[Idr] 答复: WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 to 11/16/2020)

Weiqiang Cheng <chengweiqiang@chinamobile.com> Wed, 04 November 2020 09:35 UTC

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From: Weiqiang Cheng <chengweiqiang@chinamobile.com>
To: 'Susan Hares' <shares@ndzh.com>, idr@ietf.org
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Subject: [Idr] 答复: WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 to 11/16/2020)
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·¢¼þÈË: Idr [mailto:idr-bounces@ietf.org] ´ú±í Susan Hares
·¢ËÍʱ¼ä: 2020Äê11ÔÂ2ÈÕ 13:04
ÊÕ¼þÈË: idr@ietf.org
Ö÷Ìâ: [Idr] WG Adoption for draft-zhu-idr-bgp-ls-path-mtu (11/1/2020 to


This begins a 2 week WG adoption call for 

draft-zhu-idr-bgp-ls-path-mtu-04.txt (11/1 ¨C 11/16/2020). 


The authors should send in an IPR statement for this draft 

by 11/5 so the WG can include the IPR status in their decision. 


You can access the draft at: 



Since this draft is reference by an existing IDR draft

I¡¯ve included a bit of background below to help you place  

this draft into the larger context of the SR additions to BGP-LS

and the draft-ietf-idr-tunnel-encaps-19.txt.


This draft does continue BGP-LS additions.  if you 

are opposed to any BGP-LS additions rather than 

this specific addition, please make that clear in your 

comment in this discussion.   


The authors requested a WG adoption at IETF 108.  

The IDR co-chairs thank the authors for their patience.   

This draft has been delayed by process of having a 

new document shepherd (Sue Hares) come up to speed

on draft-ietf-idr-tunnel-encapsulation. 


Cheers, Sue 




Segment Routing technology creates SR tunnels that are 

directly overlaid on MPLS or SRv6.  While existing MPLS technology 

(LDP and RSV-TE) provides mechanisms to negotiate path MTU

based on individual link MTU limits, the Segment Routing (SR) 

on BGP-LS Link Attribute does not pass information on 

MTU size per link.   


draft-ietf-idr-sr-policy-path-mtu-02.txt sends PATH MTU 

information in the tunnel-encapsulation attribute for the tunnel type  

SR-Policy that handles segment routing (SR) paths.       

However, it lacks the information to create a reasonable 

Path size since the BGP-LS Link Attribute does distribute

this information. 


The draft proposes adding a new sub-TLV for MTU size 

to the BGP-LS Link Attribute TLV, and 

draft-ietf-idr-sr-policy-path-mtu-02.txt mentions this 

draft as one possible way to distribute the per link 



Questions for the authors might be: 

a) Are there ways to pass IGP link MTUs in 

the IGPs?  If so, is this needed in BGP-LS


b) What other mechanisms pass link MTU?