[mpls] LDP Multicast to WG Document

Salability is a important issue for multicast. The load will be very heavy to maintain

large number of multicast route entry in control plane. If used in MVPN environment

mpls p2mp will face to the requirement to support more and more VPNs.

And I also think reconvergence is a tougher problem for multicast (PIM or other)

than unicast. Currently unicast routing protocols already have many techniques

to reduce the impact of route change, but multicast depends on unicast

and reconstructing forwarding tree needs more time. Further more, packet

loss caused by reconvergence have more impact on multicast traffic

than unicast traffic because of less of retransmitting mechanism for multicast

and the property of multicast application.

MPLS have bring a lot of benefit to unicast forwarding such as FRR and TE,

I think it is good if mpls solution can do something for multicast in this

aspect.

So I think more consideration at design stage on these aspects will show

its advantage.

Thanks.

Have a good day!

----- Original Message -----
From: "Thomas Morin" <thomas.morin@rd.francetelecom.com>
To: "IJsbrand Wijnands" <ice@cisco.com>
Cc: <mpls@ietf.org>
Sent: Saturday, February 11, 2006 5:52 AM
Subject: Re: [mpls] LDP Multicast to WG Document

>I believe liushuying was perhaps more worried about control plane load,
> at reconvergence, for a high number of P2MP tunnels.
> Though the concern is valid, I would say that things should roughly be
> comparable to what happens with PIM. But I think it is fair to say that
> this aspect requires consideration in the solution design.
>
> Cheers,
>
> -Thomas
>
> IJsbrand Wijnands:
>>
>> We have some ideas on how to minimize the traffic loss during
>> switchover, but I'm not sure if we can prevent it without some kind of
>> FRR mechanism.
>>
>> Thx,
>>
>> Ice.
>>
>> BTW, I support make this a WG document.
>>
>>
>> On Feb 9, 2006, at 7:56 AM, liushuying wrote:
>>
>> > Hi folks,
>> >     I support this draft becoming a WG document.
>> >
>> >     However,i am about to ask a question.
>> >
>> >    1) 2.3.2.4. Upstream LSR change
>> >
>> >    If, for a given node Z participating in a P2MP LSP <X, Y>, the
>> >    upstream LSR changes, say from U to U', then Z MUST update its
>> >    forwarding state by deleting the state for label L, allocating a new
>> >    label, L', for <X,Y>, and installing the forwarding state for L'.
>> > In
>> >    addition Z MUST send a Label Map <X, Y, L'> to U' and send a Label
>> >    Withdraw <X, Y, L> to U.
>> >
>> >   The question:
>> >   When a large quantity of P2MP LSPs exists in MPLS networks,
>> >   if unicast routing information changes, there may be many LSRs
>> >   whose upstream LSRs have changed in every P2MP LSP, each of them
>> > sends a Label Withdraw message
>> >   to its old upstream LSR and a Label Map message to its new upstream
>> > LSR at the same time,
>> >   so the load of every LSR will enhance sharply and last for a long
>> > time.
>> >   As a result, the time of traffic disruption in every P2MP LSP will
>> > last for a long time,
>> >   and so many packets will be lost.
>> >
>> >   Thanks
>> >   Shuying Liu
>> >
>> >
>> > ----- Original Message -----
>> >> Date: Mon, 06 Feb 2006 07:50:51 -0500
>> >> From: George Swallow <swallow@cisco.com>
>> >> Subject: [mpls] LDP Multicast to WG Document
>> >> To: mpls@ietf.org
>> >> Message-ID: <20060206125051.3E3BD17B472@SwallowPB.local">20060206125051.3E3BD17B472@SwallowPB.local>
>> >>
>> >> It has been requested that
>> >>
>> >> Label Distribution Protocol Extensions for Point-to-Multipoint and
>> >>             Multipoint-to-Multipoint Label Switched Paths
>> >>                 draft-minei-wijnands-mpls-ldp-p2mp-00
>> >>
>> >> become a MPLS WG document.
>> >>
>> >> Please indicate your support or objections by the end of this week.
>> >>
>> >> Thanks,
>> >>
>> >> ...George
>> >>
>> >> ======================================================================
>> >> ==
>> >> George Swallow             Cisco Systems                  (978)
>> >> 936-1398
>> >>                           1414 Massachusetts Avenue
>> >>                           Boxborough, MA 01719
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> ------------------------------
>> >>
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>>
>>
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[mpls] LDP Multicast to WG Document