There have been some pretty big release announcements relating to Genesys SIP over the last few weeks:
SIP Proxy – 22.214.171.124 [03/15/13] – General
SIP Proxy provides an interface for SIP communication between SIP devices and SIP Server components. It handles register requests, load-balances SIP transactions, and provides an alternative HA model that supports deploying primary/backup SIP Server instances within the same HA pair across different subnets and does not require a virtual IP address.
SIP Server – 126.96.36.199 [03/15/13] – General
Support for a restricted release of SIP Cluster.
Support for Resource Manager in active-active HA mode.
Support for Genesys SIP Proxy
Sipspan2 – 8.1.100.09 [03/15/13] – General
sipspan2 is a log navigation tool designed to simplify troubleshooting in a SIP Cluster environment. It processes log files generated by multiple Genesys components to build a troubleshooting view where each record represents a call flow event given as a clickable link to the corresponding place in a log file.
The primary focus of these releases are to improve the scalability and resilience of the Genesys SIP architecture. Of particular note is the introduction of a new component, SIP Proxy which removes the dependency on third party solutions such a Windows NLB, F5 BIG-IP LTM or IP Address Takeover to provide SIP server High Availability (HA).
The technical documentation relating to these releases is still being produced. However there is a link here which provides deployment information for SIP Proxy:
The primary purpose of Genesys SIP Proxy is to provide high availability without requiring a virtual IP address.
An N+1 pool of proxy instances is defined for each SIP Server HA pair. The proxy instances monitor the SIP Server pair to determine which is active and which is backup.
Incoming SIP messages are proxied to the primary SIP Server instance. It is the responsibility of external SIP user agents to select a proxy instance based either on DNS or static configuration of multiple IP addresses, and to fall back to an alternate instance if the select instance is not responding.
In a standard deployment, an N+1 pool of SIP Proxy instances handles incoming and outgoing SIP transactions between a SIP Server HA pair and external SIP elements. Each SIP transaction would be handled by a single proxy instance.
SIP Proxy is responsible for proxying SIP messages from external SIP user agents to the appropriate SIP Server. It is the responsibility of each external user agent to choose a SIP Proxy instance when sending a SIP message.
In SIP Cluster mode, Session storage ensures that each message from the same or related SIP session is routed to the same SIP Server.
SIP Proxy acts as a SIP registrar. SIP Proxy has shared registration-info storage. Any endpoint can be reached by any SIP Proxy. SIP Proxy uses SIP Server as an authentication server. It passes REGISTER requests to SIP Server and waits for a response.
SIP Proxy provides load balancing of incoming traffic across SIP Servers. This is achieved by using a random or round-robin SIP Server selection routine.
SIP Proxy depends on DNS to resolve the SIP Proxy FQDN by A and SRV records (as described in RFC 2782). More specifically, SIP endpoints must support SIP SRV Server Resolution as defined in RFC 3263 – Locating SIP Servers (don’t worry – most IP Phones do). Basically, SRV records are a nameserver record type that return the port as well as weight and priority information for a request. Hence, the SRV records are used by the SIP endpoint to discover the IP address and port of a SIP proxy it should use.