D-Link DFL-260 Product Manual - Page 266

Note: Traffic shaping will not work with the SIP ALG, SIP Components, SIP Media-related Protocols

Page 266 highlights

6.2.8. The SIP ALG Chapter 6. Security Mechanisms Note: Traffic shaping will not work with the SIP ALG Any traffic connections that trigger an IP rule with a service object that uses the SIP ALG cannot be also subject to traffic shaping. SIP Components The following components are the logical building blocks for SIP communication: User Agents These are the end points or clients that are involved in the client-to-client communication. These would typically be the workstation or device used in an IP telephony conversation. The term client will be used throughout this section to describe a user agent. Proxy Servers These act as routers in the SIP protocol, performing both as client and server when receiving client requests. They forward requests to a client's current location as well as authenticating and authorizing access to services. They also implement provider call-routing policies. The proxy is often located on the external, unprotected side of the NetDefend Firewall but can have other locations. All of these scenarios are supported by NetDefendOS. Registrars A server that handles SIP REGISTER requests is given the special name of Registrar. The Registrar server has the task of locating the host where the other client is reachable. The Registrar and Proxy Server are logical entities and may, in fact, reside on the same physical server. SIP Media-related Protocols A SIP session makes use of a number of protocols. These are: SDP Session Description Protocol (RFC4566) is used for media session initialization. RTP Real-time Transport Protocol (RFC3550) is used as the underlying packet format for delivering audio and video streaming via IP using the UDP protocol. RTCP Real-time Control Protocol (RFC3550) is used in conjunction with RTP to provide out-of-band control flow management. NetDefendOS SIP Setup When configuring NetDefendOS to handle SIP sessions the following steps are needed: • Define a single Service object for SIP communication. • Define a SIP ALG object which is associated with the Service object. • Define the appropriate IP rules for SIP communications which use the defined Service object. SIP ALG Options The following options can be configured for a SIP ALG object: 266

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Note: Traffic shaping will not work with the SIP ALG
Any traffic connections that trigger an IP rule with a service object that uses the SIP
ALG cannot be also subject to traffic shaping.
SIP Components
The following components are the logical building blocks for SIP communication:
User Agents
These are the end points or
clients
that are involved in the client-to-client
communication. These would typically be the workstation or device used in an
IP telephony conversation. The term
client
will be used throughout this
section to describe a
user agent
.
Proxy Servers
These act as routers in the SIP protocol, performing both as client and server
when receiving client requests. They forward requests to a client's current
location as well as authenticating and authorizing access to services. They also
implement provider call-routing policies.
The proxy is often located on the external, unprotected side of the NetDefend
Firewall but can have other locations. All of these scenarios are supported by
NetDefendOS.
Registrars
A server that handles SIP
REGISTER
requests is given the special name of
Registrar. The Registrar server has the task of locating the host where the
other client is reachable.
The Registrar and Proxy Server are logical entities and may, in fact, reside on
the same physical server.
SIP Media-related Protocols
A SIP session makes use of a number of protocols. These are:
SDP
Session Description Protocol
(RFC4566) is used for media session initialization.
RTP
Real-time Transport Protocol
(RFC3550) is used as the underlying packet format for
delivering audio and video streaming via IP using the UDP protocol.
RTCP
Real-time Control Protocol
(RFC3550) is used in conjunction with RTP to provide
out-of-band control flow management.
NetDefendOS SIP Setup
When configuring NetDefendOS to handle SIP sessions the following steps are needed:
Define a single
Service
object for SIP communication.
Define a
SIP ALG
object which is associated with the
Service
object.
Define the appropriate
IP rules
for SIP communications which use the defined
Service
object.
SIP ALG Options
The following options can be configured for a SIP ALG object:
6.2.8. The SIP ALG
Chapter 6. Security Mechanisms
266