[c-nsp] [nsp] NxT1 MLPPP

[Oliver Boehmer (oboehmer)]

> The facts in this scenario is as follows,
> 
> 1.	We'll have a 7206 Router. NPE-400 based.
> 2.	PA-MC-4T1 installed with 3 T1 connections to a single ISP.
> 3.	NO Routing protocols going over these links
> 4.	This is for an Educational institution that will be utilizing
> these links to provide streaming video from various places on the net
> 5.	We have decided after weighing all options to go with MLPPP
> 
> Questions that I'd appreciate being addressed. Thanks in advance.
> 
> 1.	From my understanding, MLPPP is CEF switched now, does this mean
> that the commands ip load-sharing per-destination and ip load-sharing
> per-packet are able to be used even with a SINGLE MLPPP bundle? (From
> David Curran's account below it would be best to run with per packet.)
> David, (or anyone else) if you have a chance could you answer if this
> was in regard to a single MLPPP bundle or load balancing over more
> than one bundle. This may be a moot point if the ISP is currently
> load-sharing per destination and are reluctant to change on their end.

Well, any CEF load-sharing only applies if you have mutiple L3 paths to
your neighbor. If you use MLPPP to bundle your T1's, you will only have
one Layer3 Interface, so any CEF load-sharing commands won't do any
difference. MLPPP will do the load-sharing across the physical member
links making sure pkts are delivered in order.

> 2.	Would link fragmentation and interleaving be appropriate in this
> situation? Keeping in mind that we'll want streamed Video/Audio to be
> able to get across this link fast. ( this function is documented here:
>
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/
> fqos_c/fqcprt6/qcflfi.htm#wp1003889 )

LFI is not recommended in this environment. Serialization delay for a
1500 byte fragment over a T1 link is about 8ms, which is usually well
within bounds for Voice.. And if you enable fragmentation over the
Multilink bundle (enabled by default), you would probably never see such
a large fragment to be sent over the link since it is fragmented and
sent over all three of them. See
http://www.cisco.com/warp/public/788/voice-qos/voip-mlppp.html#link_frag
for more details.

	oli