B2Bua And Stateful Proxy Operating Modes - AudioCodes Mediant 500L User Manual

•
User-defined manipulation of SIP To, From, and Request-URI host names.
•
Generates a new SIP Call-ID header value (different between legs).
•
Changes the SIP Contact header and sets it to the device's address.
•
Layer-3 topology hiding by modifying source IP address in the SIP IP header.

SIP normalization: The device supports SIP normalization, whereby the SBC
application can overcome interoperability problems between SIP user agents. This is
achieved by the following:
•
Manipulation of SIP URI user and host parts.
•
Connection to ITSP SIP trunks on behalf of an IP-PBX - the device can register
and utilize user and password to authenticate for the IP-PBX.

Survivability:
•
Routing calls to alternative routes such as the PSTN.
•
Routing calls between user agents in the local network using a dynamic database
(built according to registrations of SIP user agents).

Routing:
•
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.

ITSP accounts.

SIP URI user and host name manipulations.
29.2

B2BUA and Stateful Proxy Operating Modes

The device can operate in one or both of the following SBC modes:

Back-to-Back User Agent (B2BUA): Maintains independent sessions toward the
endpoints, processing an incoming request as a user agent server (UAS) on the
inbound leg, and processing the outgoing request as a user agent client (UAC) on the
outbound leg. SIP messages are modified regarding headers between the legs and all
the device's interworking features may be applied.

Stateful Proxy Server: SIP messages traverse the device transparently (with minimal
interference) between the inbound and outbound legs, for connecting SIP endpoints.
By default, the device's B2BUA mode changes SIP dialog identifiers and topology data in
SIP messages traversing through it:

Call identifiers: Replaces the From-header tag and Call-ID header so that they are
different for each leg (inbound and outbound).

Routing headers:
•
Removes all Via headers in incoming requests and sends the outgoing message
with its own Via header.
•
Doesn't forward any Record-Route headers from the inbound to outbound leg,
and vice versa.
•
Replaces the address of the Contact header in the incoming message with its
own address in the outgoing message.

Replaces the User-Agent/ Server header value in the outgoing message, and replaces
the original value with itself in the incoming message.
User's Manual
Mediant 500L Gateway & E-SBC
640 Document #: LTRT-10532