fragmantation

[namiky]

We need to fragment the IP packets to transfer it through a low bandwith line. But it is possible to do so if we use IP unnumbered. What is the reason for this? In any way can't we use IP addressing on serial ports while using fragmantation?

[joesantiago]

recommend using mlppp w/interleave to fragment ip over low b/w serial links.

[mschlenger]

You can always decrease the MTU of the interface to fragment.

[jorgeramonramirez]

How can you decrease the MTU, I have one with 1500 bytes, but I want to decrease it, in a 3810 and a 3640 with vofr

[g-malewski]

you don't say what kind of line you are using.

If using Frame relay, you should use FRF.11/12.

see http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120t/120t4/120tvofr/vofr3_4t.htm

If using leased lines, consider creating a multilink interface with the leased line circuit as the sole member. Under multilink interfaces you can configure interleaving.

see

http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/qos_c/qcpart6/qclfi.htm

Greg

[sachon]

I don't recommend using fragmentation for video at all. We found that the reassempbly of packets adds too much latency and jitter to the stream that the resultant video looks poor. You should use a link speed higher that 768k at a minimum to eliminate the need for fragmentation.

[c-everett]

Be careful using MTU as the fragmentation method as there are applications (IBM spring to mind) that don't like it. Also, reducing the MTU means that the packets stay smaller until they hit the destination reducing throughput and increasing bandwidth used.