Internet DRAFT - draft-chen-lsr-isis-big-tlv
draft-chen-lsr-isis-big-tlv
Network Working Group H. Chen
Internet-Draft Futurewei
Intended status: Standards Track B. Decraene
Expires: 24 May 2024 Orange
G. Mishra
Verizon
A. Wang
China Telecom
Z. Li
China Mobile
Y. Fan
Casa Systems
X. Liu
Alef Edge
L. Liu
Fujitsu
D. Eastlake
Futurewei
21 November 2023
IS-IS Extension for Big TLV
draft-chen-lsr-isis-big-tlv-02
Abstract
The IS-IS routing protocol uses TLV (Type-Length-Value) encoding in a
variety of protocol messages. The original IS-IS TLV definition
allows for 255 octets of value in maximum. This document proposes a
backward compatible IS-IS extension for encoding the TLV whose value
is bigger than 255 octets.
Requirements Language
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 [RFC2119] [RFC8174]
when, and only when, they appear in all capitals, as shown here.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on 24 May 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. IS-IS Extension for Big TLV . . . . . . . . . . . . . . . . . 3
3. Split and Glue . . . . . . . . . . . . . . . . . . . . . . . 5
4. Big TLV Capability . . . . . . . . . . . . . . . . . . . . . 9
5. Incremental Deployment . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Type-Length-Value (TLV) encoding of information is widely used in
Intermediate System to Intermediate System (IS-IS) routing protocol
messages including Link State Protocol Data Units (LSPs). Each TLV
defined in [ISO10589] allows for maximum of 255 octets of value (or
say payload). This is because the length field of the TLV is one
octet, which has 255 as its maximum value. When the size of the
value of a TLV of type T (such as the Extended IS Reachability TLV of
type 22) is bigger than 255 octets, this TLV is called a big TLV of
type T (or big TLV for short). There is no general mechanism for
encoding and distributing this big TLV in classic IS-IS in a backward
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compatible way.
IS-IS has been optionally extended by [RFC7356] which permits larger
TLV value, in principle up to 65,535 octets due to a two-octet length
field. However, the [RFC7356] extensions are not widely deployed,
are not backward compatible in the sense that they use a new Protocol
Data Unit (PDU) and new LSP types that un-extended implementations
will ignore, and in any case do not support values so large they do
not fit into a single packet which will rarely be larger than 1,500
octets or, even with jumbo frames, around 9,000 octets.
This document proposes a simple IS-IS extension for encoding and
distributing the big TLVs whose value parts are bigger than can be
accommodated by the TLV length field and bigger than can be
accommodated in a single packet. This extension uses a "Container
TLV".
2. IS-IS Extension for Big TLV
A new TLV, called the Container TLV, is defined. Figure 1 shows the
format of the new TLV in the classic [ISO10589] case. This new TLV
is used to carry a piece of the value of a big TLV of type T.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -----------+
| Type (TBD) | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+ |
| Type (T) | Resv | | Container TLV
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Value of of type TBD
| Piece of value of big TLV of | Container TLV |
~ type T (less than 254 octets) ~ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+ -----------+
Figure 1: Format of Container TLV
Type (TBD) field: The type of the Container TLV, its value is
assigned by IANA.
Length field: The length of the Value field of the Container TLV.
Value field: contains a Type (T) field, a Resv field, and a Piece of
value of big TLV of type T (Piece field for short).
Type (T) field: A one octet field giving the Type of the Big TLV that
is being transported in this Container TLV.
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Piece field: A piece of the value of the big TLV of type T that is
being transported in this Container TLV.
Resv field: One octet that MUST be sent as zero and ignored on
receipt.
When a node has a big TLV of type T to be originated, it splits the
value of the big TLV into a number of pieces, from Piece 0, Piece 1
to Piece n. The first piece (i.e., Piece 0) is less than 256 octets.
