Product specifications

Dialogic® BorderNet™ 4000 SBC Product Description Document
29
• Far-end NAT traversal
• Support for Application Services call flows
• Support for forked calls
• DNS (SRV) Application Server redundancy
IPPBX Registration Support
The BorderNet 4000 SBC can process SIP registration requests from both the consumer
devices (such as IADs, soft phones, desk phones, mobile extensions, etc.) as well as from
the IPBPBXs. IPPBX Registration Support is implemented as per the guidelines in the
SIPconnect 1.1 recommendation and RFC 6140—Registration for Multiple Phone Numbers in
the Session Initiation Protocol (SIP)-standard. Specifically, the BorderNet 4000 SBC
supports bulk registration of extensions from the IPPBXs.
SIP REFER Handling
The BorderNet 4000 SBC can be configured to terminate SIP REFER messages associated
with unattended call transfer messages. Upon termination, The BorderNet 4000 SBC
initiates a new call leg with the transfer target and later bridges the original call leg with the
transferred leg to locally complete the call transfer. This capability is often desired in contact
center and hosted IPPBX solutions where call transfer is routinely used. The advantages of
terminating call transfer requests at the border element include cost savings and seamless
user experience across various devices and user platforms.
Overload Management
Overload occurs when the BorderNet 4000 SBC cannot handle all of the incoming messages.
Overload conditions may cause traffic congestion and could result in a 503 error message
until the overload is cleared.
The BorderNet 4000 SBC generates an alarm for each overload level, escalating the alarm
as the overload increases. At the same time, the BorderNet 4000 SBC monitors the network
interface bandwidth and global system load. Packets are controlled and dropped at the
interface level, and the global system load takes precedence over the interface load levels.
Incoming packets are categorized and prioritized, and lowest priority traffic is dropped first.
Prioritization can occur at the system level or on a specific network interface.
When the next alarm level is reached, the previous alarm is turned off. When the traffic
drops below the overload threshold for a minimum period of time, the alarm is turned off.
Note: The BorderNet 4000 SBC does not drop SIP signaling associated with existing
sessions, messages related to emergency calls, or packets carrying internal system
messaging.
For rejected SIP messages, the BorderNet 4000 SBC returns a 503—Warning: Server
Overload status code to invites from authorized peers. A Retry-After message is sent with
all rejected messages, informing the client to retry the request after a specific number of
seconds (the default value is 120 seconds).
During overload conditions, the BorderNet 4000 SBC processes the first line of each
message to determine if the message should be handled or dropped. BYE or CANCEL
messages are parsed; for all other request messages, the BorderNet 4000 SBC compares
the request URI with the emergency list as follows:
• If the request URI is present in the emergency list, the message is parsed and
handled.