2.3. Do You Need an SBC?ΒΆ

Before installing an SBC it might be worth thinking whether an SBC is needed in the first place. To answer this, here are a couple of questions:

  • will you deal with SIP devices behind a NAT?  If the answer is yes then deploying an SBC is most likely the right choice. While there are already a number of NAT traversal solutions such as STUN RFC 5389, TURN RFC 5766 or ICE RFC 5245 these solutions either do not solve all issues or require certain extensions at the end devices which are not always available.
  • do you deploy SIP devices that you would not want other users or operators to be able to send SIP or media traffic directly to?  This is usually the case when a PBX or a PSTN gateway is deployed. If the answer is yes then an SBC would be the right choice as it would hide the IP addresses of these devices and prevent direct communication to them.
  • do you deploy a heterogenous set of VoIP devices?  If yes then an SBC can be the proper point in the network to fix interoperability issues by normalising the traffic and solving issues created by protocol implementation peculiarities.
  • do you want to protect your VoIP devices from Denial of Service attacks?  If there is the danger that an attacker might overload your network and VoIP devices by generating a large amount of SIP requests and RTP packets then an SBC would act as a first line of defence and filter the malicious traffic before it reaches the core VoIP components.
  • do you want to reduce the possibilities of fraud?  If there is a danger that a fraudulent user might try to make more calls than allowed then an SBC would be the best approach. With an SBC it is possible to reliably limit the number of calls made by a user.
  • do you want to protect your users from a bill shock?  When a user calls an expensive number and fails to terminate the call in a proper manner then he will most likely get a shock when receiving the bill for a call lasting for hours. An SBC on the border of the network can be configured so as to cut calls after a certain period of time and hence limit the damage.
  • will you need to transcode the media?  If different users are using different codecs - which is especially the case when connecting mobile to fixed networks - then media transcoding will be needed. Media transcoding is often an integral part of SBCs.
  • will your users be using browser telephony using WebRTC? Then you need to connect them to the rest of SIP world and SIP-PSTN gateways using the built-in WebRTC gateway.

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