AudioCodes mediapack MP-500, User Manual

Page: 456 / 574

SIP User's Manual 456 Document #: LTRT-12801
MP-500 MSBG
9.2 SBC Application
This section provides a detailed description of the device's SBC application. This section
includes the following subsections:
„ Overview of the SBC application (refer to ''Overview'' on page 456 )
„ SIP networking definitions (refer to ''SIP Network Definitions'' on page 458 )
„ SIP dialog initiation process (refer to ''SIP Dialog Initiation Process'' on page 460 )
„ User registration and the device's database (refer to ''User Registration and Internal
Database'' on page
466 )
„ Media handling (refer to ''SBC Media Handling'' on page 468 )
„ Configuration example of SBC (refer to ''SBC Configuration Example'' on page 468 )
9.2.1 Overview
The SBC application provides the following main features:
„ NAT traversal (refer to ''NAT Traversal'' on page 456 )
„ VoIP firewall and security for both signaling and media (refer to ''VoIP Firewall'' on
page
457 )
„
Topology hiding (refer to ''Topology Hiding'' on page 457 )
„ Survivability (refer to ''Survivability'' on page 458 )
„ Routing (refer to ''SIP Network Definitions'' on page 458 and ''SIP Dialog Initiation
Process'' on page 460 ):
•
IP-to-IP routing translations of SIP, UDP, TCP, TLS (when extensive transcoding
is not required)
•
Load balancing and redundancy of SIP servers
•
Routing according to Request-URI\Specific IP address\Proxy\FQDN
•
Alternative routing
•
Routing between different Layer-3 networks (e.g., LAN and WAN)
„ Load balancing\redundancy of SIP servers
„ Internet Telephony Service Providers (ITSP) accounts
„
SIP URI user and host name manipulations (refer to ''SIP Dialog Initiation Process'' on
page
460 )
9.2.1.1 NAT Traversal
The device supports NAT traversal, allowing for example, communication with ITSPs with
globally unique IP addresses, for LAN-to-WAN VoIP signaling (and bearer), using two
independent legs. In addition, it also enables communication for "far-end" users located
behind a NAT on the WAN. The device supports this by performing the following:
„ Continually registering far-end users in its dynamic database
„ Maintaining remote NAT binding state, by frequent registrations, thereby, off-loading
far-end registrations from the LAN IP PBX
„ Uses Symmetric RTP (RFC 4961) to overcome bearer NAT traversal