Each of the rest pieces from Piece 1 to Piece n is less than 254
octets. This is illustrated in Figure 2.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (T) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+
| Piece 0 (less than 256 octets)| |
~ ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Piece 1 (less than 254 octets)| |
~ ~ Bigger than
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 octets
~ : ~ |
~ . ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Piece n (less than 254 octets)| |
~ ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+
Figure 2: Big TLV of type T with value field bigger than 255 octets
Each piece carries a subset of entries in the big TLV. An entry is
an existing sub-TLV or structure.
The node originates n+1 TLVs for the big TLV of type T. These TLVs
are the TLV of type T with a normal payload (i.e., the payload less
than 256 octets), and n new TLVs of type TBD each of which has a
normal payload. The node advertises each of these TLVs to its
neighbors according to the normal IS-IS procedure. Figure 3 shows
the encoding of the big TLV with type T in Figure 2.
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0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+
| Type (T) | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ normal TLV
| Piece 0 (less than 256 octets)| of type T
~ ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+ ----------+
| Type (TBD) | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+ |
| Type (T) | Resv | | Container TLV 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ value of of type TBD
| Piece 1 (less than 254 octets)| Container TLV |
~ ~ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+ ----------+
~ : ~
~ . ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+ ----------+
| Type (TBD) | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+ |
| Type (T) | Resv | | Container TLV n
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ value of of type TBD
| Piece n (less than 254 octets)| Container TLV |
~ ~ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ --+ ----------+
Figure 3: Encoding value bigger than 255 octets
The normal TLV of type T contains Piece 0 (i.e., the first piece) of
the value of the big TLV. For each of the rest n pieces of the value
of the big TLV, a Container TLV of type TBD carries the piece.
Container TLV 1 contains Piece 1 of the value of the big TLV;
Container TLV 2 contains Piece 2 of the value of the big TLV; ...;
Container TLV n contains Piece n of the value of the big TLV.
If a node supports the extension (i.e., Container TLV), the node
understands each piece of the value of the big TLV received. The
value field in the normal TLV of type T contains Piece 0 of the big
TLV value. Each of the n Container TLVs having Type (T) contains a
piece of the big TLV value in its Piece field.
3. Split and Glue
This section discusses a couple of ways in which a big TLV is split
into pieces at originating/sending and the pieces are glued at
receiving.
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When a TLV of type T is too big at an originating node, this big TLV
is split into a sequence of pieces. Each piece carries a subset of
entries in the big TLV. An entry is an existing Sub-TLV or
structure.
The node originates a native TLV of type T containing the first piece
in the sequence. In addition, it originates container TLVs with type
T containing the other pieces directly if there is only one big TLV
of type T.
When there are multiple (big) TLVs of type T, the node originates
multiple native TLVs of type T. For each (big) TLV of type T split
into a sequence of pieces, a native TLV of type T containing the
first piece in the sequence is originated. The container TLVs with
type T containing directly the other pieces are also originated.
These container TLVs MUST follow the native TLV in order and between
the native TLV and these container TLVs there MUST NOT be any other
TLV of type T or any other container TLVs with type T.
