SSCA SDP Protocol 5

Question 1

What is the significance of the session version number in the SDP 'o=' line?

Accepted Answer

It increments with each updated SDP offer/answer to signal a change

Answer

The session version in the o= line must be incremented each time the SDP is modified so that the remote party can detect that the session description has changed.

Question 2

In SDP, what does 'a=recvonly' signify when included in an offer?

Accepted Answer

The offerer wants to receive media but not send it

Answer

An 'a=recvonly' offerer indicates it will only receive media from the remote endpoint, not transmit any.

Question 3

How does SDP represent multicast sessions in the connection (c=) line?

Accepted Answer

By specifying a multicast address with an optional TTL value appended

Answer

SDP represents multicast by including a multicast IP address in the c= field, optionally followed by a slash and TTL value (e.g., 'IN IP4 224.2.1.1/127').

Question 4

What is the purpose of the 'a=maxptime' attribute in SDP?

Accepted Answer

Specifies the maximum packet duration in milliseconds the receiver can accept

Answer

The a=maxptime attribute tells the sender the maximum length of time (in ms) of audio that can be encapsulated in a single RTP packet the receiver will accept.

Question 5

In the SDP offer/answer model, what RFC defines the core rules for offer and answer negotiation?

Accepted Answer

RFC 3264

Answer

RFC 3264 (An Offer/Answer Model with Session Description Protocol) defines the rules for how SDP is used in offer/answer exchanges within SIP.

(SSCA) Sip School Certified Associate Practice Test

(SSCA) Sip School Certified Associate Practice Test

SSCA SDP Protocol 5