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In this article, we describe how to translate SIP response in SIP to SIP calls using "Pass-thru Peer SIP Response Code".

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Background and Overview

By default, SIP responses received are passed through from one SIP peer to another by the Sonus SBC 1000/2000. The default Q.850 to SIP and SIP to Q.850 mapping tables fully conform with RFC4497. With the help of these two override tables, you can change the default mapping for any SIP response to and from any Q.850 cause.

For example, in the default Q.850 to SIP override table, QSIG Cause Codes 34, 38, 41, 42, 47, 58, and 88 map to 503 Service Unavailable. A problem occurs when the Sonus SBC 1000/2000 receives Cause Code 34 from the PSTN. The Sonus SBC 1000/2000 maps it to 503 Service Unavailable, which causes Lync to declare the Sonus SBC 1000/2000 gateway unavailable with Event ID 46046. In this case, the Sonus SBC 1000/2000 administrator may want to override the default mapping in order to prevent Lync from flagging the whole gateway as unavailable. Consider the following illustration.

Figure : Default Q.850 to SIP Override Table

 

This article expands more on this practice, and describes how to configure the Sonus SBC 1000/2000 to perform custom SIP response mapping for SIP to SIP calls.

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Sonus SBC 1000/2000 Configuration

General Overview of the Configuration

In this example we use the SIP to Q850 and Q850 to SIP Override Tables. Upon receiving a SIP response, the Sonus SBC 1000/2000 uses the SIP to Q850 Override Table to map the SIP response to a Q850 Cause Code. Once the Q850 Cause Code is found, the Sonus SBC 1000/2000 uses the Q850 Cause Code, via the Q850 to SIP mapping table, to map it to a SIP response. This behavior is achieved when the default Pass-through SIP Response Code feature is disabled.

Figure : SIP to Q.850 and Q.850 to SIP Override Tables

 

 

Default Q.850 to SIP and SIP to Q.850 Mapping Tables in Sonus SBC 1000/2000

SIP response

Q.850 Cause value

400 Bad Request

41 Temporary Failure

401 Unauthorized

21 Call rejected

402 Payment required

21 Call rejected

403 Forbidden

21 Call rejected

404 Not found

1 Unallocated number

405 Method not allowed

63 Service or option unavailable

406 Not acceptable

79 Service/option not implemented

407 Proxy authentication required

21 Call rejected

408 Request timeout

102 Recovery on timer expiry

410 Gone

22 Number changed (w/o diagnostic)

413 Request Entity too long

127 Interworking

414 Request-URI too long

127 Interworking

415 Unsupported media type

79 Service/option not implemented

416 Unsupported URI Scheme

127 Interworking

420 Bad extension

127 Interworking

421 Extension Required

127 Interworking

423 Interval Too Brief

127 Interworking

480 Temporarily unavailable

18 No user responding

481 Call/Transaction Does not Exist

41 Temporary Failure

482 Loop Detected

25 Exchange - routing error

483 Too many hops

25 Exchange - routing error

484 Address incomplete

28 Invalid Number Format

485 Ambiguous

1 Unallocated number

486 Busy here

17 User busy

487 Request Terminated

127 Interworking

488 Not Acceptable Here

65 Bearer capability not implemented

500 Server internal error

41 Temporary failure

501 Not implemented

79 Not implemented, unspecified

502 Bad gateway

38 Network out of order

503 Service unavailable

41 Temporary failure

504 Server time-out

102 Recovery on timer expiry

505 Version Not Supported

127 Interworking

513 Message Too Large

127 Interworking

600 Busy everywhere

17 User busy

603 Decline

21 Call rejected

604 Does not exist anywhere

1 Unallocated number

606 Not acceptable

31 Normal, unspecified

Q.850 Cause value

SIP response

1 Unallocated number

404 Not Found

2 No route to network

404 Not found

3 No route to destination

404 Not found

16 Normal call clearing

result in a BYE or CANCEL

17 User busy

486 Busy here

18 No user responding

408 Request Timeout

19 No answer from the user

480 Temporarily unavailable

20 Subscriber absent

480 Temporarily unavailable

21 Call rejected (location - user)

603 Forbidden

21 Call rejected (location - nonuser)

403 Forbidden

22 Number changed (w/o diagnostic)

410 Gone

22 Number changed (w/ diagnostic)

301 Moved Permanently

23 Redirection to new destination

410 Gone

26 Non-selected user clearing

404 Not Found

27 Destination out of order

502 Bad Gateway

28 Address incomplete

484 Address incomplete

29 Facility rejected

501 Not implemented

31 Normal unspecified

480 Temporarily unavailable

34 No circuit available

503 Service unavailable

38 Network out of order

503 Service unavailable

41 Temporary failure

503 Service unavailable

42 Switching equipment congestion

503 Service unavailable

46 Precedence call blocked

480 Temporarily unavailable

47 Resource unavailable

503 Service unavailable

55 Incoming calls barred within CUG

403 Forbidden

57 Bearer capability not authorized

403 Forbidden

58 Bearer capability not presently

503 Service unavailable available

65 Bearer capability not implemented

488 Not Acceptable Here

69 Requested facility not implemented

501 Not implemented

70 Only restricted digital avail

488 Not Acceptable Here

79 Service or option not implemented

501 Not implemented

87 User not member of CUG

403 Forbidden

88 Incompatible destination

503 Service unavailable

102 Recovery of timer expiry

504 Gateway timeout

111 Protocol error

500 Server internal error

127 Interworking unspecified

500 Server internal error

Sonus SBC 1000/2000 Configuration

  • Create a SIP to Q.850 mapping table, which will be used to match the SIP Response to a Q.850 Cause Code for inbound calls.

Figure : Inbound SIP to Q.850

 

  • Create a Q.850 to SIP mapping table, which will be used to match the Q.850 Cause Code to SIP Response for outbound calls.

Figure : Outbound Q.850 to SIP

 

  • Disable Pass-through Peer SIP Response Code and select the two mapping tables.

Figure : Mapping Tables

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