Internet DRAFT - draft-ietf-mpls-residence-time
draft-ietf-mpls-residence-time
MPLS Working Group G. Mirsky
Internet-Draft ZTE Corp.
Intended status: Standards Track S. Ruffini
Expires: September 8, 2017 E. Gray
Ericsson
J. Drake
Juniper Networks
S. Bryant
Huawei
A. Vainshtein
ECI Telecom
March 7, 2017
Residence Time Measurement in MPLS network
draft-ietf-mpls-residence-time-15
Abstract
This document specifies a new Generic Associated Channel for
Residence Time Measurement and describes how it can be used by time
synchronization protocols within a MPLS domain.
Residence time is the variable part of the propagation delay of
timing and synchronization messages; knowing what this delay is for
each message allows for a more accurate determination of the delay to
be taken into account in applying the value included in a Precision
Time Protocol event message.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 8, 2017.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 4
2. Residence Time Measurement . . . . . . . . . . . . . . . . . 4
2.1. One-step Clock and Two-step Clock Modes . . . . . . . . . 5
2.1.1. RTM with Two-step Upstream PTP Clock . . . . . . . . 6
2.1.2. Two-step RTM with One-step Upstream PTP Clock . . . . 7
3. G-ACh for Residence Time Measurement . . . . . . . . . . . . 7
3.1. PTP Packet Sub-TLV . . . . . . . . . . . . . . . . . . . 9
4. Control Plane Theory of Operation . . . . . . . . . . . . . . 10
4.1. RTM Capability . . . . . . . . . . . . . . . . . . . . . 10
4.2. RTM Capability Sub-TLV . . . . . . . . . . . . . . . . . 11
4.3. RTM Capability Advertisement in Routing Protocols . . . . 11
4.3.1. RTM Capability Advertisement in OSPFv2 . . . . . . . 11
4.3.2. RTM Capability Advertisement in OSPFv3 . . . . . . . 13
4.3.3. RTM Capability Advertisement in IS-IS . . . . . . . . 13
4.3.4. RTM Capability Advertisement in BGP-LS . . . . . . . 13
4.4. RSVP-TE Control Plane Operation to Support RTM . . . . . 14
4.4.1. RTM_SET TLV . . . . . . . . . . . . . . . . . . . . . 15
5. Data Plane Theory of Operation . . . . . . . . . . . . . . . 20
6. Applicable PTP Scenarios . . . . . . . . . . . . . . . . . . 20
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
7.1. New RTM G-ACh . . . . . . . . . . . . . . . . . . . . . . 21
7.2. New RTM TLV Registry . . . . . . . . . . . . . . . . . . 21
7.3. New RTM Sub-TLV Registry . . . . . . . . . . . . . . . . 22
7.4. RTM Capability sub-TLV in OSPFv2 . . . . . . . . . . . . 22
7.5. IS-IS RTM Capability sub-TLV . . . . . . . . . . . . . . 22
7.6. RTM Capability TLV in BGP-LS . . . . . . . . . . . . . . 23
7.7. RTM_SET Sub-object RSVP Type and sub-TLVs . . . . . . . . 23
7.8. RTM_SET Attribute Flag . . . . . . . . . . . . . . . . . 24
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7.9. New Error Codes . . . . . . . . . . . . . . . . . . . . . 24
8. Security Considerations . . . . . . . . . . . . . . . . . . . 25
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
10.1. Normative References . . . . . . . . . . . . . . . . . . 25
10.2. Informative References . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction
Time synchronization protocols, e.g., Network Time Protocol version 4
(NTPv4) [RFC5905] and Precision Time Protocol (PTP) Version 2
[IEEE.1588.2008], define timing messages that can be used to
synchronize clocks across a network domain. Measurement of the
cumulative time that one of these timing messages spends transiting
the nodes on the path from ingress node to egress node is termed
Residence Time and it is used to improve the accuracy of clock
synchronization. Residence Time is the sum of the difference between
the time of receipt at an ingress interface and the time of
transmission from an egress interface for each node along the network
path from an ingress node to an egress node. This document defines a
new Generic Associated Channel (G-ACh) value and an associated
residence time measurement (RTM) message that can be used in a Multi-
Protocol Label Switching (MPLS) network to measure residence time
over a Label Switched Path (LSP).
This document describes RTM over an LSP signaled using RSVP-TE
[RFC3209]. Using RSVP-TE, the LSP's path can be either explicitly
specified or determined during signaling. Although it is possible to
use RTM over an LSP instantiated using Label Distribution Protocol
[RFC5036], that is outside the scope of this document.
Comparison with alternative proposed solutions such as
[I-D.ietf-tictoc-1588overmpls] is outside the scope of this document.
1.1. Conventions used in this document
1.1.1. Terminology
MPLS: Multi-Protocol Label Switching
ACH: Associated Channel
TTL: Time-to-Live
G-ACh: Generic Associated Channel
GAL: Generic Associated Channel Label
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NTP: Network Time Protocol
ppm: parts per million
PTP: Precision Time Protocol
BC: Boundary Clock
LSP: Label Switched Path
OAM: Operations, Administration, and Maintenance
RRO: Record Route Object
RTM: Residence Time Measurement
IGP: Internal Gateway Protocol
BGP-LS: Border Gateway Protocol - Link State
1.1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
2. Residence Time Measurement
Packet Loss and Delay Measurement for MPLS Networks [RFC6374] can be
used to measure one-way or two-way end-to-end propagation delay over
LSP or PW. But these measurements are insufficient for use in some
applications, for example, time synchronization across a network as
defined in the PTP. In PTPv2 [IEEE.1588.2008], the residence time is
accumulated in the correctionField of the PTP event message, as
defined in [IEEE.1588.2008] and referred to as using a one-step
clock, or in the associated follow-up message (or Delay_Resp message
associated with the Delay_Req message), referred to as using a two-
step clock (see the detailed discussion in Section 2.1).
