12 messages in net.nether.puck.cisco-nsp[c-nsp] MTU Question on T1
FromSent OnAttachments
Richard J. SearsJan 24, 2005 12:33 pm 
Gert DoeringJan 24, 2005 12:54 pm 
Richard J. SearsJan 24, 2005 1:13 pm 
Gert DoeringJan 24, 2005 1:28 pm 
Joe MaimonJan 24, 2005 1:28 pm 
Jon LewisJan 24, 2005 1:39 pm 
Rodney DunnJan 24, 2005 2:39 pm 
Bill WichersJan 24, 2005 7:46 pm 
Richard J. SearsJan 24, 2005 8:15 pm 
Jon LewisJan 24, 2005 8:18 pm 
Jay HenniganJan 24, 2005 8:27 pm 
Gert DoeringJan 25, 2005 3:08 am 
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Subject:[c-nsp] MTU Question on T1Actions...
From:Rodney Dunn (rod@cisco.com)
Date:Jan 24, 2005 2:39:36 pm
List:net.nether.puck.cisco-nsp

The 75xx dMLPPP implementation does not do any fragmentation without LFI configured.

Even if it did, by my math the best you can get is to ship a 1500 byte packet split in half over the two T1's which is like Gert's math said about 40msec.

You'd have to send 26+ packets to get the full data over and that comes up to over 1 sec in total serialization time assuming infinite processing for reassembly on the endpoints.

Therefore it is impossible to get what you want unless you had some compression that might could get the actual data down.

Rodney

On Mon, Jan 24, 2005 at 07:28:00PM +0100, Gert Doering wrote:

Hi,

On Mon, Jan 24, 2005 at 10:01:45AM -0800, Richard J. Sears wrote:

On the dual T1 issue - correct me if I am wrong please but with ppp multilink interleaving turned on, won't it take that single 40000 byte packet and shove it down one T1 because it came in as a single packet..?

There is no single 40k packet at the router. The sending host is fragmenting the packet to 1500 byte IP fragments, because a 40k packet cannot be sent over Ethernet.

*If* there were a 40k packet, PPP might fragment it and distribute it over the multilink members, but that is a local configuration issue.

gert