SBC VOIP Peering



Service Description


This is a Business to Business category Session Border Control and VOIP Peering service that enables an Operator to Interconnect with Peering partners as a traffic aggregator. The calls are sent to the SBC from internal Soft-Switches or Signaling and Media Gateways of the Operator.
The SBC is essentially aggregating traffic from all internal Soft-Switches/Gateways, or from Originating Gateways that are customers of the Operator when the Operator is providing Whole-Sale VOIP Termination.
The service distributes traffic after searching for the longest matching destination prefix and forwarding traffic to Interconnect VOIP partners according to one of the following methods:

  • Least Cost Routing (LCR) based on rate sheets imported from Interconnect partners
  • Priority Based Routing according to priorities set by on per prefix basis

Architecture



The service acts a SIP Back-to-Back User agent with access control, comes bundled with complete Interconnect rating and charging and several other important use cases some of which are listed below:


Use Cases



Terminating Partner Management


Service enables an operator to define terminators, their trunk groups and their IP addresses. More advanced use cases include defining the capability set of the trunks especially the codecs supported by it and the capacity available on the IP.



User Authentication


User Authentication is the process of identifying the user behind any incoming request. Depending on the security framework used, different variations are used for this purpose. SBC service supports new request authentication using Radius AAA client or can also query a locally attached database or a text file.

Originator Balance Authorization


SBC service can also perform Authorization for prepaid balance checking of originating gateways which is an ideally suited feature for Wholesale terminators. It results in having Prepaid originators whose accounts cannot go into negative and thus ensure revenue loss and simplifies charging and billing.

CDR Generation


The service generates Call Data Records (CDRs) all calls and does extensive reporting for Interconnect use cases. it can also perform accounting and rating/charging of calls as per Operator’s plans for wholesale VOIP traffic.


Connection to Least Cost Router


This is part of the service described above for Peering SBC but in this case, the service only performs Routing based on responses from third party Routing Engines such as LCR or Priority/QoS based Routing Servers  in a request response model. Both SIP and SOPA/XML based APIs are available for this service.
In case of SIP, the client requests destination routes for a call by sending to the SIP Router, considering it as its next hop peer for the call. The SIP Router performs routing by looking in its database for LCR/Priority Routes etc. and sends back the selected routes in a SIP 302 Redirect message. The client redirects to one of the selected routes and proceeds with the call.


NAT Traversal


When the originating clients are behind NAT, then the SBC service needs to have arrangement to traverse the NAT to reach the endpoints behind NAT. The service supports different ways to do this. The most fail-proof way of achieving this is to do full media proxy on both sides and since the Media Routes SBC service has its own Media Proxy Servers as an integral part of it, it is fully capable of doing it.

Media Trans-coding


When the sender wants to use a codec not supported by the receiver, transcoding between codecs is needed. Transcoding requires full media proxy and is a CPU intensive process. Media Routes SBC service through its attached media server fully supports media trans-coding between most common codecs. To save on the CPU, some operators use external hardware based or even cloud based transcoding servers. SBC service fully supports both models and can forward media streams to external trans-coders and manage them accordingly.

Topology Hiding


Topology Hiding involves hiding the topology of the core network from external entities and also hiding the signaling and (optionally) media IP addresses of the originator from the terminator and vice versa. To achieve this, SBC service works as a B2BUA (Back to Back User Agent) which means that it terminates the incoming calls onto itself and then originates a fresh call towards the terminator. The two call legs belong to the same session but do not share any information of one party with the other. To complete topology hiding even of the media streams, the service comes with full media proxy functionality.

Real-Time monitoring


SBC Service comes with Session Management module that inserts each session into a database as it is authorized and then removes it from there when the session terminates. A GUI provides real-time view into the sessions and any other mechanism can be established to view ongoing sessions.

10 or 7 digit dialing


10 digit dialing requires that users within the same country can dial within the country without first dialing the country code. 7 Digit dialing requires an awareness of the caller’s area code and it then allows users to call within their area code only by dialing the last seven digits.
SBC service comes with a number translation module that allows multiple configurations and can even append the caller’s area code behind the called digits if it finds only seven digits in the called number. Digit length for countries with other lengths can be adjusted as per configuration.

Congestion Control


All elements in a system have limits on the number of requests that they can process in a given time window like a second. When originators are allowed to send multiple concurrent calls, they may cause congestion by sends requests in bursts. Even if SBC service can handle the burst, there may be terminating or Interconnect partners that may not sustain such bursts. In such situations it is important to control such bursts and the process is called Congestion Control. SBC service provides a congestion control feature for this purpose. When this feature is enabled, SBC service rate limits the traffic entering into the network from originating points to a maximum rate. Any new calls requests arriving when the configured rate limit has been already reached are discarded with appropriate SIP message indicating congestion sent back to the originator. Furthermore, to handle irregular and random bursts of incoming calls, a burst size is also configured that allows SBC service to absorb burst of up to a maximum number of requests. As an example, let’s say that we set the rate limit to be 100 new SIP session requests per second and the burst size to be 200 requests. Now, if the average incoming request rate remains within 100 per second, but a burst of 300 requests arrives in a few milliseconds, the SBC service would handle up to 200 new requests and discard the rest while keeping the overall rate per second within 100.

Terminator Capacity Control


SBC service comes with a Session Management which provides a real-time view of all ongoing sessions. This feature combined with Vendor Concurrency Management provides a way for SBC to know available capacity on all routes and discard the routes on which the capacity has met its limit. This improves the overall call completion rate and post dial delay

Incompatibility Removal


With different network elements outside communicating with others in the Operator’s core network, incompatibilities may arise at times when some of them do not conform to the details of the SIP protocol. In such situations, SBC service sitting at the border provides means through its protocol correction feature to fix such errors.

Terminator Failover


SBC service supports failover mechanisms to secondary terminators in case the primary terminator that represents the best route fails the connection. It has the ability to figure out if the call was rejected because of congestion reasons and it will give them another try through other sources.

Classes of Service


SBC service supports Technical Prefixes which are extra digits which are issued to originators that they can append behind dialed digits to indicate the class of service that they need. The service removes those digits and sends the actual dialed digits to other network elements such as AAA and Charging. It can also be configured to send the Technical-Prefix separately into any request which can then be consumed by other network elements for their configured purposes. It can also send a pre-configured Technical-Prefix to terminators when sending them VOIP traffic.

Outgoing Toll Bypass


SBC service supports ENUM based look ups to directly communicate with service providers over IP that have exposed their networks over ENUM protocol. Saves all toll charges paid to terminators for such calls and most of the times improves the voice quality as well.


Incoming Toll Bypass


Allows Operators to expose their IP addresses to originators over ENUM protocol so that other service providers can connect to it bypassing their toll charges.
  


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