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Back to SBC SIP Transparency Implementation Guide

In this section:

Signaling

Transparency Profile at the egress Trunk Group (TG_AS)

A transparency profile with “all” header is configured and associated with SIP trunk group TG_AS.

Configuration details:

% set profiles services transparencyProfile TP_AS sipHeader all
% set profiles services transparencyProfile TP_AS state enabled
% commit

% set addressContext AC1 zone ZONE_AS sipTrunkGroup TG_AS services transparencyProfile TP_AS
% commit

The  following  IPSP  flag “disableHostTranslation” has to be enabled to ensure that the host part of Request-URI, To, From headers is not replaced by SBC.

% set profiles signaling ipSignalingProfile DEFAULT_SIP commonIpAttributes flags disableHostTranslation enable
Incoming INVITE:

INVITE sip:7945422980@10.54.20.53:5060 SIP/2.0

Via:SIP/2.0/UDP 10.54.80.101:6865

Route: <sip:7945422980@10.54.20.53:5060;lr>

Max-Forwards: 70

From:+819012340001 <sip:+819012340001@10.54.80.101:6865>;tag=28293

To:<sip:7945422980@10.54.20.53:5060>

Call-ID:141415227868652203_1034102675@10.54.80.101

CSeq:6924 INVITE

Contact: <sip:10.54.80.101:6865>

Allow: OPTIONS, INVITE, CANCEL, ACK, BYE, INFO, PRACK, UPDATE

Accept: application/sdp; level=1, application/x-private, text/html

Alert-Info: <http://www.sonus-testing.com/sounds/moo.wav>

Call-Info: <http://wwww.example.com/alice/photo.jpg>;purpose=icon

Session-Expires: 1800

Content-Type: application/sdp

Content-Length: 284

 

 

Outgoing INVITE:

INVITE sip:7945422980@10.54.20.53:5060 SIP/2.0

Via: SIP/2.0/UDP 10.54.21.53:5060;branch=z9hG4bK04B00006d290dab7bde

Via:SIP/2.0/UDP 10.54.80.101:6865

From: "+819012340001" <sip:+819012340001@10.54.80.101>;tag=gK04000184

To: <sip:7945422980@10.54.20.53>

Call-ID: 262144_41283677@10.54.21.53

CSeq: 55481280 INVITE

Max-Forwards: 69

Allow: INVITE,ACK,CANCEL,BYE,REGISTER,REFER,INFO,SUBSCRIBE,NOTIFY,PRACK,UPDATE,OPTIONS,MESSAGE,PUBLISH

Route:<sip:7945422980@10.54.20.53:5060;lr>

Contact: <sip:10.54.80.101:6865>

Record-Route: <sip:10.54.21.53:5060;lr>

Accept: application/sdp; level=1, application/x-private, text/html

Alert-Info: <http://www.sonus-testing.com/sounds/moo.wav>

Call-Info:  <http://wwww.example.com/alice/photo.jpg>;purpose=icon

Session-Expires: 1800

Supported: timer,100rel,precondition,replaces

Session-Expires: 1800

Min-SE: 90

Content-Length:   187

Content-Disposition: session; handling=required

Content-Type: application/sdp

Points to Note:

Max-Forwards header is not transparently passed. It is decremented by 1.

Allow header is modified by SBC. It is not transparently sent.

 

Transparency Profile at the ingress Trunk Group (TG_IAD)

A transparency profile with “all” header is configured and associated with SIP trunk group TG_IAD.

An unknown header named “Sherlock” should not be passed in this scenario.

Configuration details:

% set profiles services transparencyProfile TP_IAD sipHeader all
% set profiles services transparencyProfile TP_IAD sipHeader sherlock ignoreTransparency yes
% set profiles services transparencyProfile TP_IAD state enabled
% commit

% set addressContext AC1 zone zone1 sipTrunkGroup TG_IAD services transparencyProfile TP_IAD
% commit
Incoming 200 OK:

SIP/2.0 200 Ok

Via: SIP/2.0/UDP 10.54.21.53:5060;branch=z9hG4bK04B00006d290dab7bde,SIP/2.0/UDP 10.54.80.101:6865

