VoIP and UC: Making the transition
It seems a very long time ago but ever since the first commercial VoIP calls were made in the 1990s the industry has predicted packetized-voice would replace traditional voice technology in enterprise networks.
Enterprises across the world are joining the growing trend of migrating their traditional TDM based telephony systems to IP-based voice and unified communications (UC) networks. There are many benefits to such a move including the merging of the voice and data networks as well the implementation of new converged voice and data services. While these make UC attractive resellers and integrators need to be fully aware of the issues and implications to ensure any UC implementation is smooth.
The deployment of UC systems with VoIP services normally involves systems and equipment made up from different vendors. Resellers and integrators often promote these multi-vendor systems as best-of-breed solutions, which offer the broadest range of features and functionality. The drawback is interoperability between multiple disparate systems. During any migration process elements within the UC system have to work seamlessly with legacy communications devices like TDM-based PBXs, analogue phones and fax machines with all these devices remaining in use across the enterprise at some point.
The interoperability between the UC and VoIP elements in the network are determined by the Session Initiation Protocol (SIP), which has become the de facto standard protocol for real-time communications on IP networks and any device supporting the protocol automatically communicates with any other SIP device. Problems have arisen as vendors have developed their own versions of SIP over the years. While they may be completely compliant with the SIP standard many aren’t necessarily compatible with another.
Resellers can overcome this by making sure the UC equipment is fully interoperable, which may require lengthy testing that some vendors might find unacceptable. The alternative is to deploy a protocol mediation solution, which acts as an intermediary between different implementations of SIP, allowing different equipment to communicate with each other without the testing.
The same issues occur with VoIP data streams. Again different vendors may deploy different compression and packetization algorithms (codecs) for transmitting voice traffic over the network. In some cases, where the two endpoints do not support the same codecs, an intermediary media transcoding device may be required to enable full interoperability throughout the network.
With interoperability addressed perhaps the most critical issue when considering a move to UC and VoIP is security. Since UC and VoIP systems are IP-based and run over the same data networks as other enterprise data services, they are exposed to threats like denial of service (DOS) attacks, eavesdropping, fraud and VoIP spam.
Other common data services can be protected by standard firewall solutions. VoIP’s reliance on SIP makes standard firewalls insufficient for protecting UC networks, as they are unable to analyse the contents of the SIP messages, an essential requirement for identifying suspicious behavior. A specialised application layer firewall device in the network, commonly known as an Enterprise Session Border Controller (E-SBC) is required.
The E-SBC performs a number of the functions we have already discussed in this article, including protocol mediation, media transcoding and facilitating interoperability between different vendors’ VoIP and legacy TDM equipment. The E-SBC provides critical features, such as call admission control, prevention of DOS attacks, topology hiding (i.e. concealing the internal structure of the enterprise VoIP network) and encryption of signaling and media streams. In a multi-vendor UC environment, the E-SBC allows different vendors’ systems to communicate seamlessly with each other, as well as providing security and enabling reliable connectivity to external SIP trunking providers.
Resellers and integrators play a very important advisory role in helping organisations transition to next generation UC and VoIP systems, providing guidance and answers to some of the migration issues.
Yaniv Epshtein is director UK & Nordics at Audiocodes (NASDAQ: AUDC)
