What must be enabled when configuring voice gateways to support SIP dialers?

The correct answer is D. 100rel. 100rel (RFC 3262) must be enabled because SIP dialers depend on reliable delivery of provisional responses (1xx messages like 180 Ringing and 183 Session Progress) to accurately track call progress and early media. Without it, these messages are sent unreliably - the gateway…

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Question

What must be enabled when configuring voice gateways to support SIP dialers?

Options

A200rel
Bsignaling forward unconditional
Csignaling forward 100
D100rel

How the community answered

(30 responses)

B
3% (1)
C
3% (1)
D
93% (28)

Explanation

100rel (RFC 3262) must be enabled because SIP dialers depend on reliable delivery of provisional responses (1xx messages like 180 Ringing and 183 Session Progress) to accurately track call progress and early media. Without it, these messages are sent unreliably - the gateway fires them and forgets - which causes dialers to misdetect answer supervision and billing events.

Option A (200rel) is wrong because 200 OK (final responses) are already reliable in core SIP; they retransmit until an ACK is received, so no extension is needed.

Options B and C (signaling forward unconditional / signaling forward 100) are Cisco IOS commands for transparently passing SIP signaling between legs - they control message forwarding, not response reliability.

Memory tip: Break it down - "100" = the 1xx provisional response series, "rel" = reliable. 100rel makes what was unreliable (provisional) into something reliable - exactly what a dialer needs to count answered calls correctly.

Topics

#SIP#Voice Gateway#100rel#Provisional Responses

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