IEEE 1588 uses this residence time to correct for the transit times
of nodes on an LSP, effectively making the transit nodes transparent.
This document proposes a mechanism that can be used as one type of
on-path support for a clock synchronization protocol or to perform
one-way measurement of residence time. The proposed mechanism
accumulates residence time from all nodes that support this extension
along the path of a particular LSP in the Scratch Pad field of an RTM
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message (Figure 1). This value can then be used by the egress node
to update, for example, the correctionField of the PTP event packet
carried within the RTM message prior to performing its PTP
processing.
2.1. One-step Clock and Two-step Clock Modes
One-step mode refers to the mode of operation where an egress
interface updates the correctionField value of an original event
message. Two-step mode refers to the mode of operation where this
update is made in a subsequent follow-up message.
Processing of the follow-up message, if present, requires the
downstream end-point to wait for the arrival of the follow-up message
in order to combine correctionField values from both the original
(event) message and the subsequent (follow-up) message. In a similar
fashion, each two-step node needs to wait for the related follow-up
message, if there is one, in order to update that follow-up message
(as opposed to creating a new one). Hence the first node that uses
two-step mode MUST do two things:
1. Mark the original event message to indicate that a follow-up
message will be forthcoming. This is necessary in order to
Let any subsequent two-step node know that there is already a
follow-up message, and
Let the end-point know to wait for a follow-up message;
2. Create a follow-up message in which to put the RTM determined as
an initial correctionField value.
IEEE 1588v2 [IEEE.1588.2008] defines this behavior for PTP messages.
Thus, for example, with reference to the PTP protocol, the PTPType
field identifies whether the message is a Sync message, Follow_up
message, Delay_Req message, or Delay_Resp message. The 10 octet long
Port ID field contains the identity of the source port
[IEEE.1588.2008], that is, the specific PTP port of the boundary
clock connected to the MPLS network. The Sequence ID is the sequence
ID of the PTP message carried in the Value field of the message.
PTP messages also include a bit that indicates whether or not a
follow-up message will be coming. This bit MAY be set by a two-step
mode PTP device. The value MUST NOT be unset until the original and
follow-up messages are combined by an end-point (such as a Boundary
Clock).
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For compatibility with PTP, RTM (when used for PTP packets) must
behave in a similar fashion. It should be noted that the handling of
Sync event messages and of Delay_Req/Delay_Resp event messages that
cross a two-step RTM node is different. The following outlines the
handling of PTP Sync event message by the two-step RTM node. The
details of handling Delay_Resp/Delay_Req PTP event messages by the
two-step RTM node are discussed in Section 2.1.1. As a summary, a
two-step RTM capable egress interface will need to examine the S-bit
in the Flags field of the PTP sub-TLV (for RTM messages that indicate
they are for PTP) and - if it is clear (set to zero), it MUST set the
S bit and create a follow-up PTP Type RTM message. If the S bit is
already set, then the RTM capable node MUST wait for the RTM message
with the PTP type of follow-up and matching originator and sequence
number to make the corresponding residence time update to the Scratch
Pad field. The wait period MUST be reasonably bounded.
Thus, an RTM packet, containing residence time information relating
to an earlier packet, also contains information identifying that
earlier packet.
In practice, an RTM node operating in two-step mode behaves like a
two-steps transparent clock.
A one-step capable RTM node MAY elect to operate in either one-step
mode (by making an update to the Scratch Pad field of the RTM message
containing the PTP event message), or in two-step mode (by making an
update to the Scratch Pad of a follow-up message when presence of a
follow-up is indicated), but MUST NOT do both.
Two main subcases identified for an RTM node operating as a two-step
clock are described in the following sub-sections.
2.1.1. RTM with Two-step Upstream PTP Clock
If any of the previous RTM capable nodes or the previous PTP clock
(e.g., the Boundary Clock (BC) connected to the first node), is a
two-step clock, the residence time is added to the RTM packet that
has been created to include the second PTP packet (i.e., follow-up
message in the downstream direction), if the local RTM-capable node
is also operating as a two-step clock. This RTM packet carries the
related accumulated residence time and the appropriate values of the
Sequence ID and Port ID (the same identifiers carried in the original
packet) and the Two-step Flag set to 1.
Note that the fact that an upstream RTM-capable node operating in the
two-step mode has created a follow-up message does not require any
subsequent RTM capable node to also operate in the two-step mode, as
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long as that RTM-capable node forwards the follow-up message on the
same LSP on which it forwards the corresponding previous message.
A one-step capable RTM node MAY elect to update the RTM follow-up
message as if it were operating in two-step mode, however, it MUST
NOT update both messages.
A PTP Sync packet is carried in the RTM packet in order to indicate
to the RTM node that residence time measurement must be performed on
that specific packet.
To handle the residence time of the Delay_Req message on the upstream
direction, an RTM packet must be created to carry the residence time
on the associated downstream Delay_Resp message.
The last RTM node of the MPLS network, in addition to updating the
correctionField of the associated PTP packet, must also react
properly to the two-step flag of the PTP packets.
