Re: [mpls] Clarification on the motivation of draft-xu-spring-islands-connection-over-ip-05

"Carlos Pignataro (cpignata)" <cpignata@cisco.com> Tue, 12 April 2016 00:23 UTC

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From: "Carlos Pignataro (cpignata)" <cpignata@cisco.com>
To: Xuxiaohu <xuxiaohu@huawei.com>
Thread-Topic: [mpls] Clarification on the motivation of draft-xu-spring-islands-connection-over-ip-05
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Date: Tue, 12 Apr 2016 00:23:01 +0000
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References: <1FEE3F8F5CCDE64C9A8E8F4AD27C19EE0D538182@NKGEML515-MBX.china.huawei.com> <57057618.8020604@juniper.net> <1FEE3F8F5CCDE64C9A8E8F4AD27C19EE0D538844@NKGEML515-MBX.china.huawei.com>
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Cc: "mpls@ietf.org" <mpls@ietf.org>, "spring@ietf.org" <spring@ietf.org>
Subject: Re: [mpls] Clarification on the motivation of draft-xu-spring-islands-connection-over-ip-05
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> On Apr 7, 2016, at 6:39 PM, Xuxiaohu <xuxiaohu@huawei.com> wrote:
> 
> On 4/6/2016 11:37 AM, Xuxiaohu wrote:
>> The situation in MPLS-SR is a little bit complex since the outgoing label for a given /32 or /128 prefix FEC could be learnt either from the IGP next-hop of that FEC or the originator of that FEC due to the IGP flooding property. In the former case, the IGP next-hop for a given FEC is taken as the next-hop of the received MPLS packet belonging to that FEC; in the latter case, the originator of that FEC is taken as the next-hop of the MPLS packet belonging to that FEC ... the latter case belongs to the "remote label distribution peer" case as defined in RFC3031
> 
> I don't believe this is correct.  In SR, the fact that label L was
> advertised by node N does not imply that a packet with L at the top of
> the stack needs to be tunneled to N.  In the typical case, the packet
> 
> [Xiaohu] The FEC associated the above label L is the /32 or 128/ prefix of node N. When the IGP next-hop towards that FEC is a non-MPLS node, the LSR receiving the above MPLS packet with top label of L is desired to forward that MPLS packet towards node N via an IP-based tunnel. In this case, the node N is the remote peer for that FEC.
> 

Is this really a “remote label distribution peer”? Or a local one by way of the forwarding adjacency of an IP Tunnel as a logical MPLS-enabled interface (towards N or bypassing the old router)?

Thanks,

— Carlos.

> Best regards,
> Xiaohu