Call Processing Language
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... language. We
call this language a call processing language.
The development of this document has been substantially informed by
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The development of this document has been substantially informed by
the development of a particular call processing language, as
described in [5]. In general, when this document refers to "a call
processing language ...
... call processing language, as
described in [5]. In general, when this document refers to "a call
processing language," it is referring to a generic language that
fills this role ...
... language that
fills this role; "the call processing language" or "the CPL" refers
to this particular language ...
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The Call Processing Language operates on a generalized model of an
Internet telephony network ...
... Creation and transport of a call processing language script ...
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Users create call processing language scripts, typically on end
devices, and transmit them through the network to signalling servers.
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... more requested features produce ambiguous or conflicting behavior
[8]. Feature interaction issues for features implemented with a call
processing language can be roughly divided into three categories:
feature-to-feature in one server, script-to-script in one server, and
server-to-server.
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... Due to the explicit nature of event conditions discussed in the
previous section, feature-to-feature interaction is not likely to be
a problem in a call processing language environment. Whereas a
subscriber to traditional telephone ...
... class of server-to-server interactions are best resolved by
the underlying signalling protocol, since they can arise whether the
signalling servers are being controlled by a call processing language
or by some entirely different means. One example of this is
forwarding loops, where user X may have calls forwarded to Y, who has
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... calls forwarded back to X. SIP has a mechanism to detect such loops.
A call processing language server thus does not need to define any
special mechanisms to prevent such occurrences; it should, however,
be possible to trigger a different set of call processing ...
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This section lists those properties of a call processing language
which we believe to be necessary to have in order to implement the
motivating examples, in line with the described architecture ...
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These are some abstract attributes which any proposed call processing
language should possess.
o Light-weight, efficient, easy to implement
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To be useful, a call processing language obviously should be able to
react to and initiate call signalling events.
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A number of other features that a call processing language should
have do not refer to call signalling per se; however, they are still
extremely desirable to implement many useful features.
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... encryption is
very useful. The specification of this mechanism can be (and probably
ought to be) a separate specification from that of the call
processing language itself.
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