Re: UBR setting for Verizon West ATM-based 3.0/768 speed

On Tue, 5 Apr 2005, Worldlink DSL Department wrote:

> Hello all,
>
> What are other people using for the UBR setting on the VC's for the 3.0/768
> speed of Verizon's? I've found that if my settings don't match Verizon's
> pretty closely, things slow to a crawl. And I'm not talking like they slow
> to the slower of the two speed definitions. If a Verizon DSL customer has a
> 768/128 line, and I set their VC for UBR 1664, it works at less than modem
> speeds.

(Downstream rate in kbps) * 53 / 48.

3000 * 53 / 48 = 3312
>
> Anyhow, early, on, Verizon gave me the following UBR values to plug into my
> router. For example, here are a few of the VC classes:
>
> vc-class atm 768-128-fr
> ubr 954

[snippage]

> I was actually given these values for UBR by Verizon way back when. And
> again, if I have it set just a little bit off, it all but destroy's the
> speed. I've asked SEVERAL people there what the UBR value should be for
> 3.0/768, and gotten no good answer. Currently I'm using UBR 3360, but
> that's just an educated guess. What are others using?

That's a little aggressive, more like 864k. If it works consistently with
latge packets and high data rates, fine. They may be giving you some extra
cushion. If they were to police traffic to 768k, it will break things
rather badly as cells are discarded in the middle of packets. This shows
up as CRC errors incrementing, and you'll be able to ping (small packet)
but not surf.

We use:
1.5M = ubr 1656
768k = ubr 848
384k = ubr 424

> I was actually given these values for UBR by Verizon way back when. And
> again, if I have it set just a little bit off, it all but destroy's the
> speed. I've asked SEVERAL people there what the UBR value should be for
> 3.0/768, and gotten no good answer. Currently I'm using UBR 3360, but
> that's just an educated guess. What are others using?

If you go a bit on the low side, you'll slightly reduce maximum speed but
be assured of avoiding the cell police. If you err on the high side
things break badly.

> I'm also double-checking this value because I've currently got a really
> wacko support issue open with a customer. They recently switched from a
> Fujitsu platform to a Westell platform, and upped their speed from 1.5/384
> to 3.0/768. Since they did that, if the customer send a bunch of SMTP
> traffic, his connection dies, and only a reboot of the modem fixes it.
>
> Other outbound traffic like heavy FTP transfers is NOT triggering it. It
> started before the speed change, but AFTER the change to the Westell
> platform. We've tried two modems and power supplies. I'm stumped and
> grasping for straws...

That's something else. Could be a good feature if we can igure a way
to apply it to only spammers. Is the modem configured for bridge, or
is it doing NAT? Can you OAM ping the modem when this happens?

--
Jay Hennigan - CCIE #7880 - Network Administration - jay@west.net
WestNet:  Connecting you to the planet.  805 884-6323      WB6RDV
NetLojix Communications, Inc.  -  http://www.netlojix.com/
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