draft: draft-ietf-idr-sr-policy-path-mtu
Type: Proposed Standard
status: WG Draft, needs revision 13
adopted: 9/1/2024 (8/1 to 8/30 call)
current version: -14
Early Allocation: yes, call (1/5/2026 - 1/19/2026)
implementations: 1 (Huawei in VRP8)
related bgp-ls draft: none
Summary: Technical issue 1 from -13 has been resolved. No open issues.
Next steps:
Summary: Technical issues 2-4 from the review of -10, -11 and -12 aare complete. An early allocation request has been sent.
**Next steps: **
**Section 3: **
Old text: /Type: to be assigned by IANA./
New text: /Type: TBD1 (to be assigned by IANA).
**Section 6: **
Old text:/
TBA Path MTU sub-TLV This document/
Next text:/
TBD1 Path MTU sub-TLV This document/
Summary: Technical issues from -10 are not resolved in -12. Also, the name of the
IANA registry is: SR Policy Segment List Sub-TLVs. Please make this correction.
email with review: TBD
Next steps:
Summary: All Technical issues and Editorial issues from the Review of -10 need to be addressed
draft: draft-ietf-idr-sr-policy-path-mtu-10
**Summary: **Revision 10 resolves all the issues listed in the shepherd report.
Needs an update to address TEA Template review.
email: https://mailarchive.ietf.org/arch/msg/idr/jP4BwLPxw286FB5ZH9xNruW0rMM/
**Section 3: **
Old text: /Type: to be assigned by IANA./
New text: /Type: TBD1 (to be assigned by IANA).
**Section 6: **
Old text:/
TBA Path MTU sub-TLV This document/
Next text:/
TBD1 Path MTU sub-TLV This document/
Can the Path-MTU appear in any other TEA TLV than SR Policy?
I believe the answer is "no", but the document needs to state
**
New text for section 4:/**
"This document specifies the Path-MTU Sub-TLV to appear only in the SR Policy TLV of
the Tunnel Encapsulation Attribute (TEA). Any other use of the Path-MTU sub-TLV is
outside the scope of this document. /
Please state clearly that this Sub-TLV does not play a part of BGP's validation of this tunnel.
current text: / The consumer of the SR policies is not the BGP process. The operation of sending information to consumers is out of scope of this document./
New text:/ The consumer of the SR policies is not the BGP process. The bgp process does not validate
the tunnel based on the SR Policy information (including the Path MTU Sub-TLV). The operation of sending information to consumers is out of scope of this document. /
Please add an section to indicate how operators may manage set or monitor the PATH MTU via existing Yang modules or BGP-LS support. If these do not exist, suggest whether these would be useful.
draft: draft-ietf-idr-sr-policy-path-mtu-09
Summary: revision suggested
Implementation status: 1 implementation
Email link: https://mailarchive.ietf.org/arch/msg/idr/TGRz8JBBGADNLQTVV9vQ0iVgohY/
**Old text:/ **
An SR policy is a set of candidate SR paths consisting of one or more
segment lists with necessary path attributes. However, the path
maximum transmission unit (MTU) information for SR path is not
available in the SR policy since the SR does not require signaling.
This document defines extensions to BGP to distribute path MTU
information within SR policies./
New text:/
An SR policy is a set of SR Policy candidate paths consisting of one or
more segments with the appropriate SR path attributes. BGP distributes
each SR Policy candidate path as combination of an prefix plus a
the BGP Tunnel Encapsulation(Tunnel-Encaps) attribute containing
an SR Policy Tunnel TLV with information on the SR Policy candidate
path as a tunnel. However, the path maximum
transmission unit (MTU) information for a segment list for SR path
is not currently passed in the BGP Tunnel-Encaps attribute. .
This document defines extensions to BGP to distribute path MTU
information within SR policies./
Old text:/
In order to distribute SR policies to the headend,
[I-D.ietf-idr-sr-policy-safi] specifies a mechanism by using BGP./
New text:/
In order to distribute SR policies to the headend,
[I-D.ietf-idr-sr-policy-safi] specifies a BGP mechanism
to pass SR Policies and Candidate SR Policies in BGP UPDATE
message. Each SR Candidate Path is passed as combination of a
specific type of NLRI and BGP Tunnel Encapsulation Attribute (Tunnel-Encaps)
with SR Policy Tunnel type tunnel. The NLRI must contain
either be the IPv4 Unicast AFI with SR Policy SAFI (AFI=1/SAFI=73),
the IPv6 Unicast AFI with the SR Policy SAFI (AFI=2/SAFI=73)./
Old text: /
But the ingress still needs to
examine the packet size for dropping too large packets to avoid
malicious traffic or error traffic. Also, the packet size may
exceeds the PMTU because of the new encapsulation of SR-MPLS or SRv6
packet at the ingress. /
New text:
/But the ingress router still needs to
examine the packet size for dropping too large packets to avoid
malicious traffic or error traffic. Also, the packet size may
exceeds the PMTU because of encapsulation of the original packet in
SR-MPLS or SRv6 packet at the ingress router./
Old text:/
However, the path maximum transmission unit (MTU)
information for SR path is not available since the SR does not
require signaling.This document defines extensions to BGP to distribute path MTU
information within SR policies. The Link MTU information can be
obtained via BGP-LS [I-D.ietf-idr-bgp-ls-link-mtu] or some other
means. With the Link MTU, the controller can compute the PMTU and
convey the information via the BGP SR policy./
**
New text:/**
However, the path maximum transmission unit (MTU)
information for SR path is not currently distributed in the
BGP Tunnel-Encaps attribute TLV for the SR Policy Tunnel.
This document defines a new sub-TLV for the BGP Tunnel-Encaps
attribute for the SR Policy Tunnel type to specify Maximum Path
MTU for a Segment list (Sub-TLV)./The Maximum Path MTU can be calculated as the maximum of
individual Link MTU information. The Link MTU information can be
obtained via BGP-LS [I-D.ietf-idr-bgp-ls-link-mtu] or some other
means. based on all Link MTUs, the controller can compute the PMTU and
convey the information via the BGP SR policy./
** Old text:/**
Length: the total length of the value field not including Type and
Length fields. /
New text:/
Length: the total length in octets the value field not including Type and
Length fields. The value must be 6./
This security section should refer to [draft-ietf-idr-sr-policy-safi].
One addition needs to be made in this text.
This security section should specifically state that the new sub-TLV PATH MTU
contains critical information for the network. Critical information is a place
where modifying the information could cause problems. Care should be taken to
protect the collection of Link MTU, the generation of PATH MTU, and the
distribution of PATH MTU.
** current:/**
[RFC3209] specify the mechanism of MTU signaling in RSVP.
Likewise, SRv6 pakcets will be dropped if the
packet size is larger than path MTU, since IPv6 packet can not be
fragmented on transmission [RFC8200] ./
** new:/**
[RFC3209] specifies the mechanism of MTU signaling in RSVP.
Similarly, the SRv6 packets will be dropped if the packet
size is larger than the path MTU, since IPv6 packet can not be
fragmented on transmission [RFC8200]./