Cisco Cisco Expressway Maintenance Manual
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An Expressway-C automatically generates neighbor zones between itself and each discovered Unified CM
node when the system is configured for
node when the system is configured for
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An Expressway automatically generates a neighbor zone named "To Microsoft Lync server via B2BUA" when
the
the
Configuring Media Encryption Policy
The media encryption policy settings allow you to selectively add or remove media encryption capabilities for SIP calls
flowing through the Expressway. This allows you to configure your system so that, for example, all traffic arriving or
leaving an Expressway-E from the public internet is encrypted, but is unencrypted when in your private network.
flowing through the Expressway. This allows you to configure your system so that, for example, all traffic arriving or
leaving an Expressway-E from the public internet is encrypted, but is unencrypted when in your private network.
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The policy is configured on a per zone basis and applies only to that leg of the call in/out of that zone.
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Encryption is applied to the SIP leg of the call, even if other legs are H.323.
Media encryption policy is configured through the Media encryption mode setting on each zone, however the
resulting encryption status of the call is also dependent on the encryption policy settings of the target system (such as
an endpoint or another Expressway).
resulting encryption status of the call is also dependent on the encryption policy settings of the target system (such as
an endpoint or another Expressway).
The encryption mode options are:
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Force encrypted: all media to and from the zone must be encrypted. If the target system/endpoint is
configured to not use encryption, then the call will be dropped.
configured to not use encryption, then the call will be dropped.
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Force unencrypted: all media must be unencrypted. If the target system/endpoint is configured to use
encryption, then the call may be dropped; if it is configured to use Best effort then the call will fall back to
unencrypted media.
encryption, then the call may be dropped; if it is configured to use Best effort then the call will fall back to
unencrypted media.
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Best effort: use encryption if available, otherwise fall back to unencrypted media.
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Auto: no specific media encryption policy is applied by the Expressway. Media encryption is purely dependent
on the target system/endpoint requests. This is the default behavior and is equivalent to how the Expressway
operated before this feature was introduced.
on the target system/endpoint requests. This is the default behavior and is equivalent to how the Expressway
operated before this feature was introduced.
Encryption policy (any encryption setting other than Auto) is applied to a call by routing it through a back-to-back user
agent (B2BUA) hosted on the Expressway.
agent (B2BUA) hosted on the Expressway.
When configuring your system to use media encryption you should note that:
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Any zone with an encryption mode of Force encrypted or Force unencrypted must be configured as a SIP-only
zone (H.323 must be disabled on that zone).
zone (H.323 must be disabled on that zone).
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TLS transport must be enabled if an encryption mode of Force encrypted or Best effort is required.
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The call component routed through the B2BUA can be identified in the call history details as having a
component type of B2BUA.
component type of B2BUA.
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) that can have a media
encryption policy applied.
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is enabled.
Configuring the B2BUA for Media Encryption
The B2BUA used for encryption (and ICE support) is a different instance to the B2BUA used for Microsoft Lync
integration. Whereas the Lync B2BUA has to be manually configured and enabled, the B2BUA used for encryption is
automatically enabled whenever an encryption policy is applied.
integration. Whereas the Lync B2BUA has to be manually configured and enabled, the B2BUA used for encryption is
automatically enabled whenever an encryption policy is applied.
Configuring ICE Messaging Support
The ICE support option is a per-zone configuration setting that controls how the Expressway supports ICE messages
to and from SIP devices within that zone.
to and from SIP devices within that zone.
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Cisco Expressway Administrator Guide