[c-nsp] SPA Module compatibility

Mark Tinka mark.tinka at seacom.mu
Tue Feb 25 04:29:35 EST 2014

On Tuesday, February 25, 2014 12:14:16 AM Gert Doering 

> Indeed.  I deeply distrust "2Mbit/s on ethernet" thingies
> and such, though that stuff seems to work surprisingly
> well today - *better* than some of the "2Mbit via ATM
> VC, with a carrier not being able to tell us which
> shaping values to use, thus losing OAM cells on
> saturated links"...
> (The same goes for 200Mbit on GE links, of course -
> anything where the router doesn't know the actual
> end-to-end speed and would need to either rely on "the
> modem" behaving "properly" in regards to
> queueing/buffering/ policing, or apply hierarchical
> shaping on the router, which will usually be not
> available in the platform you have)

I think, as you know, this is all hardware-dependent, and 
sometimes, software does come into play - and to some 
extent, different vendors may implement things differently.

But by and large, modern routing equipment does policing and 
shaping really well for this to no longer be an issue. 

One of the things providers and customers need to agree on, 
though, is whether policing happens at Layer 2 or Layer 3 
only. I see this quite a lot in NNI agreements.

In our profession, though, IP folk only trust their packet 
network. If the network is being handed off to someone else 
for purposes other than IP Transit, there is a huge 
reluctance to go for anything that is not traveling on DWDM 
or SONET/SDH. Not sure how we fix this since we are the IP 
folk :-).

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