Subject: Re: re-chartering L2TP

From: Danny McPherson <[email-masked]>
Date: Thu, 18 Jan 2001 13:08:21 -0700

> Yes, that's something they would look into.  (I don't think that's the
> solution, though, since CES includes special cases to forward with
> partly empty cells in order to minimize delay.  If 47 bytes is
> sometimes too many, it doesn't bode well for larger amortizations.)

However, if implementation could realize things such as, for
example, idle frame suppression or AIS suppression, etc.., 
there could be great bandwidth savings. 

Not to mention it's effecting on grooming in carrier networks,
and circuit provisioning times, etc...

-danny

---

From: James Carlson <[email-masked]>
Date: Thu, 18 Jan 2001 15:31:14 -0500 (EST)

> there could be great bandwidth savings. 

If you're getting a lot of benefit out of AIS suppression, you've got
some mighty unhappy users.  ;-}

That being said, I mostly agree with your points.  It's a complex
analysis to determine if it works.  (Having tried the statistical gain
argument with more than one bell-person, I'm not wild about trying it
again.  But, hey, I'm fortunately not in that game at this point.)

(For the specific CES case, I don't know if idle suppression buys
anything.  If it's channelized, any one channel active ruins your
day.  If it's unstructured, I suppose you could *guess* at the
upper level protocol used, but what if you're wrong ... ?  Eh, not my
forte anyway.)

> and circuit provisioning times, etc...

Grooming becomes, I think, a disaster on IP.  Unless you do some
really unnatural things to your IGP, you end up with no grooming
capability at all.  (Ross Callon has said, in what I interpret as a
Fermat's-last-theorem sort of way [proof too large for this tiny
margin], that TE with datagram routing only and no explicit routing is
doable.  Such things are possible, but they make my lesser brain
spin.)

In contrast, MPLS is perfect for TE applications and grooming.  In
fact, it's even better than ATM, since MPLS allows arbitrary label
stacking, but ATM's "labels" (VPI and VCI) are fixed at two deep.  You
can arrange to push labels to represent groomed chucks of traffic and
engineer them as needed across your network.

(Which likely plays into why the carrier's I've talked to are so
unimpressed with statistical gain.)

-- 
James Carlson, Internet Engineering       <[email-masked]>
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