Difference between revisions of "UDP"

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(Major revision to UDP)
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Usergram Data Protocol, an unreliable and unstreamed transmission packet format over TCP/IP networks.  To describe what UDP is, it's easier to explain in terms of what it isn't -- and that's best explained by describing the guarantee that its counterpart, Transmission Control Protocol, provides.  In TCP, each packet of data is given the following guarantee: if it arrives, it will reliably arrive in order (no data will be lost from the stream before it, and no data from the stream which was sent after it will be delivered to the application before it).
Usergram Data Protocol
 
[http://www.faqs.org/rfcs/rfc768.html UDP] is the unreliable cousin of [http://www.faqs.org/rfcs/rfc793.html TCP] on TCP/IP networks.   
 
==UDP Summary==
UDP does not guarantee delivery, or reliability, and because of this it is ideal for services such as video streaming.  For a service such as video streaming, reliability and guarantee of delivery are not the highest concern; instead it is only important that the video is transmitted from the server to ''all'' the clients, without a care for 'expired' packets.  What seperates the two protocols is that TCP requires the client to inform the server that it received all of the packets sent, and also to re-request packets that arrived corrupted or did not arrive at all.  As a result of this there is additional overhead for TCP when comparing TCP to UDP, and it is this lack of additional overhead (combined with other factors) that makes UDP superior to TCP in streaming scenarios. 
 
===DNS===
UDP also drives DNS communication, translating Internet addresses such as http://'''www.secondlife.com''' into IP addresses computers understand, such as http://'''66.150.244.168'''/ .
 
 
==Second Life and UDP==
With the exception of textures, Linden Lab's Second Life uses UDP as it's primary mode of communication with it's servers.  Little information exists about Second Life's usage of UDP, hopefully with more information soon to come.
 


In UDP, no guarantee that it will be delivered at all, in any given order, or in any given timeframe is provided by the network layer.  This may sound like a negative, and for many purposes it is -- but it also uses a little less than one half of the packets used by TCP.  This lower number of packets makes it the only useful choice in situations which are time-sensitive, including streaming audio and video.  This lower number of packets also makes it suitable for situations where not every packet must arrive perfectly intact in order, including DNS (name to address resolution on the Internet) and Second Life.


For more information on TCP and UDP, please see their respective definition documents.  (Note that these protocols use the services provided by the IP layer underneath them, be it IPv4 or IPv6.)
For more information on TCP and UDP, please see their respective definition documents.  (Note that these protocols use the services provided by the IP layer underneath them, be it IPv4 or IPv6.)

Revision as of 02:03, 23 June 2007

Usergram Data Protocol

UDP is the unreliable cousin of TCP on TCP/IP networks.

UDP Summary

UDP does not guarantee delivery, or reliability, and because of this it is ideal for services such as video streaming. For a service such as video streaming, reliability and guarantee of delivery are not the highest concern; instead it is only important that the video is transmitted from the server to all the clients, without a care for 'expired' packets. What seperates the two protocols is that TCP requires the client to inform the server that it received all of the packets sent, and also to re-request packets that arrived corrupted or did not arrive at all. As a result of this there is additional overhead for TCP when comparing TCP to UDP, and it is this lack of additional overhead (combined with other factors) that makes UDP superior to TCP in streaming scenarios.

DNS

UDP also drives DNS communication, translating Internet addresses such as http://www.secondlife.com into IP addresses computers understand, such as http://66.150.244.168/ .


Second Life and UDP

With the exception of textures, Linden Lab's Second Life uses UDP as it's primary mode of communication with it's servers. Little information exists about Second Life's usage of UDP, hopefully with more information soon to come.


For more information on TCP and UDP, please see their respective definition documents. (Note that these protocols use the services provided by the IP layer underneath them, be it IPv4 or IPv6.)

User Datagram Protocol

Transmission Control Protocol

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