RFC 5786
Advertising a Router's Local Addresses in OSPF Traffic Engineering (TE) Extensions
RFC 5786: Advertising a Router's Local Addresses in OSPF Traffic Engineering (TE) Extensions 🦋
Okay bestie, here's the title block tea ☕. This is RFC 5786 💖, written by R. Aggarwal and K. Kompella from Juniper Networks, published in March 2010. It's a Standards Track doc, so it's official IETF standards stuff (ISSN 2070-1721) ✨. It updates RFC 3630, meaning it tweaks that one rather than replacing it, and the header doesn't list anything it obsoletes 💅.
Abstract 🎀
OSPF Traffic Engineering (TE) extensions are used to advertise TE Link State Advertisements (LSAs) containing information about TE-enabled links. The only addresses belonging to a router that get advertised in TE LSAs are the local addresses corresponding to TE-enabled links, plus the local address corresponding to the Router ID.
So, to let other routers in a network compute Multiprotocol Label Switching (MPLS) Traffic Engineered Label Switched Paths (TE LSPs) to a given router's local addresses, those addresses must also be advertised by OSPF TE 🧚.
This document describes procedures that enhance OSPF TE so it can advertise a router's local addresses 🌸.
Status of This Memo 📜
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community, received public review, and has been approved for publication by the Internet Engineering Steering Group (IESG). More info on Internet Standards is in Section 2 of RFC 5741.
Info about the current status of this document, any errata, and how to give feedback on it can be found at http://www.rfc-editor.org/info/rfc5786.
Copyright Notice ©️
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Table of Contents 📚
1. Introduction ....................................................3
1.1. Motivation .................................................3
2. Specification of Requirements ...................................3
3. Rejected Potential Solution .....................................4
4. Solution ........................................................4
4.1. Node Attribute TLV .........................................4
4.2. Operation ..................................................5
5. Security Considerations .........................................6
6. IANA Considerations .............................................6
7. Acknowledgements ................................................6
8. References ......................................................7
8.1. Normative References .......................................7
8.2. Informative References .....................................71. Introduction ✨
1.1. Motivation 🦋
Sometimes you want to set up constrained shortest path first (CSPF) computed MPLS TE LSPs to local addresses of a router that aren't currently advertised in the TE LSAs. These are loopback and non-TE interface addresses 👀.
Picture a network carrying VPN and non-VPN traffic. It's super common to want different MPLS TE LSPs for the VPN traffic and the non-VPN traffic. In that setup, one loopback address may be used as the BGP next-hop for VPN traffic, while another may be used as the BGP next-hop for non-VPN traffic. It's also possible that different BGP sessions are used for VPN and non-VPN services. So two separate MPLS TE LSPs are desirable, one to each loopback address 💅.
Here's the catch though 🙃. Current routers in an OSPF network can only use CSPF to compute MPLS TE LSPs to the router ID or the local addresses of a remote router's TE-enabled links. That restriction happens because OSPF TE extensions [RFC3630, RFC5329] only advertise the router ID and the local addresses of TE-enabled links of a given router. Other routers in the network can fill their traffic engineering database (TED) with those local addresses belonging to the advertising router. But they can't fill the TED with the advertising router's other local addresses, which are the loopback and non-TE interface addresses 😭.
OSPFv2 stub links in the router LSA [RFC2328] give stub reachability info to the router, but they aren't enough to learn all of a router's local addresses. Especially for a subnetted point-to-point (P2P) interface, the stub link ID is the subnet address. For a non-subnetted interface, the stub link ID is the neighbor address. Intra-prefix LSAs in OSPFv3 [RFC5340] aren't enough to learn the local addresses either 🙈.
So, for all the reasons above, this document defines an enhancement to OSPF TE extensions to advertise the local addresses of a node 🌈.
2. Specification of Requirements 📝
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].
3. Rejected Potential Solution 🙅♀️
Okay so one idea would be to advertise a TE link TLV for each local address, maybe with a new link type. But ngl, this is inefficient, because the only meaningful info is the address. It would also make implementations process these TE link TLVs differently from everything else. For example, the TE metric is normally considered a mandatory sub-TLV, but it would have no meaning for a local address 🤷♀️.
4. Solution 💜
The solution is to advertise the local addresses of a router in a new OSPF TE LSA Node Attribute TLV. It's anticipated that the Node Attribute TLV will also prove more generally useful, which is very iconic of it 👑.
