UDP retransmissions - TCP-IP

This is a discussion on UDP retransmissions - TCP-IP ; Hi All, Is it possible to have UDP retransmissions? I didn't think UDP had the ability to retransmit lost packets and hence it was fast as opposed to TCP. Can the application layer protocol used on top of UDP create ...

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Thread: UDP retransmissions

  1. UDP retransmissions

    Hi All,

    Is it possible to have UDP retransmissions? I didn't think UDP had the
    ability to retransmit lost packets and hence it was fast as opposed to
    TCP. Can the application layer protocol used on top of UDP create this
    sort of functionality? If so is there a way to find out why the
    retransmissions are occuring on a segment. Thx


  2. Re: UDP retransmissions

    "newbie123" wrote in news:1156801618.747080.28170
    @m79g2000cwm.googlegroups.com:

    > Hi All,
    >
    > Is it possible to have UDP retransmissions? I didn't think UDP had the
    > ability to retransmit lost packets and hence it was fast as opposed to
    > TCP.


    That's correct - UDP does not do retransmissions; TCP does.

    > Can the application layer protocol used on top of UDP create this
    > sort of functionality?


    Yes, you can create an application layer protocol which could do
    retransmissions based upon a handshaking mechanism.

    > If so is there a way to find out why the
    > retransmissions are occuring on a segment. Thx
    >
    >


    Offhand, it sounds probable that your application is producing spurious
    retransmissions. You might want to revisit your application code.


  3. Re: UDP retransmissions

    newbie123 wrote:
    > Is it possible to have UDP retransmissions? I didn't think UDP had the
    > ability to retransmit lost packets and hence it was fast as opposed to
    > TCP. Can the application layer protocol used on top of UDP create this
    > sort of functionality? If so is there a way to find out why the
    > retransmissions are occuring on a segment. Thx


    Sure, even simple tftp can do error recovery (block by block, but it
    can do it). UDP has no concept of error recovery, but the application
    can do it for you. As to why something is being retransmitted (tcp or
    application based), you'll need to investigate further. It can be a
    simple packet lost due to errors on the WAN, too much congestion,
    buffer starvation, etc etc etc.

    --

    hsb


    "Somehow I imagined this experience would be more rewarding" Calvin
    **************************ROT13 MY ADDRESS*************************
    Due to the volume of email that I receive, I may not be able to
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  4. Re: UDP retransmissions

    google -> rudp
    actually; now i am implementing one (mine, my rules ...
    i am considering to make it open source...

    newbie123 wrote:
    > Hi All,
    >
    > Is it possible to have UDP retransmissions? I didn't think UDP had the
    > ability to retransmit lost packets and hence it was fast as opposed to
    > TCP. Can the application layer protocol used on top of UDP create this
    > sort of functionality? If so is there a way to find out why the
    > retransmissions are occuring on a segment. Thx



  5. Re: UDP retransmissions


    newbie123 wrote:

    > Is it possible to have UDP retransmissions? I didn't think UDP had the
    > ability to retransmit lost packets and hence it was fast as opposed to
    > TCP. Can the application layer protocol used on top of UDP create this
    > sort of functionality? If so is there a way to find out why the
    > retransmissions are occuring on a segment. Thx


    It's not clear exactly what you mean by retransmissions, but if you are
    receiving the same datagram twice, it's possible that it's a duplicate.
    UDP does not guarantee that a datagram will not be duplicated in
    transit. (Though it is quite rare in practice.)

    DS


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