RFC 4205
Intermediate System to Intermediate System (IS-IS) Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)
RFC 4205: Intermediate System to Intermediate System (IS-IS) Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS) 🎀
Okay bestie, the title block is the cast list. This one comes from the Network Working Group ✨ and is edited by K. Kompella and Y. Rekhter, both at Juniper Networks 💜. It's labelled Category: Informational and dated October 2005 📅. It doesn't obsolete anything, but it updates RFC 3784 🔥.
Status of This Memo
Quick legal bit, but it matters 🙈. This memo gives information to the Internet community. It is NOT an Internet standard of any kind. Distribution is unlimited, so share away 🦋.
Copyright Notice
Copyright (C) The Internet Society (2005). 💅
Abstract
This doc spells out how to encode the IS-IS routing protocol extensions that support Generalized Multi-Protocol Label Switching (GMPLS) 🧚.
1. Introduction ✨
Okay so, this document adds extensions to the IS-IS routing protocol so it can carry link state info for GMPLS 🌈. The list of enhancements IS-IS needs is laid out in [GMPLS-ROUTING]. If you want unnumbered interfaces, you also need the "Point-to-Point Three-Way Adjacency" IS-IS Option type from [ISIS-3way] 💖.
This section defines the upgrades to the Traffic Engineering (TE) properties of GMPLS TE links that can be announced in IS-IS Link State Protocol Data Units 👑. We're enhancing the sub-TLVs of the extended IS reachability TLV (see [ISIS-TE]) for GMPLS 🫶. Specifically, we're adding these three sub-TLVs:
Sub-TLV Type Length Name
4 8 Link Local/Remote Identifiers
20 2 Link Protection Type
21 variable Interface Switching Capability
DescriptorWe also add one brand-new TLV to the TE TLVs 🍓:
TLV Type Length Name
138 variable Shared Risk Link GroupThe 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]. These are the capitalised rule words, so read them like a contract 📜💀.
1.1. Link Local/Remote Identifiers
Okay, first up is the Link Local Interface Identifiers. It's a sub-TLV of the extended IS reachability TLV, type 4, and its length is eight octets 🌸. Its value field holds four octets of Link Local Identifier followed by four octets of Link Remote Identifier (see Section "Support for unnumbered links" of [GMPLS-ROUTING]). If the Link Remote Identifier is unknown, it gets set to 0 🙈.
Here's how the Value field of the Link Local/Remote Identifiers sub-TLV is encoded 🦋:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Local Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Remote Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Now the rule that is NOT up for debate 🚫. The Link Local/Remote Identifiers sub-TLV MUST NOT occur more than once within the extended IS reachability TLV. If it does show up more than once anyway, the receiver SHOULD ignore all of those sub-TLVs 💅.
1.2. Link Protection Type
The Link Protection Type is a sub-TLV (type 20) of the extended IS reachability TLV, and it's two octets long 🌈.
Here's the Value field encoding for the Link Protection Type sub-TLV 🧚:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Protection Cap | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+The first octet is a bit vector describing the link's protection capabilities (see Section "Link Protection Type" of [GMPLS-ROUTING]) ✨. The bits are:
0x01 Extra Traffic
0x02 Unprotected
0x04 Shared
0x08 Dedicated 1:1
0x10 Dedicated 1+1
0x20 Enhanced
0x40 Reserved
0x80 ReservedThe second octet SHOULD be set to zero by the sender, and SHOULD be ignored by the receiver 🫶.
The Link Protection Type sub-TLV MUST NOT occur more than once within the extended IS reachability TLV. If the Link Protection Type sub-TLV occurs more than once within the extended IS reachability TLV, the receiver SHOULD ignore all these sub-TLVs 🔥.
1.3. Interface Switching Capability Descriptor
The Interface Switching Capability Descriptor is a sub-TLV (type 21) of the extended IS reachability TLV 👑. Its length is the length of the value field in octets. Here's how its Value field is encoded 💖:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Switching Cap | Encoding | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max LSP Bandwidth at priority 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max LSP Bandwidth at priority 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max LSP Bandwidth at priority 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max LSP Bandwidth at priority 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max LSP Bandwidth at priority 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max LSP Bandwidth at priority 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max LSP Bandwidth at priority 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max LSP Bandwidth at priority 7 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Switching Capability-specific information |
| (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+The Switching Capability (Switching Cap) field holds one of these values 🧚:
