[Free] 2017(Apr) Ensurepass Passguide Cisco 400-051 Latest Dumps 41-50

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CCIE Collaboration Written Exam

QUESTION 41

Refer to the exhibit. Which SIP message header is used to tunnel QSIG messages across the SIP network when the OGW receives a call bound for the TGW?

 

clip_image001

 

A.

Content-Type. application/sdp

B.

Content-Type. application/qsig

C.

Content-Type. message/ISUP

D.

Content-Type. message/external-body

E.

Content-Type. application/x-q931

 

Correct Answer: B

Explanation:

Tunneling over SIP

The Cisco gateway receives QSIG messages from the PBX side and then identifies the destination of the message (or call). The QSIG messages received from the PBX are encapsulated within SIP messages as Multipurpose Internet Mail Extensions (MIME) bodies and are sent (tunneled) across the IP network to the recipient gateway. When encapsulating a QSIG message (for switch type primary-qsig) inside a SIP message, Cisco gateways include the QSIG message in a MIME body of the SIP request or response using media type application/QSIG:

Content-Type: application/QSIG

 

Reference:

http://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/empowered-branch-solution/white_paper_c11_459092.html

 

 

QUESTION 42

Refer to the exhibit. How many SIP signaling transaction(s) took place in this SIP message exchange between two SIP user agents?

 

clip_image002

 

A.

1

B.

2

C.

3

D.

4

E.

5

F.

6

 

Correct Answer: C

Explanation:

During the establishment, maintenance and termination of a SIP session, signaling messages are exchanged between the two SIP endpoints. There are two different kinds of signaling “conversations” that those messages take part in: transactions and dialogs. A transaction is a SIP message exchange between two user-agents that starts with a request and ends with its final response (it can also contain zero or more provisional responses in between). For example, during the termination of a SIP session, one user releases the call by sending a BYE request and the other party replies back with a 200 OK response. This message exchange is called a transaction.

But what happens in the case of the INVITE request? The establishment of a SIP session starts basically with an INVITE request and is considered as completed upon the receipt of the ACK. In this case, the transaction starts with the INVITE request and ends with the 200 OK, so the ACK is not part of the transaction. The ACK can be considered as a transaction on its own. However, when the final response to an INVITE is not a 2xx response, then the ACK is considered as part of the transaction. A dialog is a complete exchange of SIP messages between two user-agents. That means that transactions are actually parts of a dialog. For example, in the case of a SIP session establishment, a dialog starts with the INVITE-200 OK transaction, continues with the ACK and ends with the BYE-200 OK transaction.

The picture below depicts the dialog and transactions that take place during the establishment of a SIP session:

 

clip_image003

 

Note:

There can also be subsequent requests that belong to the same dialog, such as a BYE or a re-INVITE message. As out-of-dialog requests are considered messages such as an initial INVITE request for a new session or an OPTIONS message for checking capabilities.

There are different SIP headers/parameters that identify the dialogs and transactions, and they will be analyzed in later posts.

 

Reference:

https://telconotes.wordpress.com/2013/03/13/sip-transactions-vs-dialogs/

 

 

QUESTION 43

Which SIP request method enables reliability of SIP 1xx response types?

 

A.

ACK

B.

PRACK

C.

OPTIONS

D.

CANCEL

E.

REGISTER

 

Correct Answer: B

Explanation:

In order to achieve reliability for provisional responses, we do nearly the same thing. Reliable provisional responses are retransmitted by the TU with an exponentialbackoff. Those retransmissions cease when a PRACK message is received. The PRACK request plays the same role as ACK, but for provisional responses. There is an important difference, however. PRACK is a normal SIP message, like BYE. As such, its own.

 

 

QUESTION 44

Which device is the initiator of a StationInit message in a Cisco Unified Communications Manager SDI trace?

 

A.

Cisco Unified Communications Manager

B.

MGCP gateway

C.

Cisco Music on Hold server

D.

SCCP IP phone

E.

