[c-nsp] Cisco MultiLink PPP

[Andre Beck]

Hi,

On Fri, Mar 25, 2005 at 11:40:00PM -0800, Lawrence Wong wrote:
> Woops, looks like I have to give up the trusty old
> 2514 that has been working fine for the past 9 years.
> :(

If you're going to build MP bundles on E1, surely.
 
> Any idea how many E1 MLPPP is supported on the 2621? I

The 2621 is quasi-identical to the 2620. I have first hand experience
with trying to upgrade a 2xE1 MP bundle on such box to 3xE1. It did
work in principle, but the CPU load on this box reached peaks beyond
60% when that bundle got fully loaded with traffic. This caused an
unusual amount of RTT jitter and response loss on pings to that router
what finally convinced us to give up the MP and retry with CEF load
sharing per-packet. The box has 15 to 20% less CPU load this way.

However, keep in mind that this was with a late 12.1, not really a
recent IOS. As already pointed out by others here, newer IOSs can do
MP CEF switched, so the numbers might be better there. This is something
I'd actually want to lab test soon as I'd really like to get back to MP
there if possible.

> don't think I will grow beyond 2 channels but if I

Two channels is working great. You get all the advantage of MP including
perfect load balancing, guaranteed no reordering and load balancing of
IP multicast (something I can't stop repeating you *don't* ever get with
CEF per-packet).

> need to replace the 2514, it would be on the safe side
> to cater for 3-4 E1 MLPPP just in case (would a 3620
> be good enough?) .

Forget 3620. Rather consider the newer 26xx models or even 18xx/28xx. They
aren't even really expensive compared to former gear. If ever going 3k
series, rather consider 37xx or 38xx, with exception for the 3660.
 
> I am thinking of using the VWIC-2MFT-G703 module on
> the 2621 to connect the individual links instead of
> getting external v.35 convertors.

Do you *really* need unframed E1? It's the only additional virtue of the
-G703 over the -E1 and surely not worth the significant price step except
you must have it. You can even stamp a G.704 frame onto a line that is
provided unframed, so the only reason you must have unframed is when
talking to a remote CSU/DSU that is limited to unframed either by design
or by not beeing under your control.

> Anyone has experience with it?

So far only with the -E1. Work like a charm. We've got several 26xx
(including 2620) packed with those VWICs and they are doing great.
For proper MP operation with 2xE1 and CBAC we prefer the 2650 class,
but otherwise a 2620 can well deal with 4 individual E1 interfaces at
full load without a tendency to fall over.

HTH,
Andre.
-- 
                  The _S_anta _C_laus _O_peration
  or "how to turn a complete illusion into a neverending money source"

-> Andre Beck    +++ ABP-RIPE +++    IBH Prof. Dr. Horn GmbH, Dresden <-