1 Packet-Switch Capable-1 (PSC-1)
2 Packet-Switch Capable-2 (PSC-2)
3 Packet-Switch Capable-3 (PSC-3)
4 Packet-Switch Capable-4 (PSC-4)
51 Layer-2 Switch Capable (L2SC)
100 Time-Division-Multiplex Capable (TDM)
150 Lambda-Switch Capable (LSC)
200 Fiber-Switch Capable (FSC)The Encoding field holds one of the values specified in Section 3.1.1 of [GMPLS-SIG] 🌸.
Maximum LSP Bandwidth is encoded as a list of eight 4-octet fields in the IEEE floating point format [IEEE], with priority 0 first and priority 7 last. The units are bytes (not bits!) per second 💀.
What's inside the Switching Capability specific information field depends on the value of the Switching Capability field 🦋.
When the Switching Capability field is PSC-1, PSC-2, PSC-3, or PSC-4, the Switching Capability specific information field includes Minimum LSP Bandwidth and Interface MTU 🌈:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum LSP Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface MTU |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Minimum LSP Bandwidth is encoded in a 4-octet field in the IEEE floating point format. The units are bytes (not bits!) per second. Interface MTU is encoded as a 2-octet integer, and carries the MTU value in bytes 🫶.
When the Switching Capability field is L2SC, there is no Switching Capability specific information field present 💅.
When the Switching Capability field is TDM, the Switching Capability specific information field includes Minimum LSP Bandwidth and an indication of whether the interface supports Standard or Arbitrary SONET/SDH 👑:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum LSP Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Indication |
+-+-+-+-+-+-+-+-+Minimum LSP Bandwidth is encoded in a 4-octet field in the IEEE floating point format. The units are bytes (not bits!) per second. The indication of whether the interface supports Standard or Arbitrary SONET/SDH is encoded as 1 octet. The value of this octet is 0 if the interface supports Standard SONET/SDH, and 1 if the interface supports Arbitrary SONET/SDH 💖.
When the Switching Capability field is LSC, there is no Switching Capability specific information field present 🌸.
To support interfaces that have more than one Interface Switching Capability Descriptor (see Section "Interface Switching Capability Descriptor" of [GMPLS-ROUTING]), the Interface Switching Capability Descriptor sub-TLV MAY occur more than once within the extended IS reachability TLV ✨. Main character energy, the rules are finally clear 💜.
1.4. Shared Risk Link Group TLV ✨
okay so the SRLG TLV (type 138) is the one that carries all the Shared Risk Link Group info 🔥 its Value is basically a little struct, and it goes like this 💅
6 octets of System ID
1 octet of Pseudonode Number
1 octet Flag
4 octets of IPv4 interface address or 4 octets of a Link Local
Identifier
4 octets of IPv4 neighbor address or 4 octets of a Link Remote
Identifier
(variable) list of SRLG values, where each element in the list
has 4 octets.here's the visual so you can see how it lines up 🦋
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| System ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| System ID (cont.) | Pseudonode num| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 interface address/Link Local Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 neighbors address/Link Remote Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ............ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+the neighbor is identified by its System Id (6 octets), plus one extra octet for the pseudonode number if the neighbor sits on a LAN interface 🧚
the Least Significant Bit of the Flag octet tells you if the interface is numbered (set to 1) or unnumbered (set to 0) 🎀 all the other bits are reserved and should be set to 0, so don't get creative with them 🙈
the length of this TLV is 16 + 4 * (number of SRLG values) 🧮
this TLV carries the Shared Risk Link Group info (go check Section "Shared Risk Link Group Information" of [GMPLS-ROUTING] for the full story) 📚
the SRLG TLV MAY occur more than once within the IS-IS Link State Protocol Data Units 💜
1.5. Link Identifier for Unnumbered Interfaces 🌸
link identifiers get passed around in the Extended Local Circuit ID field of the "Point-to-Point Three-Way Adjacency" IS-IS Option type [ISIS-3way] 🫶
2. Implications on Graceful Restart 🔄
so when a node is restarting, it SHOULD follow the ISIS restart procedures [ISIS-RESTART] and the RSVP-TE restart procedures [GMPLS-RSVP] 💅
when the restarting node is about to originate its IS-IS Link State PDUs for TE links, those PDUs SHOULD be originated with 0 unreserved bandwidth, a Traffic Engineering Default metric set to 0xffffff, and, if the link has LSC or FSC as its Switching Capability, also 0 as Max LSP Bandwidth ✨ this keeps going until the node can figure out how much is actually unreserved, counting the resources held by the LSPs that were preserved across the restart. once it has that number, the node SHOULD advertise those resources in its Link State PDUs 🔥
also, for a planned restart, the restarting node SHOULD originate its IS-IS Link State PDUs for TE links with 0 as unreserved bandwidth before it restarts, and with 0 as Max LSP Bandwidth if the link has LSC or FSC as its Switching Capability 🙅♀️ this basically discourages new LSP establishment through the restarting router, which is very much the vibe 🧊
and the neighbors of the restarting node SHOULD continue to advertise the actual unreserved bandwidth on the TE links from them to that node 🫶
3. Contributors 🌈
Ayan Banerjee
Calient Networks
5853 Rue Ferrari
San Jose, CA 95138
Phone: +1 408 972 3645
EMail: abanerjee@calient.net
John Drake
Calient Networks
5853 Rue Ferrari
San Jose, CA 95138
Phone: +1 408 972 3720
EMail: jdrake@calient.net
Greg Bernstein
Grotto Networking
EMail: gregb@grotto-networking.com
Don Fedyk
Nortel Networks Corp.
