Date: Fri, 07 Jul 1995 17:51:50 -0700 From: "Amancio Hasty Jr." <hasty@rah.star-gate.com> To: Bill Fenner <fenner@parc.xerox.com> Cc: hackers@freebsd.org Subject: Re: current SOTA in ISDN support? Message-ID: <199507080051.RAA00276@rah.star-gate.com> In-Reply-To: Your message of "Fri, 07 Jul 1995 09:37:58 PDT." <95Jul7.093807pdt.49860@crevenia.parc.xerox.com>
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>>> Bill Fenner said:
> In message <199507070351.UAA00815@rah.star-gate.com> you write:
> >o voice communication with vat point to point since the MBONE is
> > not quite upto ip multicasting yet due to old routers or tcp/ip routing
> > software still being used. And hopefully in the not too distant
> > future teleconferencing.
>
> That's odd, I use the MBONE over my ISDN line almost every day, and I have
> successfully participated in teleconferences over my ISDN line (getting poor
> quality video, but perfect audio).
>
> Bill
>
First of I don't have problems with vat other than the existing problems
with vat but I am going to keep this short. A couple of years ago
while working for Cisco, I had no problems on FreeBSD using vat or nv.
>From and old posting:
> As Bill Fenner pointed out yesterday, host viviane.usl.edu
> (130.70.40.162) appears to be causing the >50% packet loss that
> most people are seeing on the Shuttle video session. It is
> causing the loss by sending an ICMP unreachable packet in
> reponse to every multicast packet put on the 130.70.40 subnet at
> USL. For a few hours yesterday evening, it appears that
> alpha.noc.usl.edu (the mbone tunnel endpoint at USL) was off the
> mbone and the NASA video reception here was perfect (0% loss).
> At around 12:50am, I started to see ICMP unreachables from
> viviane again (sent in response to my session msgs in the
> shuttle audio session) and the NASA video loss rate immediately
> went up to 50%.
So old routers that are in your path may cause problems thats one.
If there is a PIM cloud in your path it may cause problems.
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To: Saku Setala <setala@mits.mdata.fi>
Cc: mbone@ISI.EDU
Subject: Re: Packet duplication on NASA session
In-Reply-To: Your message of Sun, 02 Jul 95 14:09:57 JDT.
Date: Mon, 03 Jul 95 07:44:09 PDT
From: Van Jacobson <van@ee.lbl.gov>
> Currently, my nv reports ~ 200kbps on Nasa session, with up to
> ~ -45% loss.
>
> Pretty strange, huh?
I wish it were unusual. Ever since cisco's PIM got widely
deployed, the number of duplicate packets on the MBone has
skyrocketed & a 45% dup rate is actually lower than normal.
I find that almost all the traffic coming from Europe & the UK
is duplicated at least once.
The duplicates you're seeing are probably due to either
- A PIM cloud hooked to the MBone at two or more topologically
distinct points or
- Someone trying to use a PIM cloud as an MBone transit net.
Neither of these things will work. But, despite numerous pious
claims from cisco that they have told their customers these
things won't work, several major providers & backbone sites keep
trying them. I would guess that the duplicates you're seeing
are happening either in Stockholm or near mae-east in the US
(there are pim routers both places). Someone needs to look at
the traffic going into & coming out of the international links
to localize it better. FYI, I'm not seeing any duplicates on
the NASA session but, of course, there aren't any pim routers
between NASA & my workstation.
- Van
----------------
Amancio
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