The MPLS WG Archive

[Bora Akyol <akyol@pluris.com>]

One can presume to enable or disable functionality related to
PHP using CLI or MIB commands as well as centralized
configuration distribution. I know of at least one ISP that uses
a centralized configuration engine to control all of their
routers.

Bora

>>>>> "Eric" == Eric Gray <eric.gray@sandburst.com> writes:

    Eric> Bora, This explanation presupposes the existence of a
    Eric> standard way for the knowledgeable network operator to
    Eric> "configure their equipment" to compensate for a
    Eric> mismatch in equipment models relative to PHP.  To my
    Eric> knowledge, the only such "standard" way at present is
    Eric> for the knowledgeable network operator to buy
    Eric> compatible equipment.  Did I miss something?

    Eric> -- Eric Gray

    Eric> You wrote:

    >> There is no such mechanism. The assumption is that the
    >> network operator knows how to configure their equipment
    >> and they know their network.
    >> 
    >> Bora
    >> 
    >> >>>>> "James" == James Huang <James_Huang@Mitel.COM>
    >> writes:
    >> 
    James> From: James Huang@MITEL on 01/24/2001 12:03 PM PST Hi
    James> Bora: Maybe I did not express my concern clear
    James> enough.  As you said, the LSP setup will fail when
    James> the egress LSR assigns an Implicit NULL label to the
    James> penultimate hop, if the penultinate hop does not
    James> support PHP.  So there should be some negotiation
    James> mechanism in LDP or RSVP/TE such that an egress
    James> router will know not to assign an Implicit NULL label
    James> to a penultimate hop that does not support PHP.  But
    James> I can not find such mechanism in the documents.
    >>
    James> -- James Huang
    >>
    James> Bora Akyol <akyol@pluris.com> on 01/23/2001 08:24:45
    James> PM
    >>
    James> To: James Huang/USA/Mitel@Mitel cc: mpls@UU.NET
    >>
    James> Subject: PHP negotiation
    >>
    James> You should also read the label encapsulation
    James> RFC. What happens is that the egress LSR assigns an
    James> (...) NULL label (I think it should be Implicit Null)
    James> to the penultimate hop, if penultimate hop does not
    James> support this, then LSP setup should fail.
    >>
    James> There was a LOOONG discussion on this sometime last
    James> year.
    >>
    James> Some people think this stuff is really clear. I think
    James> that it is in about three different RFCs, and someone
    James> needs to write a BCP that explains common usage and
    James> tricks that network operators that use MPLS should
    James> use.
    >>
    James> BTW, this question comes up about once a month on the
    James> list, maybe we should have an MPLS FAQ.
    >>
    James> Bora
    >>  >>>>> "James" == James Huang <James_Huang@Mitel.COM>
    >> writes:
    >> 
    James> Hi all, The following paragraph is from Section
    James> 3.16. (Penultimate Hop Popping) of RFC3031.
    >>
    James> "Initial label distribution protocol negotiations
    James> MUST allow each LSR to determine whether its
    James> neighboring LSRS are capable of popping the label
    James> stack.  A LSR MUST NOT request a label distribution
    James> peer to pop the label stack unless it is capable of
    James> doing so."
    >>
    James> However, I can not find any mechanism in LDP/CR-LDP
    James> or RSVP-TE to accomplish this PHP negotiation.
    >>
    James> Am I missing something here?
    >>
    James> -- James Huang