use of TRILL OAM Alert Flag ........................... 7
3.2.1. Handling of TRILL frames with the "A" Flag ....... 8
3.3. OAM Capability Announcement ........................... 8
3.4. Identification of the OAM message .................... 10
4. TRILL OAM Layering vs. IEEE Layering ...................... 10
4.1. Processing at ISS Layer .............................. 12
4.1.1. Receive Processing .............................. 12
4.1.2. Transmit Processing ............................. 12
4.2. End Station VLAN and Priority Processing ............. 12
4.2.1. Receive Processing .............................. 12
4.2.2. Transmit Procession ............................. 12
4.3. TRILL Encapsulation and De-capsulation Layer ......... 12
4.3.1. Receive Processing for Unicast packets .......... 12
4.3.2. Transmit Processing for unicast packets ......... 13
4.3.3. Receive Processing for Multicast packets ........ 14
4.3.4. Transmit Processing of Multicast packets ........ 15
4.4. TRILL OAM Layer Processing ........................... 16
5. Maintenance Associations (MA) in TRILL .................... 17
6. MEP Addressing ............................................ 18
6.1. Use of MIP in TRILL .................................. 21
7. Continuity Check Message (CCM) ............................ 23
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8. TRILL OAM Message Channel ................................. 25
8.1. TRILL OAM Message header ............................. 25
8.2. TRILL Specific OAM Opcodes ........................... 26
8.3. Format of TRILL OAM TLV .............................. 26
8.4. TRILL OAM TLVs ....................................... 27
8.4.1. Common TLVs between CFM and TRILL ............... 27
8.4.2. TRILL OAM Specific TLVs ......................... 28
8.4.3. TRILL OAM Application Identifier TLV ............ 28
8.4.4. Out Of Band Reply Address TLV ................... 30
8.4.5. Diagnostics Label TLV ........................... 31
8.4.6. Original Data Payload TLV ....................... 32
8.4.7. RBridge scope TLV ............................... 32
8.4.8. Previous RBridge nickname TLV ................... 33
8.4.9. Next Hop RBridge List TLV ....................... 34
8.4.10. Multicast Receiver Port count TLV .............. 35
8.4.11. Flow Identifier (flow-id) TLV .................. 35
8.4.12. Reflector Entropy TLV .......................... 36
8.4.13. Authentication TLV ............................. 37
9. Loopback Message .......................................... 39
9.1. Loopback OAM Message format .......................... 39
9.2. Theory of Operation .................................. 39
9.2.1. Actions by Originator RBridge ................... 39
9.2.2. Intermediate RBridge ............................ 40
9.2.3. Destination RBridge ............................. 40
10. Path Trace Message ....................................... 41
10.1. Theory of Operation ................................. 42
10.1.1. Action by Originator RBridge ................... 42
10.1.2. Intermediate RBridge ........................... 42
10.1.3. Destination RBridge ............................ 44
11. Multi-Destination Tree Verification Message (MTVM) ....... 44
11.1. Multi-Destination Tree Verification Message (MTVM)
Format .................................................... 44
11.2. Theory of Operation ................................. 45
11.2.1. Actions by Originator RBridge .................. 45
11.2.2. Receiving RBridge .............................. 46
11.2.3. In scope RBridges .............................. 46
12. Application of Continuity Check Message (CCM) in TRILL ... 47
12.1. CCM Error Notification .............................. 48
12.2. Theory of Operation ................................. 49
12.2.1. Actions by Originator RBridge .................. 49
12.2.2. Intermediate RBridge ........................... 50
12.2.3. Destination RBridge ............................ 50
13. Fragmented Reply ......................................... 51
14. Security Considerations .................................. 51
15. IANA Considerations ...................................... 53
15.1. OAM Capabilitiy Flags ............................... 53
15.2. CFM Code Points ..................................... 53
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15.3. MAC Addresses ....................................... 54
15.4. Return codes and sub codes .......................... 54
15.5. TRILL RBridge Nickname Address Family ............... 55
16. References ............................................... 55
16.1. Normative References ................................ 55
16.2. Informative References .............................. 56
17. Acknowledgments .......................................... 57
Appendix A. Backwards Compatibility .......................... 58
Appendix B. Base Mode for TRILL OAM .......................... 61
Appendix C. MAC Addresses Request ............................ 63
1. Introduction
The general structure of TRILL OAM messages is presented in
[RFC7174]. TRILL OAM messages consist of five parts: link header,
TRILL header, flow entropy, OAM message channel, and link
trailer.
The OAM message channel carries various control information and
OAM related data between TRILL switches, also known as RBridges
or Routing Bridges.
A common OAM message channel representation can be shared between
different technologies. This consistency between different OAM
technologies promotes nested fault monitoring and isolation
between technologies that share the same OAM framework.
The TRILL OAM message channel is formatted as specified in IEEE
Connectivity Fault Management (CFM) [8021Q].
The ITU-T Y.1731 [Y1731] standard utilizes the same messaging
format as [8021Q] OAM messages where applicable. This document
takes a similar stance and reuses [8021Q] in TRILL OAM. It is
assumed readers are familiar with [8021Q] and [Y1731]. Readers
who are not familiar with these documents are encouraged to
review them.
This document updates [RFC6325] as specified in Section 3.1.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
RFC-2119 [RFC2119].
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Capitalized IANA Considerations terms such as "Standards Action"
are to be interpreted as described in [RFC5226].
Acronyms used in the document include the following:
CCM - Continuity Check Message [8021Q]
ECMP - Equal Cost Multipath
ISS - Internal Sub Layer Service [8021Q]
LBM - Loop Back Message [8021Q]
LBR - Loop Back Reply Message [8021Q]
MP - Maintenance Point [RFC7174]
MEP - Maintenance End Point [RFC7174] [8021Q]
MIP - Maintenance Intermediate Point [RFC7174] [8021Q]
MA - Maintenance Association [8021Q] [RFC7174]
MD - Maintenance Domain [8021Q]
MTVM - Multi-destination Tree Verification Message
MTVR - Multi-destination Tree Verification Reply Message
OAM - Operations, Administration, and Maintenance [RFC6291]
PRI - Priority of Ethernet Frames [8021Q]
PTM - Path Trace Message
PTR - Path Trace Reply Message
TRILL - Transparent Interconnection of Lots of Links [RFC6325]
SAP - Service Access Point [8021Q]
3. General Format of TRILL OAM Packets
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The TRILL forwarding paradigm allows an implementation to select
a path from a set of equal cost paths to forward a unicast TRILL
Data packet. For multi-destination TRILL Data packets, a
distribution tree is chosen by the TRILL switch that ingresses or
creates the packet. Selection of the path of choice is
implementation dependent at each hop for unicast and at the
ingress for multi-destination. However, it is a common practice
to utilize Layer 2 through Layer 4 information in the frame
payload for path selection.
For accurate monitoring and/or diagnostics, OAM Messages are
required to follow the same path as corresponding data packets.
[RFC7174] presents the high-level format of the OAM messages. The
details of the TRILL OAM frame format are defined in this
document.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Link Header . (variable)
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ TRILL Header + 6 or more bytes
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Flow Entropy . 96 bytes
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OAM Ethertype |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. OAM Message Channel . Variable
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Trailer | Variable
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1 Format of TRILL OAM Messages
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Link Header: Media-dependent header. For Ethernet, this includes
Destination MAC, Source MAC, VLAN (optional) and Ethertype
fields.
TRILL Header: Fixed size of 6 bytes when the Extended Header is
not included [RFC6325]
Flow Entropy: This is a 96-byte fixed size field. The rightmost
bits of the field MUST be padded with zeros, up to 96 bytes, when
the flow entropy is less than 96 bytes. Flow entropy enables
emulation of the forwarding behavior of the desired data packets.
The Flow Entropy field starts with the Inner.MacDA. The offset of
the Inner.MacDA depends on whether extensions are included or not
as specified in [RFC7179] and [RFC6325]. Such extensions are not
commonly supported in current TRILL implementations.
OAM Ethertype: OAM Ethertype is 16-bit Ethertype that identifies
the OAM Message channel that follows. This document specifies
using the Ethertype 0x8902 allocated for CFM [8021Q]. OAM Message
Channel: This is a variable size section that carries OAM related
information. The message format is as specified in [8021Q].
Link Trailer: Media-dependent trailer. For Ethernet, this is the
FCS (Frame Check Sequence).
3.1. Identification of TRILL OAM frames
TRILL, as originally specified in [RFC6325], did not have a
specific flag or a method to identify OAM frames. This document
updates [RFC6325] to include specific methods to identify TRILL
OAM frames. Section 3.2. below explains the details of the
method.
3.2. Use of TRILL OAM Alert Flag
The TRILL Header, as defined in [RFC6325], has two reserved bits.
This document specifies use of the reserved bit next to Version
field in the TRILL header as the Alert flag. Alert flag will be
denoted by "A". RBridges MUST NOT use the "A" flag for forwarding
decisions such as the selection of which ECMP path or multi-
destination tree to select.
Implementations that comply with this document MUST utilize "A"
flag and CFM Ethertype to identify TRILL OAM frames.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| V |A|R|M|Op-Length| Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Egress RBridge Nickname | Ingress RBridge Nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options...
+-+-+-+-+-+-+-+-+-+-+-+-
Figure 2 TRILL Header with the "A" Flag
A (1 bit) - Indicates this is a possible OAM frame and is subject
to specific handling as specified in this document.
All other TRILL Header fields carry the same meaning as defined
in RFC6325.
3.2.1. Handling of TRILL frames with the "A" Flag
Value "1" in the A flag indicates TRILL frames that may qualify
as OAM frames. Implementations are further REQUIRED to validate
such frames by comparing the value at the OAM Ethertype (Figure
1) location with the CFM Ethertype "0x8902" [8021Q]. If the value
matches, such frames are identified as TRILL OAM frames and
SHOULD be processed as discussed in Section 4.
Frames with the "A" flag set that do not contain CFM Ethertype
are not considered as OAM frames. Such frames MUST be silently
discarded.
OAM capable RBridges MUST NOT generate OAM frames to an RBridge
that is not OAM capable.
Intermediate RBridges, that are not OAM capable (i.e. do not
understand the "A" flag) follow the process defined in [RFC6325]
section 3.3 and forward OAM frames with "A" flag unaltered.
3.3. OAM Capability Announcement
Any given RBridge can be (1) OAM incapable or (2) OAM capable
with new extensions or (3) OAM capable with backwards-compatible
method. The OAM request originator, prior to origination of the
request is required to identify the OAM capability of the target
and generate the appropriate OAM message.
