Subject: Re: I-D Action: draft-ietf-l2vpn-vpls-pim-snooping-02.txt

From: Olivier Dornon <[email-masked]>
Date: Mon, 10 Sep 2012 10:31:16 +0200

This draft describes the procedures for pim snooping and introduces pim 
proxying in a vpls.

Amongst other things, both modes handle Join/Prune messages in a 
different way.  In a nutshell, when running in snooping mode the J/P 
messages remain untouched, while they're consumed and proxied to 
relevant upstream ports on proxy mode.  I refer to the draft for a 
detailed description.

Running in snooping mode has some drawbacks, as J/P messages are just 
flooded, it's not very network efficient and it forces the peers to 
disable join suppression.  To counter this we could only forward the J/P 
messages to relevant upstream ports in snooping mode too, this would 
save on network resources and allow peers to maintain join suppression.

We can imagine there might be objections to this, we know from past 
experiences that some operators are reluctant to process/forward control 
messages instead of just snooping and transparently forward them.
I raised the question during my presentation in Vancouver 
(http://www.ietf.org/proceedings/84/slides/slides-84-l2vpn-1.ppt) but 
didn't get any feedback.

Hence this posting, we'd love to hear some feedback on this, especially 
from operators/service providers.

Thanks,
Olivier.

On 07/16/2012 05:12 PM, [email-masked] wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>   This draft is a work item of the Layer 2 Virtual Private Networks Working Group of the IETF.
>
> 	Title           : PIM Snooping over VPLS
> 	Author(s)       : Olivier Dornon
>                            Jayant Kotalwar
>                            Jeffrey Zhang
>                            Venu Hemige
> 	Filename        : draft-ietf-l2vpn-vpls-pim-snooping-02.txt
> 	Pages           : 39
> 	Date            : 2012-07-16
>
> Abstract:
>     In Virtual Private LAN Service (VPLS), as also in IEEE Bridged
>     Networks, the switches simply flood multicast traffic on all ports in
>     the LAN by default.  IGMP Snooping is commonly deployed to ensure
>     multicast traffic is not forwarded on ports without IGMP receivers.
>     The procedures and recommendations for IGMP Snooping are defined in
>     [IGMP-SNOOP].  But when any protocol other than IGMP is used, the
>     common practice is to simply flood multicast traffic to all ports.
>     PIM-SM, PIM-SSM, PIM-BIDIR are widely deployed routing protocols.
>     PIM Snooping procedures are important to restrict multicast traffic
>     to only the routers interested in receiving such traffic.
>
>     While most of the PIM Snooping procedures defined here also apply to
>     IEEE Bridged Networks, VPLS demands certain special procedures due to
>     the split-horizon rules that require the Provider Edge (PE) devices
>     to co-operate.  This document describes the procedures and
>     recommendations for PIM-Snooping in VPLS to facilitate replication to
>     only those ports behind which there are interested PIM routers and/or
>     IGMP hosts.  This document also describes procedures for PIM Proxy.
>     PIM Proxy is required on PEs for VPLS Multicast to work correctly
>     when Join suppression is enabled in the VPLS.  PIM Proxy also helps
>     scale VPLS Multicast much better than just PIM Snooping.
>
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-l2vpn-vpls-pim-snooping
>
> There's also a htmlized version available at:
> http://tools.ietf.org/html/draft-ietf-l2vpn-vpls-pim-snooping-02
>
> A diff from previous version is available at:
> http://tools.ietf.org/rfcdiff?url2=draft-ietf-l2vpn-vpls-pim-snooping-02
>
>
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
>