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Altera_Forum's avatar
Altera_Forum
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14 years ago

Maximum UDP packet Size for NIOS-ii

Hello Friend's,

finally i have come out from "no free buffer for rx":).

Just by increasing the UDP packet size from 512 to 1472 bytes.

So if we increase the UDP packet size the number of call "recivefrom"

minimize. and processor have enough time to handel the receive packets.

now can any one tell me what is the maximum limit for udp packet size for

nios-ii, because as i increase the UDP packet size from 1472 to 2048. it stop

receiving the packets.

Regards

kaushal

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    A UDP packet can have a size of up to 64k (including headers), but if the transport interface used under IP doesn't support packets this size, it will either be fragmented or dropped. I think that a most IP stacks just choose to drop them. In order to avoid fragmentation on an Ethernet link, the biggest payload size is 1472 bytes.

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    Thanking you Daixiwen/Socrates,

    i have set the packet size 1472 bytes for further processing.

    as in UDP case fragmented packet increase unreliability because of chance of dropping packet,so fix my packet size 1472.

    Thanx

    Kaushal
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    Most 'real' UDP/IP stacks fragment UDP datagrams that exceed the ethernet (or other network) frame size.

    For instance NFS (over UDP) will typically do 8k transfers as a single UDP packet that gets transferred as 6 back-to-back ethernet frames.