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Capability flags defined in TRILL version sub-TLV (TRILL-VER)
[RFC7176] will be utilized for announcing OAM capabilities. The
following OAM related capability flags are defined:
O - OAM Capable
B - Backwards Compatible OAM
A capability announcement, with "O" Flag set to 1 and "B" flag
set to 1, indicates that the originating RBridge is OAM capable
but utilizes the backwards compatible method defined in Appendix
A. A capability announcement with "O" Flag set to 1 and "B" flag
set to 0, indicates that the originating RBridge is OAM capable
and utilizes the method specified in section 3.2.
When "O" Flag is set to 0, the announcing implementation is
considered not capable of OAM and the "B" flag is ignored.
+-+-+-+-+-+-+-+-+
| Type | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+
| Max-version | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+
|A|F|O|B|Other Capabilities and Header Flags| (4 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+
0 1 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 0 1
Figure 3 TRILL-VER sub-TLV [RFC7176] with O and B flags
Capability flags "A" and "F" are defined by [RFC7176] and
[RFC7172]. "O" and "B" Flags are located after "F" flag in the
Capability and Header Flags field of TRILL-VER sub-TLV, as
depicted in Figure 3 above. Usage of "O" and "B" flags are as
discussed above.
Absence of TRILL-VER sub-TLV means the announcing RBridge is not
OAM capable.
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3.4. Identification of the OAM message
The ingress RBridge nickname allows recipients to identify the
origin of the message in most cases. However, when an out of band
reply is generated, the responding RBridge nickname is not easy
to identify.
The [8021Q] Sender ID TLV (1) provides methods to identify the
device by including the chassis ID. Chassis ID allows different
addressing formats such as IANA Address Family enumerations. IANA
has allocated Address Family Number 16396 for TRILL RBridge
nickname. In TRILL OAM the Chassis ID subtype of Sender ID TLV is
set to 16396 and Chassis ID field contains the corresponding
TRILL RBridge nickname.
When the Sender ID TLV is present and chassis sub type is set to
16396, the sender RBridge nickname SHOULD be derived from the
nickname embedded in the Chassis ID. Otherwise, sender RBridge
nickname SHOULD be derived from the ingress RBridge nickname.
4. TRILL OAM Layering vs. IEEE Layering
This section presents the placement of the TRILL OAM shim within
the IEEE 802.1 layers. The Transmit and Receive processing are
explained.
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+-+-+-+-+-+-+-+-+-+-+
| RBridge Layer |
| Processing |
+-+-+-+-+-+-+-+-+-+-+
|
|
+-+-+-+-+-+-+
| TRILL OAM | UP MEP
| Layer | MIP
+-+-+-+-+-+-+ Down MEP
|
|
+-+-+-+-+-+-+
(3)--------> | TRILL |
| Encap/Decap
+-+-+-+-+-+-+
|
+-+-+-+-+-+-+
(2)--------> |End station|
| VLAN & priority Processing
+-+-+-+-+-+-+
|
+-+-+-+-+-+-+
(1)--------> |ISS |
|Processing |
+-+-+-+-+-+-+
|
|
|
Figure 4 Placement of TRILL MP within IEEE 802.1
[RFC6325] Section 4.6 as updated by [RFC7180] provides a detailed
explanation of frame processing. Please refer to those documents
for additional details and for processing scenarios not covered
herein.
Sections 4.1 and 4.2 below apply to links using a broadcast LAN
technology such as Ethernet.
On links using an inherently point-to-point technology, such as
PPP [RFC6361], there is no Outer.MacDA, Outer.MacSA, or
Outer.VLAN because these are part of the link header for
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Ethernet. Point-to-point links typically have link headers
without these fields.
4.1. Processing at ISS Layer
4.1.1. Receive Processing
The ISS Layer receives an indication from the port. It extracts
DA, SA and marks the remainder of the payload as M1. ISS Layer
passes on (DA, SA, M1) as an indication to the higher layer.
For TRILL Ethernet frames, this is Outer.MacDA and Outer.MacSA.
M1 is the remainder of the packet.
4.1.2. Transmit Processing
The ISS layer receives an indication from the higher layer that
contains (DA, SA, M1). It constructs an Ethernet frame and passes
down to the port.
4.2. End Station VLAN and Priority Processing
4.2.1. Receive Processing
Receives (DA, SA, M1) indication from ISS Layer. Extracts the
VLAN ID and priority from the M1 part of the received indication
(or derive them from the port defaults or other default
parameters) and constructs (DA, SA, VLAN, PRI, M2). VLAN+PRI+M2
map to M1 in the received indication. Pass (DA, SA, VLAN, PRI,
M2) to the TRILL encap/decap procession layer.
4.2.2. Transmit Procession
Receive (DA, SA, VLAN, PRI, M2) indication from TRILL encap/decap
processing layer. Merge VLAN, PRI, M2 to form M1. Pass down (DA,
SA, M1) to the ISS processing Layer.
4.3. TRILL Encapsulation and De-capsulation Layer
4.3.1. Receive Processing for Unicast packets
Receive indication (DA, SA, VLAN, PRI, M2) from End Station VLAN
and Priority Processing Layer.
o If DA matches port Local DA and Frame is of TRILL Ethertype
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. Discard DA, SA, VLAN, PRI. From M2, derive (TRILL-HDR, iDA,
iSA, i-VL, M3)
. If TRILL nickname is Local and TRILL-OAM Flag is set
Pass on to OAM processing
. Else pass on (TRILL-HDR, iDA, iSA, i-VL, M3) to RBridge
Layer
o If DA matches port Local DA and EtherType is RBridge-Channel
[RFC7178]
. Process as a possible unicast native RBridge Channel packet
o If DA matches port Local DA and Ethertype is neither TRILL
nor RBridge-Channel
. Discard packet
o If DA does not match and port is Appointed Forwarder for VLAN
and Ethertype is not TRILL or RBridge-Channel
. Insert TRILL-Hdr and send (TRILL-HDR, iDA, iSA,i-VL, M3)
indication to RBridge Layer <- This is the TRILL Ingress
Function.
4.3.2. Transmit Processing for unicast packets
o Receive indication (TRILL-HDR, iDA, iSA, iVL, M3) from
RBridge Layer
o If egress TRILL nickname is local
o If port is Appointed Forwarder for iVL and the port is
not configured as a trunk or p2p port and (TRILL Alert
Flag set and OAM Ethertype present) then
. Strip TRILL-HDR and construct (DA, SA, VLAN, M2)
<- This is the TRILL Egress Function.
o Else
. Discard packet
o If egress TRILL nickname is not local
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o Insert Outer.MacDA, Outer.MacSA, Outer.VLAN, TRILL
Ethertype and construct (DA, SA, VLAN, M2). Where M2 is
(TRILL-HDR, iDA, iSA, iVL, M)
o Forward (DA, SA, V, M2) to the VLAN End Station processing
Layer.
4.3.3. Receive Processing for Multicast packets
o Receive (DA, SA, V, M2) from VLAN aware end station
processing layer
o If the DA is All-RBridges and the Ethertype is TRILL
o Strip DA, SA and V. From M2, extract (TRILL-HDR, iDA,
iSA, iVL and M3).
o If TRILL Alert Flag is set and OAM Ethertype is present
at the end of Flow entropy
. Perform OAM Processing
o Else extract the TRILL header, inner MAC addresses and
inner VLAN and pass indication (TRILL-HDR, iDA, iSA,
iVL and M3) to TRILL RBridge Layer
o If the DA is All-IS-IS-RBridges and the Ethertype is L2-IS-
IS then pass frame up to TRILL IS-IS processing
o If the DA is All-RBridges or All-IS-IS-RBridges but
Ethertype is not TRILL or L2-IS-IS respectively
o Discard the packet
o If the Ethertype is TRILL but the multicast DA is not All-
RBridges; or if the Ethertype is L2-IS-IS but the multicast
DA is not All-IS-IS-RBridges
o Discard the packet
o If DA is All-Edge-RBridges and Ethertype is RBridge-Channel
[RFC7178]
o Process as a possible multicast native RBridge
Channel packet
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o If the DA is in the initial bridging/link protocols block
(01-80-C2-00-00-00 to 01-80-C2-00-00-0F) or is in the TRILL
block and not assigned for Outer.MacDA use (01-80-C2-00-00-
42 to 01-80-C2-00-00-4F) then
o The frame is not propagated through an RBridge although
some special processing may be done at the port as
specified in [RFC6325] and the frame may be dispatched
to Layer 2 processing at the port if certain protocols
are supported by that port (examples: Link Aggregation
Protocol, Link Layer Discovery Protocol).
o If the DA is some other multicast value
o Insert TRILL-HDR and construct (TRILL-HDR, iDA, iSA,
IVL, M3)
o Pass the (TRILL-HDR, iDA, iSA, IVL, M3) to RBridge Layer
4.3.4. Transmit Processing of Multicast packets
The following ignores the case of transmitting TRILL IS-IS
packets.
o Receive indication (TRILL-HDR, iDA, iSA, iVL, M3) from
RBridge layer.
o If TRILL-HDR multicast flag set and TRILL-HDR Alert flag
set and OAM Ethertype present then:
o (DA, SA, V, M2) by inserting TRILL Outer.MacDA of All-
RBridges, Outer.MacSA, Outer.VLAN and TRILL Ethertype.
M2 here is (Ethertype TRILL, TRILL-HDR, iDA, iSA, iVL,
M)
NOTE: Second copy of native format is not made.
o Else If TRILL-HDR multicast flag set and Alert flag not set
o If the port is appointed Forwarder for iVL and the port
is not configured as a trunk port or a p2p port, Strip
TRILL-HDR, iSA, iDA, iVL and construct (DA, SA, V, M2)
for native format.
o Make a second copy (DA, SA, V, M2) by inserting TRILL
Outer.MacDA, Outer.MacSA, Outer.VLAN and TRILL
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Ethertype. M2 here is (Ethertype TRILL, TRILL-HDR, iDA,
iSA, iVL, M)
o Pass the indication (DA, SA, V, M2) to End Station VLAN
processing layer.
4.4. TRILL OAM Layer Processing
TRILL OAM Processing Layer is located between the TRILL
Encapsulation / De-capsulation layer and RBridge Layer. It
performs the following: 1. Identification of OAM frames that
need local processing and 2. performs OAM processing or redirect
to the CPU for OAM processing.
o Receive indication (TRILL-HDR, iDA, iSA, iVL, M3) from
RBridge layer. M3 is the payload after inner VLAN iVL.
o If the TRILL Multicast Flag is set and TRILL Alert Flag is
set and TRILL OAM Ethertype is present then
o If MEP or MIP is configured on the Inner.VLAN/FGL of the
packet then
. discard packets that have MD-LEVEL Less than that
of the MEP or packets that do not have MD-LEVEL
present (e.g., due to packet truncation).
