Inline, thanks.
-----Original Message-----
From: Joel M. Halpern [mailto:jmh(_at_)joelhalpern(_dot_)com]
Sent: 2014年10月22日 0:06
To: lizho(_dot_)jin(_at_)gmail(_dot_)com
Cc: gen-art(_at_)ietf(_dot_)org; mpls(_at_)ietf(_dot_)org;
ietf(_at_)ietf(_dot_)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(_dot_)jin(_at_)gmail(_dot_)com wrote:
Hi Joel, see inline below, thanks.
Lizhong
2014.10.21，PM9:30，Joel M. Halpern <jmh(_at_)joelhalpern(_dot_)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