Cisco Cisco Expressway Maintenance Manual
Call types and licensing
This section describes the different call types recognized by the Expressway and how they are licensed.
Call types
The Expressway distinguishes between the following 2 types of call:
n
Unified CM remote sessions: these are "mobile and remote access" calls i.e.video or audio calls from
devices located outside the enterprise that are routed via the Expressway firewall traversal solution to
endpoints registered to Unified CM. These calls do not consume any rich media session licenses.
devices located outside the enterprise that are routed via the Expressway firewall traversal solution to
endpoints registered to Unified CM. These calls do not consume any rich media session licenses.
n
Rich media sessions: these calls consume rich media session licenses and consist of every other type
of video or audio call that is routed through the Expressway. This includes business-to-business calls,
B2BUA calls, and interworked or gatewayed calls to third-party solutions. The Expressway may take the
media (traversal) or just the signaling (non-traversal).
Audio-only SIP traversal calls are treated distinctly from video SIP traversal calls. Each rich media
session license allows either 1 video call or 2 audio-only SIP traversal calls. Hence, a 100 rich media
session license would allow, for example, 90 video and 20 SIP audio-only simultaneous calls. Any other
audio-only call (non-traversal, H.323 or interworked) will consume a rich media session license.
of video or audio call that is routed through the Expressway. This includes business-to-business calls,
B2BUA calls, and interworked or gatewayed calls to third-party solutions. The Expressway may take the
media (traversal) or just the signaling (non-traversal).
Audio-only SIP traversal calls are treated distinctly from video SIP traversal calls. Each rich media
session license allows either 1 video call or 2 audio-only SIP traversal calls. Hence, a 100 rich media
session license would allow, for example, 90 video and 20 SIP audio-only simultaneous calls. Any other
audio-only call (non-traversal, H.323 or interworked) will consume a rich media session license.
Both types of call consume system resources and each Expressway has a maximum limit of 150 concurrent
calls (500 calls on Large VM servers).
calls (500 calls on Large VM servers).
Note that:
n
Expressway defines an "audio-only" SIP call as one that was negotiated with a single “m=” line in the SDP.
Thus, for example, if a person makes a “telephone” call but the SIP UA includes an additional m= line in the
SDP, the call will consume a video call license.
Thus, for example, if a person makes a “telephone” call but the SIP UA includes an additional m= line in the
SDP, the call will consume a video call license.
n
While an "audio-only" SIP call is being established, it is treated (licensed) as a video call. It only becomes
licensed as "audio-only" when the call setup has completed. This means that if your system approaches its
maximum licensed limit, you may be unable to connect some "audio-only" calls if they are made
simultaneously.
licensed as "audio-only" when the call setup has completed. This means that if your system approaches its
maximum licensed limit, you may be unable to connect some "audio-only" calls if they are made
simultaneously.
What are traversal calls?
A traversal call is any call passing through the Expressway that includes both the signaling (information
about the call) and media (voice and video). The only other type of call is a non-traversal call, where the
signaling passes through the Expressway but the media goes directly between the endpoints (or between
one endpoint and another system in the call route).
about the call) and media (voice and video). The only other type of call is a non-traversal call, where the
signaling passes through the Expressway but the media goes directly between the endpoints (or between
one endpoint and another system in the call route).
A call is “traversal” or “non-traversal” from the point of view of the Expressway through which it is being
routed at the time. Traversal calls use more resource than non-traversal calls.
routed at the time. Traversal calls use more resource than non-traversal calls.
The following types of calls require the Expressway to take the media. They are classified as traversal calls
and always pass through the Traversal Subzone:
and always pass through the Traversal Subzone:
n
Unified CM remote sessions (these do not require a rich media session license)
n
all other firewall traversal calls that are not Unified CM remote sessions, where the local Expressway is
either the traversal client or traversal server
either the traversal client or traversal server
n
calls that are gatewayed (interworked) between H.323 and SIP on the local Expressway
n
calls that are gatewayed (interworked) between IPv4 and IPv6 on the local Expressway
Cisco Expressway Administrator Guide (X8.1.1)
Page 267 of 343
Reference material
Call types and licensing