. If MD-LEVEL matches MD-LEVEL of the MEP then
. Re-direct to OAM Processing (Do not forward
further)
. If MD-LEVEL matches MD-LEVEL of MIP then
. Make a Copy for OAM processing and continue
. If MD-LEVL matches MD-LEVEL of MEP then
. Redirect the OAM packet to OAM processing
and do not forward along or forward as a
native packet.
o Else if TRILL Alert Flag is set and TRILL OAM Ethertype is
present then
o If MEP or MIP is configured on the Inner.VLAN/FGL of the
packet then
. discard packets that have MD-LEVEL not present or
MD-LEVEL is Less than that of the MEP.
. If MD-LEVEL matches MD-LEVEL of the MEP then
. Re-direct to OAM Processing (Do not forward
further)
. If MD-LEVEL matches MD-LEVEL of MIP then
. Make a Copy for OAM processing and continue
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o Else // Non-OAM Packet
o Continue
o Pass the indication (DA, SA, V, M2) to End Station VLAN
processing layer.
NOTE: In the Receive path, processing above compares against Down
MEP and MIP Half functions. In the transmit processing it
compares against Up MEP and MIP Half functions.
Appointed Forwarder is a function the TRILL Encap/De-Cap layer
performs. The TRILL Encap/De-cap Layer is responsible for
prevention of leaking of OAM packets as native frames.
5. Maintenance Associations (MA) in TRILL
[8021Q] defines a maintenance association as a logical
relationship between a group of nodes. Each Maintenance
Association (MA) is identified with a unique MAID of 48 bytes
[8021Q]. CCM and other related OAM functions operate within the
scope of an MA. The definition of MA is technology independent.
Similarly it is encoded within the OAM message, not in the
technology dependent portion of the packet. Hence the MAID as
defined in [8021Q] can be utilized for TRILL OAM, without
modifications. This also allows us to utilize CCM and LBM
messages defined in [8021Q], as is.
In TRILL, an MA may contain two or more RBridges (MEPs). For
unicast, it is likely that the MA contains exactly two MEPs that
are the two end-points of the flow. For multicast, the MA may
contain two or more MEPs.
For TRILL, in addition to all of the standard [8021Q] CFM MIB
definitions, each MEP's MIB contains one or more flow entropy
definitions corresponding to the set of flows that the MEP
monitors.
[8021Q] CFM MIB is augmented to add the TRILL specific
information. Figure 5, below depicts the augmentation of the CFM
MIB to add the TRILL specific Flow Entropy.
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MA---
|
--- MEP
|
. - Remote MEP List
.
|
--- MEP-A
|
--- MEP-B
.
|
. - Flow Entropy List { Augments IEEE8021-CFM-MIB}
|
--- (Flow Entropy-1)
|
--- (Flow-entropy-2)
|
. --- (Flow Entropy n)
|
Other MIB entries
Figure 5 Correlation of TRILL augmented MIB
The detailed TRILL OAM MIB will be specified in a separate
document [TRILLOAMMIB].
6. MEP Addressing
In IEEE CFM [8021Q], OAM messages address the target MEP by
utilizing a unique MAC address. In TRILL a MEP is addressed by
combination of the egress RBridge nickname and the Inner
VLAN/FGL.
Additionally, MEPs are represented by 2 octet MEP-ID that is
independent of the underlying technology. In CFM [8021Q] the
value of MEP-ID is restricted to 1 to 8191. However, on CFM
[8021Q] packet, MEP-ID are encoded as a 2 octet field. In TRILL
Base Mode operation presented in Appendix B MEP-IDs are mapped 1
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to 1 with the RBridge nicknames. Hence, In TRILL, MEP-ID MUST be
a number in the range from 1 to 65535.
At the MEP, OAM packets go through a hierarchy of op-code de-
multiplexers. The op-code de-multiplexers channel the incoming
OAM packets to the appropriate message processor (e.g. LBM) The
reader may refer to Figure 6 below for a visual depiction of
these different de-multiplexers.
1. Identify the packets that need OAM processing at the Local
RBridge as specified in Section 4.
a. Identify the MEP that is associated with the
Inner.VLAN/FGL.
2. The MEP first validates the MD-LEVEL and then
a. Redirect to MD-LEVEL De-multiplexer
3. MD-LEVEL de-multiplexer compares the MD-Level of the packet
against the MD level of the local MEPs of a given MD-Level on
the port (Note: there can be more than one MEP at the same MD-
Level but belonging to different MAs)
a. If the packet MD-LEVEL is equal to the configured MD-
LEVEL of the MEP, then pass to the Opcode de-multiplexer
b. If the packet MD-LEVEL is less than the configured MD-
LEVEL of the MEP, discard the packet
c. If the packer MD-LEVEL is greater than the configured
MD-LEVEL of the MEP, then pass on to the next higher MD-
LEVEL de-multiplexer, if available. Otherwise, if no such
higher MD-LEVEL de-multiplexer exists, then forward the
packet as normal data.
4. Opcode De-multiplexer compares the opcode in the packet with
supported opcodes
a. If Op-code is CCM, LBM, LBR, PTM, PTR, MTVM, MTVR, then
pass on to the correct Processor
b. If Op-code is Unknown, then discard.
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|
.CCM LBM PTM MTVM . .
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+
| OP Code DE-Mux |--- Unknown
+-+-+-+-+-+-+-+-+-+-+-+-+
^ ^ ^
MD==Li | | |
+-+-+ +-+-+ +-+-+
| L |-->|L2 |-.- |Ln |---- >
+-+-+ +-+-+ +-+-+ |
| ^ | | |
MD<LI Drop | Drop Drop |
| |
MD not --- |TRILL OAM need local |
Present | Processing |
| |
TRILL Data ---- TRILL Data ----
------->| T |----------------- >| M |--- >
+ TRILL OAM ---- + pass through OAM ----
Figure 6 OAM De-Multiplexers at MEP for active SAP
T : Denotes Tap, that identifies OAM frames that need local
processing. These are the packets with Alert flag set and
OAM Ethertype is present after the flow entropy of the
packet
M : Is the post processing merge, merges data and OAM
messages that are passed through. Additionally, the Merge
component ensures, as explained earlier, that OAM packets
are not forwarded out as native frames.
L : Denotes MD-Level processing. Packets with MD-Level less
than the Level will be dropped. Packets with equal MD-Level
are passed on to the opcode de-multiplexer. Others are
passed on to the next level MD processors or eventually to
the merge point (M).
NOTE: LBM, LBR, MTVM, MTVR, PTM and PTR are not subject to
MA de-multiplexers. These packets do not have an MA encoded
in the packet. Adequate response can be generated to these
packets, without loss of functionality, by any of the MEPs
present on that interface or an entity within the RBridge.
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6.1. Use of MIP in TRILL
Maintenance Intermediate Points (MIP) are mainly used for fault
isolation. Link Trace Messages in [8021Q] utilize a well-known
multicast MAC address and MIPs generate responses to Link Trace
messages. Response to Link Trace messages or lack thereof can be
used for fault isolation in TRILL.
As explained in section 10. , a hop-count expiry approach will be
utilized for fault isolation and path tracing. The approach is
very similar to the well-known IP trace-route approach. Hence,
explicit addressing of MIPs is not required for the purpose of
fault isolation.
Any given RBridge can have multiple MIPs located within an
interface. As such, a mechanism is required to identify which MIP
should respond to an incoming OAM message. Any MIP residing
within the ingress interface may reply to the incoming Path Trace
message without loss of functionality or information. As
specified in Section 3.4. , the address of the responding RBridge
can be identified by means of Sender ID TLV (1). The Reply
Ingress TLV (5) identifies the interface id. The combination of
these allows recipient of the response to uniquely identify the
responder.
A similar approach to that presented above for MEPs can be used
for MIP processing. It is important to note that "M", the merge
block of a MIP, does not prevent OAM packets leaking out as
native frames. On edge interfaces, MEPs MUST be configured to
prevent the leaking of TRILL OAM packets out of the TRILL Campus.
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PTM PTR MTVM MTVR
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OP Code De-Mux |-> Unknown
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
^ ^ ^
MD==Li | | |
+-+-+ +-+-+ +-+-+
| L |- >|L2 |-.- |Ln |------+
+-+-+ +-+-+ +-+-+ |
^ |
| |
Drop | |
MD not --- |TRILL OAM |
Present | |
| v
TRILL Data ---- TRILL Data -----
------- >| T |------------------ >| M |---->
+ TRILL OAM ---- ----
Figure 7 OAM De-Multiplexers at MIP for active SAP
T: TAP processing for MIP. All packets with OAM flag set are
captured.
L : MD Level Processing, Packet with matching MD Level are
"copied" to the Opcode de-multiplexer and original packet is
passed on to the next MD level processor. Other packets are
simply passed on to the next MD level processor, without copying
to the OP code de-multiplexer.
M : Merge processor, merge OAM packets to be forwarded along with
the data flow.
Packets that carry Path Trace Message (PT) or Multi-destination
Tree Verification (MTVM) OpCodes are passed on to the respective
processors.
Packets with unknown OpCodes are counted and discarded.
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7. Continuity Check Message (CCM)
CCMs are used to monitor connectivity and configuration errors.
[8021Q] monitors connectivity by listening to periodic CCM
messages received from its remote MEP partners in the MA. An
[8021Q] MEP identifies cross-connect errors by comparing the MAID
in the received CCM message with the MEP's local MAID. The MAID
[8021Q] is a 48-byte field that is technology independent.
Similarly, the MEPID is a 2-byte field that is independent of the
technology. Given this generic definition of CCM fields, CCM as
defined in [8021Q] can be utilized in TRILL with no changes.
TRILL specific information may be carried in CCMs when encoded
using TRILL specific TLVs or sub-TLVs. This is possible since
CCMs may carry optional TLVs.
Unlike classical Ethernet environments, TRILL contains multipath
forwarding. The path taken by a packet depends on the payload of
the packet. The Maintenance Association identifies the interested
end-points (MEPs) of a given monitored path. For unicast there
are only two MEPs per MA. For multicast there can be two or more
MEPs in the MA. The entropy values of the monitored flows are
defined within the MA. CCM transmit logic will utilize these flow
entropy values when constructing the CCM packets. Please see
section 12. below for the theory of operation of CCM.