From: "+819012340001" <sip:+819012340001@10.54.80.101>;tag=gK04000184

To: <sip:7945422980@10.54.20.53>;tag=41777

Call-ID: 262144_41283677@10.54.21.53

Contact: <sip:9786148000@10.54.80.110:8865>

CSeq: 55481280 INVITE

Sherlock: Elementary, my dear Watson

Content-Type: application/sdp

 

 

Outgoing 200 OK:

SIP/2.0 200 OK

Via:SIP/2.0/UDP 10.54.80.101:6865

From:+819012340001 <sip:+819012340001@10.54.80.101:6865>;tag=28293

To:<sip:7945422980@10.54.20.53:5060>;tag=gK048000b7

Call-ID: 141415227868652203_1034102675@10.54.80.101

CSeq: 6924 INVITE

Accept: application/sdp, application/isup, application/dtmf, application/dtmf-relay,  multipart/mixed

Contact: <sip:7945422980@10.54.20.53:5060>

Allow: INVITE,ACK,CANCEL,BYE,REGISTER,REFER,INFO,SUBSCRIBE,NOTIFY,PRACK,UPDATE,OPTIONS,MESSAGE,PUBLISH

Supported: timer,replaces

Session-Expires: 1800;refresher=uas

Content-Length:   187

Content-Disposition: session; handling=required

Content-Type: application/sdp


Points to Note:
The unknown header “Sherlock” received in the 200 OK will not be sent out.

Click to view Header details:

 

SIP Domain Flags for Require-URI header:

  • useSipDomainNameInRequestUri
  • preserveIngressRUriDomainName

SIP Domain Flags for From header:

  • useSipDomainNameInFromField
  • preserveIngressFromDomainName

DHT flag flag in IP Signaling Profile is disableHostTranslation.

Media

The SBC has the ability to anchor the following  media types:

  • Audio
  • Video Main
  • Video Extended – for Content Share
  • Binary Floor Control Protocol ( UDP and TCP)
  • Far End Camera Control ( FECC)
  • Message Session Relay Protocol ( MSRP)

For all the above mentioned media types (with the exception of Audio), the SBC consumes (i.e. does not transparently relay) the following attributes required to anchor the media:

  1. C line
  2. RTCP attributes
  3. Media direction ( a= sendrecv/sendonly/inactive/recvonly)
  4. Crypto  (the SBC terminates SRTP on a leg by leg basis)

For Audio, in addition to the above mentioned, the SBC does not transparently relay the following:

To achieve the above described behavior, enable Video (assign a valid video bandwidth) and Audio transparency by associating the following configuration with both Trunk Groups:

% set profiles media packetServiceProfile <packetServiceProfileName> packetToPacketControl transcode transcoderFreeTransparency
% set addressContext <addressContextName> zone <zoneName> sipTrunkGroup <trunkGroupName> media sdpAttributesSelectiveRelay enabled
% set profiles media packetServiceProfile <packetServiceProfileName>  videoCalls maxVideoBandwith <bandwidth>

Example of SDP transparency with both the flags enabled the SDP relayed by SBC.

Transparency is not supported for attributes in blue font.

Incoming SDP:

c=IN IP4 10.128.44.159

b=AS:1920   

t=0 0

a=sendrecv

m=audio 3230 RTP/AVP 118 103 99 9 18 15 0 8 119

a=sendrecv

a=unknown

a=rtpmap:118 SIRENLPR/48000/1

a=fmtp:118 bitrate=64000

a=rtpmap:103 G7221/16000

a=fmtp:103 bitrate=16000

a=rtpmap:99 SIREN14/16000

a=fmtp:99 bitrate=48000

a=rtpmap:9 G722/8000

a=fmtp:9 bitrate=64000

a=rtpmap:18 G729/8000

a=fmtp:18 annexb=yes

a=rtpmap:15 G728/8000

a=rtpmap:0 PCMU/8000

a=rtpmap:8 PCMA/8000

a=rtpmap:119 telephone-event/8000

a=fmtp:119 0-15,36

a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:kW4x9MxypxiVK1ZeQlsSXpHBvLEekL8CFvpVXu7c