For example, suppose that a node has a big TLV of type T = 22 as
shown in Figure 4. This TLV is too big and split into two pieces
piece 0 and piece 1 at boundary between Sub-TLV K and K+1.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (T=22) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+-----------+
|system ID for neighbor 10.2.2.2| | |
+ (6 octets) + | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| Metric (continue) | Piece 0 |
+ +-+-+-+-+-+-+-+-+ < 256 octets |
| |sub-TLVs-length| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bigger than
| sub-TLV 1 | | 255 octets
: : : | |
: sub-TLV K : | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+ |
| sub-TLV K+1 | | |
: : : Piece 1 |
: sub-TLV N : | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+-----------+
Figure 4: Example Big TLV of type T=22 with Value Field > 255 Octets
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For this big TLV of type T = 22, the node originates a native TLV of
type T = 22 containing the first piece (i.e., piece 0) and a
container TLV with type T = 22 containing the other piece (i.e.,
piece 1) directly. This native TLV and container TLV is illustrated
in Figure 5.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+
| Type (T=22) | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
|system ID for neighbor 10.2.2.2| |
+ (6 octets) + |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Metric (continue) | Native TLV
+ +-+-+-+-+-+-+-+-+ of type T=22
| |sub-TLVs-length| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| sub-TLV 1 | |
: : : |
: sub-TLV K : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -----------------------+
| Type (TBD) | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----------+ Container TLV
| Type (T=22) | Resv | | of type TBD
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+ value of |
| sub-TLV K+1 | | Container TLV |
: : : Piece 1 | |
: sub-TLV N : | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+-----+------------+
Figure 5: Example Encoding of Value Field > 255 Octets
After receiving the native TLV of type T = 22, followed the container
TLV, another node glues the piece 0 and piece 1 directly.
Alternatively, when a node has multiple (big) TLVs of type T, for
each (big) TLV of type T split into a sequence of pieces, the node
originates a native TLV of type T containing the first piece in the
sequence and container TLVs with type T containing the other pieces;
where each container TLV also contains a key or header of value in
the native TLV (or big TLV). There is no order requirement between
the native TLV and the container TLVs.
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For example, Figure 6 shows the container TLV containing neighbor ID
(i.e., system ID for neighbor) of the value field in the big TLV as
the key and piece 1.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -----------------------+
| Type (TBD) | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----------+ Container TLV
| Type (T=22) | Resv | | of type TBD
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+ | |
|system ID for neighbor 10.2.2.2| | | |
+ (6 octets) + Key | |
| | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+ value of |
| sub-TLV K+1 | | Container TLV |
: : : Piece 1 | |
: sub-TLV N : | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+-----+------------+
Figure 6: Example Container TLV with Key
After receiving the native TLV of type T = 22, and the container TLV
with type T = 22, another node glues the piece 0 and piece 1 through
the same neighbor ID in the TLVs as the key.
Figure 7 shows the container TLV containing the header of the value
field in the big TLV and piece 1.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -----------------------+
| Type (TBD) | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----------+ Container TLV
| Type (T=22) | Resv | | of type TBD
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+ | |
|system ID for neighbor 10.2.2.2| | | |
+ (6 octets) + | | |
| | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Header | |
| Metric (continue) | | | |
+ +-+-+-+-+-+-+-+-+ | | |
| |sub-TLVs-length| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+ value of |
| sub-TLV K+1 | | Container TLV |
: : : Piece 1 | |
: sub-TLV N : | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----+-----+------------+
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Figure 7: Example Container TLV with Structure Header
After receiving the native TLV of type T = 22, and the container TLV
with type T = 22, another node glues the piece 0 and piece 1 through
the same header (except for sub-TLVs-length) in the TLVs as the key.
4. Big TLV Capability
A new sub-TLV, called Big TLV Capability sub-TLV, is defined in the
Router Capability TLV [RFC7981]. A node advertising this sub-TLV
indicates that the node supports the Big TLV. The format of the sub-
TLV is shown in Figure 8.
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 (TBDa) | Length (1) | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Big TLV Capability sub-TLV
Type (TBDa) field: The type of the Big TLV Capability sub-TLV, its
value is assigned by IANA.
Length field: Its value is 1.
Flags field: A one octet field of flags. No flag is defined now.
A node supporting the Big TLV MUST advertise this sub-TLV in a Router
Capability TLV.
5. Incremental Deployment
For a network using IS-IS, users can deploy the extension for big TLV
in a part of the network step by step. The network has some nodes
supporting the extension (or say new nodes for short) and the other
nodes not supporting the extension (or say old nodes for short)
before the extension is deployed in the entire network.
