Configuring Gateway Encryption - Cisco 3521 Administrator's Manual

Configuring Gateway Settings
The gateway supports up to 30 video calls on two B channels. If transcoding or T.120 capabilities are
required, the gateway has to reserve resources for these. The gateway can differentiate between those
calls that support T.120 and those that do not. When receiving calls, the gateway can check whether you
are reserving resources for transcoding or for T.120 capabilities.
Procedure
In the Gateway interface, on the sidebar, click Gateway (if not already selected).
Step 1
Step 2 Click the Settings tab.
Click the Resources button.
Step 3
In the Maximum number of T.120 calls field, enter the number of T.120 enabled calls that you want to
Step 4
reserve gateway resources for. The maximum number is 18.
In the Maximum number of video calls with audio transcoding field, enter the number of audio
Step 5
transcoded video calls you want to reserve gateway resources for. The maximum number is 20.
Note
In the Total call capacity in n calls of n Kbps field, choose a bandwidth.
Step 6
Click Update total call capacity.
Step 7
The number of calls that the gateway can support at that bandwidth automatically appears.

Configuring Gateway Encryption

The gateway supports encrypted calls over IP networks. The encryption conforms to the H.325 standard
and supports the following encryption algorithms:
•
•
Gateway encryption operates in one of the following modes or can be disabled entirely:
•
•
•
An encrypted call uses double the resources of a regular call for all bandwidth rates. Gateway capacity
Note
when encryption is supported is therefore half of regular gateway capacity, rounded up to the nearest
whole call.
Table 3-7
Administrator's Guide for Cisco IPVC 3521 BRI Gateway, Cisco IPVC 3526 PRI Gateway, and Cisco IPVC 3540 PRI Gateway
3-22
The term audio transcoded video calls refers to the process whereby an audio stream in a
multimedia call is transcoded from one codec type to another.
DES—With an encryption key of 56 bits
AES—With an encryption key of 128 bits
Best effort—Implements a "best effort" encryption algorithm. If an endpoint supports encryption, it
connects in an encrypted way. If not, it connects without encryption.
Encryption required—Only connects encrypted calls. Encryption can either be AES 128 or DES 56.
The gateway does not allow non-encrypted calls to connect.
Strong encryption required—Only allows AES 128 encrypted calls. The gateway does not allow
endpoints that do not support AES 128 to connect.
summarizes the encryption-related capabilities that the gateway offers.
Chapter 3 Configuring the Cisco IPVC 3500 Series Gateway
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