Some important website for a telecommunication engineer

1.ITU

http://www.itu.int/net/search/searchframe.aspx

here we can search the ITU standard documents by imput the key words

 

2.RFC

http://www.rfc-editor.org/rfcsearch.html

here we can search the RFC standard documents by imput the key words

 

3.3GPP

http://www.3gpp.org/technologies

Here we can find the 3GPP standard documents.

 

4.Tech-invite

http://www.tech-invite.com/Ti-sip-ex3261.html

Here we can see the beautiful call flow examples of SIP and IMS and so on.