The MIB of [8021Q] is augmented with the definition of flow-
entropy. Please see [TRILLOAMMIB] for definition of these and
other TRILL related OAM MIB definitions. The below Figure depicts
the correlation between MA, CCM and the flow-entropy.
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MA---
|
--- MEP
|
. - Remote MEP List
.
|
--- MEP-A
|
--- MEP-B
.
|
. - Flow Entropy List {Augments IEEE8021-CFM-MIB}
|
--- (Flow Entropy-1)
|
--- (Flow-entropy-2)
|
. ---(Flow Entropy n)
|
. - CCM
|
--- (standard 8021ag entries)
|
--- (hop-count) { Augments IEEE8021-CFM-MIB}
|
--- (Other TBD TRILL OAM specific entries)
{Augmented}
|
.
|
- Other MIB entries
Figure 8 Augmentation of CCM MIB in TRILL
In a multi-pathing environment, a Flow - by definition - is
unidirectional. A question may arise as to what flow entropy
should be used in the response. CCMs are unidirectional and have
no explicit reply; as such, the issue of the response flow
entropy does not arise. In the transmitted CCM, each MEP reports
local status using the Remote Defect Indication (RDI) flag.
Additionally, a MEP may raise SNMP TRAPs [TRILLOAMMIB] as Alarms
when a connectivity failure occurs.
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8. TRILL OAM Message Channel
The TRILL OAM Message Channel can be divided into two parts:
TRILL OAM Message header and TRILL OAM Message TLVs. Every OAM
Message MUST contain a single TRILL OAM message header and a set
of one or more specified OAM Message TLVs.
8.1. TRILL OAM Message header
As discussed earlier, a common messaging framework between
[8021Q], TRILL, and other similar standards such as Y.1731 is
accomplished by re-using the OAM message header defined in
[8021Q].
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|MD-L | Version | OpCode | Flags |FirstTLVOffset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Opcode Specific Information .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. TLVs .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9 OAM Message Format
o MD-L: Maintenance Domain Level (3 bits). Identifies the
maintenance domain level. For TRILL, in general, this field
is set to a single value across the TRILL campus. When using
TRILL base mode as specified in Appendix B, MD-L is set to
3. However, extension of TRILL, for example to support
multilevel, may create different MD-LEVELs and MD-L field
must be appropriately set in those scenarios. (Please refer
to [8021Q] for the definition of MD-Level)
o Version: Indicates the version (5 bits) as specified in
[8021Q]. This document does not require changing the Version
defined in [8021Q].
o OpCode: Operation Code (8 bits). Specifies the operation
performed by the message. See Section 8.2.
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o Flags: Includes operational flags (1 byte). The definition
of flags is Opcode-specific and is covered in the applicable
sections.
o FirstTLVOffset: Defines the location of the first TLV, in
bytes, starting from the end of the FirstTLVOffset field (1
byte). (Refer to [8021Q] for the definition of the
FirstTLVOffset.)
MD-L, Version, Opcode, Flags and FirstTLVOffset fields
collectively are referred to as the OAM Message Header.
The Opcode specific information section of the OAM Message may
contain Session Identification number, time-stamp, etc.
8.2. TRILL Specific OAM Opcodes
The following TRILL specific CFM Opcodes are defined. Each of the
Opcodes indicates a separate type of TRILL OAM message. Details
of the messages are presented in the related sections.
TRILL OAM Message Opcodes:
TBD1: Path Trace Reply
TBD2: Path Trace Message
TBD3: Multicast Tree Verification Reply
TBD4: Multicast Tree Verification Message
Loopback and CCM Messages reuse the opcodes defined by [8021Q]
8.3. Format of TRILL OAM TLV
The same CFM TLV format as defined in [8021Q] is used for TRILL
OAM. The following figure depicts the general format of a TRILL
OAM TLV:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Value(variable) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10 TRILL OAM TLV
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Type (1 octet): Specifies the Type of the TLV (see sections 8.4.
for TLV types).
Length (2 octets): Specifies the length of the 'Value' field in
octets. Length of the 'Value' field can be either zero or more
octets.
Value (variable): The length and the content of this field depend
on the type of the TLV. Please refer to applicable TLV
definitions for the details.
Semantics and usage of Type values allocated for TRILL OAM
purpose are defined by this document and other future related
documents.
8.4. TRILL OAM TLVs
TRILL related TLVs are defined in this section. [8021Q] defined
TLVs are reused, where applicable.
8.4.1. Common TLVs between CFM and TRILL
The following TLVs are defined in [8021Q]. We re-use them where
applicable. The format and semantics of the TLVs are as defined
in [8021Q].
Type Name of TLV in [8021Q]
---- ----------------------
0 End TLV
1 Sender ID TLV
2 Port Status TLV
3 Data TLV
4 Interface Status TLV
5 Reply Ingress TLV
6 Reply Egress TLV
7 LTM Egress Identifier TLV
8 LTR Egress Identifier TLV
9-30 Reserved
31 Organization Specific TLV
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8.4.2. TRILL OAM Specific TLVs
Listed below is a summary of TRILL OAM TLVs and their
corresponding codes. Format and semantics of TRILL OAM TLVs are
defined in subsequent sections.
Type TLV Name
----------- ----------------------
TBDa TRILL OAM Application Identifier TLV
TBDb Out of Band Reply Address TLV
TBDc Diagnostic Label TLV
TBDd Original Data Payload TLV
TBDe RBridge scope TLV
TBDf Previous RBridge nickname TLV
TBDg Next Hop RBridge List (ECMP) TLV
TBDh Multicast Receiver Port count TLV
TBDi Flow Identifier TLV
TBDj Reflector Entropy TLV
TBDk Authentication TLV
The TRILL OAM Application Identifier TLV (TBDa) MUST be the first
TLV. An End TLV (0) MUST be included as the last TLV. All other
TLVs can be included in any order.
8.4.3. TRILL OAM Application Identifier TLV
The TRILL OAM Application Identifier TLV carries TRILL OAM
application specific information. The TRILL OAM Application
Identifier TLV MUST always be present and MUST be the first TLV
in TRILL OAM messages. Messages that do not include the TRILL OAM
Application Identifier TLV as the first TLV MUST be discarded by
a TRILL MP.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved1 | Fragment-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Code |Return sub-code| Reserved2 |F|C|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11 TRILL OAM Application Identifier TLV
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Type (1 octet) = TBDa indicate that this is the TRILL OAM
Application Identifier TLV.
Length (2 octets) = 9.
TRILL OAM Version (1 octet), currently set to zero. Indicates the
TRILL OAM version. TRILL OAM version can be different than the
[8021Q] version.
Reserved1 (3 octets): set to zero on transmission and ignored on
reception.
Fragment-ID (1 octet): Indicates the fragment number of the
current message. This applies only to reply messages; in request
messages it must be set to zero on transmission and ignored on
receipt. F flag defined below MUST be set with the final message
whether it is the last fragment of the fragmented message or only
message of the reply. Section 13. below provides more details on
OAM Message fragmentation.
Return Code (1 octet): Set to zero on requests. Set to an
appropriate value in response messages.
Return sub-code (1 Octet): Return sub-code is set to zero on
transmission of request message. Return sub-code identifies
categories within a specific Return code. Return sub-code MUST be
interpreted within a Return code.
Reserved2 (12 bits): Set to zero on transmission and ignored on
reception.
F (1 bit): Final flag, when set, indicates this is the last
response.
C (1 bit): Cross connect error flag(VLAN/Label mapping error), if
set indicates that the label (VLAN/FGL) in the flow entropy is
different than the label included in the diagnostic TLV. This
field is ignored in request messages and MUST only be interpreted
in response messages.
O (1 bit): If set, indicates, OAM out-of-band response requested.
I (1 bit): If set, indicates, OAM in-band response requested.
NOTE: When both O and I bits are set to zero, indicates that no
response is required (silent mode). User MAY specify both O and I
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or one of them or none. When both O and I bits are set response
is sent both in-band and out-of-band.
8.4.4. Out Of Band Reply Address TLV
Out of Band Reply Address TLV specifies the address to which an
out of band OAM reply message MUST be sent. When O bit in the
TRILL Version TLV is not set, Out of Band Reply Address TLV is
ignored.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Address Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Addr Length | |
+-+-+-+-+-+-+-+-+ |
| |
. Reply Address .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12 Out of Band IP Address TLV
Type (1 octet) = TBDb
Length (2 octets) = Variable. Minimum length is 2 + the length
(in octets) of the shortest address. Currently the minimum value
of this field is 4, but this could change in the future if a new
address shorter than the TRILL RBridge nickname is defined.
Address Type (1 octet) = 0 - IPv4. 1 - IPv6. 2 - TRILL RBridge
nickname. All other values reserved.
Addr Length (1 octet) = Depends on the Address Type. Currently
defined values are: 4 - IPv4. 16 - IPv6, 2 - TRILL RBridge
nickname. Other lengths may be acceptable for future Address
Types.
Reply Address (variable): Address where the reply needed to be
sent. Length depends on the address specification.
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8.4.5. Diagnostics Label TLV
Diagnostic label specifies the data label (VLAN or FGL) in which
the OAM messages are generated. Receiving RBridge MUST compare
the data label of the Flow entropy to the data label specified in
the Diagnostic Label TLV. Label Error Flag in the response (TRILL
OAM Message Version TLV) MUST be set when the two VLANs do not
match.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | L-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Label(VLAN) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13 Diagnostic VLAN TLV
Type (1 octet) = TBDc indicates that this is the TRILL Diagnostic
VLAN TLV
Length (2 octets) = 5
L-Type (Label type, 1 octet)
0- indicate 802.1Q 12 bit VLAN.
1 - indicate TRILL 24 bit fine grain label
Reserved (1 octet) = set to zero on transmission and ignored on
reception.
Label (24 bits)= Either 12 bit VLAN or 24 bit fine grain label.
RBridges do not perform Label error checking when the Label TLV
is not included in the OAM message. In certain deployments
intermediate devices may perform label translation. In such
scenarios, originator should not include the diagnostic Label TLV
in OAM messages. Inclusion of diagnostic TLV will generate
unwanted label error notifications.
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8.4.6. Original Data Payload TLV
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
. Original Payload .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14 Original Data Payload TLV
Type (1 octet) = TBDd
Length (2 octets) = variable
Original Payload: The original TRILL Header and Entropy. Used in
constructing replies to the Loopback Message (see Section 9) and
the Path Trace Message (see Section 10).