2.1.2. Two-step RTM with One-step Upstream PTP Clock
When the PTP network connected to the MPLS operates in one-step clock
mode and an RTM node operates in two-step mode, the follow-up RTM
packet must be created by the RTM node itself. The RTM packet
carrying the PTP event packet needs now to indicate that a follow-up
message will be coming.
The egress RTM-capable node of the LSP will be removing RTM
encapsulation and, in case of two-step clock mode being indicated,
will generate PTP messages to include the follow-up correction as
appropriate (according to the [IEEE.1588.2008]). In this case, the
common header of the PTP packet carrying the synchronization message
would have to be modified by setting the twoStepFlag field indicating
that there is now a follow up message associated to the current
message.
3. G-ACh for Residence Time Measurement
RFC 5586 [RFC5586] and RFC 6423 [RFC6423] define the G-ACh to extend
the applicability of the Pseudowire Associated Channel (ACH)
[RFC5085] to LSPs. G-ACh provides a mechanism to transport OAM and
other control messages over an LSP. Processing of these messages by
selected transit nodes is controlled by the use of the Time-to-Live
(TTL) value in the MPLS header of these messages.
The message format for Residence Time Measurement (RTM) is presented
in Figure 1
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0 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | RTM G-ACh |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Scratch Pad |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLV (optional) |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: RTM G-ACh message format for Residence Time Measurement
o First four octets are defined as G-ACh Header in [RFC5586]
o The Version field is set to 0, as defined in RFC 4385 [RFC4385].
o The Reserved field MUST be set to 0 on transmit and ignored on
receipt.
o The RTM G-ACh field, value (TBA1) to be allocated by IANA,
identifies the packet as such.
o The Scratch Pad field is 8 octets in length. It is used to
accumulate the residence time spent in each RTM capable node
transited by the packet on its path from ingress node to egress
node. The first RTM-capable node MUST initialize the Scratch Pad
field with its residence time measurement. Its format is IEEE
double precision and its units are nanoseconds. Note that
depending on whether the timing procedure is one-step or two-step
operation (Section 2.1), the residence time is either for the
timing packet carried in the Value field of this RTM message or
for an associated timing packet carried in the Value field of
another RTM message.
o The Type field identifies the type and encapsulation of a timing
packet carried in the Value field, e.g., NTP [RFC5905] or PTP
[IEEE.1588.2008]. This document asks IANA to create a sub-
registry in Generic Associated Channel (G-ACh) Parameters Registry
called "MPLS RTM TLV Registry" Section 7.2.
o The Length field contains the length, in octets, of the of the
timing packet carried in the Value field.
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o The optional Value field MAY carry a packet of the time
synchronization protocol identified by Type field. It is
important to note that the packet may be authenticated or
encrypted and carried over LSP edge to edge unchanged while the
residence time is accumulated in the Scratch Pad field.
o The TLV MUST be included in the RTM message, even if the length of
the Value field is zero.
3.1. PTP Packet Sub-TLV
Figure 2 presents the format of a PTP sub-TLV that MUST be included
in the Value field of an RTM message preceding the carried timing
packet when the timing packet is PTP.
0 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |PTPType|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port ID |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Sequence ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: PTP Sub-TLV format
where Flags field has format
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 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Flags field format of PTP Packet Sub-TLV
o The Type field identifies PTP packet sub-TLV and is set to 1
according to Section 7.3.
o The Length field of the PTP sub-TLV contains the number of octets
of the Value field and MUST be 20.
o The Flags field currently defines one bit, the S-bit, that defines
whether the current message has been processed by a two-step node,
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where the flag is cleared if the message has been handled
exclusively by one-step nodes and there is no follow-up message,
and is set if there has been at least one two-step node and a
follow-up message is forthcoming.
o The PTPType field indicates the type of PTP packet carried in the
TLV. PTPType is the messageType field of the PTPv2 packet whose
values are defined in Table 19 of [IEEE.1588.2008].
o The 10 octet long Port ID field contains the identity of the
source port.
o The Sequence ID is the sequence ID of the PTP message carried in
the Value field of the message.
Tuple of PTPType, Port ID, and Sequence ID uniquely identifies PTP
control packet encapsulated in RTM message and are used in two-step
RTM mode Section 2.1.1.
4. Control Plane Theory of Operation
The operation of RTM depends upon TTL expiry to deliver an RTM packet
from one RTM capable interface to the next along the path from
ingress node to egress node. This means that a node with RTM capable
interfaces MUST be able to compute a TTL which will cause the expiry
of an RTM packet at the next node with RTM capable interfaces.
4.1. RTM Capability
Note that the RTM capability of a node is with respect to the pair of
interfaces that will be used to forward an RTM packet. In general,
the ingress interface of this pair must be able to capture the
arrival time of the packet and encode it in some way such that this
information will be available to the egress interface of a node.
The supported mode (one-step or two-step) of any pair of interfaces
is determined by the capability of the egress interface. For both
modes, the egress interface implementation MUST be able to determine
the precise departure time of the same packet and determine from
this, and the arrival time information from the corresponding ingress
interface, the difference representing the residence time for the
packet.
An interface with the ability to do this and update the associated
Scratch Pad in real-time (i.e., while the packet is being forwarded)
is said to be one-step capable.
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Hence while both ingress and egress interfaces are required to
support RTM for the pair to be RTM-capable, it is the egress
interface that determines whether or not the node is one-step or two-
step capable with respect to the interface-pair.
