Ethernet NAPs (was Re: Miami ...)

Wed Aug 22 19:56:37 UTC 2001

At 15:06 22/08/01, Daniel Golding wrote:
>Currently, it is an Ethernet NAP, similar to PAIX. I doubt you'll see 
>any more ATM NAPs. Basically, you can pull whatever kind of ckt you 
>want into the facility, then terminate it on your own router. Then 
>you run Ethernet to the switching fabric.

        I agree that ATM NAPs are probably on their way out over time.
GigE Ethernet switches are a whole lot cheaper than ATM switches
and are currently scaling much better than ATM switches.
For example, at least one vendor has a GigE switch that has
256 GB of non-blocking switch fabric and can support up to
192 GigE ports or 1440 10/100baseT ports (or some mixture in
between if preferable).  10 GigE products will likely be available
from multiple vendors by end of this calendar year.

        Folks building Ethernet based NAPs might want to consider 
building them with Ethernet equipment that can support non-IEEE-standard
large frame sizes (e.g. 4K is popular with POS-oriented folks;
9K is popular with folks who run server farms) in the interest 
of side-stepping PMTU-Discovery/IP-Fragmentation issues.  Many
GigE or 10 GigE vendors support the 9K MTU on switched Ethernet
ports (jumbo frames generally won't work if the link is half-duplex, 
btw, because of adverse interactions with CSMA/CD timers).

        Similarly, folks connecting at such NAPs might want to
find out if large non-IEEE-standard frames are supported in the
switch fabric.  If yes, those folks might want to think about
whether they want to deploy IP routers that can support such
large frames (e.g. Juniper's current GigE interface reportedly
supports 9K frames if configured that way) for the same reasons.

        Your mileage might vary, this is just something to mull over.
Any flames to /dev/null please.

Ran
rja at inet.org