[c-nsp] MTU at Gb/sec transit and higher

[Arie Vayner (avayner)]

I am not completely sure what you would find on exchange points, but for
pure Internet service I would assume that 1500 (or ~1500) is still the
most common MTU mostly because of the support on lower end CPEs and lots
of legacy hardware/configuration.

The only real exception I see around is when carriers build modern
MetroE and MPLS/VPN cores. They are all being deployed today with higher
MTU values as close as possible to the ~9000 Byte MTU value. This is
done as there is demand for this kind of services especially from
enterprises buying circuits and VPNs to interconnect their DCs etc.

Most of the modern devices (or newer modules for older systems) support
something close to ~9000 Byte MTUs.

Arie

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Lawrence E.
Bakst
Sent: Thursday, March 18, 2010 06:39
To: cisco-nsp at puck.nether.net
Cc: leb at iridescent.org
Subject: [c-nsp] MTU at Gb/sec transit and higher

I apologize if this is somewhat off-topic. I searched for this and found
almost no information. I found this, but it's almost 10 years old and it
seems like he gave up:
http://staff.psc.edu/mathis/MTU/

1. If I purchase GbE transit from a provider what size is the MTU likely
to be? Is it still ~1500 bytes?

2. At any point closer to the core of the "internet" does the MTU step
up from 1500 bytes to some larger value and are jumbo frames utilized?
Or worse does the  MTU step down from 1500 bytes?

3. What size MTU is used at (major) peering points?

I am expecting the answers to all the above to be "it's all ~1500 bytes"
but I want to confirm that.

4. Does most of the current Cisco gear used by NSPs support jumbo frame
on GbE and faster interfaces?

If anyone has any insight or comments I'd be happy to get them either on
or off list. If off list please use the email below.

Best,

leb 
-- 
leb at iridescent.org

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