The RTM capability used in the sub-TLV shown in Figure 4 and Figure 5
is thus a non-routing related capability associated with the
interface being advertised based on its egress capability. The
ability of any pair of interfaces on a node that includes this egress
interface to support any mode of RTM depends on the ability of the
ingress interface of a node to record packet arrival time and convey
it to the egress interface on the node.
When a node uses an IGP to support the RTM capability advertisement,
the IGP sub-TLV MUST reflect the RTM capability (one-step or two-
step) associated with the advertised interface. Changes of RTM
capability are unlikely to be frequent and would result, for example,
from operator's decision to include or exclude a particular port from
RTM processing or switch between RTM modes.
4.2. RTM Capability Sub-TLV
[RFC4202] explains that the Interface Switching Capability Descriptor
describes the switching capability of an interface. For bi-
directional links, the switching capabilities of an interface are
defined to be the same in either direction. I.e., for data entering
the node through that interface and for data leaving the node through
that interface. That principle SHOULD be applied when a node
advertises RTM Capability.
A node that supports RTM MUST be able to act in two-step mode and MAY
also support one-step RTM mode. Detailed discussion of one-step and
two-step RTM modes is contained in Section 2.1.
4.3. RTM Capability Advertisement in Routing Protocols
4.3.1. RTM Capability Advertisement in OSPFv2
The format for the RTM Capability sub-TLV in OSPF is presented in
Figure 4
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0 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RTM | Value ...
+-+-+-+-+-+-+-+-+-+- ...
Figure 4: RTM Capability sub-TLV in OSPFv2
o Type value (TBA2) will be assigned by IANA from appropriate
registry for OSPFv2 Section 7.4.
o Length value equals number of octets of the Value field.
o Value contains variable number of bit-map fields so that overall
number of bits in the fields equals Length * 8.
o Bits are defined/sent starting with Bit 0. Additional bit-map
field definitions that may be defined in the future SHOULD be
assigned in ascending bit order so as to minimize the number of
bits that will need to be transmitted.
o Undefined bits MUST be transmitted as 0 and MUST be ignored on
receipt.
o Bits that are NOT transmitted MUST be treated as if they are set
to 0 on receipt.
o RTM (capability) - is a three-bit long bit-map field with values
defined as follows:
* 0b001 - one-step RTM supported;
* 0b010 - two-step RTM supported;
* 0b100 - reserved.
The capability to support RTM on a particular link (interface) is
advertised in the OSPFv2 Extended Link Opaque LSA described in
Section 3 [RFC7684] via the RTM Capability sub-TLV.
Its Type value will be assigned by IANA from the OSPF Extended Link
TLV Sub-TLVs registry Section 7.4, that will be created per [RFC7684]
request.
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4.3.2. RTM Capability Advertisement in OSPFv3
The capability to support RTM on a particular link (interface) can be
advertised in OSPFv3 using LSA extensions as described in
[I-D.ietf-ospf-ospfv3-lsa-extend]. The sub-TLV SHOULD use the same
format as in Section 4.3.1. The type allocation and full details of
exact use of OSPFv3 LSA extensions is for further study.
4.3.3. RTM Capability Advertisement in IS-IS
The capability to support RTM on a particular link (interface) is
advertised in a new sub-TLV which may be included in TLVs advertising
Intermediate System (IS) Reachability on a specific link (TLVs 22,
23, 222, and 223).
The format for the RTM Capabilities sub-TLV is presented in Figure 5
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 4 5 ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
| Type | Length | RTM | Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...
Figure 5: RTM Capability sub-TLV
o Type value (TBA3) will be assigned by IANA from the Sub-TLVs for
TLVs 22, 23, 141, 222, and 223 registry for IS-IS Section 7.5.
o Definitions, rules of handling, and values for fields Length and
Value are as defined in Section 4.3.1
o RTM (capability) - is a three-bit long bit-map field with values
defined in Section 4.3.1.
4.3.4. RTM Capability Advertisement in BGP-LS
The format for the RTM Capabilities TLV is as presented in Figure 4.
Type value TBA9 will be assigned by IANA from the BGP-LS Node
Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs
sub-registry Section 7.6.
Definitions, rules of handling, and values for fields Length, Value,
and RTM are as defined in Section 4.3.1.
The RTM Capability will be advertised in BGP-LS as a Link Attribute
TLV associated with the Link NLRI as described in section 3.3.2 of
[RFC7752].
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4.4. RSVP-TE Control Plane Operation to Support RTM
Throughout this document we refer to a node as RTM capable node when
at least one of its interfaces is RTM capable. Figure 6 provides an
example of roles a node may have with respect to RTM capability:
----- ----- ----- ----- ----- ----- -----
| A |-----| B |-----| C |-----| D |-----| E |-----| F |-----| G |
----- ----- ----- ----- ----- ----- -----
Figure 6: RTM capable roles
o A is a BC with its egress port in Master state. Node A transmits
IP encapsulated timing packets whose destination IP address is G.
o B is the ingress LER for the MPLS LSP and is the first RTM capable
node. It creates RTM packets and in each it places a timing
packet, possibly encrypted, in the Value field and initializes the
Scratch Pad field with its residence time measurement
o C is a transit node that is not RTM capable. It forwards RTM
packets without modification.
o D is RTM capable transit node. It updates the Scratch Pad field
of the RTM packet without updating the timing packet.
o E is a transit node that is not RTM capable. It forwards RTM
packets without modification.
o F is the egress LER and the last RTM capable node. It removes the
RTM ACH encapsulation and processes the timing packet carried in
the Value field using the value in the Scratch Pad field. In
particular, the value in the Scratch Pad field of the RTM ACH is
used in updating the Correction field of the PTP message(s). The
LER should also include its own residence time before creating the
outgoing PTP packets. The details of this process depend on
whether or not the node F is itself operating as one-step or two-
step clock.
o G is a Boundary Clock with its ingress port in Slave state. Node
G receives PTP messages.
