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I hava installed nginx on my localhost, then I copy test.avi to html directory, then i can watch the video by http://localhost/test.avi in browser, i want to know, is the video traffic based on UDP? and any other applications which based UDP ? thanks!

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6 Answers 6

up vote 1 down vote accepted

Firstly i would like to point out that you have not installed a webserver on your "localhost" but rather on your computer as the term "localhost" or 127.0.0.1 merely refers to the current computer on the loopback interface.

Getting to your question, I do not believe that this is a UDP data transfer as ningx would send the file over a HTTP session, which in turn uses TCP.

I would like to point out that UDP is very unreliable as it does not make sure the packets are transmitted in order, There is no verification if all the packets sent have been received and is usually only used to transmit small amounts of information.

Common uses of UDP are for DHCP (Dynamic host configuration protocol), RIP (Routing information protocol), SNMP (Simple network management protocol) and DNS (Domain name service).

As you can see these protocols do not usually transmit a lot of information i.e. a DNS request:

Dig rayquang.com:

; <<>> DiG 9.7.1-P2 <<>> rayquang.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 41762 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION: ;rayquang.com. IN A

;; ANSWER SECTION: rayquang.com. 1531 IN A 220.255.220.72

;; Query time: 17 msec ;; SERVER: 8.8.8.8#53(8.8.8.8) ;; WHEN: Thu Dec 30 21:23:22 2010 ;; MSG SIZE rcvd: 46

I hope that this clarifies things, RayQuang

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I don't think "very unreliable" give the right idea. UDP is connectionless which my defination means it's "unreliable" but in this context, that's what you want for video if it's streaming. –  JamesBarnett Dec 31 '10 at 8:22

Syslog is an example of a service that uses UDP. Many tools, such as log4net, implement logging over this protocol. Applications such as Kiwi receive syslog messages from clients such as log4net.

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Good question, there are protocols for video and audio transmission that use udp (good because this media is not really effected by packet loss and can do without delays from RST and additional overhead from control packets). I am pretty sure nginx is using http as the protocol (which is a tcp based protocol).

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Regarding the first question, then HTTP is usually served over TCP.

For the second question... You can take a look to http://www.iana.org/assignments/port-numbers (or run 'grep udp /etc/services' command) to get an idea about services that use UDP protocol.

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Some video players use RTSP (Real Time Streaming Protocol), which is UDP based.

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UDP is used by applications not aware of connection status.

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