Last time in this series of posts on telephony protocols, I looked at H.323, a complex framework of standards and protocols that are used to enable multimedia communication over packet networks. This time I'll be taking a look at a comparatively simple protocol, the Skinny Client Control Protocol (SCCP). In contrast to some of the other telephony protocols, you'll be glad to know that there comparatively little that you need to remember about it for the exams!
SCCP is a Cisco proprietary master/slave protocol that is used by call agents such as CallManager/Unified Communications Manager to communicate with devices such as Cisco IP phones using TCP port 2000. SCCP can be used to signal events such as on-hook, off-hook, and phone button presses.
Here is a list of call states that can be signalled using SCCP:
1 : Off-hook
2: On-hook
3: Ring Out
4: Ring In
5: Connected
6: Busy
7: Line in Use
8: Hold
9: Call Waiting
10: Call Transfer
11: Call Park
12: Call Proceed
13: In Use Remotely
14: Invalid Number
These call states can be seen when troubleshooting using CallManager traces.
Mark
Mark Lewis (CCIE#6280) is an independent consultant who helps service provider and large enterprise clients design and implement leading-edge technologies. Over the last couple of years, Mark has designed and implemented a variety of large-scale technology solutions including VPN, MPLS, QoS, data center, and IP telephony. Mark is the author of three books for Cisco Press: Comparing, Designing, and Deploying VPNs, Troubleshooting Virtual Private Networks, and CCIE Voice Exam Quick Reference Sheets.
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