An ingress node that is configured to perform RTM along a path
through an MPLS network to an egress node MUST verify that the
selected egress node has an interface that supports RTM via the
egress node's advertisement of the RTM Capability sub-TLV, as covered
in Section 4.3. In the Path message that the ingress node uses to
instantiate the LSP to that egress node, it places an LSP_ATTRIBUTES
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Object [RFC5420] with RTM_SET Attribute Flag set, as described in
Section 7.8, which indicates to the egress node that RTM is requested
for this LSP. The RTM_SET Attribute Flag SHOULD NOT be set in the
LSP_REQUIRED_ATTRIBUTES object [RFC5420], unless it is known that all
nodes recognize the RTM attribute (but need not necessarily implement
it), because a node that does not recognize the RTM_SET Attribute
Flag would reject the Path message.
If an egress node receives a Path message with the RTM_SET Attribute
Flag in LSP_ATTRIBUTES object, the egress node MUST include an
initialized RRO [RFC3209] and LSP_ATTRIBUTES object where the RTM_SET
Attribute Flag is set and the RTM_SET TLV Section 4.4.1 is
initialized. When the Resv message is received by the ingress node,
the RTM_SET TLV will contain an ordered list, from egress node to
ingress node, of the RTM capable nodes along the LSP's path.
After the ingress node receives the Resv, it MAY begin sending RTM
packets on the LSP's path. Each RTM packet has its Scratch Pad field
initialized and its TTL set to expire on the closest downstream RTM
capable node.
It should be noted that RTM can also be used for LSPs instantiated
using [RFC3209] in an environment in which all interfaces in an IGP
support RTM. In this case the RTM_SET TLV and LSP_ATTRIBUTES Object
MAY be omitted.
4.4.1. RTM_SET TLV
RTM capable interfaces can be recorded via RTM_SET TLV. The RTM_SET
sub-object format is of generic Type, Length, Value (TLV), presented
in Figure 7 .
0 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 |I| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Value ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: RTM_SET TLV format
The type value (TBA4) will be assigned by IANA from its RSVP-TE
Attributes TLV Space sub-registry Section 7.7.
The Length contains the total length of the sub-object in bytes,
including the Type and Length fields.
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The I bit flag indicates whether the downstream RTM capable node
along the LSP is present in the RRO.
The Reserved field must be zeroed on initiation and ignored on
receipt.
The content of an RTM_SET TLV is a series of variable-length sub-
TLVs. Only a single RTM_SET can be present in a given LSP_ATTRIBUTES
object. The sub-TLVs are defined in Section 4.4.1.1 below.
The following processing procedures apply to every RTM capable node
along the LSP. In this paragraph, an RTM capable node is referred to
as a node for sake of brevity. Each node MUST examine the Resv
message for whether the RTM_SET Attribute Flag in the LSP_ATTRIBUTES
object is set. If the RTM_SET flag is set, the node MUST inspect the
LSP_ATTRIBUTES object for presence of an RTM_SET TLV. If more than
one is found, then the LSP setup MUST fail with generation of the
ResvErr message with Error Code Duplicate TLV (Section 7.9) and Error
Value that contains Type value in its 8 least significant bits. If
no RTM_SET TLV is found, then the LSP setup MUST fail with generation
of the ResvErr message with Error Code RTM_SET TLV Absent
Section 7.9. If one RTM_SET TLV has been found, the node will use
the ID of the first node in the RTM_SET in conjunction with the RRO
to compute the hop count to its downstream node with reachable RTM
capable interface. If the node cannot find a matching ID in the RRO,
then it MUST try to use the ID of the next node in the RTM_SET until
it finds the match or reaches the end of the RTM_SET TLV. If a match
has been found, the calculated value is used by the node as the TTL
value in the outgoing label to reach the next RTM capable node on the
LSP. Otherwise, the TTL value MUST be set to 255. The node MUST add
an RTM_SET sub-TLV with the same address it used in the RRO sub-
object at the beginning of the RTM_SET TLV in the associated outgoing
Resv message before forwarding it upstream. If the calculated TTL
value has been set to 255, as described above, then the I flag in the
node's RTM_SET TLV MUST be set to 1 before the Resv message is
forwarded upstream. Otherwise, the I flag MUST be cleared (0).
The ingress node MAY inspect the I bit flag received in each RTM_SET
TLV contained in the LSP_ATTRIBUTES object of a received Resv
message. The presence of the RTM_SET TLV with the I bit field set to
1 indicates that some RTM nodes along the LSP could not be included
in the calculation of the residence time. An ingress node MAY choose
to resignal the LSP to include all RTM nodes or simply notify the
user via a management interface.
There are scenarios when some information is removed from an RRO due
to policy processing (e.g., as may happen between providers) or the
RRO is limited due to size constraints. Such changes affect the core
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assumption of this method and the processing of RTM packets. RTM
SHOULD NOT be used if it is not guaranteed that the RRO contains
complete information.
4.4.1.1. RTM_SET Sub-TLVs
The RTM Set sub-object contains an ordered list, from egress node to
ingress node, of the RTM capable nodes along the LSP's path.
