![]() This is based on a very practical observation that a typical Ethernet MTU is 1500 then, allowing for various encapsulations (such as those in PPPoE etc.) and header sizes, we’ll have around 1400 bytes left for our UDP payload.Ĭlose results will be obtained if we take IPv6 minimum MTU of 1280 bytes as a baseline (which will lead us to around-1200 bytes for our UDP payload). Moderate school says that we should limit ourselves to UDP payload sizes of around 1400-something. MTU maximum transmission unit (MTU) of a communications protocol of a layer is the size (in bytes or octets) of the largest protocol data unit that the layer can pass onwards - Wikipedia -Conservative school of thought with regards to UDP datagram size says that we need to fit the whole packet into 576 bytes (which is often considered minimum practical MTU for the Internet 3), which effectively means that we should limit UDP payload to 512 bytes or so (number 548=576-20-8 is a bit too optimistic due to IPv4 header options). For answering the question “what maximum size of UDP datagram is acceptable for the public Internet”, there are several different schools of thought. On the flip side of it, you DO need to care about maximum datagram size. With UDP (unlike TCP) you do have control over the datagrams/packets which you’re sending. If making parallels with programming languages, you may think of UDP as of an analog of good old C: you can do pretty much everything, but it is not because the language helps you – it is rather because it doesn’t stand in the way □. Just to give you some feeling about “how on-your-own you are with UDP”: for UDP, even checksum is optional. With UDP, you don’t have any built-in reliability (though you can implement it yourself), no flow control (though you can implement it yourself), and so on, and so forth. In other words, you have full control but need to do everything yourself. ![]() “you may think of UDP as of an analog of good old C: you can do pretty much everything, but it is not because the language helps you – it is rather because it doesn’t stand in the way □It means that working with UDP is logically very much the same as working with IP directly. More importantly, for UDP there is one-to-one correspondence of UDP datagrams with IP packets. UDP Payload (see discussion about sizes below) Typical UDP datagram has the following structure: IP Header (20-60 bytes for IPv4, 40 bytes + Extension Headers for IPv6) ]Īs it was mentioned above, UDP is all about datagrams 1, and UDP datagram sits right on top of IP packet. To navigate through the book, you may want to use Development&Deployment of MOG: Table of Contents.]] All the content published during Beta Testing, is subject to change before the book is published. Beta-testing is intended to improve the quality of the book, and provides free e-copy of the “release” book to those who help with improving for further details see “ Book Beta Testing“. ![]() [[ This is Chapter 13(b) from “beta” Volume IV of the upcoming book “Development&Deployment of Multiplayer Online Games”, which is currently being beta-tested.
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