Aastra Telecom 9143i Series User Manual

Page of 1184
Advanced Operational Features
6-26
41-001160-03, Rev 00, Releaes 2.4 
IP Phone Administrator Guide
Transport Layer Security (TLS)
The IP Phones support a transport protocol called Transport Layer Security 
(TLS) 
and Persistent TLS. TLS is a protocol that ensures communication 
privacy between the SIP phones and the Internet. TLS ensures that no third party 
may eavesdrop or tamper with any message.
TLS is composed of two layers: the TLS Record Protocol and the TLS handshake 
protocol. The TLS Record Protocol provides connection security with some 
encryption method such as the Data Encryption Standard (DES). The TLS 
Handshake Protocol allows the server and client to authenticate each other and to 
negotiate an encryption algorithm and cryptographic keys before data is 
exchanged. TLS requires the use of the following security certificate files to 
perform TLS handshake:
Root and Intermediate Certificates
Local Certificate
Private  Key
Trusted Certificate
When the phones use TLS to authenticate with the server, each individual call 
must setup a new TLS connection. This can take more time when placing each 
call. Thus, the IP phones also have a feature that allows you to setup the 
connection to the server once and re-use that one connection for all calls from the 
phone. It is called Persistent TLS. The setup connection for Persistent TLS is 
established during the registration of the phone. If the phones are set to use 
Persistent TLS, and a call is made from the phone, this call and all subsequent 
calls use the same authenticated connection. This significantly reduces the delay 
time when placing a call.
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