Extra latency at ATT exchange for UVerse

Paul WALL pauldotwall at gmail.com
Thu Nov 11 20:04:06 CST 2010

On Thu, Nov 11, 2010 at 2:11 PM, Srikanth Sundaresan <srknth.s at gmail.com> wrote:
> Here are the traceroutes (without the first 3 hops)

The U-Verse infrastructure is a bit of a mess when you get closer to
the end subscriber. There will be a few more L3 hops as your packets
egress the metro area towards what was the legacy BellSouth IP network

The first few hops will be the U-Verse "LIO" (Intermediate Office),
which serves as your first layer 3 hop. After, you'll end up in the
U-Verse VHO (Video Hub Office), which is where all the IPTV gear and
U-Verse IP aggregation occurs. You'll hop through a few more devices
within the VHO until you end up on a legacy BellSouth IP backbone
device (AS6389). From there you'll then route to the AT&T CBB (AS7018)
and onto a AT&T MIS (IP transit) router where Google is a customer.

The legacy BellSouth ADSL product doesn't have to go through as many
hoops to reach an actual IP network. One thing to keep in mind is that
the BellSouth U-Verse customers are numbered out of classic SBC
(AS7132) IP address space, which is advertised to the Internet
originating from AS7132. I wonder if some of that return traffic is
routing into AS7132 or AS7018 at a sub-optimal location rather than
directly back to that MIS connection in Atlanta.

Another note regarding the latency, you can probably attribute some
that to the Alcatel DSLAM you terminate on. They're known for setting
a static interleaving value on all customers, regardless of line
conditions. Customers should really reach out and ask for this to be a
configurable option, just like AT&T offered it for its legacy ADSL
broadband subscribers.

Drive Slow, but not due to Alcatel interleaving
Paul Wall

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