RFC 3630
Traffic Engineering (TE) Extensions to OSPF Version 2
Traffic Engineering (TE) Extensions to OSPF Version 2 🎀
okay bestie, this is RFC 3630 and it's part 1 of 3 ✨ it's a Standards Track doc from the Network Working Group, dated September 2003. the authors are D. Katz and K. Kompella (Juniper Networks) and D. Yeung (Procket Networks) 💅 and it updates RFC 2370. (it doesn't say anything about obsoleting anything, so we're just going with updates 🫶)
Status of This Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
this doc describes extensions to OSPF version 2 so it can do intra-area Traffic Engineering (TE) 🦋 using Opaque Link State Advertisements.
1. Introduction ✨
okay so this doc is all about adding traffic engineering powers to OSPF Version 2 [1] 💖 the architecture of TE is described in [5] and the semantic content of these extensions is basically identical to the matching extensions for IS-IS [6]. the OSPF TE extensions are expected to keep mirroring the IS-IS ones, so they're like twins 👯♀️
the extensions give you a way to describe the TE topology (including bandwidth and administrative constraints) and to distribute that info inside a given OSPF area 🌸 this topology doesn't necessarily match the regular routed topology, though this proposal depends on Network LSAs to describe multi-access links. the doc purposely doesn't say how any of this works across multiple OSPF areas, bc that's a job for future documents 🧚 and no changes were made to OSPFv2 flooding. in particular, if non-TE capable nodes exist in the topology, they MUST flood TE LSAs as any other type 10 (area-local scope) Opaque LSAs (see [3]). main character energy for the existing flooding rules 👑
1.1. Applicability
so a lot of the extensions here answer the requirements in [5], which is why people call them "traffic engineering extensions" and why they're so tied to MPLS Traffic Engineering 🍓 a more accurate (but kinda bland 💀) name would be "extended link attributes", because the whole move is just adding more attributes to links in OSPF advertisements.
the info these extensions make available can be used to build an extended link state database, the same way router LSAs build a "regular" link state database 💜 the difference is that this extended one (called the traffic engineering database below) has extra link attributes. the uses of the traffic engineering database are:
- monitoring the extended link attributes;
- local constraint-based source routing; and
- global traffic engineering.
for example, an OSPF-speaking device can join an OSPF area, build a traffic engineering database, and then report on the reservation state of links in that area 🫶
for "local constraint-based source routing", a router R can compute a path from a source node A to a destination node B. usually A is R itself, and B is specified by a "router address" (more on that below). this path can be subject to various constraints on the attributes of the links and nodes it goes through, e.g., use green links that have unreserved bandwidth of at least 10Mbps 🍏 the path can then carry some subset of the traffic from A to B, which makes it a simple but effective way to do traffic engineering ✨ how the subset of traffic gets picked, and how the path actually gets set up, is out of scope here. suffice it to say that one way to pick the subset is "those packets whose IP destinations were learned from B", and one way to set up paths is with MPLS tunnels 🎀 as an aside (and this is lowkey important), constraint-based routing can be NP-hard, or even unsolvable, depending on what the attributes and constraints look like. so lots of implementations use heuristics, and that's why we don't try to sketch an algorithm here 🙈
finally, for "global traffic engineering", a device can build a traffic engineering database, take in a traffic matrix and an optimization function, crunch the numbers, and compute optimal or near-optimal routing for the entire network 🔥 the device can then keep an eye on the traffic engineering topology and react to changes by recomputing the optimal routes. iconic 💅
1.2. Limitations
so as mentioned up top, this doc only specifies extensions and procedures for intra-area distribution of TE information 🦋 methods for inter-area and inter-AS (Autonomous System) distribution aren't discussed here.
