Internet DRAFT - draft-ietf-trill-o-pw
draft-ietf-trill-o-pw
TRILL Working Group Lucy Yong
INTERNET-DRAFT Donald Eastlake
Intended status: Proposed Standard Sam Aldrin
Huawei Technologies
Jon Hudson
Brocade
Expires: July 29, 2014 January 30, 2014
Transport of TRILL Using Pseudowires
<draft-ietf-trill-o-pw-06.txt>
Abstract
This document specifies how to interconnect a pair of TRILL
(Transparent Interconnection of Lots of Links) switch ports using
pseudowires under existing TRILL and PWE3 (Pseudowire Emulation End-
to-End) standards.
Status of This Memo
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Table of Contents
1. Introduction............................................3
1.1 Conventions used in this document......................3
2. PWE3 Interconnection of TRILL Switches..................4
2.1 PWE3 Type Independent Details..........................4
2.2 PPP PWE3 Transport of TRILL............................5
3. IANA Considerations.....................................7
4. Security Considerations.................................7
Appendix A: Use of Other Pseudowire Types..................8
Appendix Z: Change History................................10
Acknowledgements..........................................12
Normative References......................................12
Informative References....................................13
Authors' Addresses........................................14
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1. Introduction
The TRILL (Transparent Interconnection of Lots of Links) protocol
[RFC6325] provides optimal pair-wise data frame routing without
configuration in multi-hop networks with arbitrary topology. TRILL
supports multipathing of both unicast and multicast traffic. Devices
that implement TRILL are called TRILL Switches or RBridges (Routing
Bridges).
Links between TRILL Switches can be based on arbitrary link
protocols, for example PPP [RFC6361], as well as Ethernet [RFC6325].
A set of connected TRILL Switches together form a TRILL campus which
is bounded by end stations and layer 3 routers.
This document specifies how to interconnect a pair of TRILL Switch
ports using a pseudowire under existing TRILL and PWE3 (Pseudowire
Emulation End-to-End) standards.
1.1 Conventions used in this document
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].
Acronyms used in this document include the following:
IS-IS - Intermediate System to Intermediate System [IS-IS]
MPLS - Multi-Protocol Label Switching
PPP - Point-to-Point Protocol [RFC1661]
PW - Pseudowire [RFC3985]
PWE3 - PW Emulation End-to-End
RBridge - Routing Bridge, an alternative name for a TRILL Switch
TRILL - Transparent Interconnection of Lots of Links [RFC6325]
TRILL Switch - A device implementing the TRILL protocol
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2. PWE3 Interconnection of TRILL Switches
When a pseudowire is used to interconnect a pair of TRILL Switch
ports, a PPP [RFC4618] pseudowire is used as described below. The
pseudowire between such ports can be signaled [RFC4447] or manually
configured. In this context, the TRILL Switch ports at the ends of
the pseudowire are acting as native service processing elements (NSP
[RFC3985]) and, assuming the pseudowires are over MPLS or IP
[RFC4023] networks, as label switched or IP routers at the TRILL
Switch ports.
Pseudowires provide transparent transport and the two TRILL Switch
ports appear directly interconnected with a transparent link. With
such an interconnection the TRILL adjacency over the link is
automatically discovered and established through TRILL IS-IS control
messages [RFC6327bis].
A pseudowire is carried over a packet switched network tunnel
[RFC3985], for example, an MPLS or MPLS-TP label switched path tunnel
in MPLS networks. Either a signaling protocol or manual configuration
can be used to configure a label switched path tunnel between two
TRILL Switch ports. This application needs no additions to the
existing pseudowire standards.
2.1 PWE3 Type Independent Details
The sending pseudowire TRILL Switch port SHOULD map the inner
priority of the TRILL Data packets being sent to the Traffic Class
field of the pseudowire label [RFC5462] so as to minimize the
probability that higher priority TRILL Data packets will be discarded
due to excessive TRILL Data packets of lower priority.
TRILL IS-IS PDUs critical to establishing and maintaining adjacency
(Hello and MTU PDUs) SHOULD be sent with the MPLS Traffic Class that
calls for handling with the maximum priority. Other TRILL IS-IS PDUs
SHOULD be sent with the MPLS Traffic Class denoting the highest
priority that is less than the maximum priority. TRILL Data packets
SHOULD be sent with appropriate MPLS Traffic Classes, typically
mapped from the TRILL Data packet priority, such that TRILL Data
packet Traffic Classes denote priorities less than the priorities
used for TRILL IS-IS PDUs. This minimizes the probability of other
traffic interfering with these important control PDUs and causing
false loss of adjacency or other control problems.