The contents of a RTM_SET sub-object are a series of variable-length
sub-TLVs. Each sub-TLV has its own Length field. The Length
contains the total length of the sub-TLV in bytes, including the Type
and Length fields. The Length MUST always be a multiple of 4, and at
least 8 (smallest IPv4 sub-object).
Sub-TLVs are organized as a last-in-first-out stack. The first-out
sub-TLV relative to the beginning of RTM_SET TLV is considered the
top. The last-out sub-TLV is considered the bottom. When a new sub-
TLV is added, it is always added to the top.
The RTM_SET TLV is intended to include the subset of the RRO sub-TLVs
that represents those egress interfaces on the LSP that are RTM-
capable. After a node chooses an egress interface to use in the RRO
sub-TLV, that same egress interface, if RTM-capable, SHOULD be placed
into the RTM_SET TLV using one of the IPv4 sub-TLV, IPv6 sub-TLV, or
Unnumbered Interface sub-TLV. The address family chosen SHOULD match
that of the RESV message and that used in the RRO; the unnumbered
interface sub-TLV is used when the egress interface has no assigned
IP address. A node MUST NOT place more sub-TLVs in the RTM_SET TLV
than the number of RTM-capable egress interfaces the LSP traverses
that are under that node's control. Only a single RTM_SET sub-TLV
with the given Value field MUST be present in the RTM_SET TLV. If
more than one sub-TLV with the same value (e.g., a duplicated
address) is found the LSP setup MUST fail with the generation of a
ResvErr message with the Error Code "Duplicate sub-TLV" Section 7.9
and Error Value contains 16-bit value composed of (Type of TLV, Type
of sub-TLV).
Three kinds of sub-TLVs for RTM_SET are currently defined.
4.4.1.1.1. IPv4 Sub-TLV
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0 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: IPv4 sub-TLV format
Type
0x01 IPv4 address
Length
The Length contains the total length of the sub-TLV in bytes,
including the Type and Length fields. The Length is always 8.
IPv4 address
A 32-bit unicast host address.
Reserved
Zeroed on initiation and ignored on receipt.
4.4.1.1.2. IPv6 Sub-TLV
0 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: IPv6 sub-TLV format
Type
0x02 IPv6 address
Length
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The Length contains the total length of the sub-TLV in bytes,
including the Type and Length fields. The Length is always 20.
IPv6 address
A 128-bit unicast host address.
Reserved
Zeroed on initiation and ignored on receipt.
4.4.1.1.3. Unnumbered Interface Sub-TLV
0 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: IPv4 sub-TLV format
Type
0x03 Unnumbered interface
Length
The Length contains the total length of the sub-TLV in bytes,
including the Type and Length fields. The Length is always 12.
Node ID
The Node ID interpreted as Router ID as discussed in Section 2
[RFC3477].
Interface ID
The identifier assigned to the link by the node specified by the
Node ID.
Reserved
Zeroed on initiation and ignored on receipt.
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5. Data Plane Theory of Operation
After instantiating an LSP for a path using RSVP-TE [RFC3209] as
described in Section 4.4, the ingress node MAY begin sending RTM
packets to the first downstream RTM capable node on that path. Each
RTM packet has its Scratch Pad field initialized and its TTL set to
expire on the next downstream RTM-capable node. Each RTM-capable
node on the explicit path receives an RTM packet and records the time
at which it receives that packet at its ingress interface as well as
the time at which it transmits that packet from its egress interface.
These actions should be done as close to the physical layer as
possible at the same point of packet processing striving to avoid
introducing the appearance of jitter in propagation delay whereas it
should be accounted as residence time. The RTM-capable node
determines the difference between those two times; for one-step
operation, this difference is determined just prior to or while
sending the packet, and the RTM-capable egress interface adds it to
the value in the Scratch Pad field of the message in progress. Note,
for the purpose of calculating a residence time, a common free
running clock synchronizing all the involved interfaces may be
sufficient, as, for example, 4.6 ppm accuracy leads to 4.6 nanosecond
error for residence time on the order of 1 millisecond. This may be
acceptable for applications where the target accuracy is in the order
of hundreds of ns. As an example, several applications being
considered in the area of wireless applications are satisfied with an
accuracy of 1.5 microseconds [ITU-T.G.8271].
For two-step operation, the difference between packet arrival time
(at an ingress interface) and subsequent departure time (from an
egress interface) is determined at some later time prior to sending a
subsequent follow-up message, so that this value can be used to
update the correctionField in the follow-up message.
See Section 2.1 for further details on the difference between one-
step and two-step operation.
The last RTM-capable node on the LSP MAY then use the value in the
Scratch Pad field to perform time correction, if there is no follow-
up message. For example, the egress node may be a PTP Boundary Clock
synchronized to a Master Clock and will use the value in the Scratch
Pad field to update PTP's correctionField.
6. Applicable PTP Scenarios
This approach can be directly integrated in a PTP network based on
the IEEE 1588 delay request-response mechanism. The RTM capable
nodes act as end-to-end transparent clocks, and typically boundary
clocks, at the edges of the MPLS network, use the value in the
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Scratch Pad field to update the correctionField of the corresponding
PTP event packet prior to performing the usual PTP processing.
7. IANA Considerations
7.1. New RTM G-ACh
IANA is requested to reserve a new G-ACh as follows:
+-------+----------------------------+---------------+
| Value | Description | Reference |
+-------+----------------------------+---------------+
| TBA1 | Residence Time Measurement | This document |
+-------+----------------------------+---------------+
Table 1: New Residence Time Measurement
7.2. New RTM TLV Registry
IANA is requested to create a sub-registry in the Generic Associated
Channel (G-ACh) Parameters Registry called "MPLS RTM TLV Registry".
