IGMP or GMRP for multicast management?

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I'm looking at Seifert's "The Switch Book" and I'm a little surprised
that his chapter on multicast talks about GMRP but not at all about
IGMP. I know that the book is a few years old (2000) and technology
moves fast but IGMP dates back to at least 1989 (RFC 1112). Is IGMP
dominant in the market and Seifert missed the boat on this one, or am
I missing something?

Chris

 

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"Chris Nelson" <cnelson@nycap.rr.com> wrote:

> I'm looking at Seifert's "The Switch Book" and I'm a little surprised
> that his chapter on multicast talks about GMRP but not at all about
> IGMP. I know that the book is a few years old (2000) and technology
> moves fast but IGMP dates back to at least 1989 (RFC 1112). Is IGMP
> dominant in the market and Seifert missed the boat on this one, or am
> I missing something?

I'm sure that Rich will provide his first-hand response. From my
perspective, (a) GMRP is the proper layer 2 version of multicast
management, which applies to a layer 2 device like an Ethernet switch,
(b) IGMP/MLD are instead protocols meant to support layer 3 multicast
management, and (c) IGMP snooping was not so popular yet, back then. In
fact, plain old IP multicast was not so popular back then either.

I don't think that today GMRP is all that widely used. But it's still
the only game in town if you're using Ethernet *without* IP layered on
top.

Bert

 

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In article <I807Fx.FGs@news.boeing.com>,
"Albert Manfredi" <albert.e.manfredi@nospam.com> wrote:

> "Chris Nelson" <cnelson@nycap.rr.com> wrote:
>
> > I'm looking at Seifert's "The Switch Book" and I'm a little surprised
> > that his chapter on multicast talks about GMRP but not at all about
> > IGMP. I know that the book is a few years old (2000) and technology
> > moves fast but IGMP dates back to at least 1989 (RFC 1112). Is IGMP
> > dominant in the market and Seifert missed the boat on this one, or am
> > I missing something?
>
> I'm sure that Rich will provide his first-hand response. From my
> perspective, (a) GMRP is the proper layer 2 version of multicast
> management, which applies to a layer 2 device like an Ethernet switch,
> (b) IGMP/MLD are instead protocols meant to support layer 3 multicast
> management, and (c) IGMP snooping was not so popular yet, back then. In
> fact, plain old IP multicast was not so popular back then either.
>
> I don't think that today GMRP is all that widely used. But it's still
> the only game in town if you're using Ethernet *without* IP layered on
> top.
>

Exactly. I "punted" on IGMP because it presumes an IP stack, which is
not required either in switches or end stations. If and when I ever do
"The Layer-3 Switch Book" (or more aptly, "The Router Book"), I will
surely cover this topic.


--
Rich Seifert Networks and Communications Consulting
21885 Bear Creek Way
(408) 395-5700 Los Gatos, CA 95033
(408) 228-0803 FAX

Send replies to: usenet at richseifert dot com

 

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Archived from groups: comp.dcom.lans.ethernet (More info?)

Chris Nelson wrote:
> I'm looking at Seifert's "The Switch Book" and I'm a little surprised
> that his chapter on multicast talks about GMRP but not at all about
> IGMP. I know that the book is a few years old (2000) and technology
> moves fast but IGMP dates back to at least 1989 (RFC 1112). Is IGMP
> dominant in the market and Seifert missed the boat on this one, or am
> I missing something?

It is important to distinguish between IGMP and IGMP snooping, the
latter being what Layer 2 switches do. IGMP is router protocol.
People found that if they got their switches to "snoop" on
IGMP messages (i.e. pick up ever message) then you would know which
switch ports have receivers interested in receiving multicast traffic
for a certain IP address (and therefore, a certain MAC address), and
the flow of that traffic can be restricted to a subset of the
spanning tree that is interested in receiving it. I don't believe
that there exists a standard for IGMP snooping. IGMP snooping was
popular even back in the day when they created the GMRP standard,
but at the time, there were other protocols (non-IP) that were
thought could benefit from GMRP.

Since then, however, IP has become the dominant protocol, and
the need for GMRP is questionable. Most mid to high-end L2
switches provide IGMP snooping.

Anoop