If a pseudowire supports fragmentation and re-assembly (a feature
that has received little or no deployment), then there is no reason
to do TRILL MTU testing on it and the pseudowire will not be a
constraint on the TRILL campus wide MTU size (Sz) (see Section 4.3.1
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[RFC6325]). If the pseudowire does not support fragmentation (the
more common case), then the available TRILL IS-IS packet payload size
over the pseudowire (taking into account MPLS encapsulation with a
control word) or some lower value, MUST be used in helping to
determine MTU size (Sz) (see Section 5 [ClearCorrect]).
An intervening MPLS label switched router or similar packet switched
network device has no awareness of TRILL. Such devices will not
change the TRILL Header hop count.
2.2 PPP PWE3 Transport of TRILL
For a PPP pseudowire (PW type = 0x0007), the two TRILL Switch ports
being connected are configured to form a pseudowire with PPP
encapsulation [RFC4618]. After the pseudowire is established and
TRILL use is negotiated within PPP, the two TRILL Switch ports appear
directly connected with a PPP link [RFC1661] [RFC6361].
If pseudowire interconnection of two TRILL Switch ports is signaled
[RFC4447], the initiating TRILL Switch port MUST attempt the
connection set-up with pseudowire type PPP (0x0007).
Behavior for TRILL with a PPP pseudowire continues to follow that of
TRILL over PPP as specified in Section 3 of [RFC6361].
The following figures show what a TRILL Data and TRILL IS-IS packet
look like over such a pseudowire in the MPLS case assuming no TRILL
Header extensions:
L. Yong, et al [Page 5]
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+-------------------------------+
| Server MPLS Tunnel Label(s) | n*4 octets (4 octets per label)
+-------------------------------+
| PW Label | 4 octets
+-------------------------------+
| Control Word | 4 octets
+-------------------------------+
| PPP Header 0x005d | 2 octets
+-------------------------------+
| TRILL Header | 4 octets
+-------------------------------+
| Destination MAC Address | 6 octets
+-------------------------------+
| Source MAC Address | 6 octets
+-------------------------------+
| Data Label | 4 or 8 octets
+-------------------------------+
| Payload Body | variable
+-------------------------------+
Figure 1. TRILL Data Packet in Pseudowire
"Data Label" is the VLAN Label or Fine Grained Label [FGL] of the
payload.
+-------------------------------+
| Server MPLS Tunnel Label(s) | n*4 octets (4 octets per label)
+-------------------------------+
| PW Label | 4 octets
+-------------------------------+
| Control Word | 4 octets
+-------------------------------+
| PPP Header 0x405d | 2 octets
+-------------------------------+
| Common IS-IS Header | 8 octets
+-------------------------------+
| IS-IS PDU Type Specifc Header | variable
+-------------------------------+
| IS-IS TLVs | variable
+-------------------------------+
Figure 2. TRILL IS-IS Packet in Pseudowire
The PPP Header fields (0x005d and 0x405d respectively) for TRILL Data
and IS-IS packets shown above are specified in [RFC6361].
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3. IANA Considerations
No IANA actions are required by this document. RFC Editor: Please
remove this section before publication.
4. Security Considerations
TRILL level secuirty mechanisms, such as the ability to use
authentication with TRILL IS-IS PDUs [RFC6325], are not affected by
link technology, such as the use of pseudowire links as specified in
this document.
Link security may be useful in improving TRILL campus security.
TRILL is transported over pseudowires as TRILL over PPP over
pseudowires, pseudowires are over MPLS or IP, and MPLS and IP are
over some lower level link technology. Thus link security below the
TRILL level for a pseudowire link could be provided by PPP security,
pseudowire security, MPLS or IP security, or security of the link
technolgy supporting MPLS or IP.
PPP TRILL security considerations are discussed in [RFC6361]. For
security considerations introduced by carrying PPP TRILL links over
pseudowires, see [RFC3985], which discusses the risks introduced by
sending protocols that previously assumed a point-to-point link on a
pseudo wire built on a packet switched network (PSN). However, the
PPP layer in TRILL transport by pseudowire is somewhat vestigial and
intended primarily as a convenient way to use existing PPP code
points to identify TRILL data packets and TRILL IS-IS packets.
