""Tim Benner"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Any one running MPPP out there? Specifically on mulitple point-to-point T-1 > interfaces? I am doing some research on using MPPP to bundle mulitple T-1s > together to look like 1 fat pipe. I have some documentation that states > there > is 12.5% overhead. I was wondering if anyone else has played around with > it.
MPPP can increase the encapsulation overhead, but it does so only when it fragments a packet. The standard PPP encapsulation is 48bits (32bit header + 16bit FCS), with MPPP fragments an additional fragment header (16 or 32bit) is added. The amount that this increases the overhead compared to standard PPP would depend on your average packet size. I would imagine that it's going to be considerably less than 12.5% though. A more relevant thing to consider is the way that IOS deals with the packets. With MPPP the router first looks up the packet's destination in the route-cache, hands the packet to the virtual interface, the virtual interface code then decides whether to fragment the packet and passes the fragments to the physical interface(s) for encapsulation. If you use equal cost load balancing, the packet is passed directly to the physical interface without virtual interface processing. Also, traditionally cisco's HDLC implementation was more efficient than the PPP implementation, but take that with a pinch of salt, as software changes, and IOS PPP may have improved by now. Here's a sample config from CCO doing exactly what you're talking about. Personally I'd probably go with equal cost load balancing over HDLC encapsulation if it's an all cisco network though. It makes the config simpler, and I'm a big believer in Occam's Razor :) http://www.cisco.com/warp/public/131/7.html -- Russell Heilling http://www.ccie.org.uk/ Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54699&t=54691 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
