ip-protocol

Why does UDP have a length field in the header and TCP does not?

由 て烟熏妆下的殇ゞ 提交于 2020-05-24 10:12:21
问题 Why does UDP have a length field in the header and TCP does not? I am guessing that the length of the segment in TCP is inferred from the IP header but one should be able to do the same for a UDP datagram 回答1: According to TCP/IP Illustrated Volume 1 , the length field is redundant. That's all Stevens says on the matter. I personally believe it was to make the UDP header length (in bits) divisible by 32 :) 回答2: There is a 96 bit pseudo header conceptually prefixed to the TCP header that

Calculate an Internet (aka IP, aka RFC791) checksum in C#

由 感情迁移 提交于 2020-01-23 12:58:57
问题 Interestingly, I can find implementations for the Internet Checksum in almost every language except C#. Does anyone have an implementation to share? Remember, the internet protocol specifies that: "The checksum field is the 16 bit one's complement of the one's complement sum of all 16 bit words in the header. For purposes of computing the checksum, the value of the checksum field is zero." More explanation can be found from Dr. Math. There are some efficiency pointers available, but that's

Calculate an Internet (aka IP, aka RFC791) checksum in C#

由 空扰寡人 提交于 2019-12-06 12:20:38
Interestingly, I can find implementations for the Internet Checksum in almost every language except C#. Does anyone have an implementation to share? Remember, the internet protocol specifies that: "The checksum field is the 16 bit one's complement of the one's complement sum of all 16 bit words in the header. For purposes of computing the checksum, the value of the checksum field is zero." More explanation can be found from Dr. Math . There are some efficiency pointers available, but that's not really a large concern for me at this point. Please include your tests! (Edit: Valid comment
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