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Re: [mpls] [Gen-art] review: draft-ietf-mpls-lsp-ping-relay-reply-04

"Lizhong Jin" <lizho.jin@gmail.com> Wed, 22 October 2014 02:06 UTC

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From: Lizhong Jin <lizho.jin@gmail.com>
To: "'Joel M. Halpern'" <jmh@joelhalpern.com>
References: <012001cfec30$18d91920$4a8b4b60$@gmail.com> <54465FED.6030005@joelhalpern.com> <B16F6336-3E7B-41E1-AB92-A7A7D818594A@gmail.com> <5446847D.4030500@joelhalpern.com>
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Date: Wed, 22 Oct 2014 10:06:15 +0800
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Cc: mpls@ietf.org, gen-art@ietf.org, "'draft-ietf-mpls-lsp-ping-relay-reply.all'" <draft-ietf-mpls-lsp-ping-relay-reply.all@tools.ietf.org>, ietf@ietf.org
Subject: Re: [mpls] [Gen-art] review: draft-ietf-mpls-lsp-ping-relay-reply-04
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Inline, thanks.

> -----Original Message-----
> From: Joel M. Halpern [mailto:jmh@joelhalpern.com]
> Sent: 2014年10月22日 0:06
> To: lizho.jin@gmail.com
> Cc: gen-art@ietf.org; mpls@ietf.org; ietf@ietf.org;
draft-ietf-mpls-lsp-ping-
> relay-reply.all
> Subject: Re: [mpls] [Gen-art] review:
draft-ietf-mpls-lsp-ping-relay-reply-04
> 
> In line.
> 
> On 10/21/14, 10:36 AM, lizho.jin@gmail.com wrote:
> > Hi Joel, see inline below, thanks.
> >
> > Lizhong
> >
> >
> >> 2014.10.21，PM9:30，Joel M. Halpern <jmh@joelhalpern.com> wrote ：
> >>
> >> If the process for this draft is to use the top address that can be
> >> reached in the routing table, then there is a significant probability
> >> that the original source address, which is always at the top of the
> >> list, will be used.  As such, the intended problem will not be
> >> solved.
> > [Lizhong] let me give an example to explain: the source address A is
> > firstly added to the stack, then a second routable address B for
> > replying AS is also added. The reply node will not use address A since
> > it's not routable, then it will use address B. So it will work and I
> > don't see the problem.
> 
> The whole point of this relay mechanism, as I understand it, is to cope
with
> the case when the responder X can not actually reach the source A.
>  Now suppose that the packet arrives at X with the Address stack A, B, ...
X
> examines the stack.  The domain of A was numbered using net 10.
> The domain of X is numbered using net 10.  A's address is probably
routable
> in X's routing table.  The problem is, that routing will not get to A.  X
examines
> the stack, determines that A is "routable", and sends the packet.  This
fails to
> meet the goal.
[Lizhong] The source A you are referring is the initiator, right? The goal
of relay mechanism is to reach the initiator. If X is routable to the
initiator (address A), then it is great, other relay node in the stack will
be skipped.
If the source A you are referring is the interface address of one
intermediate node, then I do not understand "routing will not get to A.  X
examines the stack, determines that A is "routable", and sends the packet".
Why routing will not get to A, but A is routable?

Regards
Lizhong


> 
> Yours,
> Joel

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