moving packets, smaller or bigger

carl_townshend · ‎01-16-2009

Hi all, when moving packets on a network, what is best, lots of small packets, or less bigger packets ?

John Blakley · ‎01-16-2009

Your main concern should be if packets are being fragmented too much. Your mtu should be set to allow throughput without too much fragmentation. Default mtu is 1500, and is generally optimal for most networks.

HTH,

John

HTH, John *** Please rate all useful posts ***

Joseph W. Doherty · ‎01-16-2009

Efficiency improves (less overhead vs. payload) as packet size increases. Also, network devices, such as many software based routers, can process a certain number of packets per second which, although decreases as packet size increases, can forward more "volume" as packet size increases. (These are reasons why later Ethernet devices often support some type of "jumbo" packets.)

carl_townshend · ‎01-16-2009

what is the reasons for this?

Joseph W. Doherty · ‎01-17-2009

Reasons for what?

carl_townshend · ‎01-17-2009

why is it more efficient to send bigger packets ?

Joseph W. Doherty · ‎01-17-2009

L2 and L3 have overhead per frame and packet. For instance, a typical Ethernet non-VLAN tagged frame has 38 bytes of overhead (interfame GAP, preamble, src/dest MAC addresses, CRC, etc.) IP has 20 bytes of overhead, mostly IP addresses. TCP usually adds another 20 bytes of overhead (or more with some TCP options). So to send 1 character/byte in a single TCP packet on Ethernet, you're looking at something like 78 bytes, or more, on the wire to pass your 1 byte of data. Rather poor efficiency. As the number of data payload bytes is increased, since overhead stays the same, efficiency improves.