CHAPTER30 SBC Overview
Mediant 800 Gateway & E-SBC | User's Manual
Interworking RTCP Attribute in SDP
The device supports interworking the RTCP attribute 'a=rtcp' in the SDP between SIP entities.
Employing IP Profiles, you can configure RTCP attribute handling (add, remove or transparent) per
SIP entity, using the IpProfile_ SBCSDPHandleRTCPAttribute parameter (see Configuring IP
Profiles).
Interworking Crypto Lifetime Field
The device supports interworking the lifetime field in the 'a=crypto' attribute of the SDP, between
SIP entities. Employing IP Profiles, you can configure the lifetime field handling (remove or retain)
per SIP entity, using the IpProfile_SBCRemoveCryptoLifetimeInSDP parameter (see Configuring
IP Profiles).
Interworking Media Security Protocols
The device supports interworking media security protocols for SRTP, between SIP entities.
Employing IP Profiles, you can configure the security protocol (SDES and DTLS) per SIP entity,
using the IPProfile_SBCMediaSecurityMethod parameter (see Configuring IP Profiles). For more
information on SDES and DTLS, see Configuring Media (SRTP) Security.
Interworking ICE Lite for NAT Traversal
The device supports interworking ICE for NAT traversal, between SIP entities. Employing IP
Profiles, you can enable ICE Lite per SIP entity, using the IPProfile_SBCIceMode parameter (see
Configuring IP Profiles).
Fax Negotiation and Transcoding
The device can allow fax transmissions to traverse transparently without transcoding or it can
handle the fax as follows:
■ Allow interoperability between different fax machines, supporting fax transcoding if required.
■ Restrict usage of specific fax coders to save bandwidth, enhance performance, or comply with
supported coders. These coders include G.711 (A-Law or Mu-Law), VBD (G.711 A-Law or
G.711 Mu-Law), and T38.
Fax configuration is done in the Coder Groups table and IP Profiles table. The Coder Groups table
defines the supported coders, which is assigned to the IP Profile associated with the SIP entity.
The IP Profiles table also defines the negotiation method used between the incoming and outgoing
fax legs, using the following fax-related parameters:
■ IPProfile_SBCFaxBehavior: defines the offer negotiation method - pass fax transparently,
negotiate fax according to fax settings in IP Profile, or enforce remote UA to first establish a
voice channel before fax negotiation.
■ IPProfile_SBCFaxCodersGroupName: defines the supported fax coders (from the Coder
Groups table).
■ IPProfile_SBCFaxOfferMode: determines the fax coders sent in the outgoing SDP offer.
■ IPProfile_SBCFaxAnswerMode: determines the fax coders sent in the outgoing SDP answer.
■ IPProfile_SBCRemoteRenegotiateOnFaxDetection: You can also configure the device to
detect for faxes (CNG tone) immediately after the establishment of a voice channel (i.e., after
200 OK) and within a user-defined interval. If detected, it can then handle the subsequent fax
renegotiation by sending re-INVITE messages to both SIP entities (originating and terminating
faxes). For more information, see the parameter in Configuring IP Profiles.
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