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:Jon Lewis (jle@lewis.org)
Date:Jan 24, 2005 1:39:08 pm
List:net.nether.puck.cisco-nsp

On Mon, 24 Jan 2005, 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..?

That might depend on whether you have multilink fragmentation enabled...but since that packet is much larger than MTU anyway, it's going to be fragmented and I suspect multilink fragmentation won't matter...its still lots of 1500 byte packets. You've got the gear setup. What are you seeing?

I started doing the math from the other direction before I saw Gert's reply...and to move 40,000 bytes in 50ms, that'd be 800bytes/ms, or 6400 bits/ms, which is 6400000 bits/s (6.4Mbit/s). Since you need to go back and forth, you really need 40,000 bytes in 25ms (assuming no delay in processing/responding), so that's 12.8Mbit/s. Did the vendor say you'd be able to do this with T1s? It looks to me like you'd need a DS3 to meet their specs. Maybe doable with a whole bunch of (like >8) T1s.

BTW...given fast enough links, this is possible. From my workstation, I can ping -s 40000 an IP on our network that's separated from me by 1FE-router-1DS3-router-2DS3-router-1FE-router-1FE-host (several L2 switch hops are omitted). rtt avg was 33ms.