Question

This questions related to VoIP please solve them

1. What are the types of Media Gateway?
2. What is the function of the subfield attribute? Give an example
3. What is the Dialog ID in SIP?
4. Describe the functions of the following SIP headers: To, From, Contact, Via, CSeq, Expires, Content-Type, Retry-After, Record-Route and Route
5. Which SIP methods create dialogs? Which SIP methods end dialogs?

Answer 1

1.)Different types of media gateways are:-

Voice Over Internet Protocol ( VOIP)

Internet Protocol (IP)

Radio Frequency Identification Tag(RFID Tag)

Asynchronous Transfer Mode (ATM)

Signaling Gateway (SGW)

2.) The Subfield attribute has very imperative use in order to encode the message to be sent via the media gateway.

It also contains various sub fileds in it inorder to perform various actions . For example encoding/decoding the message. raising request.

3.) DialogId in SIP is a combination of Call-ID, From, To tag. Dialog represents a persistent peer-to-peer relationship between two user agent.

4.) Funcrions of various SIP headers are:

a.) To :- it specifies the desired recipient of the request

b.) From:- It specifies the desired identity of the initiator of request.

c.) Call-Id :- It acts as a unique identifier to group together a series of messages.

d.) cseq:- serves as away to identify and order transactions

e.) Contact:- it provides SIP or SIPS URI that can be used to contact that specific instance of request.

f.)Expires;- Gives relative time after which the message gets expire.

g.) Retry-after:- shows how long the service is unavailable to request client again.