QoS Policing

Policing can be used in either the inbound or outbound direction and it discards packets which are exceeding a configured rate limit.

Pay attention to the fact that policing is dropping packets , it can result in retransmissions (TCP acknowledge), so it is better to use policing on higher bandwidth links !!!

Qos Policing is also considered as an Traffic Conditioner

MIC,LSC, Security Endpoints

Regarding security endpoints, you have 2 opportunities :

  • Newer phones are using more an existing Mafufacturing Installed Certificate , this is the MIC
  • Meanwhile , old phones will use a Locally Significant Certificate ( LSC) which will be installed by the Certificate Authority Proxy Function (CAPF)

As LSC must be a transaction between the Ip phone and the CAPF , here is the process as it is issued :

  1. IP Phone generates a public/private key pair
  2. A TLS Session is established with the CAPF Service and the keys and identity are sent from the phone to CAPF
  3. The CAPF Service creates and sends an LSC to the phone
  4. The IP Phone installs the LSC

Also for info, the CAPF Service must be in the phone CTL file , which is downloaded from the TFTP when the phone boots .

CAST – Cisco Audio Session Tunnel

Cast is the protocol used into the conversation between the webcam and your IP Phone.

It uses TCP/4224 in both direction ( easy to implement if you are firewalling your networks).

Pay also attention that the communication is only between the IP Phone and the webcam . CUCM is not involved at all in that “conversation” except for the TFTP config download.