session border contoller

8/12/2019 Session Border Contoller

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IMS Training


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What is an SBC? Session Border Controller is an element regularly used

VoIP networks, whose role is to control the signallingbetween 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 SBC

Border: 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

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Position of SBC in VoIP networks

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Lets take a closer look to SBCs function

Security- protects the network (and devices inside)

Prevents DoS, DDoS attacks

Topology hiding

Encryption of signaling (TLS, IPSec)

Encryption of media (SRTP)

Connectivity- allow different parts of the network to communicate

through the use of a variety of techniques NAT traversal

SIP normalization via SIP message and header manipulation (SMM)

IPv4 to IPv6 interworking

Protocol translations between SIP, SIP-I, H.323

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Quality of service QoS

Traffic policing

Resource allocation

Rate limiting

Call admission control

ToS/DSCP bit setting

RegulatorySBC can optionally provide regulatoryrequierements

emergency calls prioritization

lawful interception

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Media services DTMF relay and interworking

Media transcoding

Tones and announcements

Data and fax interworking Support for voice and video calls

Statistics and billing information

Since all sessions that pass through the edge of the network passthrough the SBC, it is a natural point to gather statistics and usagebased information on these sessions

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Rolesof SBC Depending of the position where SBC is deployed, it can take different

roles

SBC can be configured for more than one role at the same time

Roles of SBC in access part of the network: A-ALG/P-CSCF

IWF

SPDF

Role of SBC between two different networks:

IBCF

IWF

SPDF

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3GPP Network Architecture for Fixed

Access

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A-ALG/P-CSCF

Forwarding of the SIP REGISTER request received fromthe UE to an entry point determined using the home domain

name, as provided by the UE Forwarding of SIP messages received from the UE to

the SIP server (for example S-CSCF)

Forwarding of the SIP request or response to the UE

Generation of Accounting Charging Records (ACRs).

SIP message compression/decompression

Acting as an ALG by changing the appropriate SIP/SDPparameters

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

standard

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IBCF Controlling transport plane functions

Supporting functions to allow the establishment of communicationbetween SIP applications in disparate address realms

Providing network configuration hiding to restrict the subsequentinformation from being passed outside of an operator's network:

exact number of S-CSCFs, capabilities of S-CSCFs, or capacity of thenetwork, and so on

Screening of SIP signaling information based on source, destination,and operator policy

Generation of Accounting Charging Records (ACRs)


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SDPF

Service Policy Decision Function (Tispan architecture only)

Checks if the request information received from the AF isconsistent with the policy rules defined in the SPDF

Authorizes the requested resources for the AF session

Requests resources of the A-RACF/C-RACF

Requests one or more services from the BGF

Hides the details of the RACS from the AF

Hides the details of the transport layer from the AF

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Media Proxy Similar 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 protocol

Relation between SBC and MP, is much like MGC and MGW

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SBG in an access network

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Thank you for your attention!

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session border contoller

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