Subject: Re: Multicast for dialup cus

From: "Dead Mail" <[email-masked]>
Date: 23 May 1997 15:40:25 U

Mail*Link( SMTP               RE>Multicast for dialup customers?

At 11:24 AM -0700 5/22/97, Richard Williams wrote:
> Does anyone know of any working models or tests for providing multicast to
> dialup customers? Specifically Win95 dialup. What are some of the more
> obvious problems? What equipment is being used? Most importantly why not?
> ANY information is greatly appreciated!

This reminds me of another question I have.  During the multicast tutorial
that I co-taught at Interop a couple weeks ago, the usual question came
up of how someone with a dialup PC at home can connect to the MBone, in
the case where the dialup access router does not itself support IP multicast
forwarding and IGMP across the dialup link.  I gave the two answers I was
aware of:

	(1) Run some flavor of BSD on the PC, plus mrouted, and establish
	    a DVMRP tunnel from the PC to an MBone router somewhere in
	    the Internet.  This doesn't satisfy those who want to run
	    Windows or NT on the PC.  (As far as I know, neither Windows
	    nor NT currently support any flavor of mrouted.)

	(2) Take a second PC and place it between the dialup line and the
	    original PC, e.g., like this:

		PC1 ---<ethernet>--- PC2 ---<dialup>--- AccessRouter

	    Then run Windows or NT on PC1 and run BSD and mrouted on PC2,
	    with a DVMRP tunnel from PC2 to an MBone router somewhere
	    in the Internet, and IGMP and native IP multicast being spoken
	    between PC1 and PC2.

Then someone in the class suggested another mechanism that might work.
Supposedly, Microsoft is pushing a protocol for tunneling PPP over IP
(called LTTP -- layer two tunneling protocol -- or something like that;
with great effort, I will suppress my architect's jerking knee).  I believe
this development is being pursued in the IETF, so other vendors may also
have bought into this LTTP.  So, if all the following statements are true:

	(1) LTTP support is built into Windows and/or NT.

	(2) Windows and/or NT can perform the host part of IGMP over an
	    LTTP tunnel (which it naturally ought to do, but one must not
	    make any assumptions...).

	(3) LTTP is supported by some vendor's multicast-capable router.

	(4) The LTTP-supporting router can perform the router part of IGMP
	    over an LTTP tunnel (which it naturally ought to do, but...).

THEN, it ought to be possible to connect a lone dialup PC into the MBone
via an LTTP tunnel.  So, my question is: are the all of the above statements
true?  If someone can confirm that the first two statements are true, I can
check the veracity of the last two statements for at least one router vendor.
:-)

(If this works, I hope it won't be used as an excuse not to upgrade the
dialup access routers to support native IP multicast.  Tunnels, whether
of the DVMRP flavor or the LTTP flavor, have significant performance and
management costs which are best avoided whenever possible)

Steve

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Date: Thu, 22 May 1997 14:46:46 -0700
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From: Steve Deering <[email-masked]>
Subject: Re: Multicast for dialup customers?
Cc: Richard Williams <[email-masked]>, [email-masked]
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