Global Routing Operations C. Petrie
Internet-Draft RIPE NCC
Intended status: Standards Track T. King
Expires: July 18, 2017 DE-CIX
January 14, 2017
Multi-Threaded Routing Toolkit (MRT) Routing Information Export Format
with BGP Additional Paths Extensions
draft-ietf-grow-mrt-add-paths-03
Abstract
This document updates the Multi-threaded Routing Toolkit (MRT) export
format for Border Gateway Protocol (BGP) routing information by
extending it to support the Advertisement of Multiple Paths in BGP
extensions.
Status of This Memo
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Copyright Notice
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document authors. All rights reserved.
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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 . . . . . . . . . . . . . 3
4.2. RIB_GENERIC_ADDPATH Subtype . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5.1. BGP4MP/BGP4MP_ET Subtype codes: . . . . . . . . . . . . . 4
5.2. TABLE_DUMP_V2 Subtype codes: . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The MRT record format [RFC6396] was developed to provide researchers
and engineers a means to encapsulate, export, and archive routing
protocol transactions and routing information base snapshots.
The Advertisement of Multiple Paths in BGP [RFC7911] defines a BGP
extension to allow the advertisement of multiple paths for the same
address prefix without the new paths implicitly replacing any
previous ones.
This document contains an optional extension to the MRT format
[RFC6396] and introduces additional definitions of MRT subtype fields
to permit representation of multiple path advertisements [RFC7911].
2. Rationale
MRT parsers are usually stateless. In order to parse BGP messages
which contain data structures that depend on the capabilities
negotiated during the BGP session setup, the so-called MRT subtypes
are utilized. The Advertisement of Multiple Path [RFC7911] extension
for BGP alters the encoding of the BGP NLRI format for withdraws and
announcements. Therefore new BGP4MP/BGP4MP_ET subtypes as defined in
[RFC6396] are required to signal to a MRT parser how to parse the
NLRI.
In section 4.3 [RFC6396] of the MRT specification RIB subtypes are
specified. Prefix length and prefix fields are encoded in the same
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manner as the BGP NLRI encoding. In order to support path identifier
information as defined in [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 the following new Subtypes:
o BGP4MP_MESSAGE_ADDPATH
o BGP4MP_MESSAGE_AS4_ADDPATH
o BGP4MP_MESSAGE_LOCAL_ADDPATH
o BGP4MP_MESSAGE_AS4_LOCAL_ADDPATH
The fields of these message types are identical to the equivalent
non-additional-path versions specified in section 4.4 [RFC6396].
These enhancements continues to encapsulate the entire BGP message in
the BGP message field.
4. MRT Subtypes for Type TABLE_DUMP_V2
This document defines the following new Subtypes:
o RIB_IPV4_UNICAST_ADDPATH
o RIB_IPV4_MULTICAST_ADDPATH
o RIB_IPV6_UNICAST_ADDPATH
o RIB_IPV6_MULTICAST_ADDPATH
o RIB_GENERIC_ADDPATH
The fields of these message types are identical to the equivalent
non-additional-path versions specified in section 4.3 [RFC6396].
However, for the specific case of the 4 AFI/SAFI specific RIB
subtypes, the existing RIB Entries field is re-defined as detailed in
the sections below.
4.1. AFI/SAFI specific RIB Subtypes
In order to preserve the record compaction achieved by using the most
common subtypes, and allowing multiple RIB Entries to be stored in a
single TABLE_DUMP_V2 record, the existing RIB Entries field is
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redefined for use within the new AFI/SAFI specific RIB Subtypes
defined by this document 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originated Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Attribute Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BGP Attributes... (variable)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: RIB Entries for AFI/SAFI-specific RIB Subtypes with
additional-paths support
This adds a field to the RIB Entries record, to store the path
identifier, when used with the RIB_IPV4_UNICAST_ADDPATH,
RIB_IPV4_MULTICAST_ADDPATH, RIB_IPV6_UNICAST_ADDPATH and
RIB_IPV6_MULTICAST_ADDPATH subtypes.
4.2. RIB_GENERIC_ADDPATH Subtype
The fields of this subtype are identical to the equivalent non-
additional-path versions specified in section 4.3.3 [RFC6396]. These
fields continue to encapsulate the raw and additional-path enabled
AFI/SAFI/NLRI in the record, and the raw attributes in the RIB
Entries.
For clarity, the RIB Entries in this subtype are not redefined.
5. IANA Considerations
This document requests that IANA assign the following subtype codes
to the MRT name space [1]:
5.1. BGP4MP/BGP4MP_ET Subtype codes:
BGP4MP_MESSAGE_ADDPATH = 8 (Section 3)
BGP4MP_MESSAGE_AS4_ADDPATH = 9 (Section 3)
BGP4MP_MESSAGE_LOCAL_ADDPATH = 10 (Section 3)
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BGP4MP_MESSAGE_AS4_LOCAL_ADDPATH = 11 (Section 3)
The values provided above are suggested as they are used in
implementations.
5.2. TABLE_DUMP_V2 Subtype codes:
RIB_IPV4_UNICAST_ADDPATH = 8 (Section 4.1)
RIB_IPV4_MULTICAST_ADDPATH = 9 (Section 4.1)
RIB_IPV6_UNICAST_ADDPATH = 10 (Section 4.1)
RIB_IPV6_MULTICAST_ADDPATH = 11 (Section 4.1)
RIB_GENERIC_ADDPATH = 12 (Section 4.2)
The values provided above are suggested as they are used in
implementations.
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, and this document permits the export of
more detailed routing data.
An organization that uses the MRT format to store their 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 their environment.
An organization that peers with public BGP collectors, and enables
the additional-paths capability 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. References
7.1. 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>.
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[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>.
7.2. URIs
[1] https://www.iana.org/assignments/mrt/mrt.xhtml
Authors' Addresses
Colin Petrie
RIPE NCC
Stationsplein 11
Amsterdam 1012 AB
NL
Email: cpetrie@ripe.net
Thomas King
DE-CIX Management GmbH
Lichtstrasse 43i
Cologne 50825
Germany
Email: thomas.king@de-cix.net
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