8.4.7. RBridge scope TLV
RBridge scope TLV identifies nicknames of RBridges from which a
response is required. The RBridge scope TLV is only applicable to
Multicast Tree Verification messages. This TLV SHOULD NOT be
included in other messages. Receiving RBridges MUST ignore this
TLV on messages other than Multicast Verification Message.
Each TLV can contain up to 255 nicknames of in-scope RBridges. A
Multicast Verification Message may contain multiple "RBridge
scope TLVs", in the event that more than 255 in scope RBridges
need to be specified.
Absence of the "RBridge scope TLV" indicates that a response is
needed from all the RBridges. Please see section 11. for details.
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | nOfnicknames |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| nickname-1 | nickname-2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | nickname-n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15 RBridge Scope TLV
Type (1 octet) = TBDe indicates that this is the "RBridge scope
TLV"
Length (2 octets) = variable. Minimum value is 1.
nOfnicknames (1 octet) = indicates number of nicknames included
in this TLV. Zero (0) indicates no nicknames are included in the
TLV. When this field is set to zero (0), length field MUST be set
to 1.
Nickname (2 octets) = 16 bit RBridge nickname.
8.4.8. Previous RBridge nickname TLV
The "Previous RBridge nickname TLV" identifies the nickname or
nicknames of the Previous RBridge. [RFC6325] allows a given
RBridge to hold multiple nicknames.
The "Previous RBridge nickname TLV" is an optional TLV. Multiple
instances of this TLV MAY be included when an upstream RBridge is
represented by more than 255 nicknames (highly unlikely).
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (continued) | nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16 Previous RBridge nickname TLV
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Type (1 octet) = TBDf indicates that this is the "Previous
RBridge nickname"
Length (2 octets) = 5.
Reserved (3 octet) = set to zero on transmission and ignored on
reception.
Nickname (2 octets) = RBridge nickname.
8.4.9. Next Hop RBridge List TLV
"Next Hop RBridge List TLV" identifies the nickname or nicknames
of the downstream next hop RBridges. [RFC6325] allows a given
RBridge to have multiple Equal Cost Paths to a specified
destination. Each next hop RBridge is represented by one of its
nicknames.
"Next Hop RBridge List TLV" is an optional TLV. Multiple
instances of this TLV MAY be included when there are more than
255 Equal Cost Paths to the destination.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | nOfnicknames |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| nickname-1 | nickname-2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | nickname-n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17 Next Hop RBridge List TLV
Type (1 octet) = TBDg indicates that this is the "Next nickname"
Length (2 octets) = variable. Minimum value is 1.
Nickname (2 octets) = 16 bit RBridge nickname.
nOfnicknames (1 octet) = indicates number of nicknames included
in this TLV. Zero (0) indicates no nicknames are included in the
TLV. When this field is set to zero (0), length field MUST be set
to 1.
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8.4.10. Multicast Receiver Port count TLV
"Multicast Receiver Port Count TLV" identifies the number of
ports interested in receiving the specified multicast stream
within the responding RBridge on the label (VLAN or FGL)
specified by the Diagnostic Label TLV.
Multicast Receiver Port count is an Optional TLV.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| number of Receivers |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18 Multicast Receiver Availability TLV
Type (1 octet) = TBDh indicates that this is the "Multicast
Availability TLV"
Length (2 octets) = 5.
Reserved (1 octet) = set to zero on transmission and ignored on
reception.
Number of Receivers (4 octets) = Indicates the number of
Multicast receivers available on the responding RBridge on the
label specified by the diagnostic label.
8.4.11. Flow Identifier (flow-id) TLV
Flow Identifier (flow-id) uniquely identifies a specific flow.
The flow-id value is unique per MEP and needs to be interpreted
as such.
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MEP-ID | flow-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 19 Flow Identifier TLV
Type (1 octet) = TBDi
Length (2 octets) = 5.
Reserved (1 octet) set to 0 on transmission and ignored on
reception.
MEP-ID (2 octets) = MEP-ID of the originator [8021Q]. In TRILL
MEP-ID can take a value from 1 to 65535.
Flow-id (2 octets) = uniquely identifies the flow per MEP.
Different MEPs may allocate the same flow-id value. The {MEP-ID,
flow-id} pair is globally unique.
Inclusion of the MEP-ID in the flow-id TLV allows the inclusion
of a MEP-ID for messages that do not contain a MEP-ID in their
OAM header. Applications may use MEP-ID information for different
types of troubleshooting.
8.4.12. Reflector Entropy TLV
Reflector Entropy TLV is an optional TLV. This TLV, when present,
tells the responder to utilize the Reflector Entropy specified
within the TLV as the flow-entropy of the response message.
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Reflector Entropy .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 20 Reflector Entropy TLV
Type (1 octet) = TBDj Reflector Entropy TLV.
Length (2 octets) = 97.
Reserved (1 octet) = set to zero on transmission and ignored by
the recipient.
Reflector Entropy (96-octet) = Flow Entropy to be used by the
responder. May be padded with zero if the desired flow entropy is
less than 96 octets.
8.4.13. Authentication TLV
The Authentication TLV is an optional TLV that can appear in any
OAM Message or Reply in TRILL.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Auth Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Authentication Value .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type (1 octet) = TBDk Authentication TLV.
Length (2 octets) = variable length
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The Auth Type and following Authentication Value are the same as
the Auth Type and following value for the [IS-IS] Authentication
TLV. It is RECOMMENDED that Auth Type 3 be used. Auth Types 0, 1,
2, and 54 MUST NOT be used. With Type 3, the Authentication TLV
is as follows:
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Auth Type = 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
. Authentication Data (variable) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
With Auth Type 3, the process is generally as specified in
[RFC5310] using the same Key ID space as TRILL [IS-IS]. The area
covered by the Authentication TLV is from the beginning of the
TRILL Header to the end of the TRILL OAM Message Channel - the
Link Header and Trailer are not included. The TRILL Header Alert
and Reserved bit and Hop Count are treated as if zero for the
purposes of computing and verifying the Authentication Data.
Key distribution is out of scope for this document as the keying
distributed for IS-IS is used.
An RBridge supporting OAM authentication can be configured to
either (1) ignore received OAM Authentication TLVs and not send
them, (2) ignore received OAM Authentication TLVs but include
them in all OAM packets sent, or (3) to include Authentication
TLVs in all OAM messages sent and enforce authentication of OAM
messages received. When an RBridge is enforcing authentication,
it discards any OAM message subject to OAM processing that does
not contain an Authentication TLV or if the Authentication TLV
does not verify.
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9. Loopback Message
9.1. Loopback OAM Message format
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|MD-L | Version | OpCode | Flags |FirstTLVOffset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Loopback Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. TLVs .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 21 Loopback OAM Message Format
The above figure depicts the format of the Loopback Request and
response messages as defined in [8021Q]. The Opcode for Loopback
Message is set to 3 and the Opcode for the Reply Message is set
to 2 [8021Q]. The Loopback Transaction Identifier (commonly
called the Session Identification Number or Session ID in this
document) is a 32-bit integer that allows the requesting RBridge
to uniquely identify the corresponding session. Responding
RBridges, without modification, MUST echo the received "Loopback
Transaction Identifier" number.
9.2. Theory of Operation
9.2.1. Actions by Originator RBridge
The originator RBridge takes the following actions:
Identifies the destination RBridge nickname based on user
specification or based on the specified destination MAC or IP
address.
Constructs the flow entropy based on user specified parameters or
implementation specific default parameters.
Constructs the TRILL OAM header: sets the opcode to Loopback
message type (3)[8021Q]. Assigns applicable Loopback Transaction
Identifier number for the request.
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The TRILL OAM Application Identifier TLV MUST be included and
with the flags set to applicable values.
Include following OAM TLVs, where applicable
o Out of Band Reply Address TLV
o Diagnostic Label TLV
o Sender ID TLV
Specify the Hop count of the TRILL data frame per user
specification or utilize an applicable Hop count value.
Dispatch the OAM frame for transmission.
RBridges may continue to retransmit the request at periodic
intervals, until a response is received or the re-transmission
count expires. At each transmission Session Identification number
MUST be incremented.
9.2.2. Intermediate RBridge
Intermediate RBridges forward the frame as a normal data frame
and no special handling is required.
9.2.3. Destination RBridge
If the Loopback message is addressed to the local RBridge and
satisfies the OAM identification criteria specified in section
3.1. then, the RBridge data plane forwards the message to the CPU
for further processing.
The TRILL OAM application layer further validates the received
OAM frame by checking for the presence of OAM-Ethertype at the
end of the flow entropy. Frames that do not contain OAM-Ethertype
at the end of the flow entropy MUST be discarded.
Construction of the TRILL OAM response:
TRILL OAM application encodes the received TRILL header and flow
entropy in the Original payload TLV and includes it in the OAM
message.
Set the Return Code to (1) "Reply" and Return sub code to zero
(0) "Valid Response". Update the TRILL OAM opcode to 2 (Loopback
Message Reply)
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Optionally, if the VLAN/FGL identifier value of the received flow
entropy differs from the value specified in the diagnostic Label,
set the Label Error Flag on TRILL OAM Application Identifier TLV.
Include the sender ID TLV (1)
If in-band response was requested, dispatch the frame to the
TRILL data plane with request-originator RBridge nickname as the
egress RBridge nickname.
If out-of-band response was requested, dispatch the frame to the
IP forwarding process.
10. Path Trace Message
The primary use of the Path Trace Message is for fault isolation.
It may also be used for plotting the path taken from a given
RBridge to another RBridge.
[8021Q] accomplishes the objectives of the TRILL Path Trace
Message using Link Trace Messages. Link Trace Messages utilize a
well-known multicast MAC address. This works for [8021Q], because
for 802.1 both the unicast and multicast paths are congruent.
However, in TRILL multicast and unicast are not congruent. Hence,
TRILL OAM uses a new message format: the Path Trace message.
The Path Trace Message has the same format as Loopback Message.
The Opcode for Path Trace Reply is TBD1 and for Path Trace
Message is TBD2.
Operation of the Path Trace message is identical to the Loopback
message except that it is first transmitted with a TRILL Header
Hop count field value of 1. The sending RBridge expects an
"Intermediate RBridge" Return sub-code from the next hop or a
"Valid response" Return sub-Code response from the destination
RBridge. If an "Intermediate RBridge" Return sub-code is
received in the response, the originator RBridge records the
information received from intermediate node that generated the
message and resends the message by incrementing the previous Hop
count value by 1. This process is continued until, a response is
received from the destination RBridge or Path Trace process
timeout occur or Hop count reaches a configured maximum value.
