Re: [Idr] [idr] FW: I-D Action: draft-zeng-idr-bgp-mtu-extension-00.txt

Hi,

I was reading this draft and can you please clarify the below,

<snip>
A. If BGP speaker A is originator of the labeled IPv4 (or IPv6)
   route, A sets its BGP LSP Path MTU to the maximal value, advertises
   the labeled IPv4 (or IPv6) route with the MTU Extended Community to
   its BGP Peer (its upstream BGP LSR).

1.  Any reason to specify the MTU with maximal value on egress side?. I understand RFC3988 have the same behavior, but I am not aware of any reason. Per my understanding, setting the MTU value as the link MTU to the respective FEC value will help avoid IP fragmentation upto egress side. For example, if on egress PE, the link MTU is 1500 while the calculated Path MTU (based on this draft) is 9000, it still needs IP fragmentation on egress side.

2. After advertising the UPDATE to neighbor what will be the action when the MTU changes?.

3. Since we already have RFC3988 that helps calculate MTU with LDP, Am I assuming right that this ID helps in Inter-AS scenarios (Option B) or scenarios where RSVP is used for LSP establishment?. Should we specify that in ID?.

Thanks,
Nagendra

-----Original Message-----
From: l3vpn-bounces@ietf.org [mailto:l3vpn-bounces@ietf.org] On Behalf Of Zengqing
Sent: Monday, July 11, 2011 9:12 AM
To: idr@ietf.org; l3vpn@ietf.org
Subject: [idr] FW: I-D Action: draft-zeng-idr-bgp-mtu-extension-00.txt

FYI.  
Any comments will be appreciated.

Best Regards!   
Qing & Jie

> -----Original Message-----
> From: i-d-announce-bounces@ietf.org
> [mailto:i-d-announce-bounces@ietf.org] On Behalf Of
> internet-drafts@ietf.org
> Sent: Monday, July 04, 2011 6:48 PM
> To: i-d-announce@ietf.org
> Subject: I-D Action: draft-zeng-idr-bgp-mtu-extension-00.txt
> 
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> 
> 	Title           : Maximum Transmission Unit Extended Community
> for BGP-4
> 	Author(s)       : Qing Zeng
>                           Jie Dong
> 	Filename        : draft-zeng-idr-bgp-mtu-extension-00.txt
> 	Pages           : 6
> 	Date            : 2011-07-04
> 
>    Proper functioning of [RFC1191] path Maximum Transmission Unit (MTU)
>    discovery requires that IP routers have knowledge of the MTU for each
>    link to which they are connected.  As MPLS progresses, [RFC3988]
>    specifies some extensions to LDP in support of LDP LSP MTU discovery.
>    For the LSP created using Border Gateway Protocol (BGP) [RFC3107], it
>    does not have the ability to signal the path MTU to the ingress Label
>    Switching Router (LSR).  In the absence of this functionality, the
>    MTU for the BGP LSP must be statically configured by network
>    operators or by equivalent off-line mechanisms.
> 
>    This document defines the MTU Extended Community for BGP in support
>    of BGP LSP MTU discovery.
> 
> 
> 
> A URL for this Internet-Draft is:
> http://www.ietf.org/internet-drafts/draft-zeng-idr-bgp-mtu-extension-00.txt
> 
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
> 
> This Internet-Draft can be retrieved at:
> ftp://ftp.ietf.org/internet-drafts/draft-zeng-idr-bgp-mtu-extension-00.txt
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