SIP Proxy Server

 

Correct Answer: D

Explanation:

Station Init means that an inbound Transmission Control Protocol (TCP) message from a Skinny station reached CallManager. A Skinny station is any endpoint that uses the Skinny protocol to communicate with CallManager.

 

 

QUESTION 45

Refer to the exhibit. If this SIP call is initiated using delayed offer, which SIP message will UA#1 use to communicate its media capability to UA#2?

 

clip_image004

 

A.

INVITE

B.

180 Ringing

C.

200 OK

D.

ACK

E.

RTP Media

 

Correct Answer: D

Explanation:

In the Delayed Offer process, the calling does not send its offer in the SIP INVITE Message. The callee sends the offer within the SDP fields of its answer (SIP 200 OK). The calling answers within the ACK message.

 

 

QUESTION 46

To which SIP response class do the SIP response codes 300 to 399 belong?

 

A.

Provisional

B.

Client Failure

C.

Server Failure

D.

Successful

E.

Redirection

 

Correct Answer: E

Explanation:

Redirection — further action needs to be taken in order to complete the request. That is what this class implies.

 

 

QUESTION 47

Which two statements describe characteristics of Binary Floor Control Protocol? (Choose two.)

 

A.

Its binary encoding is designed to work in high-bandwidth environments.

B.

It is designed for audio or video conference sessions of three or more participants.

C.

It enables management of shared content resources independent of video streams.

D.

It supports TLS-based authentication.

E.

It supports SIP as well as H.323.

 

Correct Answer: CD

Explanation:

BFCP is a deliverable developed as part of the Internet Engineering Task Force (IETF) XCON Centralized Conferencing working group. The IETF XCON working group was formed to focus on delivering a standards-based approach to managing IP conferencing while promoting broad interoperability between software and equipment vendors.

 

 

QUESTION 48

How are DTMF digits transported in RFC 2833?

 

A.

In the RTP stream with the named telephone events payload format.

B.

In the RTP stream with the regular audio payload format.

C.

In SIP NOTIFY messages.

D.

In SIP INFO messages.

E.

In SIP SUBSCRIBE messages.

 

Correct Answer: A

Explanation:

DTMF digits and named telephone events are carried as part of the audio stream, and MUST use the same sequence number and time-stamp base as the regular audio channel to simplify the generation of audio waveforms at a gateway. The default clock frequency is 8,000 Hz, but the clock frequency can be redefined when assigning the dynamic payload type.

 

 

QUESTION 49

Which two VoIP protocols use SDP to describe streaming media sessions? (Choose two.)

 

A.

SCCP

B.

H.323

C.

SIP

D.

MGCP

E.

RAS

F.

cRTP

 

Correct Answer: CD

Explanation:

The Session Description Protocol (SDP), defined in RFC 2327, describes the content of sessions, including telephony, Internet radio, and multimedia applications. SDP includes information about [8]:

 

Media streams: A session can include multiple streams of differing content. SDP currently defines audio, video, data, control, and application as stream types, similar to the MIME types used for Internet mail.

Addresses: SDP indicates the destination addresses, which may be a multicast address, for a media stream.

Ports: For each stream, the UDP port numbers for sending and receiving are specified.

Payload types: For each media stream type in use (for example, telephony), the payload type indicates the media formats that can be used during the session.

Start and stop times: These apply to broadcast sessions, for example, a television or radio program. The start, stop, and repeat times of the session are indicated.

Originator: For broadcast sessions, the originator is specified, with contact information. This may be useful if a receiver encounters technical difficulties.

 

 

QUESTION 50

Which two responses are examples of client error responses in SIP protocol? (Choose two.)

 

A.

302 Moved Temporarily

B.

404 Not Found

C.

503 Service Unavailable

D.

502 Bad Gateway

E.

604 Does Not Exist Anywhere

F.

408 Request Timeout

 

Correct Answer: BF

Explanation:

Client Error (400 to 499)–Request contains bad syntax or cannot be fulfilled at this server. This class of 400 to 499 contains only error messages.

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