m=video 3232 RTP/AVP 111 96 34 31 106 116

b=TIAS:1920100

a=sendrecv

a=rtcp-fb:* nack pli

a=rtcp-fb:* ccm fir

a=rtcp-fb:* ccm tmmbr

a=vnd.polycom.forceVideoMode:9

a=rtpmap:111 H264/90000

a=fmtp:111 profile-level-id=64001f; packetization-mode=1; max-br=20010; sar=13

a=rtpmap:96 H263-1998/90000

a=fmtp:96 CIF4=1;CIF=1;QCIF=1;SQCIF=1;CUSTOM=352,240,1;CUSTOM=704,480,1;CUSTOM=1024,768,1;CUSTOM=800,600,1;CUSTOM=640,480,1;T

a=rtpmap:34 H263/90000

a=fmtp:34 CIF4=1;CIF=1;QCIF=1;SQCIF=1

a=rtpmap:31 H261/90000

a=fmtp:31 CIF=1;QCIF

a=rtpmap:106 H264-SVC/90000

a=fmtp:106 profile-level-id=56001f; packetization-mode=1; max-br=20010; sar=13

a=rtpmap:116 vnd.polycom.lpr/9000

a=fmtp:116 V=1;minPP=0;PP=150;RS=52;RP=10;PS=1400

a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:kRZIbW6v1+qXylRem15tbZJq0ym+zvDTGJpSX0nf

m=application 3238 UDP/BFCP *

a=setup:actpass

a=connection:new

a=floorctrl:c-s

m=application 3236 RTP/AVP 100

a=rtpmap:100 H224/

 

Note following missing attributes from egress invite:

  • Siren codec - not supported by SBC.
  • Telephone event 36
  • Crypto attribute – Egress not Configured for SRTP
  • Change in Video Band width
Outgoing SDP:

c=IN IP4 10.7.15.83

b=AS:1920

t=0 0

m=audio 1036 RTP/AVP 103 9 18 15 0 8 119

a=rtpmap:103 G7221/16000

a=fmtp:103 bitrate=16000

a=rtpmap:9 G722/8000

a=rtpmap:18 G729/8000

a=rtpmap:15 G728/8000

a=rtpmap:0 PCMU/8000

a=rtpmap:8 PCMA/8000

a=rtpmap:119 telephone-event/8000

a=fmtp:119 0-15

a=sendrecv

a=maxptime:40

a=unknwon

m=video 1038 RTP/AVP 111 96 34 31 106 116

b=TIAS:1920100

a=rtcp-fb:* nack pli

a=rtcp-fb:* ccm fir

a=rtcp-fb:* ccm tmmbr

a=vnd.polycom.forceVideoMode:9

a=rtpmap:111 H264/90000

a=fmtp:111 profile-level-id=64001f;packetization-mode=1;max-br=20010;sar=13

a=rtpmap:96 H263-1998/90000

a=fmtp:96 CIF4=1;CIF=1;QCIF=1;SQCIF=1;CUSTOM=352,240,1;CUSTOM=704,480,1;CUSTOM=1024,768,1;CUSTOM=800,600,1;CUSTOM=640,480,1;

a=rtpmap:34 H263/90000

a=fmtp:34 CIF4=1;CIF=1;QCIF=1;SQCIF=1

a=rtpmap:31 H261/90000

a=fmtp:31 CIF=1;QCIF=1

a=rtpmap:106 H264-SVC/90000

a=fmtp:106 profile-level-id=56001f;packetization-mode=1;max-br=20010;sar=13

a=rtpmap:116 vnd.polycom.lpr/9000

a=fmtp:116 V=1;minPP=0;PP=150;RS=52;RP=10;PS=1400

a=sendrecv

m=application 1040 UDP/BFCP *

a=setup:actpass

a=connection:new

a=floorctrl:c-s

a=sendrecv

m=application 1042 RTP/AVP 100

a=rtpmap:100 H224/4800

a=sendrecv

 

Register

Click to view Header details:

 

 

The SIP Domain flags do not have any effect on Request-URI,  From header.  If request-uri transparency is configured in transparency profile, transparency is achieved if DHT flag was enabled. If not, SBC replaced the host with the IP Peer.

 

Out-Of-Dialog message (SUBSCRIBE)

Click to view Header details:

 

 

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