the extensions here capture the reservation state of point-to-point links. the reservation state of multi-access links may not be accurately reflected, except in the special case where there are only two devices in the multi-access subnetwork 😭 operation over multi-access networks with more than two devices isn't specifically prohibited. a more accurate description of the reservation state of multi-access networks is for further study 🌈
also, this doc does not support unnumbered links. that gap will be addressed in future documents, so see also [7] and [8] 🧚
1.3. Conventions
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 BCP 14, RFC 2119 [2] 💖
2. LSA Format 🌸
2.1. LSA type
this extension uses the Opaque LSA [3] 💜
there are three types of Opaque LSAs, and each one has a different flooding scope. this proposal only uses Type 10 LSAs, which have an area flooding scope 🫶
one new LSA is defined, the Traffic Engineering LSA. it describes routers, point-to-point links, and connections to multi-access networks (kinda like a Router LSA) 🦋 for TE purposes, the existing Network LSA is good enough for describing multi-access links, so no extra LSA is defined for that 🍓
2.2. LSA ID
the LSA ID of an Opaque LSA is defined as having eight bits of type data and 24 bits of type-specific data 🎀 the Traffic Engineering LSA uses type 1. the remaining 24 bits are the Instance field, as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+the Instance field is an arbitrary value used to keep track of multiple Traffic Engineering LSAs 🧚 a single system can source a maximum of 16777216 Traffic Engineering LSAs. the LSA ID has no topological significance ✨
2.3. LSA Format Overview
2.3.1. LSA Header
the Traffic Engineering LSA starts with the standard LSA header 💅
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+2.3.2. TLV Header
the LSA payload is made of one or more nested Type/Length/Value (TLV) triplets, which is what makes it extensible 🌈 the format of each TLV is:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+the Length field defines the length of the value portion in octets (so a TLV with no value portion would have a length of zero) 🍓 the TLV is padded to four-octet alignment, but padding is not included in the length field. so a three octet value would have a length of three, but the total size of the TLV would be eight octets 🫧 nested TLVs are also 32-bit aligned. unrecognized types are ignored 🙈
this memo defines Types 1 and 2. see the IANA Considerations section for allocation of new Types 💖
2.4. LSA payload details
an LSA contains one top-level TLV 🎀
there are two top-level TLVs defined:
1 - Router Address
2 - Link2.4.1. Router Address TLV
the Router Address TLV specifies a stable IP address of the advertising router that is always reachable if there is any connectivity to it. this is typically implemented as a "loopback address" 🦋 the key attribute is that the address does not become unusable if an interface is down. in other protocols this is known as the "router ID," but for obvious reasons this nomenclature is avoided here 🙈 if a router advertises BGP routes with the BGP next hop attribute set to the BGP router ID, then the Router Address SHOULD be the same as the BGP router ID 🫶
if IS-IS is also active in the domain, this address can also be used to compute the mapping between the OSPF and IS-IS topologies 🧚 for example, suppose a router R is advertising both IS-IS and OSPF Traffic Engineering LSAs, and suppose further that some router S is building a single Traffic Engineering Database (TED) based on both IS-IS and OSPF TE information. R may then appear as two separate nodes in S's TED 😭 but if both the IS-IS and OSPF LSAs generated by R contain the same Router Address, then S can determine that the IS-IS TE LSA and the OSPF TE LSA from R are indeed from a single router 👑
the router address TLV is type 1, has a length of 4, and a value that is the four octet IP address. it must appear in exactly one Traffic Engineering LSA originated by a router ✨
2.4.2. Link TLV 🔗✨
Okay bestie, the Link TLV is the one that describes a single link 🦋. It's built out of a set of sub-TLVs, and there are no ordering requirements for those, so they can show up in any order 💅
Only one Link TLV shall be carried in each LSA, which is giving fine-grained topology changes 🎀
The Link TLV is type 2, and its length is variable 💖
These sub-TLVs of the Link TLV are defined:
1 - Link type (1 octet)
2 - Link ID (4 octets)
3 - Local interface IP address (4 octets)
4 - Remote interface IP address (4 octets)
5 - Traffic engineering metric (4 octets)
6 - Maximum bandwidth (4 octets)
7 - Maximum reservable bandwidth (4 octets)
8 - Unreserved bandwidth (32 octets)
9 - Administrative group (4 octets)This memo defines sub-Types 1 through 9. For new sub-Types, check the IANA Considerations section 🌈
Here's the tea 🫖: the Link Type and Link ID sub-TLVs are mandatory, i.e., they must appear exactly once. All the other sub-TLVs defined here may occur at most once. Those restrictions need not apply to future sub-TLVs. And unrecognized sub-TLVs get ignored, no drama 🙈
