I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.
Please resolve these comments along with any other Last Call comments
you may receive.
Document: draft-ietf-mpls-lsp-ping-relay-reply-04
Relayed Echo Reply mechanism for LSP Ping
Reviewer: Joel M. Halpern
Review Date: 8-October-2014
IETF LC End Date: 13-October-2014
IESG Telechat date: (if known)
Summary: This document is not ready for publication as a Proposed Standard
Major issues:
There is either a major technical flaw in this document, or there
is a need for significantly better explanation. The following is what I
was able to understand from reading the document.
The procedure in the document calls for a responding or relaying
LSR to search the response addresses from the top to the bottom (top
being the originator of the request, bottom being visible originators).
The responder then sends the reply to the first usable address it can
find in the stack. Usable is variously described as "public routable"
and as "routable" (in sections 4.2), the converse is described as
"unroutable" in section 4.3, while section 4.4 uses "routable".
If it means "routable", then this assumes that the private addresses
used by one AS will not happen to also be used in another AS (which
would make them routable in that domain, directing the reply to
completely the wrong place.
If it means "publicly routable", this would seem to fail since routers
do not know whether routable addresses are public, private, or simply
not martian.
Minor issues:
The procedures assume that border routers will know the correct
address to put in the reply stack. It is not bovious that even if the
router has a public address, it will get put on. The requirement stated
here is that the address put on be the same one used to originate the
reply. Which would seem likely to be na internal address in many cases.
The procedure for setting k=0 allowing entries to be removed from
the stack seems fragile. It relies on routers being able to determine
that their address will not be needed for relay by the next hop.
Nits/editorial comments:
Some of the procedure for originating a reply is described in
section 4.2 on Receiving a request, rather than in seciton 4.3 on
originating the reply. (Information such as the address to put on the
stack, where it goes on the stack, and the handling of the reply packet
being too large all belong in 4.3.)