RFC 8050

Multi-Threaded Routing Toolkit (MRT) Routing Information Export Format with BGP Additional Path Extensions

📅 published May 2017, from ietf

Okay bestie, let's get into this 🎀✨

Title and Vibes 💖

RFC 8050 is the Multi-Threaded Routing Toolkit (MRT) Routing Information Export Format with BGP Additional Path Extensions 🦋. It's a Standards Track doc from the IETF, dated May 2017, and it's by C. Petrie (RIPE NCC) and T. King (DE-CIX) 🫶. It doesn't obsolete anything or update anything, so it's a clean new entry 💅. Its ISSN is 2070-1721.

Abstract ✨

So the whole point is this: it extends the MRT export format for BGP routing info so it can carry multiple paths in BGP extensions 🔥.

Status of This Memo 📜

This is an Internet Standards Track document 💅. It's a product of the IETF and it has the consensus of the IETF community, plus public review and IESG approval 🌸. Want more on Internet Standards? Check Section 2 of RFC 7841 🧚. Errata and feedback live at http://www.rfc-editor.org/info/rfc8050 💜.

Copyright Notice 🎀

Copyright (c) 2017 IETF Trust and the document authors, all rights reserved 🌈. This doc is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) as of the publication date, so read those carefully because they spell out your rights 🙈. Code pulled out of this doc has to include Simplified BSD License text, as described in Section 4.e of the Trust Legal Provisions, and it comes with no warranty 🫶.

Table of Contents 🦋

1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
2.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . .   2
3.  MRT Subtypes for Types BGP4MP/BGP4MP_ET . . . . . . . . . . .   3
4.  MRT Subtypes for Type TABLE_DUMP_V2 . . . . . . . . . . . . .   3
  4.1.  AFI/SAFI-Specific RIB Subtypes  . . . . . . . . . . . . .   4
  4.2.  RIB_GENERIC_ADDPATH Subtype . . . . . . . . . . . . . . .   4
5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
  5.1.  BGP4MP/BGP4MP_ET Subtype Codes  . . . . . . . . . . . . .   5
  5.2.  TABLE_DUMP_V2 Subtype Codes . . . . . . . . . . . . . . .   5
6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
7.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1. Introduction 🌸

The MRT record format [RFC6396] was built so researchers and engineers could encapsulate, export, and archive routing protocol transactions and RIB snapshots 📦.

The Advertisement of Multiple Paths in BGP [RFC7911] is the BGP extension that lets you advertise multiple paths for the same address prefix without the new ones quietly replacing the old ones 👑.

This doc adds an optional extension to the MRT format [RFC6396] and defines extra MRT subtype fields so multiple path advertisements [RFC7911] can be represented 🧚.

2. Rationale 💭

MRT parsers are usually stateless 🫠. To parse BGP messages whose data structures depend on capabilities negotiated during BGP session setup, the MRT subtypes come in clutch 💅. The Advertisement of Multiple Paths [RFC7911] extension changes how the BGP NLRI encoding works for withdraws and announcements, so new BGP4MP/BGP4MP_ET subtypes from [RFC6396] are REQUIRED to tell an MRT parser how to parse that NLRI 😭.

Section 4.3 of the MRT specification [RFC6396] is where the RIB subtypes live. Prefix length and prefix fields are encoded the same way as BGP NLRI. To support Path Identifier info from [RFC7911], new subtypes need to be added 🎀.

The following two sections define the required subtypes 🍓.

3. MRT Subtypes for Types BGP4MP/BGP4MP_ET 🦋

This document defines these new subtypes:

BGP4MP_MESSAGE_ADDPATH
BGP4MP_MESSAGE_AS4_ADDPATH
BGP4MP_MESSAGE_LOCAL_ADDPATH
BGP4MP_MESSAGE_AS4_LOCAL_ADDPATH

The fields of these message types are identical to the non-additional-path versions in Section 4.4 of [RFC6396] 💅. These still encapsulate the entire BGP message in the BGP message field 🫶.

4. MRT Subtypes for Type TABLE_DUMP_V2 💖

This document defines these new subtypes:

RIB_IPV4_UNICAST_ADDPATH
RIB_IPV4_MULTICAST_ADDPATH
RIB_IPV6_UNICAST_ADDPATH
RIB_IPV6_MULTICAST_ADDPATH
RIB_GENERIC_ADDPATH

The fields match the non-additional-path versions in Section 4.3 of [RFC6396] 🌈. The one twist: for the 4 AFI/SAFI-specific RIB subtypes, the existing RIB Entries field gets redefined, as detailed below ⭐.