The first piece of a big TLV, advertised in the native TLV, is
backward compatible and will be understood by both old and new nodes.
The subsequent pieces of the big TLV, advertised in the Container
TLVs, will only be understood by the new nodes and will be ignored by
the old nodes.
The originator of the big TLV MUST consider the above properties when
splitting the big TLV into multiple pieces.
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If the size of the existing Sub-TLVs in a TLV is bigger than 255, for
a piece of new information in existing Sub-TLVs, when adding this new
information into a TLV makes the TLV bigger than 255, this new
information in existing Sub-TLVs can be put into a container TLV. If
all the nodes need to have the same new information for using the new
information, every node needs to check if all the nodes support the
big TLV capability which is distributed by the nodes supporting it.
If all the nodes support it, every node uses the new information. If
it is not required that all the nodes must have the same new
information for using the new information, the nodes supporting the
big TLV capability can use the new information, the nodes not
supporting the big TLV capability ignore the new information.
6. Security Considerations
The mechanism described in this document does not raise any new
security issues for the IS-IS protocols.
7. IANA Considerations
IANA is requested to make a new allocation in the "IS-IS TLV
Codepoint Registry" under the registry name "IS-IS TLV Codepoints" as
follows:
+=========+==========+=====+=====+=====+======+==============+
| Type | Name | IIH | LSP | SNP |Purge | reference |
+=========+==========+=====+=====+=====+======+==============+
| TBD | Container| Y | Y | N | N |This document |
+---------+----------+-----+-----+-----+------+--------------+
IANA is requested to make a new allocation under the registry name
"IS-IS Sub-TLVs for IS-IS Router CAPABILITY TLV" as follows:
+======+==================+===+=====+===+=====+==============+
|Value | Description |IIH| LSP |SNP|Purge| reference |
+======+==================+===+=====+===+=====+==============+
| TBDa |Big TLV Capability| N | Y | N | N |This document |
+------+------------------+---+-----+---+-----+--------------+
8. References
8.1. Normative References
[ISO10589] ISO, "Information technology -- Telecommunications and
information exchange between systems -- Intermediate
System to Intermediate System intra-domain routing
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information exchange protocol for use in conjunction with
the protocol for providing the connectionless-mode network
service (ISO 8473)", ISO/IEC 10589:2002, Second Edition,
November 2002.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
for Advertising Router Information", RFC 7981,
DOI 10.17487/RFC7981, October 2016,
<https://www.rfc-editor.org/info/rfc7981>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References
[RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
Scope Link State PDUs (LSPs)", RFC 7356,
DOI 10.17487/RFC7356, September 2014,
<https://www.rfc-editor.org/info/rfc7356>.
Acknowledgments
The authors would like to thank Chris Hopps for the comments to this
work.
Authors' Addresses
Huaimo Chen
Futurewei
Boston, MA,
United States of America
Email: Huaimo.chen@futurewei.com
Bruno Decraene
Orange
France
Email: bruno.decraene@orange.com
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Gyan S. Mishra
Verizon
13101 Columbia Pike
Silver Spring, MD 20904
United States of America
Phone: 301 502-1347
Email: gyan.s.mishra@verizon.com
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing
102209
China
Email: wangaj3@chinatelecom.cn
Zhenqiang Li
China Mobile
No.32 Xuanwumenxi Ave., Xicheng District
Beijing
100032
P.R. China
Email: li_zhenqiang@hotmail.com
Yanhe Fan
Casa Systems
United States of America
Email: yfan@casa-systems.com
Xufeng Liu
Alef Edge
United States of America
Email: xufeng.liu.ietf@gmail.com
Lei Liu
Fujitsu
United States of America
Email: liulei.kddi@gmail.com
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Donald E. Eastlake 3rd
Futurewei
2386 Panoramic Circle
Apopka, FL, 32703
United States of America
Phone: +1-508-333-2270
Email: d3e3e3@gmail.com
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