Furthermore, existing PPP security standards are arguably
questionable in terms of current security criteria. For these
reasons, it is NOT RECOMMENDED to use PPP security in the transport
of TRILL by pseudowires as sepecified in this document.
It is RECOMMENDED that link security be provided at the layers
supporting pseudowires transporting TRILL, that is, at the MPLS or IP
layer or the link layer transporting MPLS or IP.
For applications involving sensitive data, end-to-end security should
always be considered, in addition to link security, to provide
security in depth. In this context, such end-to-end security should
be between the end stations involved so as to protect the entire path
to, through, and from the TRILL campus.
For general TRILL protocol security considerations, see [RFC6325].
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Appendix A: Use of Other Pseudowire Types
This informational Appendix briefly discusses use of pseudowire types
other than PPP for the transport of TRILL.
The use of Ethernet pseudowires [RFC4448] was examined by the authors
and would be possible without change to such pseudowires; however,
this would require an additional 12 or 16 bytes per packet within the
payload being transmitted over the pseudowire as shown in the
following figures for a TRILL Data and TRILL IS-IS packet over such
an Ethernet pseudowire in the MPLS case assuming no TRILL Header
extensions (compare with Figures 1 and 2):
+-------------------------------+
| Server MPLS Tunnel Label(s) | n*4 octets (4 octets per label)
+-------------------------------+
| PW Label | 4 octets
+-------------------------------+
| Optional Control Word | 4 octets
+-------------------------------+
| TRILL Hop Dest. MAC Address | 6 octets
+-------------------------------+
| TRILL Hop Source MAC Address | 6 octets
+-------------------------------+
|Optional VLAN and/or other tags| variable
+-------------------------------+
| TRILL Ethertype (0x22f3) | 2 octets
+-------------------------------+
| TRILL Header | 4 octets
+-------------------------------+
| Destination MAC Address | 6 octets
+-------------------------------+
| Source MAC Address | 6 octets
+-------------------------------+
| Data Label | 4 or 8 octets
+-------------------------------+
| Payload Body | variable
+-------------------------------+
Figure 3. TRILL Data Packet in Ethernet Pseudowire
"Data Label" is the VLAN Label or Fine Grained Label [FGL] of the
payload.
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+-------------------------------+
| Server MPLS Tunnel Label(s) | n*4 octets (4 octets per label)
+-------------------------------+
| PW Label | 4 octets
+-------------------------------+
| Optional Control Word | 4 octets
+-------------------------------+
| TRILL Hop Dest. MAC Address | 6 octets
+-------------------------------+
| TRILL Hop Source MAC Address | 6 octets
+-------------------------------+
|Optional VLAN and/or other tags| variable
+-------------------------------+
|Layer 2 IS-IS Ethertype 0x22f4 | 2 octets
+-------------------------------+
| Commmon IS-IS Header | 8 octets
+-------------------------------+
| IS-IS PDU Type Specifc Header | variable
+-------------------------------+
| IS-IS TLVs | variable
+-------------------------------+
Figure 4. TRILL IS-IS Packet in Ethernet Pseudowire
It would also be possible to specify a new pseudowire type for TRILL
traffic but the authors feel that any efficiency gain over PPP
pseudowires would be too small to be worth the complexity of adding
such a specification. Furthermore using PPP pseudowire encoding means
that any traffic dissector that understands TRILL PPP encoding
[RFC6361] and understands PPP pseudowires [RFC4618] will
automatically be able to recursively decode TRILL transported by
pseudowire.
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Appendix Z: Change History
RFC Editor Note: Please remove this appendix prior to publication.
From -00 to -01
Add information on Traffic Classes that should be used for TRILL IS-
IS PDUs.
Other changes to resolve WG Last Call comments:
Change title from "TRILL Over Psuedowires".
Change "Class of Service" to "Traffic Class".
Expand informational paragraph about the consideration of using
other pseudowire types for the transport of TRILL and make that
paragraph into Appendix A.
Add this Change History Appendix Z.
From -01 to -02
Add packet diagrams.
Minor editing changes.