4.1. AFI/SAFI-Specific RIB Subtypes ✨

To keep the record compaction you get from the most common subtypes, and to let multiple RIB Entries live in one TABLE_DUMP_V2 record, the existing RIB Entries field is redefined for these new AFI/SAFI-specific RIB subtypes like so 🧚:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Peer Index            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Originated Time                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         Path Identifier                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Attribute Length         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    BGP Attributes... (variable)
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Figure 1: RIB Entries for AFI/SAFI-Specific RIB Subtypes with
                    Support for Additional Paths

This adds a field to the RIB Entries record to store the Path Identifier when used with RIB_IPV4_UNICAST_ADDPATH, RIB_IPV4_MULTICAST_ADDPATH, RIB_IPV6_UNICAST_ADDPATH, and RIB_IPV6_MULTICAST_ADDPATH 🦋.

4.2. RIB_GENERIC_ADDPATH Subtype 💅

The fields of this subtype match the non-additional-path versions in Section 4.3.3 of [RFC6396] 🫶. They still encapsulate the raw and additional-path-enabled AFI/SAFI/NLRI in the record, plus the raw attributes in the RIB Entries 🌸.

For clarity, the RIB Entries in this subtype are not redefined 💜.

5. IANA Considerations 📋

IANA has assigned the subtype codes below in the "Multi-threaded Routing Toolkit (MRT)" registry <https://www.iana.org/assignments/mrt> 🌈.

5.1. BGP4MP/BGP4MP_ET Subtype Codes 🎀

These have been registered in the "BGP4MP Subtype Codes" and "BGP4MP_ET Subtype Codes" registries:

   8 BGP4MP_MESSAGE_ADDPATH (RFC 8050)

   9 BGP4MP_MESSAGE_AS4_ADDPATH (RFC 8050)

   10 BGP4MP_MESSAGE_LOCAL_ADDPATH (RFC 8050)

   11 BGP4MP_MESSAGE_AS4_LOCAL_ADDPATH (RFC 8050)

5.2. TABLE_DUMP_V2 Subtype Codes 🍓

These have been registered in the "TABLE_DUMP_V2 Subtype Codes" registry:

   8 RIB_IPV4_UNICAST_ADDPATH (RFC 8050)

   9 RIB_IPV4_MULTICAST_ADDPATH (RFC 8050)

   10 RIB_IPV6_UNICAST_ADDPATH (RFC 8050)

   11 RIB_IPV6_MULTICAST_ADDPATH (RFC 8050)

   12 RIB_GENERIC_ADDPATH (RFC 8050)

6. Security Considerations 🔥

It is not believed that this document adds any additional security considerations 🙈. However, the security considerations of [RFC6396] are equally applicable to this document, because this document permits the export of more detailed routing data 💀.

An organization that uses the MRT format to store its BGP routing information SHOULD be aware that supporting these extensions permits more detailed network path information to be stored, and SHOULD consider the implications of this within its environment 😭.

An organization that peers with public BGP collectors and enables the capability for additional paths on a peering session SHOULD be aware that it is exporting not only its best paths, but potentially other paths within its networks. The BGP peer SHOULD consider any and all implications of exposing this additional data. 💀🔥

7. Normative References 📚

   [RFC6396]  Blunk, L., Karir, M., and C. Labovitz, "Multi-Threaded
              Routing Toolkit (MRT) Routing Information Export Format",
              RFC 6396, DOI 10.17487/RFC6396, October 2011,
              <http://www.rfc-editor.org/info/rfc6396>.

   [RFC7911]  Walton, D., Retana, A., Chen, E., and J. Scudder,
              "Advertisement of Multiple Paths in BGP", RFC 7911,
              DOI 10.17487/RFC7911, July 2016,
              <http://www.rfc-editor.org/info/rfc7911>.

Authors' Addresses 🧚

   Colin Petrie
   RIPE NCC
   Stationsplein 11
   Amsterdam  1012 AB
   The Netherlands

   Email: cpetrie@ripe.net


   Thomas King
   DE-CIX Management GmbH
   Lichtstrasse 43i
   Cologne  50825
   Germany

   Email: thomas.king@de-cix.net

📦 where this page comes from

ietf: rfc8050 2017-05
💖 girlified by claude-haiku-5-5 on 2026-10-18: a language model's rewrite of the original, under its terms