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10.1. Theory of Operation
10.1.1. Action by Originator RBridge
Identify the destination RBridge based on user specification or
based on location of the specified MAC address.
Construct the flow entropy based on user specified parameters or
implementation specific default parameters.
Construct the TRILL OAM header: Set the opcode to Path Trace
Request message type (TBD2). Assign an applicable Session
Identification number for the request. Return-code and sub-code
MUST be set to zero.
The TRILL OAM Application Identifier TLV MUST be included and set
the flags to applicable values.
Include following OAM TLVs, where applicable
o Out of Band Reply Address TLV
o Diagnostic Label TLV
o Include the Sender ID TLV
Specify the Hop count of the TRILL data frame as 1 for the first
request.
Dispatch the OAM frame to the TRILL data plane for transmission.
An RBridge may continue to retransmit the request at periodic
intervals, until a response is received or the re-transmission
count expires. At each new re-transmission, the Session
Identification number MUST be incremented. Additionally, for
responses received from intermediate RBridges, the RBridge
nickname and interface information MUST be recorded.
10.1.2. Intermediate RBridge
Path Trace Messages transit through Intermediate RBridges
transparently, unless Hop-count has expired.
TRILL OAM application layer further validates the received OAM
frame by examining the presence of TRILL Alert Flag and OAM-
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Ethertype at the end of the flow entropy and by examining the MD
Level. Frames that do not contain OAM-Ethertype at the end of the
flow entropy MUST be discarded.
Construction of the TRILL OAM response:
TRILL OAM application encodes the received TRILL header and flow
entropy in the Original payload TLV and include it in the OAM
message.
Set the Return Code to (1) "Reply" and Return sub code to zero
(2) "Intermediate RBridge". Update the TRILL OAM opcode to TBD1
(Path Trace Reply).
If the VLAN/FGL identifier value of the received flow entropy
differs from the value specified in the diagnostic Label, set the
Label Error Flag on TRILL OAM Application Identifier TLV.
Include following TLVs
Previous RBridge nickname TLV (69)
Reply Ingress TLV (5)
Reply Egress TLV (6)
Interface Status TLV (4)
TRILL Next Hop RBridge (Repeat for each ECMP) (70)
Sender ID TLV (1)
If Label error detected, set C flag (Label error detected) in the
version.
If in-band response was requested, dispatch the frame to the
TRILL data plane with request-originator RBridge nickname as the
egress RBridge nickname.
If out-of-band response was requested, dispatch the frame to the
standard IP forwarding process.
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10.1.3. Destination RBridge
Processing is identical to section 10.1.2. With the exception
that TRILL OAM Opcode is set to Path Trace Reply (TBD1).
11. Multi-Destination Tree Verification Message (MTVM)
Multi-Destination Tree Verification messages allow verifying
TRILL distribution tree integrity and pruning. TRILL VLAN/FGL and
multicast pruning are described in [RFC6325] [RFC7180] and
[RFC7172]. Multi-destination tree verification and Multicast
group verification messages are designed to detect pruning
defects. Additionally, these tools can be used for plotting a
given multicast tree within the TRILL campus.
Multi-Destination tree verification OAM frames are copied to the
CPU of every intermediate RBridge that is part of the
distribution tree being verified. The originator of the Multi-
destination Tree verification message specifies the scope of
RBridges from which a response is required. Only the RBridges
listed in the scope field respond to the request. Other RBridges
silently discard the request. Inclusion of the scope parameter is
required to prevent receiving an excessive number of responses.
The typical scenario of distribution tree verification or group
verification, involves verifying multicast connectivity to a
selected set of end-nodes as opposed to the entire network.
Availability of the scope facilitates narrowing down the focus to
only the RBridges of interest.
Implementations MAY choose to rate-limit CPU bound multicast
traffic. As a result of rate-limiting or due to other congestion
conditions, MTVM messages may be discarded from time to time by
the intermediate RBRidges and the requester may be required to
retransmit the request. Implementations SHOULD narrow the
embedded scope of retransmission request only to RBridges that
have failed to respond.
11.1. Multi-Destination Tree Verification Message (MTVM) Format
Format of MTVM is identical to that of Loopback Message format
defined in section 9. with the exception that the Op-Code used is
TBD4.
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11.2. Theory of Operation
11.2.1. Actions by Originator RBridge
The user is required at a minimum to specify either the
distribution trees that need to be verified, or the Multicast MAC
address and VLAN/FGL, or VLAN/FGL and Multicast destination IP
address. Alternatively, for more specific multicast flow
verification, the user MAY specify more information e.g. source
MAC address, VLAN/FGL, Destination and Source IP addresses.
Implementations, at a minimum, must allow the user to specify a
choice of distribution trees, Destination Multicast MAC address
and VLAN/FGL that needs to be verified. Although, it is not
mandatory, it is highly desired to provide an option to specify
the scope. It should be noted that the source MAC address and
some other parameters may not be specified if the Backwards
Compatibility Method of Appendix A is used to identify the OAM
frames.
Default parameters MUST be used for unspecified parameters. Flow
entropy is constructed based on user specified parameters and/or
default parameters.
Based on user specified parameters, the originating RBridge does
the following:
Identifies the nickname that represents the multicast tree.
Obtains the applicable Hop count value for the selected
multicast tree.
Constructs TRILL OAM message header and include Session
Identification number. Session Identification number facilitate
the originator mapping the response to the correct request.
Includes TRILL OAM Application Identifier TLV, which MUST be
included.
Includes the Op-Code Multicast Tree Verification Message
(TBD4)
Includes RBridge scope TLV (TBDe)
Optionally, include following TLV, where applicable
o Out-of-band IP address (TBDb)
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o Diagnostic Label (TBDd)
o Sender ID TLV (1)
Specify the Hop count of the TRILL data frame per user
specification or alternatively utilize the applicable Hop count
value if TRILL Hop count is not being specified by the user; and
Dispatch the OAM frame to the TRILL data plane to be ingressed
for transmission.
The RBridge may continue to retransmit the request at a periodic
interval until either a response is received or the re-
transmission count expires. At each new re-transmission, the
Session Identification number MUST be incremented. At each re-
transmission, the RBridge may further reduce the scope to the
RBridges that it has not received a response from.
11.2.2. Receiving RBridge
Receiving RBridges identify multicast verification frames per the
procedure explained in sections 3.2.
The RBridge validates the frame and analyzes the scope RBridge
list. If the RBridge scope TLV is present and the local RBridge
nickname is not specified in the scope list, it will silently
discard the frame. If the local RBridge is specified in the scope
list OR RBridge scope TLV is absent, the receiving RBridge
proceeds with further processing as defined in section 11.2.3.
11.2.3. In scope RBridges
Construction of the TRILL OAM response:
TRILL OAM application encodes the received TRILL header and flow
entropy in the Original payload TLV and includes them in the OAM
message.
Set the Return Code to (0) and Return sub code to zero (0).
Update the TRILL OAM opcode to TBD3 (Multicast Tree Verification
Reply).
Include following TLVs:
Previous RBridge nickname TLV (TBDf)
Reply Ingress TLV (5)
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Interface Status TLV (4)
TRILL Next Hop RBridge List (TBDg)
Sender ID TLV (1)
Multicast Receiver Availability TLV (TBDh)
If a Label (VLAN or FGL) cross connect error is detected, set the
C flag (Cross connect error detected) in the Application
Identifier TLV.
If in-band response was requested, dispatch the frame to the
TRILL data plane with request-originator RBridge nickname as the
egress RBridge nickname.
If out-of-band response was requested, dispatch the frame to the
standard IP forwarding process.
12. Application of Continuity Check Message (CCM) in TRILL
Section 7. provides an overview of CCM Messages defined in
[8021Q] and how they can be used within the TRILL OAM. This
section, presents the application and Theory of Operations of CCM
within the TRILL OAM framework. Readers are referred to [8021Q]
for CCM message format and applicable TLV definitions and usages.
Only the TRILL specific aspects are explained below.
In TRILL, between any two given MEPs there can be multiple
potential paths. Whereas in [8021Q], there is always a single
path between any two MEPs at any given time. [RFC6905] requires
solutions to have the ability to monitor continuity over one or
more paths.
CCM Messages are uni-directional, such that there is no explicit
response to a received CCM message. Connectivity status is
indicated by setting the applicable flags (e.g. RDI) of the CCM
messages transmitted by an MEP.
It is important that the solution presented in this document
accomplishes the requirements specified in [RFC6905] within the
framework of [8021Q] in a straightforward manner and with minimum
changes. Section 8 above defines multiple flows within the CCM
object, each corresponding to a flow that a given MEP wishes to
monitor. Hence, CCM, in multipath environments like TRILL,
monitors per flow connectivity and cross connect errors.
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Receiving MEPs do not cross check whether a received CCM belongs
to a specific flow from the originating RBridge. Any attempt to
track status of individual flows may explode the amount of state
information that any given RBridge has to maintain.
The obvious question arises: How does the originating RBridge
know which flow or flows are at fault?
This is accomplished with a combination of the RDI flag in the
CCM header, flow-id TLV, and SNMP Notifications (Traps). Section
12.1. below discuss the procedure.
12.1. CCM Error Notification
Each MEP transmits 4 CCM messages per each flow. ([8021Q] detects
CCM fault when 3 consecutive CCM messages are lost). Each CCM
Message has a unique sequence number (Session ID) and unique
flow-identifier. The flow identifier is included in the OAM
message via flow-id TLV.
When an MEP notices a CCM timeout from a remote MEP (MEP-A), it
sets the RDI flag on the next CCM message it generates.
Additionally, it logs and sends SNMP notification that contain
the remote MEP Identification, flow-id and the Sequence Number of
the last CCM message it received and if available, the flow-id
and the Sequence Number of the first CCM message it received
after the failure. Each MEP maintains a unique flow-id per each
flow, hence the operator can easily identify flows that
correspond to the specific flow-id.
The following example illustrates the above.
Assume there are two MEPs, MEP-A and MEP-B.
Assume there are 3 flows between MEP-A and MEP-B.
Let's assume MEP-A allocates sequence numbers as follows
Flow-1 Sequence={1,2,3,4,13,14,15,16,.. } flow-id=(1)
Flow-2 Sequence={5,6,7,8,17,18,19,20,.. } flow-id=(2)
Flow-3 Sequence={9,10,12,11,21,22,23,24,.. } flow-id=(3)
Let's Assume Flow-2 is at fault.
