Session Initiation Protocol (SIP) Services and Networking
SIP InterOp (PBX, Carrier, 3rd Party)
There are many different interpretations of the SIP standard in the telephony world. More than 100 additions have been published to the SIP standard with different vendors supporting different standardized features. As a result, not all SIP carriers, PBXes, and SIP tie lines interoperate correctly.
In cases where SIP doesn’t work, SIP normalization is required to get the SIP format spoken by one device working correctly with another device. Often, this role is provided by a Session Border Controller (SBC).
Curvature is able to provide interoperability and normalization support between differing devices and standards due to having many years’ experience in SIP, and employing engineers with SIP application programming backgrounds.
SBC Planning and Deployment
Session Border Controllers (SBC) act as a point of demarcation and application-layer firewall between the SIP carrier and your internal network. The configuration of a SBC can range from simple to complex, depending on the normalization, security, and routing required by your unique deployment. Curvature can design SBC configurations to meet your complexity needs.
SIP Capacity Planning, especially when moving from TDM
When making the move from PRI services to SIP, many companies overbuy SIP trunk capacity, especially in multisite environments. One reason this occurs is traditional telephony strategies encourage overbuying and transition into SIP when companies migrate. Another reason is PRIs tend to be used in a single site, whereas SIP trunks lend themselves towards being shared amongst sites. Sharing trunks allows for oversubscription in relation to peak times and call spikes, and thus less trunks need to be purchased.
Using various methods and metrics, Curvature can help determine a high watermark of concurrent calls across many sites, helping determine a company-wide trunk requirement for your upcoming purchase.
Note: This service is dependent on PBX type and other telephony technologies in use. Not available on all platforms.
Disaster Recovery and Failover of SIP Trunks
Disaster Recovery (DR) is an important topic for companies attempting to deploy SIP. In most deployments, the SIP carrier offers to deliver multiple circuits, typically to different physical company locations, in case a power, network, or SBC outage happens at one of the two sites. Therefore, services will still be operational through the DR or backup location. Most carriers have options when deploying redundant trunks. Example: Should all calls be sent to one location, failing to the other location only if the primary is down? Alternatively, should load sharing be employed, passing active traffic over both circuits?
Firewall Configurations for SIP
Sometimes, SIP is delivered directly over the Internet. Most companies have an edge firewall between the Internet and PBX or SBC. SIP does not necessarily transit firewalls gracefully, as the endpoint IPs are embedded in the traffic. As such, the firewall is sometimes required to perform the function of an Application Layer Gateway (ALG), modifying the SIP packets as they pass through the firewall and are NATed to the internal IP schema. However, sometimes the SIP carrier also performs the function of an ALG, and this function needs to be disabled on the firewall.
Curvature can inspect SIP traffic at a packet layer and determine the best way for your company’s firewall to react to the SIP traffic.
Carrier Quality of Service
Some SIP carriers provide private IP services not only for SIP, the carrier network. Often, markings are lost due to misconfigurations between the phone and the SBC. Curvature can review your company’s end-to-end QoS policies to ensure desired functionality through your network and the carrier with new VoIP deployments.
Migration Between Old and New
Most transitions to VoIP and SIP do not happen overnight. Interoperability between a legacy PBX and new VoIP deployment have to work together. In some cases, this may even mean converting media between legacy PBX and PureCloud. Curvature has extensive experience integrating legacy PBXes with new VoIP deployments.