Inline, thanks. > -----Original Message----- > From: Joel M. Halpern [mailto:jmh@xxxxxxxxxxxxxxx] > Sent: 2014年10月22日 0:06 > To: lizho.jin@xxxxxxxxx > Cc: gen-art@xxxxxxxx; mpls@xxxxxxxx; ietf@xxxxxxxx; 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@xxxxxxxxx wrote: > > Hi Joel, see inline below, thanks. > > > > Lizhong > > > > > >> 2014.10.21，PM9:30，Joel M. Halpern <jmh@xxxxxxxxxxxxxxx> 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