Various values below use the (32 bit) IEEE Floating Point format 🧮. For quick reference, the layout looks like this:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Exponent | Fraction |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+S is the sign, Exponent is the exponent base 2 in "excess 127" notation, and Fraction is the mantissa - 1, with an implied binary point in front of it. So the above represents the value:
(-1)**(S) * 2**(Exponent-127) * (1 + Fraction)For more details, refer to [4] 📚
2.5. Sub-TLV Details 🎀
2.5.1. Link Type 🔗
The Link Type sub-TLV defines the type of the link:
1 - Point-to-point
2 - Multi-accessThe Link Type sub-TLV is TLV type 1, and is one octet in length 💕
2.5.2. Link ID 🆔
The Link ID sub-TLV identifies the other end of the link 👀. For point-to-point links, this is the Router ID of the neighbor. For multi-access links, this is the interface address of the designated router. The Link ID is identical to the contents of the Link ID field in the Router LSA for these link types, so it's giving consistency 💅
The Link ID sub-TLV is TLV type 2, and is four octets in length ✨
2.5.3. Local Interface IP Address 🏠
The Local Interface IP Address sub-TLV specifies the IP address(es) of the interface corresponding to this link. If there are multiple local addresses on the link, they are all listed in this sub-TLV 🌸
The Local Interface IP Address sub-TLV is TLV type 3, and is 4N octets in length, where N is the number of local addresses 🧁
2.5.4. Remote Interface IP Address 🌍
The Remote Interface IP Address sub-TLV specifies the IP address(es) of the neighbor's interface corresponding to this link. This and the local address are used to discern multiple parallel links between systems 👯♀️. If the Link Type of the link is Multi-access, the Remote Interface IP Address is set to 0.0.0.0. Alternatively, an implementation MAY choose not to send this sub-TLV 🫶
The Remote Interface IP Address sub-TLV is TLV type 4, and is 4N octets in length, where N is the number of neighbor addresses 💜
2.5.5. Traffic Engineering Metric 🚦
The Traffic Engineering Metric sub-TLV specifies the link metric for traffic engineering purposes. This metric may be different than the standard OSPF link metric. Typically, a network administrator assigns this metric 🧑💼
The Traffic Engineering Metric sub-TLV is TLV type 5, and is four octets in length 🦋
2.5.6. Maximum Bandwidth 🚀
The Maximum Bandwidth sub-TLV specifies the maximum bandwidth that can be used on this link, in this direction (from the system originating the LSA to its neighbor), in IEEE floating point format. This is the true link capacity. The units are bytes per second 🌊
The Maximum Bandwidth sub-TLV is TLV type 6, and is four octets in length 💖
2.5.7. Maximum Reservable Bandwidth 📦
The Maximum Reservable Bandwidth sub-TLV specifies the maximum bandwidth that may be reserved on this link, in this direction, in IEEE floating point format. Note that this may be greater than the maximum bandwidth, in which case the link may be oversubscribed 😬. This SHOULD be user-configurable. The default value should be the Maximum Bandwidth. The units are bytes per second 🌈
The Maximum Reservable Bandwidth sub-TLV is TLV type 7, and is four octets in length 🎀
2.5.8. Unreserved Bandwidth 🫧
The Unreserved Bandwidth sub-TLV specifies the amount of bandwidth not yet reserved at each of the eight priority levels, in IEEE floating point format. The values correspond to the bandwidth that can be reserved with a setup priority of 0 through 7, arranged in increasing order. Priority 0 sits at the start of the sub-TLV, and priority 7 sits at the end 📶. The initial values (before any bandwidth is reserved) are all set to the Maximum Reservable Bandwidth. Each value will be less than or equal to the Maximum Reservable Bandwidth. The units are bytes per second 💫
The Unreserved Bandwidth sub-TLV is TLV type 8, and is 32 octets in length 🧚
2.5.9. Administrative Group 🏷️
The Administrative Group sub-TLV contains a 4-octet bit mask assigned by the network administrator. Each set bit corresponds to one administrative group assigned to the interface. A link may belong to multiple groups, which is so relatable 👑
By convention, the least significant bit is referred to as 'group 0', and the most significant bit is referred to as 'group 31' 🔢
The Administrative Group is also called Resource Class/Color [5] 🎨
The Administrative Group sub-TLV is TLV type 9, and is four octets in length 🍓
3. Elements of Procedure 🧩
Routers shall originate Traffic Engineering LSAs whenever the LSA contents change, and whenever otherwise required by OSPF (an LSA refresh, for example). Note that this does not mean every change must be flooded immediately. An implementation MAY set thresholds (for example, a bandwidth change threshold) that trigger immediate flooding, and initiate flooding of other changes after a short time interval ⏱️. In any case, the origination of Traffic Engineering LSAs SHOULD be rate-limited to at most one every MinLSInterval [1] 🚧
