The Telecom Protocols

SIP responses generated by the UAS or SIP servers. SIP Response Classes: 1xx - Informational - Indicates the status of call prior to the completion. 2xx - Success -  Request has succeeded. 3xx - Redirection - The client should try to complete the request at another server. 4xx - Client Error - The request has failed due to error due to the client.  The client may retry. 5xx - Server failure - The request has failed due to server error. request may retry to another server. 6xx - Global failure - the request has failed and can not retry to any server. 1xx --Informational : 100 Trying : This response is used to indicate the next node receives the request and stop the retransmission. This response is sent if there is delay in sending the final response more the 200ms. 180 Ringing: The response is generated if UA receives the INVITE and started the ringing. It may used to initiate local ring back. 181 Call is being Forwarded: This response is indicat...

SIP Servers: Proxy Servers:  - A stateless proxy server processes each SIP request or response based solely on the message contents. Once the message has been parsed, processed, and forwarded or responded to,no information about the message is stored—no dialog information is stored. A stateless proxy never re-transmits a message, and does not use any SIP timers. - A stateful proxy server keeps track of requests and responses received in the past and uses that information in processing future requests and responses. For example, a stateful proxy server starts a timer when a request is forwarded. If no response to the request is received within the timer period, the proxy will re-transmit the request, relieving the user agent of this task. Also, a stateful proxy can require user agent authentication. Back-to-Back User Agents (B2BUA): An B2BUA is a type of SIP device that receives the SIP request, that reformulates the request and send it out as new reques...

BICC Bearer establishment procedures: Four variants of BICC IP bearer set-up procedures are defined: -             Fast Forward -             Delayed Forward -             Fast Backward -             Delayed Backward  Those procedures differ on the way the bearer control information are exchanged, and on whether an APM (Connected) message shall be sent by the originating BICC node once the bearer is ready for use. -             Bearer control information exchanges : -             In Fast bearer setup (forward or backward) and in delayed forward bearer establishment procedures, the IP bearer establishment is done in the ...

The interfaces and protocols supported towards the networks are mentioned below: Network Interfaces and Protocols

Codec Management Objectives Codec Management has following goals: 1.) Optimize the voice quality. 2.) Optimize the bandwidth efficiency 3.) Optimize the transcoder resource in MGW. 4.) Optimize the delay Voice Quality: Voice quality is measured in terms of the level, attenuation, delay, echo, and so on and may be used as a basis for the iQoS assessments for conventional VoIP. Voice Quality is measured in terms of R-value and below 50 are not recommended. Standards                                     Intrinsic quality (R) ------------------------------------------------------ ITU G.711 (64kbps)                                  94.3 ITU G.728 (12.kbps)                               ...

In Early legacy telephone network, A call between the two mobiles involved with two transcoding function at both the end which decrease the voice quality. The Transcoding Function done by the TRAU (Transcoding and Rate Adaptation Unit) to compress and decompress the speech.  TFO (Tandem Free Operation) enables to avoid the traditional double speech encoding / decoding in MS to MS call configurations. TFO uses in-band signalling and procedures for transcoders to enable compressed speech to be maintained between a pair of transcoders.   So the main objective of TFO is the improvement of the voice quality for calls between 2 mobile subscribers, but no resource optimisation is introduced  as transcoder functions are always present in the path. If TFO is activated between two end nodes, TFO Frames with compressed speech (e.g. AMR in LSB) as payload are carried over 8 or 16 kbit/s channels mapped onto the least or two least significant bits of the 64 kbit/s...

In Early legacy telephone network, A call between the two mobiles involved with two transcoding function at both the end which decrease the voice quality. The Transcoding Function done by the TRAU (Transcoding and Rate Adaptation Unit) to compress and decompress the speech.  Transcoder Free Operation (TrFO) is transport of compressed speech, which eliminates unnecessary coding and decoding of the signals when both end uses the same codecs. TrFO utilizes out of band signaling capabilities that include the ability to determine the negotiated codec type to be used at the two end nodes.  If the two end nodes are capable of the same codec operations, it may be possible to traverse the entire packet network using only the compressed speech (of the preferred codec). TrFO is basic function of codec Management.  Following are the benefits of achieving the TrFO:  1.) Improve the voice quality because of eliminati...