Yealink SIP-T2 SERIES Administrator's Manual page 25

request to its destination, as the request URI always specifies the host which is essential.
The port and protocol are not always specified by the request URI. Thus if the request
does not specify a port or protocol, a default port or protocol is contacted. It may be
preferential to use this method when not using an application layer firewall. Application
layer firewalls like to know what applications are flowing through which ports and it is
possible to use content types of other applications other than the one you are trying to
let through what has been denied.
User Agent Server (UAS)
UAS is a server that hosts the application responsible for receiving the SIP requests from
a UAC, and on reception it returns a response to the request back to the UAC. The UAS
may issue multiple responses to the UAC, not necessarily a single response.
Communication between UAC and UAS is client/server and peer-to–peer.
Typically, a SIP endpoint is capable of functioning as both a UAC and a UAS, but it
functions only as one or the other per transaction. Whether the endpoint functions as a
UAC or a UAS depends on the UA that initiates the request.
This section introduces SIP VP-T49G, SIP-T48G, SIP-T46G, SIP-T42G, SIP-T41P , SIP-T40P ,
SIP-T29G, SIP-T27P , SIP-T23P/G, SIP-T21(P) E2, SIP-T19(P) E2 and CP860 IP phone models.
These IP phones are endpoints in the overall network topology, which are designed to
interoperate with other compatible equipments including application servers, media
servers, internet-working gateways, voice bridges, and other endpoints. These IP
phones are characterized by a large number of functions, which simplify business
communication with a high standard of security and can work seamlessly with a large
number of SIP PBXs.
IP phones provide a powerful and flexible IP communication solution for Ethernet TCP/IP
networks, delivering excellent voice quality. The high-resolution graphic display
supplies content in multiple languages for system status, call log and directory access.
IP phones also support advanced functionalities, including LDAP , Busy Lamp Field, Sever
Redundancy and Network Conference.
IP phones comply with the SIP standard
network that supports this model of phone.
For a list of key features available on Yealink IP phones running the latest firmware, refer
to Key Features of IP Phones
In order to operate as SIP endpoints in your network successfully, IP phones must meet
the following requirements:
A working IP network is established.

VoIP gateways are configured for SIP .

The latest (or compatible) firmware of IP phones is available.

(RFC 3261), and they can only be used within a
on page 15.
Product Overview
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