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MEP-B, receives CCM from MEP-A with sequence numbers 1,2,3,4, but
did not receive 5,6,7,8. CCM timeout is set to 3 CCM intervals in
[8021Q]. Hence MEP-B detects the error at the 8'th CCM message.
At this time the sequence number of the last good CCM message
MEP-B has received from MEP-A is 4 and flow-id of the last good
CCM Message is (1). Hence MEP-B will generate a CCM error SNMP
notification with MEP-A and Last good flow-id (1) and sequence
number 4.
When MEP-A switches to flow-3 after transmitting flow-2, MEP-B
will start receiving CCM messages. In the foregoing example it
will be CCM message with Sequence Numbers 9,10,11,12,21 and so
on. When in receipt of a new CCM message from a specific MEP,
after a CCM timeout, the TRILL OAM will generate an SNMP
Notification of CCM resume with remote MEP-ID and the first valid
flow-id and the Sequence number after the CCM timeout. In the
foregoing example, it is MEP-A, flow-id (3) and Sequence Number
9.
The remote MEP list under the CCM MIB Object is augmented to
contain "Last Sequence Number", flow-id and "CCM Timeout"
variables. Last Sequence Number and flow-id are updated every
time a CCM is received from a remote MEP. CCM Timeout variable is
set when the CCM timeout occurs and is cleared when a CCM is
received.
12.2. Theory of Operation
12.2.1. Actions by Originator RBridge
Derive the flow entropy based on flow entropy specified in the
CCM Management object.
Construct the TRILL CCM OAM header as specified in [8021Q].
TRILL OAM Version TLV MUST be included as the first TLV and set
the flags to applicable values.
Include other TLVs specified in [8021Q]
Include the following optional TLV, where applicable
o Sender ID TLV (1)
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Specify the Hop count of the TRILL data frame per user
specification or utilize an applicable Hop count value.
Dispatch the OAM frame to the TRILL data plane for transmission.
An RBridge transmits a total of 4 requests, each at CCM
retransmission interval. At each transmission the Session
Identification number MUST be incremented by one.
At the 5'th retransmission interval, flow entropy of the CCM
packet is updated to the next flow entropy specified in the CCM
Management Object. If current flow entropy is the last flow
entropy specified, move to the first flow entropy specified and
continue the process.
12.2.2. Intermediate RBridge
Intermediate RBridges forward the frame as a normal data frame
and no special handling is required.
12.2.3. Destination RBridge
If the CCM Message is addressed to the local RBridge or multicast
and satisfies OAM identification methods specified in sections
3.2. then the RBridge data plane forwards the message to the CPU
for further processing.
The TRILL OAM application layer further validates the received
OAM frame by examining the presence of OAM-Ethertype at the end
of the flow entropy. Frames that do not contain OAM-Ethertype at
the end of the flow entropy MUST be discarded.
Validate the MD-LEVEL and pass the packet to the Opcode de-
multiplexer. The Opcode de-multiplexer delivers CCM packets to
the CCM process.
The CCM Process performs processing specified in [8021Q].
Additionally the CCM process updates the CCM Management Object
with the sequence number of the received CCM packet. Note: The
last received CCM sequence number and CCM timeout are tracked per
each remote MEP.
If the CCM timeout is true for the sending remote MEP, then clear
the CCM timeout in the CCM Management object and generate the
SNMP notification as specified above.
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13. Fragmented Reply
TRILL OAM allows Fragmented reply messages. In case of Fragmented
Replies, all part of the reply MUST follow the procedure defined
in this section.
The same session Identification Number MUST be included in all
related fragments of the same message.
The TRILL OAM Application Identifier TLV MUST be included, with
fragment-ID field monotonically increasing with each fragment
transmitted with the appropriate Final Flag field. The Final
Flag, MUST, only be equal to one on the final fragment of the
reply.
On the receiver, process MUST order the fragments based on the
fragment id. Any fragments received after final fragment MUST be
discarded. Messages with incomplete fragments (i.e. messages with
one or missing fragments after the receipt of the fragment with
the final flag set) MUST be discarded as well.
If number of fragments exceed the maximum supported fragments
(255), then return code of MUST be set according to the message
and return sub code MUST be set to 1 indicating fragment limit
exceed.
14. Security Considerations
Forged OAM packets could cause false error or failure indications
or mask actual errors or failures or be used for denial of
service. Source addresses for messages can be forged and the Out
of Band reply facility (Section 8.4.4) provides for explicitly
supplying the address for replies. For protection against forged
OAM packets, the Authentication TLV (see Section 8.4.13) can be
used in an OAM message in TRILL. This TLV depends on IS-IS keying
material and the current state of IS-IS keying and the use of the
virtually identical IS-IS Authentication TLV is analyzed in
[KARPISIS]. In particular, there is currently no standardized IS-
IS automated key management.
Of course, authentication is ineffective unless verified and
ineffective against senders who have the keying material needed
to produce OAM messages that will pass authentication checks.
Implementations MUST implement rate-limiting functionality to
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protect against exploitation of OAM messages as a means of denial
of service attacks. Aggressive rate limiting may trigger false
positive errors against CCM and LBM based session monitoring.
Even with authentication, replay of authenticated messages may be
possible. There are four types of messages: Continuity Check
(CCM), Loopback, Path Trace, and Multi-Destination Tree
Verification (MTVM). In the case of CCM messages, sequence
numbers are required (see Section 12.1) that can protect against
replay. In the case of Loopback Messages (see Section 9.1), a
Loopback Transaction Identifier is included that, as required by
[8021Q], is incremented with each transmission and can detect
replays. Path Trace Messages (see Section 10) and MTVM (see
section 11.1) are specified to have the same format, although
with a different OpCodes, as the Loopback Message and so also
have an identifier increment with each transmission that can
detect replays. Thus all TRILL OAM messages have a field that can
be used for replay protection.
For general TRILL related security considerations, please refer
to [RFC6325].
[8021Q] requires that the MEP filters or pass through OAM
messages based on the MD-Level. The MD-Level is embedded deep in
the OAM message. Hence, conventional methods of frame filtering
may not be able to filter frames based on the MD-Level. As a
result, OAM messages that must be dropped due to MD level
mismatch may leak into a TRILL domain with different MD-Level.
This leaking may not cause any functionality loss. The receiving
MEP/MIP is required to validate the MD-level prior to acting on
the message. Any frames received with an incorrect MD-Level need
to be dropped.
Generally, a single operator manages each TRILL campus, hence
there is no risk of security exposure. However, in the event of
multi operator deployments, operators should be aware of possible
exposure of device specific information and appropriate measures
must be taken.
It is also important to note that the MPLS OAM [RFC4379]
framework does not include the concept of domains and OAM
filtering based on operators. It is our opinion that the lack of
OAM frame filtering based on domains does not introduce
significant functional deficiency or security risk.
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It is possible to mandate requiring different credentials to use
different OAM functions or capabilities within a specific OAM
function. Implementations may consider grouping users to
different security clearance levels and restricting functions and
capabilities to different clearance levels. However, Exact
implementation details of such a framework are outside the scope
of this document.
15. IANA Considerations
IANA is requested to assign the following:
15.1. OAM Capabilitiy Flags
Assign two TRILL-VER sub-TLV Capability Flags (see Section 3.3)
as follows:
Bit Description Reference
--- ----------- ---------
TBD[2] OAM capable [this document]
TBD[3] Backwards compatible OAM [this document]
15.2. CFM Code Points
IANA is requested to assign four Op-Codes from the CFM OAM IETF
Op-Codes sub-registry as follows [suggested values in square
brackets]:
Value Assignment Reference
===== ========== =========
TBD1[64] Path Trace Reply [this document]
TBD2[65] Path Trace Message [this document]
TBD3[66] Multicast Tree Verification Reply
[this document]
TBD4[67] Multicast Tree Verification Message
[this document]
IANA is requested to assign eleven TLV Types from the CFM OAM
IETF TLV Types sub-registry as follows [suggested values in square
brackets]:
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Value Assignment Reference
===== ========== =========
TBDa[64] TRILL OAM Application Identifier TLV
[this document]
TBDb[65] Out of Band Reply Address TLV [this document]
TBDc[66] Diagnostic Label TLV [this document]
TBDd[67] Original Data Payload TLV [this document]
TBDe[68] RBridge Scope TLV [this document]
TBDf[69] Previous RBridge nickname TLV
[this document]
TBDg[70] Next Hop RBridge List TLV
[this document]
TBDh[71] Multicast Receiver Port count TLV
[this document]
TBDi[72] Flow Identifier TLV [this document]
TBDj[73] Reflector Entropy TLV [this document]
TBDk[74] Authentication TLV [this document]
15.3. MAC Addresses
IANA is requested to assigned a unicast and a multicast MAC
address under the IANA OUI, for identification of OAM packets as
discussed for the backward compatibility method (Appendix A,
Section A.2) based on the request template in Appendix C. The
assigned addresses are TBDmac1 [00-00-5E-90-01-00] (unicast) and
TBDmac2 [01-5E-90-01-00] (multicast).
15.4. Return codes and sub codes
IANA is requested to create TRILL OAM Return Code registry within
the TRILL Parameter Registry and, for each return code a separate
sub code Sub-Registry as below:
Registry: TRILL OAM Return Codes.
Registration Procedure: Standards Action.
Return Code Assignment References
=========== ========== ==========
0 Request message [this document]
1 Reply message [this document]
2-255 Unassigned [this document]
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Sub-Registry: Sub Codes for TRILL OAM Return Code 0.
Registration Procedure: Standards Action.
Sub Code Assignment References
=========== ========== ==========
0 Valid request [this document]
1-255 Unassigned [this document]
Sub-Registry: Sub Codes for TRILL OAM Return Code 1.
Registration Procedure: Standards Action.
Sub Code Assignment References
=========== ========== ==========
0 Valid response [this document]
1 Fragment limit exceeded [this document]
2 Intermediate RBridge [this document]
3-255 Unassigned [this document]
15.5. TRILL RBridge Nickname Address Family
IANA has allocated 16396 as the Address Family Number for TRILL
RBridge nicknames.
16. References
16.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
an IANA Considerations Section in RFCs", BCP 26, RFC
5226, May 2008.
[RFC5310] Bhatia, M., "IS-IS Cryptographic Generic Cryptographic
Authentication", RFC 5310, February 2009.
[RFC6325] Perlman, R., et.al., "Routing Bridges (RBridges): Base
Protocol Specification", RFC 6325, July 2011.