All code points in the range 0 through 127 in this registry shall be
allocated according to the "IETF Review" procedure as specified in
[RFC5226]. Code points in the range 128 through 191 in this registry
shall be allocated according to the "First Come First Served"
procedure as specified in [RFC5226]. This document defines the
following new values RTM TLV types:
+-----------+-------------------------------+---------------+
| Value | Description | Reference |
+-----------+-------------------------------+---------------+
| 0 | Reserved | This document |
| 1 | No payload | This document |
| 2 | PTPv2, Ethernet encapsulation | This document |
| 3 | PTPv2, IPv4 Encapsulation | This document |
| 4 | PTPv2, IPv6 Encapsulation | This document |
| 5 | NTP | This document |
| 6-127 | Unassigned | |
| 128 - 191 | Unassigned | |
| 192 - 254 | Private Use | This document |
| 255 | Reserved | This document |
+-----------+-------------------------------+---------------+
Table 2: RTM TLV Type
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7.3. New RTM Sub-TLV Registry
IANA is requested to create a sub-registry in the MPLS RTM TLV
Registry, requested in Section 7.2, called "MPLS RTM Sub-TLV
Registry". All code points in the range 0 through 127 in this
registry shall be allocated according to the "IETF Review" procedure
as specified in [RFC5226]. Code points in the range 128 through 191
in this registry shall be allocated according to the "First Come
First Served" procedure as specified in [RFC5226]. This document
defines the following new values RTM sub-TLV types:
+-----------+-------------+---------------+
| Value | Description | Reference |
+-----------+-------------+---------------+
| 0 | Reserved | This document |
| 1 | PTP | This document |
| 2-127 | Unassigned | |
| 128 - 191 | Unassigned | |
| 192 - 254 | Private Use | This document |
| 255 | Reserved | This document |
+-----------+-------------+---------------+
Table 3: RTM Sub-TLV Type
7.4. RTM Capability sub-TLV in OSPFv2
IANA is requested to assign a new type for RTM Capability sub-TLV
from the OSPFv2 Extended Link TLV Sub-TLVs registry as follows:
+-------+----------------+---------------+
| Value | Description | Reference |
+-------+----------------+---------------+
| TBA2 | RTM Capability | This document |
+-------+----------------+---------------+
Table 4: RTM Capability sub-TLV
7.5. IS-IS RTM Capability sub-TLV
IANA is requested to assign a new Type for the RTM Capability sub-TLV
from the Sub-TLVs for TLVs 22, 23, 141, 222, and 223 registry as
follows:
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+------+----------------+----+----+-----+-----+-----+---------------+
| Type | Description | 22 | 23 | 141 | 222 | 223 | Reference |
+------+----------------+----+----+-----+-----+-----+---------------+
| TBA3 | RTM Capability | y | y | n | y | y | This document |
+------+----------------+----+----+-----+-----+-----+---------------+
Table 5: IS-IS RTM Capability sub-TLV Registry Description
7.6. RTM Capability TLV in BGP-LS
IANA is requested to assign a new code point for the RTM Capability
TLV from the BGP-LS Node Descriptor, Link Descriptor, Prefix
Descriptor, and Attribute TLVs sub-registry in its Border Gateway
Protocol - Link State (BGP-LS) Parameters registry as follows:
+---------------+----------------+------------------+---------------+
| TLV Code | Description | IS-IS TLV/Sub- | Reference |
| Point | | TLV | |
+---------------+----------------+------------------+---------------+
| TBA9 | RTM Capability | 22/TBA3 | This document |
+---------------+----------------+------------------+---------------+
Table 6: RTM Capability TLV in BGP-LS
7.7. RTM_SET Sub-object RSVP Type and sub-TLVs
IANA is requested to assign a new Type for the RTM_SET sub-object
from the RSVP-TE Attributes TLV Space sub-registry as follows:
+-----+------------+-----------+---------------+---------+----------+
| Typ | Name | Allowed | Allowed on | Allowed | Referenc |
| e | | on LSP_A | LSP_REQUIRED_ | on LSP | e |
| | | TTRIBUTES | ATTRIBUTES | Hop Att | |
| | | | | ributes | |
+-----+------------+-----------+---------------+---------+----------+
| TBA | RTM_SET | Yes | No | No | This |
| 4 | sub-object | | | | document |
+-----+------------+-----------+---------------+---------+----------+
Table 7: RTM_SET Sub-object Type
IANA requested to create a new sub-registry for sub-TLV types of the
RTM_SET sub-object. All code points in the range 0 through 127 in
this registry shall be allocated according to the "IETF Review"
procedure as specified in [RFC5226]. Code points in the range 128
through 191 in this registry shall be allocated according to the
"First Come First Served" procedure as specified in [RFC5226]. This
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document defines the following new values of RTM_SET object sub-
object types:
+-----------+----------------------+---------------+
| Value | Description | Reference |
+-----------+----------------------+---------------+
| 0 | Reserved | This document |
| 1 | IPv4 address | This document |
| 2 | IPv6 address | This document |
| 3 | Unnumbered interface | This document |
| 4-127 | Unassigned | |
| 128 - 191 | Unassigned | |
| 192 - 254 | Private Use | This document |
| 255 | Reserved | This document |
+-----------+----------------------+---------------+
Table 8: RTM_SET object sub-object types
7.8. RTM_SET Attribute Flag
IANA is requested to assign new flag from the RSVP-TE Attribute Flags
registry
+-----+--------+-----------+------------+-----+-----+---------------+
| Bit | Name | Attribute | Attribute | RRO | ERO | Reference |
| No | | Flags | Flags Resv | | | |
| | | Path | | | | |
+-----+--------+-----------+------------+-----+-----+---------------+
| TBA | RTM_SE | Yes | Yes | No | No | This document |
| 5 | T | | | | | |
+-----+--------+-----------+------------+-----+-----+---------------+
Table 9: RTM_SET Attribute Flag
7.9. New Error Codes
IANA is requested to assign new Error Codes from RSVP Error Codes and
Globally-Defined Error Value Sub-Codes registry
+------------+--------------------+---------------+
| Error Code | Meaning | Reference |
+------------+--------------------+---------------+
| TBA6 | Duplicate TLV | This document |
| TBA7 | Duplicate sub-TLV | This document |
| TBA8 | RTM_SET TLV Absent | This document |
+------------+--------------------+---------------+
Table 10: New Error Codes
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8. Security Considerations
Routers that support Residence Time Measurement are subject to the
same security considerations as defined in [RFC4385] and [RFC5085] .