From -02 to -03
Editorial and minor Security Considerations changes based on the
Shepherd review by Erik Nordmark. See
http://www.ietf.org/mail-archive/web/trill/current/msg06029.html
and ensuing conversation.
From -03 to -04
Security Considerations changes based on SECDIR review.
Minor Editorial change to the first sentence of Section 1 based on
GENART review.
Add final sentence to first paragraph of Section 2.1 to resolve
COMMENT by Barry Leiba.
From -04 to -05
Assorted changes resulting from IESG review:
Replace "autoconfigured" with "signaled".
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Clarify that it is the inner TRILL Data packet priority that is
used to determine pseudowire Traffic Class and that the priority is
mapped to the Traffic Class.
Clarify that if Ethernet pseudowires were used no change would be
required in the Ethernet pseudowire standard.
Expand "Sz" to "MTU size (Sz)".
Note that pseudowire fragmentation has little if any deployment.
Minor editorial improvements.
From -05 to -06
Change wording concerning suggested Traffic Classes for TRILL IS-IS
and TRILL Data packets in Section 2.1.
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Acknowledgements
Thanks for the valuable comments from the following who are listed in
alphabetic order:
Stewart Bryant, Stephen Farrell, Brain Haberman, Christer
Holmberg, Joel Jaeggli, Barry Leiba, Erik Nordmark, Yaron Sheffer,
and Yaakov (J) Stein
The document was prepared in raw nroff. All macros used were defined
within the source file.
Normative References
[RFC1661] - Simpson, W., Ed., "The Point-to-Point Protocol (PPP)",
STD 51, RFC 1661, July 1994.
[RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4447] - Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
G. Heron, "Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4618] - Martini, L., "Encapsulation Methods for Transport of
PPP/High-Level Data Link Control (HDLC) over MPLS Networks",
BCP 116, RFC 4618, September 2006.
[RFC5462] - Andersson, L. and R. Asati, "Multiprotocol Label
Switching (MPLS) Label Stack Entry: "EXP" Field Renamed to
"Traffic Class" Field", RFC 5462, February 2009.
[RFC6325] - Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC6325, July 2011.
[RFC6361] - Carlson, J., and D. Eastlake, "PPP Transparent
Interconnection of Lots of Links (TRILL) Protocol Control
Protocol", RFC6361, August 2011.
[ClearCorrect] - Eastlake, D., M. Zhang, A. Ghanwani, V. Manral, and
A. Banerjee, "TRILL: Clarifications, Corrections, and Updates",
draft-ietf-trill-clear-correct, in RFC Editor's queue.
[FGL] - D. Eastlake, M. Zhang, P. Agarwal, R. Perlman, D. Dutt,
"TRILL (Transparent Interconnection of Lots of Links): Fine-
Grained Labeling", draft-ietf-trill-fine-labeling, in RFC
Editor's queue.
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Informative References
[IS-IS] - International Organization for Standardization,
"Intermediate system to Intermediate system intra-domain
routing information exchange protocol for use in conjunction
with the protocol for providing the connectionless-mode Network
Service (ISO 8473)", ISO/IEC10589:2002, Second Edition, Nov
2002
[RFC3985] - Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC4023] - Worster, T., Rekhter, Y., and E. Rosen, Ed.,
"Encapsulating MPLS in IP or Generic Routing Encapsulation
(GRE)", RFC 4023, March 2005.
[RFC4448] - Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, April 2006.
[RFC6327bis] - Eastlake 3rd, D., Perlman, R., Ghanwani, A., Howard,
Y., and V. Manral, "TRILL: Adjacency", draft-ietf-trill-
rfc6327bis, work in progress.
L. Yong, et al [Page 13]
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Authors' Addresses
Lucy Yong
Huawei Technologies
5340 Legacy Drive
Plano, TX 75025 USA
Phone: +1-469-227-5837
Email: lucy.yong@huawei.com
Donald E. Eastlake, 3rd
Huawei Technologies
155 Beaver Street
Milford, MA 01757 USA
Phone: +1-508-333-2270
Email: d3e3e3@gmail.com
Sam Aldrin
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95050 USA
Phone: +1-408-330-4517
Email: sam.aldrin@huawei.com
Jon Hudson
Brocade
130 Holger Way
San Jose, CA 95134 USA
Phone: +1-408-333-4062
jon.hudson@gmail.com
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