Avaya SIP Software 3.2 for 1200 Series User Manual download pdf (Page 250)

Note:

The server must be configured with the appropriate protocols enabled for the success

condition to be realized. Failure results are possible if the server configuration is changed

to disallow protocols.

Managing connection persistence

The IP Deskphone attempts to establish and maintain a persistent connection with the proxy

when TCP and TLS are active protocols. After this connection is established, the IP Deskphone

sends all outgoing connections over this persistent connection.

SIP IP Deskphones and servers, which use UDP to communicate, listen for incoming

connections on known ports, and originate each request on a randomly selected UDP port.

Even if TCP is used, new requests can potentially be sent using a new source port unless the

connection between the IP Deskphone and proxy is kept active.

Connection persistence does the following:

• Keeps a connection established between a client and the outgoing proxy.

• Reuses the open connection for future incoming and outgoing requests.

Figure 49: Incoming/Outgoing with connection reuse

When using UDP, an IP Deskphone behind a firewall must periodically send a request to the

server to maintain an open pinhole in the firewall so that the server can contact the IP

Deskphone when sending requests.

When using TCP/TLS and connection persistence, it is not necessary to send a SIP_PING to

the server in order to keep a pinhole alive, and the keep-alive mechanism is reduced to a

method which involves significantly less overhead.

The following figure demonstrates how critical it is that the server can communicate directly

with the IP Deskphone through the use of the established TCP connection because it has no

way of getting through the firewall in order to contact port 5060 on the IP Deskphone.

Security

250 SIP Software for Avaya 1200 Series IP Deskphones-Administration January 2012

1 2 ... 245 246 247 248 249 250 251 252 253 254 255 ... 319 320

No comments

Avaya SIP Software 3.2 for 1200 Series User Manual Page 250