600 Technology Park Drive
Billerica, MA 01821
Phone: +1 978 288 4506
EMail: dwfedyk@nortelnetworks.com
Eric Mannie
Independent Consultant
EMail: eric_mannie@hotmail.com
Debanjan Saha
Tellium Optical Systems
2 Crescent Place
P.O. Box 901
Ocean Port, NJ 07757
Phone: +1 732 923 4264
EMail: dsaha@tellium.com
Vishal Sharma
EMail: v.sharma@ieee.org4. Acknowledgements 💖
the authors want to thank Jim Gibson, Suresh Katukam, Jonathan Lang and Quaizar Vohra for their comments on the draft 🥹
5. Security Considerations 💀
⚠️ this part is seriously important, bestie, so read it properly 🙈
this document specifies the contents of GMPLS TE TLVs in ISIS. these TLVs aren't used for SPF computation or normal routing, so the extensions here have no direct effect on IP routing 🫠 BUT tampering with GMPLS TE TLVs may have an effect on the underlying transport (optical and/or SONET-SDH) network 😱 mechanisms to secure ISIS Link State PDUs and/or the TE TLVs [ISIS-HMAC] can be used to secure the GMPLS TE TLVs as well 🔐
6. IANA Considerations 📋
this document defines one new ISIS TLV type that needs to get reflected in the ISIS TLV code-point registry:
Type Description IIH LSP SNP
---- ---------------------- --- --- ---
138 Shared Risk Link Group n y nit also defines new sub-TLV types of top-level TLV 22 that need to get reflected in the ISIS sub-TLV registry for TLV 22:
Type Description Length
---- ------------------------------ --------
4 Link Local/Remote Identifiers 8
20 Link Protection Type 2
21 Interface Switching Capability variable
DescriptorReferences 📚
Normative References 🔗
[GMPLS-ROUTING] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4202, October 2005.
[GMPLS-RSVP] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[GMPLS-SIG] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003.
[IEEE] IEEE, "IEEE Standard for Binary Floating-Point Arithmetic", Standard 754-1985, 1985 (ISBN 1-5593-7653-8).
[ISIS-3way] Katz, D. and R. Saluja, "Three-Way Handshake for Intermediate System to Intermediate System (IS-IS) Point-to-Point Adjacencies", RFC 3373, September 2002.
[ISIS-RESTART] Shand, M. and L. Ginsberg, "Restart Signaling for Intermediate System to Intermediate System (IS-IS)", RFC 3847, July 2004.
[ISIS-TE] Smit, H. and T. Li, "Intermediate System to Intermediate System (IS-IS) Extensions for Traffic Engineering (TE)", RFC 3784, June 2004.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[ISIS-HMAC] Li, T. and R. Atkinson, "Intermediate System to Intermediate System (IS-IS) Cryptographic Authentication", RFC 3567, July 2003.
Authors' Addresses 🖊️
Kireeti Kompella
Juniper Networks, Inc.
1194 N. Mathilda Ave
Sunnyvale, CA 94089
EMail: kireeti@juniper.net
Yakov Rekhter
Juniper Networks, Inc.
1194 N. Mathilda Ave
Sunnyvale, CA 94089
EMail: yakov@juniper.netFull Copyright Statement ©️
Copyright (C) The Internet Society (2005).
this document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.
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