In addition - particularly as applied to use related to PTP - there
is a presumed trust model that depends on the existence of a trusted
relationship of at least all PTP-aware nodes on the path traversed by
PTP messages. This is necessary as these nodes are expected to
correctly modify specific content of the data in PTP messages and
proper operation of the protocol depends on this ability. In
practice, this means that those portions of messages cannot be
covered by either confidentiality or integrity protection. Though
there are methods that make it possible in theory to provide either
or both such protections and still allow for intermediate nodes to
make detectable but authenticated modifications, such methods do not
seem practical at present, particularly for timing protocols that are
sensitive to latency and/or jitter.
The ability to potentially authenticate and/or encrypt RTM and PTP
data for scenarios both with and without participation of
intermediate RTM/PTP-capable nodes is left for further study.
While it is possible for a supposed compromised node to intercept and
modify the G-ACh content, this is an issue that exists for nodes in
general - for any and all data that may be carried over an LSP - and
is therefore the basis for an additional presumed trust model
associated with existing LSPs and nodes.
Security requirements of time protocols are provided in RFC 7384
[RFC7384].
9. Acknowledgments
Authors want to thank Loa Andersson, Lou Berger, Acee Lindem, Les
Ginsberg, and Uma Chunduri for their thorough reviews, thoughtful
comments and, most of all, patience.
10. References
10.1. Normative References
[IEEE.1588.2008]
"Standard for a Precision Clock Synchronization Protocol
for Networked Measurement and Control Systems",
IEEE Standard 1588, July 2008.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<http://www.rfc-editor.org/info/rfc3209>.
[RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
in Resource ReSerVation Protocol - Traffic Engineering
(RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003,
<http://www.rfc-editor.org/info/rfc3477>.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
February 2006, <http://www.rfc-editor.org/info/rfc4385>.
[RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
Circuit Connectivity Verification (VCCV): A Control
Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
December 2007, <http://www.rfc-editor.org/info/rfc5085>.
[RFC5420] Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A.
Ayyangarps, "Encoding of Attributes for MPLS LSP
Establishment Using Resource Reservation Protocol Traffic
Engineering (RSVP-TE)", RFC 5420, DOI 10.17487/RFC5420,
February 2009, <http://www.rfc-editor.org/info/rfc5420>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<http://www.rfc-editor.org/info/rfc5586>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<http://www.rfc-editor.org/info/rfc5905>.
[RFC6423] Li, H., Martini, L., He, J., and F. Huang, "Using the
Generic Associated Channel Label for Pseudowire in the
MPLS Transport Profile (MPLS-TP)", RFC 6423,
DOI 10.17487/RFC6423, November 2011,
<http://www.rfc-editor.org/info/rfc6423>.
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[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <http://www.rfc-editor.org/info/rfc7684>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<http://www.rfc-editor.org/info/rfc7752>.
10.2. Informative References
[I-D.ietf-ospf-ospfv3-lsa-extend]
Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-13
(work in progress), October 2016.
[I-D.ietf-tictoc-1588overmpls]
Davari, S., Oren, A., Bhatia, M., Roberts, P., and L.
Montini, "Transporting Timing messages over MPLS
Networks", draft-ietf-tictoc-1588overmpls-07 (work in
progress), October 2015.
[ITU-T.G.8271]
"Packet over Transport aspects - Synchronization, quality
and availability targets", ITU-T Recomendation
G.8271/Y.1366, July 2016.
[RFC4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005,
<http://www.rfc-editor.org/info/rfc4202>.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
October 2007, <http://www.rfc-editor.org/info/rfc5036>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374,
DOI 10.17487/RFC6374, September 2011,
<http://www.rfc-editor.org/info/rfc6374>.
Mirsky, et al. Expires September 8, 2017 [Page 27]
Internet-Draft Residence Time Measurement March 2017
[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, <http://www.rfc-editor.org/info/rfc7384>.
Authors' Addresses
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
Stefano Ruffini
Ericsson
Email: stefano.ruffini@ericsson.com
Eric Gray
Ericsson
Email: eric.gray@ericsson.com
John Drake
Juniper Networks
Email: jdrake@juniper.net
Stewart Bryant
Huawei
Email: stewart.bryant@gmail.com
Alexander Vainshtein
ECI Telecom
Email: Alexander.Vainshtein@ecitele.com; Vainshtein.alex@gmail.com
Mirsky, et al. Expires September 8, 2017 [Page 28]