4.1. Node Attribute TLV 🎀
The Node Attribute TLV carries the attributes associated with a router. The TLV type is 5 and the length is variable. It contains one or more sub-TLVs. This document defines the following sub-TLVs:
- Node IPv4 Local Address sub-TLV
- Node IPv6 Local Address sub-TLV
The Node IPv4 Local Address sub-TLV has a type of 1 and contains one or more local IPv4 addresses. It has the following format:
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Len 1 | IPv4 Prefix 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix 1 cont. | :
+-+-+-+-+-+-+-+-+ ~
: . :
~ . +-+-+-+-+-+-+-+-+
: . | Prefix Len n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Prefix n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Each local IPv4 address is encoded as a <Prefix Length, Prefix> tuple. Prefix Length is encoded in 1 byte. It's the number of bits in the Address and can be at most 32. Prefix is an IPv4 address prefix and is encoded in 4 bytes, with zero bits as necessary 🧁.
The Node IPv4 Local Address sub-TLV length is in octets. It's the sum of the lengths of all n IPv4 Address encodings in the sub-TLV, where n is the number of local addresses included in the sub-TLV 🔢.
The Node IPv6 Local Address sub-TLV has a type of 2 and contains one or more local IPv6 addresses. It has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Len 1 | Prefix 1 Opt. | IPv6 Prefix 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix 1 cont. :
: . ~
~ .
: .
: +-+-+-+-+-++-+-+-+-+-++-+-+-+-+-+
: | Prefix Len n | Prefix n Opt. |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix n :
| :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--Each local IPv6 address is encoded using the procedures in [RFC5340]. Each IPv6 address MUST be represented by a combination of three fields: PrefixLength, PrefixOptions, and Address Prefix. PrefixLength is the length in bits of the prefix and is an 8-bit field. PrefixOptions is an 8-bit field describing various capabilities associated with the prefix [RFC5340]. Address Prefix is an encoding of the prefix itself as an even multiple of 32-bit words, padding with zero bits as necessary. This encoding consumes (PrefixLength + 31) / 32) 32-bit words 🌷.
The Node IPv6 Local Address sub-TLV length is in octets. It's the sum of the lengths of all n IPv6 Address encodings in the sub-TLV, where n is the number of local addresses included in the sub-TLV 💖.
4.2. Operation 🦋
okay so a router announces one or more local addresses in the Node Attribute TLV 💖 the local addresses that can already be learned from TE LSAs, aka the router address and TE interface addresses, SHOULD NOT be advertised in the node local address sub-TLV 🙈 which addresses end up there depends on the local configuration of the advertising router. the default MAY be to advertise all the loopback interface addresses ✨
the Node Attribute TLV MUST NOT appear in more than one TE LSA originated by a router 💅 and that LSA MUST NOT include more than one Node Attribute TLV either 🫶 a Node Attribute TLV MUST NOT carry more than one Node IPv4 Local Address sub-TLV 🌸 and it MUST NOT carry more than one Node IPv6 Local Address sub-TLV 💀 very strict, very iconic 👑
5. Security Considerations 💜
okay this part is serious bestie 😭 this document does not introduce any further security issues other than the ones already discussed in [RFC3630] and [RFC5329] 🔥 go read those too, no skipping!!
6. IANA Considerations 🍓
IANA has assigned the Node Attribute TLV (value 5) type from the range 3-32767 as specified in [RFC3630], from the top level types in TE LSAs registry maintained by IANA at http://www.iana.org 🧚
IANA has created and now maintains the registry for the sub-TLVs of the Node Attribute TLV ✨ value 1 is reserved for Node IPv4 Local Address sub-TLV, and value 2 is reserved for Node IPv6 Local Address sub-TLV 🌈
the guidelines for assigning types for sub-TLVs of the Node Attribute TLV go like this:
- 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. 🔒
7. Acknowledgements 🫶
we would like to thank Nischal Sheth for his contribution to this work 💖 we would also like to thank Jean Philippe Vasseur, Acee Lindem, Venkata Naidu, Dimitri Papadimitriou, and Adrian Farrel for their comments 🎀
8. References 📚
8.1. Normative References
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.8.2. Informative References
[RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
"Traffic Engineering Extensions to OSPF Version 3", RFC
5329, September 2008.Authors' Addresses 🌟
Rahul Aggarwal
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
Phone: +1-408-936-2720
EMail: rahul@juniper.net
Kireeti Kompella
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
EMail: kireeti@juniper.net📦 where this page comes from
- ietf: rfc5786 2010-03
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms