© 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v5.05-1 Implementatation of Multiple Site Deployment Understanding Call Admission Control in Cisco. - презентация

1 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Implementatation of Multiple Site Deployment Understanding Call Admission Control in Cisco Unified CallManager Release 5.0

2 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Cisco Unified CallManager Example: WAN bandwidth can support only two calls. What happens when the third call is attempted? Call No. 1 Call No. 2 Call No. 3 Causes poor quality for all calls Call No. 3 Why Call Admission Control? IP WAN Many tools give voice priority over data. Call admission control is about preventing voice oversubscription. Cisco Unified CallManager You need call admission control only for calls that traverse the IP WAN.

3 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Two Methods of Call Admission Control Distributed call processing: Use gatekeepers and intercluster (gatekeeper- controlled) trunks Cisco IOS Gatekeeper Centralized call processing: Use locations feature Cisco Unified CallManager Cluster PSTN IP WAN GK PSTN IP WAN

4 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Call Admission Control Mechanisms in Cisco Unified CallManager Topology-unaware Static configuration within call-processing agent to limit number of calls Two mechanisms implemented on Cisco Unified CallManager: –Locations-based call admission control –H.323 Gatekeeper-based call admission control Topology-aware Real-time communication between call-processing agent and the network about the available resources Implemented with RSVP between Cisco Unified CallManager and RSVP agentCisco IOS router

5 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Limitations of Locations-Based Call Admission Control IP WAN 1 st Tier Hub site Second-Tier Hub sites Spokes x x Primary (10 calls) Backup (2 calls) Both Active (10 calls each) ABCD How many calls admitted to B? How many calls admitted to D?

6 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Centralized Call Processing: Locations-Based Call Admission Control LocationBandwidth (kbps) San JoseUnlimited New York256 Dallas64 San Jose (Main) Cisco Unified CallManager Cluster New York (Remote) Dallas (Remote) Location: Defines the amount of bandwidth available Region: Defines the compression type used IP WAN

7 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Cisco Unified CallManager blocks a call over the WAN. The call is automatically rerouted over the PSTN. Automated Alternate Routing Headquarters Branch B 1 2 Phone A Phone B 1 2 Branch A PSTN WAN CAC

8 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v AAR Features Works only in conjunction with locations and regions Cisco Unified CallManager automatically attempts to reroute the call by using the alternate number. Uses the device-based AAR calling search space and external phone number mask to reroute a call to PSTN gateway. AAR supports the following call scenarios: Call originates from an IP phone within one location and terminates at an IP phone within another location. Incoming call through a gateway device within one location terminates at an IP phone within another location. AAR does not work with SRST; AAR will not function in the case of a WAN failure.

9 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Automated Alternate Routing Call Example Headquarters Branch A Location HQ Location A dials OnNet to 1234; call admission control denies the call. 2. The external phone number mask XXXX is added to the internal directory number 1234; the result is a fully qualified number, To access the PSTN gateway, dial the 91 prefix is the new alternate dial string dials 1234 New alternate dial string: PSTN WAN CAC

10 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Gatekeeper Zone Gatekeeper call admission control reduces configuration overhead and provides flexibility. Cisco Unified CallManager registers with the gatekeeper using an IP address. A single gatekeeper can manage up to 100 Cisco Unified CallManager clusters. Gatekeeper Distributed Call Processing: Gatekeeper Call Admission Control IP WAN

11 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Gatekeeper Registration and Unregistration GatekeeperH.323 Endpoint RRQ (1) RCF/RRJ (2) Registration Gatekeeper-Initiated Unregistration Request Endpoint-Initiated Unregistration Request URQ (1) UCF (2) URQ (1) UCF/URJ (2)

12 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Admission Request Gatekeeper H.323 Endpoint 2 ARQ (1) ACF/ARJ (2) Setup (3) Call Proceeding (4) Alerting (7) Connect (8) H.323 Endpoint 1 ARQ (5) ACF/ARJ (6) RAS Messages Call Signaling

13 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Disengage and Bandwidth Request GatekeeperH.323 Endpoint DRQ (1) DCF(2) Disengage Bandwidth BRQ (1) BCF/BRJ (2)

14 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v RSVP-Based Call Admission Control Overview A protocol for reserving resources in IP networks. RSVP reservations are made for a particular session. RSVP messages travel along the same path as that of the media flow. RSVP is unidirectional; flows are reserved in one direction only. RSVP is receiver-oriented. The receiver of the stream requests the reservation.

15 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v RSVP Call Admission Control Operation PATHFollows the direction of the data path, and includes the unicast IP address of the previous hop node, which is used to route the RESV messages in the reverse direction Reservation Request (RESV)Follows reverse of the data path and used to create and maintain the reservation RSVP PATH Received RSVP RESV PATH RSVP RESV Received RSVP Sender RSVP Receiver Data Flow R2R1 R3

16 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v RSVP Advantages over Locations-Based Call Admission Control Supports redundant links Supports mesh and triangular topologies Supports equal-cost or non-equal- cost paths GK

17 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Cisco Unified CallManager RSVP Implementation Location B Location A RSVP Agent SCCP Phone SIP Phone PSTN GW RSVP Agent SCCP Phone SIP Phone PSTN GW SCCP MGCP or H.323 SIP RSVP RTP Cisco Unified CallManager Supported in IOS Release 12.4(6)T on 26xx-XM, 2691, 28xx, 37xx, and 38xx Series platforms IP WAN Implemented Using RSVP Agent PSTN

18 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Cisco Unified CallManager RSVP Capabilities Supports all signaling protocols: SIP, H.323, MGCP, and SCCP. RSVP provides four policy levels. RSVP contains a Retry reservation capability. RSVP integrates with DiffServ QoS. RSVP has a midcall failure policy. RSVP works with all Cisco Unified CallManager supplementary services, MLPP, and MOH.

19 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Cisco Unified CallManager RSVP Capabilities (Cont.) RSVP enabled and disabled on location pairs. RSVP supports bandwidth reservation for audio and video.

20 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v RSVP Sample Scenarios: Shared Line During alerting phase, RSVP agents in all three locations communicate. Once the call is answered, connections between agents not involved torn down. RSVP Agent RSVP Agent RSVP Agent RSVP Agent Location 2 Location 3 Location 4 Location 1 Phone A Phone B1 DN: 2000 Phone B2 DN: 2000 Phone B3 DN: 2000 Phone B4 DN: 2000 Phone B2 answers!

21 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v RSVP Sample Scenarios: MOH RSVP Agent RSVP Agent Location 2 Location 1 Phone A Phone B DN: 2000 MOH RSVP Agent Location 3 Phone C DN: 3000 Two scenarios: MOH server is in the same location as the phone putting another on hold MOH server is in a third location

22 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v RSVP Sample Scenarios: Call Transfer RSVP Agent RSVP Agent Location 3 Location 1 Phone A MOH RSVP Agent Location 2 Phone B DN: 2000 RSVP Agent Location 4 Phone C DN: 3000

23 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Summary Call admission control provides mechanisms to control the volume of calls between two endpoints, which is key to maintaining the QoS of all calls. Cisco Unified CallManager supports three call admission control mechanisms: locations-based, gatekeeper-based, and RSVP. Cisco Unified CallManager supports locations-based call admission control for centralized call-processing environments. AAR automatically reroutes calls through the PSTN or other networks when there is insufficient bandwidth in a centralized call-processing deployment. Cisco Unified CallManager supports gatekeeper basic call admission control for distributed environments.

24 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v Summary (Cont.) Gatekeeper-based call admission control exchanges messages sent to and from the gatekeeper. These messages allow endpoints to register, unregister, request admission, disengage, and request bandwidth. RSVP extends the locations-based call admission control by specifying a resource-reservation, transport-level protocol for reserving resources in IP networks to solve locations-based call admission control issues. Cisco Unified CallManager uses an RSVP agent to implement RSVP functions in its cluster. An RSVP agent is an IOS-based RSVP proxy with an SCCP interface. When RSVP interacts with various Cisco Unified CallManager features and services, such as shared-line, MOH, or call transfer, an RSVP agent establishes necessary connections or tears down those not needed any longer.

25 © 2006 Cisco Systems, Inc. All rights reserved. CIPT1 v