Session Border ControllerTGS Fundamental Training

*What is an SBC?Session Border Controller is an element regularly used VoIP networks, whose role is to control the signalling between service providers network and access (customers) network, and also between two different VoIP providers; Session: communication between two points session (e.g. call) is controlled by SBCBorder: it is deployed at the edge of the VoIP network (border demarcation point)Controller : it controls communications (once again) provides access control, measurements, data conversion, modification of signalling messages, etc

Position of SBC in VoIP networks

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Lets take a closer look to SBCs functionSecurity - protects the network (and devices inside)Prevents DoS, DDoS attacksTopology hidingEncryption of signaling (TLS, IPSec)Encryption of media (SRTP)

Connectivity - allow different parts of the network to communicate through the use of a variety of techniquesNAT traversalSIP normalization via SIP message and header manipulation (SMM)IPv4 to IPv6 interworkingProtocol translations betweenSIP, SIP-I,H.323

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Quality of service QoSTraffic policingResource allocationRate limitingCall admission controlToS/DSCPbit setting

Regulatory SBC can optionally provide regulatory requierementsemergency callsprioritizationlawful interception

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Media servicesDTMF relay and interworkingMedia transcodingTones and announcementsData and fax interworkingSupport for voice and video calls

Statistics and billing informationSince all sessions that pass through the edge of the network pass through the SBC, it is a natural point to gather statistics and usage based information on these sessions

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Roles of SBCDepending of the position where SBC is deployed, it can take different rolesSBC can be configured for more than one role at the same timeRoles of SBC in access part of the network:A-ALG/P-CSCFIWFSPDFRole of SBC between two different networks:IBCFIWFSPDF*

3GPP Network Architecture for Fixed Access*

A-ALG/P-CSCFForwarding of theSIPREGISTER request received from theUEto an entry point determined using the home domain name, as provided by theUEForwarding ofSIPmessages received from theUEto theSIPserver (for exampleS-CSCF)Forwarding of theSIPrequest or response to theUEGeneration of Accounting Charging Records (ACRs).SIPmessage compression/decompressionActing as anALGby changing the appropriate SIP/SDP parameters*

IWF

Typically, IWF is used for translation between H.323 and SIP standard*IBCF

Controlling transport plane functionsSupporting functions to allow the establishment of communication betweenSIPapplications in disparate address realmsProviding network configuration hiding to restrict the subsequent information from being passed outside of an operator's network: exact number ofS-CSCFs, capabilities ofS-CSCFs, or capacity of the network, and so onScreening ofSIPsignaling information based on source, destination, and operator policyGeneration of Accounting Charging Records (ACRs)

SDPFService Policy Decision Function (Tispan architecture only)Checks if the request information received from theAFis consistent with the policy rules defined in theSPDFAuthorizes the requested resources for theAFsessionRequests resources of the A-RACF/C-RACFRequests one or more services from theBGFHides the details of theRACSfrom theAFHides the details of the transport layer from theAF

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Media ProxySimilar to SBC, which acts as a signalling proxy (in a signalling plane), Media Proxy (MP) operates in the media plane Together with SBC forms an SBG (Session Border Gateway)SBC and MP communicate via standardized Ia interface, through H.248 protocolRelation between SBC and MP, is much like MGC and MGW

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SBG in an access network*

Thank you for your attention!*