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Editorial Team
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Asked: 2026-06-15T14:48:20+00:00

I’ve been doing some work with C# Networking using UDP. I’m getting on fine

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I’ve been doing some work with C# Networking using UDP. I’m getting on fine but need the answer to a couple of fundamental questions I’m having problems testing:

  • Currently I’m sending data in a ~16000 byte datagrams, which according to wireshark is getting split into several 1500 byte packets (because of max packet size limits) and then reassembled at the other end.

Am I right in understanding the datagram will be received complete at the other end OR not at all. IE it’s an all or nothing thing. There is no chance of ending up with a fragmented datagram due to packet loss?

Therefore, I only need to ACK per datagram, rather than ensuring my datagrams are < 1500 bytes and ACK each one?

I’ve looked in a lot of places but there seems to be a lot of confusion between the differences between datagrams and the underlying packets…

Thanks for you help!

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  1. Editorial Team

    There is no chance of ending up with a fragmented datagram due to packet loss?

    I believe that’s true: that fragmentation and fragment reassembly is handled by the protocol layer below UDP, i.e. that it’s handled by the "IP" layer, which will error if it fails to reassemble the packet-fragments into a datagram (for example, search for "fragment" in RFC 792).

    http://www.pcvr.nl/tcpip/udp_user.htm#11_5 says,

    "The IP layer at the destination performs the reassembly. The goal is to make fragmentation and reassembly transparent to the transport layer (TCP and UDP), which it is, except for possible performance degradation."

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