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[RFC7172] Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R.,
and D. Dutt, "Transparent Interconnection of Lots of
Links (TRILL): Fine-Grained Labeling", RFC 7172, May
2014.
[8021Q] IEEE, "Media Access Control (MAC) Bridges and Virtual
Bridged Local Area Networks", IEEE Std 802.1Q-2011,
August, 2011.
[IS-IS] ISO/IEC 10589:2002, Second Edition, "Intermediate System
to Intermediate System Intra-Domain Routing Exchange
Protocol for use in Conjunction with the Protocol for
Providing the Connectionless-mode Network Service (ISO
8473)", 2002.
16.2. Informative References
[RFC4379] Kompella, K. et.al, "Detecting Multi-Protocol Label
Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[RFC6291] Andersson, L., et.al., "Guidelines for the use of the
"OAM" Acronym in the IETF" RFC 6291, June 2011.
[RFC6361] Carlson, J. and Eastlake, D. "PPP Transparent
Interconnection of Lots of Links (TRILL) Protocol
Control Protocol", RFC 6361, August 201.
[RFC6905] Senevirathne, T. et.al, "Requirements for Operations,
Administration, and Maintenance (OAM) in Transparent
Interconnection of Lots of Links (TRILL)", RFC 6905,
March 2013.
[RFC7176] Eastlake, D., Senevirathne, T., Ghanwani, A., Dutt, D.,
and A. Banerjee, "Transparent Interconnection of Lots
of Links (TRILL) Use of IS-IS", RFC 7176 May 2014.
[RFC7180] Eastlake, Donald, et.al. "TRILL: Clarifications,
Corrections, and Updates, RFC 7180 May 2014.
[RFC7174] Salam, S., et.al., "TRILL OAM Framework", RFC 7174 ,
May 2014.
[RFC7179] Eastlake, Donald, et.al. "TRILL: Header Extension", RFC
7179, May 2014.
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[Y1731] ITU-T Recommendation Y.1731, "OAM functions and
mechanisms for Ethernet based networks", ITU-T
G.8013/Y.1731, July 2013.
[RFC7178] D. Eastlake, et.al. , "TRILL: RBridge Channel Support",
RFC 7178, May 2014.
[TRILLOAMMIB] Deepak Kumar et.al, "TRILL OAM MIB", draft-deepak-
trill-oam-mib, May 2013, work in progress.
[KARPISIS] U. Chunduri, et.a., "KARP IS-IS security analysis",
draft-karp-isis-analysis, September 2014, work in
progress.
17. Acknowledgments
Work in this document was largely inspired by the directions
provided by Stewart Bryant in finding a common OAM solution
between SDOs.
Acknowledgments are due for many who volunteered to review this
document, notably, Jari Arkko, Adrian Farrel, Pete Resnick,
Stephen Farrell, Dan Romascanu, Gayle Nobel and Tal Mizrahi.
Special appreciations are due for Dinesh Dutt for his support and
encouragement, especially during the initial discussion phase of
TRILL OAM.
This document was prepared using 2-Word-v2.0.template.dot.
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Appendix A. Backwards Compatibility
Methodology presented above in this document is in-line with the
[8021Q] framework for providing fault management coverage.
However, in practice, some TRILL platforms may not have the
capabilities to support some of the required techniques. In this
section, we present a method that allows RBridges, which do not
have the required hardware capabilities, to participate in the
TRILL OAM solution.
There are two broad areas to be considered; 1. Maintenance Point
(MEP/MIP) Model 2. Data plane encoding and frame identification
A.1 Maintenance Point (MEP/MIP) Model
For backwards compatibility, MEPs and MIPs are located in the
CPU. This will be referred to as the "central brain" model as
opposed to "port brain" model.
In the "central brain" model, an RBridge using either ACLs or
some other method, forwards qualifying OAM messages to the CPU.
The CPU then performs the required processing and multiplexing to
the correct MP (Maintenance Point).
Additionally, RBridges MUST have the capability to prevent the
leaking of OAM packets, as specified in [RFC6905].
A.2 Data plane encoding and frame identification
The backwards compatibility method presented in this section
defines methods to identify OAM frames when implementations do
not have capabilities to utilize TRILL OAM Alert flag presented
earlier to identify OAM frames, in the hardware.
It is assumed ECMP path selection of non-IP flows utilize MAC DA,
MAC SA and VLAN, IP Flows utilize IP DA, IP SA and TCP/UDP port
numbers and other Layer 3 and Layer 4 information. The well-known
fields to identify OAM flows are chosen such that they mimic the
ECMP selection of the actual data along the path. However, it is
important to note that, there may be implementations that would
utilize these well-known fields for ECMP selections. Hence,
implementations that support OAM SHOULD move to utilizing TRILL
Alert Flag, as soon as possible and methods presented here SHOULD
be used only as an interim solution.
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Identification methods are divided in to 4 broader groups:
1. Identification of Unicast non-IP OAM Flows,
2. Identification of Multicast non-IP OAM Flows,
3. Identification of Unicast IP OAM Flows and
4. Identification of Multicast IP OAM Flows
As presented in the table below, based on the flow type (as
defined above), implementations are required to use a well-known
value in either the Inner.MacSA field or OAM Ethertype field to
identify OAM flows.
Receiving RBridge identifies OAM flows based on the presence of
the well-known values in the specified fields, and additionally,
for unicast flows, egress RBridge nickname of the packet MUST
match that of the local RBridge or for multicast flows, TRILL
header mutlicast flag MUST be set.
Unicast OAM flows that qualify for local processing MUST be
redirected to the OAM process and MUST NOT be forwarded (that to
prevent leaking of the packet out of the TRILL campus).
A copy of Multicast OAM flows that qualify for local processing
MUST be sent to the OAM process and packet MUST be forwarded
along the normal path. Additionally, methods MUST be in place to
prevent multicast packets leaking out of the TRILL campus.
The following table summarizes the identification of different
OAM frames from data frames.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Flow Entropy |Inner |OAM Ether|Egress |
| |MacSA |Type |nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|unicast no IP | N/A |Match |Match |
| | | | |
|Multicast no IP| N/A |Match |N/A |
| | | | |
|Unicast IP | Match |N/A |Match |
| | | | |
|Multicast IP | Match |N/A |N/A |
| | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 22 Identification of TRILL OAM Frames
The unicast and multicast Inner.MacSAs used for the unicast and
multicast IP cases, respectively, are TBDmac1 [00-00-5E-90-01-00]
and TBDmac2 [01-00-5E-90-01-01] assigned by the request in
Appendix C.
It is important to note that all RBridges MUST generate OAM flows
with "A" flag set and CFM EtherType "0x8902" at the flow entropy
off-set. However, well-known values MUST be utilized as part of
the flow-entropy when generating OAM messages destined for older
RBridges that are compliant to the backwards compatibility method
defined in this appendix.
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Appendix B. Base Mode for TRILL OAM
CFM, as defined in [8021Q], requires configuration of several
parameters before the protocol can be used. These parameters
include MAID, Maintenance Domain Level (MD-LEVEL) and MEPIDs. The
Base Mode for TRILL OAM defined here facilitates ease of use and
provides out of the box plug-and-play capabilities, supporting
the Operational and Manageability considerations described in
Section 6 of [RFC7174].
All RBridges that support TRILL OAM MUST support Base Mode
operation.
All Rbridges MUST create a default MA with MAID as specified
herein.
MAID [8021Q] has a flexible format and includes two parts:
Maintenance Domain Name and Short MA name. In the Based Mode of
operation, the value of the Maintenance Domain Name must be the
character string "TrillBaseMode" (excluding the quotes "). In
Base Mode operation Short MA Name format is set to 2-octet
integer format (value 3 in Short MA Format field) and Short MA
name set to 65532 (0xFFFC).
The Default MA belongs to MD-LEVEL 3.
In the Base Mode of operation, each RBridge creates a single UP
MEP associated with a virtual OAM port with no physical layer
(NULL PHY). The MEPID associated with this MEP is the 2-octet
RBridge Nickname.
By default, all RBridges operating in the Base Mode for TRILL OAM
are able to initiate LBM, PT and other OAM tools with no
configuration.
Implementations MAY provide default flow-entropy to be included
in OAM messages. Content of the default flow-entropy is outside
the scope of this document.
Figure 23, below depicts encoding of MAID within CCM messages.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Field Name |Size |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Maintenance | 1 |
|Domain Format | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Maintenance | 2 |
|Domain Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Maintenance | variable|
|Domain Name | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Short MA | 1 |
|Name Format | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Short MA | 2 |
|Name Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Short MA | variable|
|Name | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Padding | Variable|
+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 23 MAID structure as defined in [8021Q]
Maintenance Domain Name Format is set to Value: 4
Maintenance Domain Name Length is set to value: 13
Maintenance Domain Name is set to: TrillBaseMode
Short MA Name Format is set to value: 3
Short MA Name Length is set to value: 2
Short MA Name is set to: FFFC
Padding: set of zero up to 48 octets of total length of the MAID.
Please refer to [8021Q] for details.
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Appendix C. MAC Addresses Request
Applicant Name: IETF TRILL Working Group
Applicant Email: tsenevir@cisco.com
Applicant Telephone: +1-408-853-2291
Use Name: TRILL OAM
Document: draft-tissa-trill-oam-fm
Specify whether this is an application for EUI-48 or EUI-64
identifiers: EUI-48
Size of Block requested: 1
Specify multicast, unicast, or both: Both
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Authors' Addresses
Tissa Senevirathne
CISCO Systems
375 East Tasman Drive.
San Jose, CA 95134
USA.
Phone: +1 408-853-2291
Email: tsenevir@cisco.com
Norman Finn
CISCO Systems
510 McCarthy Blvd
Milpitas, CA 95035
USA
Email: nfinn@cisco.com
Samer Salam
CISCO Systems
595 Burrard St. Suite 2123
Vancouver, BC V7X 1J1, Canada
Email: ssalam@cisco.com
Deepak Kumar
CISCO Systems
510 McCarthy Blvd,
Milpitas, CA 95035, USA
Phone : +1 408-853-9760
Email: dekumar@cisco.com
Donald Eastlake
Huawei Technologies
155 Beaver Street
Milford, MA 01757
Phone: +1-508-333-2270
Email: d3e3e3@gmail.com
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Sam Aldrin
Huawei Technologies
2330 Central Express Way
Santa Clara, CA 95951
USA
Email: aldrin.ietf@gmail.com
Yizhou Li
Huawei Technologies
101 Software Avenue,
Nanjing 210012
China
Phone: +86-25-56625375
Email: liyizhou@huawei.com
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