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

["Joel M. Halpern" <[e-mail]>]

In line.

On 10/21/14, 10:36 AM, [e-mail] wrote:
> Hi Joel, see inline below, thanks.
> 
> Lizhong
> 
> 
>> 2014.10.21，PM9:30，Joel M. Halpern <[e-mail]> 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.

Yours,
Joel