Upon receipt of a changed Traffic Engineering LSA or Network LSA (since these are used in traffic engineering calculations), the router should update its traffic engineering database 📥. No Shortest Path First (SPF) or other route calculations are necessary, so that's a whole vibe 😌
4. Compatibility Issues 🤝
There should be no interoperability issues with routers that do not implement these extensions, as the Opaque LSAs will be silently ignored 🫥
The result of having routers that do not implement these extensions is that the traffic engineering topology will be missing pieces. However, if the topology is connected, TE paths can still be calculated and ought to work 🧩✨
5. Security Considerations 🔐
This document specifies the contents of Opaque LSAs in OSPFv2. As Opaque LSAs are not used for SPF computation or normal routing, the extensions specified here have no affect on IP routing. However, tampering with TE LSAs may have an effect on traffic engineering computations 😱. It is suggested that any mechanisms used for securing the transmission of normal OSPF LSAs be applied equally to all Opaque LSAs, including the TE LSAs specified here 🛡️
Note that the mechanisms in [1] and [9] apply to Opaque LSAs. It is suggested that any future mechanisms proposed to secure or authenticate OSPFv2 LSA exchanges be made general enough to be used with Opaque LSAs. Bestie, this part is serious 💀🔒
6. IANA Considerations 📋
The top level Types in a TE LSA, as well as Types for sub-TLVs for each top level Type, have been registered with IANA, except as noted 🗂️
Here are the guidelines (using terms defined in [10]) for the assignment of top level Types in TE LSAs:
- Types in the range 3-32767 are to be assigned via Standards Action.
- Types in the range 32768-32777 are for experimental use. These will not be registered with IANA, and MUST NOT be mentioned by RFCs.
- Types in the range 32778-65535 are not to be assigned at this time. Before any assignments can be made in this range, there MUST be a Standards Track RFC that specifies IANA Considerations that covers the range being assigned.
The guidelines for the assignment of types for sub-TLVs in a TE LSA are as follows:
- Types in the range 10-32767 are to be assigned via Standards Action.
- Types in the range 32768-32777 are for experimental use. These will not be registered with IANA, and MUST NOT be mentioned by RFCs.
- Types in the range 32778-65535 are not to be assigned at this time. Before any assignments can be made in this range, there MUST be a Standards Track RFC that specifies IANA Considerations that covers the range being assigned.
7. Intellectual Property Rights Statement ⚖️
The IETF takes no position on the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document. It also doesn't say whether any license under such rights might or might not be available, and it doesn't claim to have tried to find any such rights 🤷♀️. Information on the IETF's procedures for rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication, and any assurances of licenses to be made available, or the result of an attempt to get a general license or permission for implementers or users of this specification to use such proprietary rights, can be obtained from the IETF Secretariat 📄
The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please send that information to the IETF Executive Director 💌
8. References 📚
8.1. Normative References 🌟
- [1] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
- [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
- [3] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, July 1998.
- [4] IEEE, "IEEE Standard for Binary Floating-Point Arithmetic", Standard 754-1985, 1985 (ISBN 1-5593-7653-8).
8.2. Informative References 🌸
- [5] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M. and J. McManus, "Requirements for Traffic Engineering Over MPLS", RFC 2702, September 1999.
- [6] Smit, H. and T. Li, "ISIS Extensions for Traffic Engineering", work in progress.
- [7] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links in Resource ReSerVation Protocol - Traffic Engineering (RSVP-TE)", RFC 3477, January 2003.
- [8] Kompella, K., Rekhter, Y. and A. Kullberg, "Signalling Unnumbered Links in CR-LDP (Constraint-Routing Label Distribution Protocol)", RFC 3480, February 2003.
- [9] Murphy, S., Badger, M. and B. Wellington, "OSPF with Digital Signatures", RFC 2154, June 1997.
- [10] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
9. Authors' Addresses ✨
Meet the squad! 🫶
Dave Katz
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089 USA
Phone: +1 408 745 2000
EMail: dkatz@juniper.netDerek M. Yeung
Procket Networks, Inc.
1100 Cadillac Court
Milpitas, CA 95035 USA
Phone: +1 408 635-7900
EMail: myeung@procket.comKireeti Kompella
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089 USA
Phone: +1 408 745 2000
EMail: kireeti@juniper.net10. Full Copyright Statement 🎀
Okay, this part is legal stuff, so I'm keeping it word for word. No cap. 💅
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees.
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement 🌸
Funding for the RFC Editor function is currently provided by the Internet Society. 🧚
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