Cisco's Catalyst 4224 combines the functionality of a 24-port Fast Ethernet switch capable of providing inline power to Cisco IP phones with a Catalyst 2600/3600 branch-office router, an eight-port analog voice gateway and a scaled-down AVVID call manager--all in a 2U form factor. It even includes hardware-accelerated VPN and firewall capabilities (I concentrated on the voice capabilities in my tests).

I hooked up the Catalyst 4224 to our lab environment, connecting the T1 WAN interface to our Cisco 7200 VXR central site router. Configuring the 4224 was a relatively straightforward process. The 4224 does not support MGCP (Media Gateway Control Protocol), though Cisco promises that support for that protocol will be included in a firmware upgrade later this quarter. As a result, I had to configure the Catalyst 4224 to use H.323 to communicate with the CallManager.

I tested the throughput of the switching element using Spirent Communications' SmartBits. The 24-port switch delivers wire speed throughput between Ethernet interfaces. After validating the basic Layer 2 performance of the switch, I tested the WAN functionality using a Cisco Catalyst 7200 VXR as the central site router. The Catalyst 4224 can run frame relay, MLPPP (Multilink Point-to-Point Protocol), PPP and HDLC (High-Level Data Link Control) over its (optional) T1 interface.

Cisco warned me that the initial release of the Catalyst 4224's IOS software does not support priority or weighted fair queuing when the interface is in frame relay or MLPPP mode. This limitation will be addressed in a future software release; however, enterprises that run frame relay or MLPPP should be aware that QoS (Quality of Service) support is very limited for these encapsulation types at this time. In contrast, PPP and HDLC connections support priority queuing and class-based weighted fair queuing.

I configured the Catalyst 4224 to communicate with our Cisco 7200 VXR router using PPP encapsulation. The 4224 provided QoS to IP phone conversations that are routed from the Ethernet interfaces across the WAN and vice versa, and did so with reasonable finesse. I used Caw Networks' WebAvalanche to generate background traffic, filling the T1 pipe while maintaining a voice call across the routed network.

I also tested the Catalyst 4224's analog voice interfaces. The eight interfaces can be mapped into CallManager's software using H.323 as the intermediate protocol. The interfaces must be configured individually at the router using the dial-peer command of the Cisco IOS interface.

The Crowning Jewel

After testing the basic functionality of the Catalyst 4224, I turned to Cisco's newest IOS enhancement, the SRST. When combined with the built-in IOS services on the Catalyst 4224, SRST lets remote sites remain functional in the event of a WAN failure. Although SRST--which costs $500--has been available since FCS, the firmware necessary to take advantage of this feature on Cisco IP phones became available only with CallManager 3.1.

I configured SRST to take over basic call-processing features in the event of a lost WAN connection, and then deliberately pulled the plug on our T1 link. In less than a minute, the "remote-office" LAN had switched over to the Catalyst 4224 as a backup call manager. Although some features, such as voicemail and access to the Personal Assistant were lost (they existed only on the other side of the WAN), I still could place calls between phones in the office and make connections across the gateway to the PSTN.

Vendor Information Cisco Catalyst 4224 Access Gateway Switch, $12,995; Cisco CallManager 3.1, $5,995; Cisco Personal assistant 1.2, $4,995. Available: Now. Cisco Systems, (800) 553-6387, (408) 526-7208; fax (408) 525-9155. www.cisco.com

The implications of SRST are significant: Enterprises can roll out VoIP (voice over IP) without betting the farm on a single WAN link. SRST provides a mechanism for conducting business over the PSTN should a WAN link temporarily collapse. It also ensures that emergency services such as 911 are always available in an IP-only environment.

While the WAN link was down, the IP phones notified me that a backup call manager was in use, and I noted that a restricted set of features was available. I eventually plugged the WAN link back in and discovered that the connections were transferred back to the full-featured CallManager automatically, without interrupting the existing call.

The Perks of a Personal Assistant

Finally, I tested Cisco's Personal Assistant 1.2 software, which is being released with CallManager 3.1. Personal Assistant adds voice recognition features to CallManager and lets users define their own follow-me rules based on a multitude of parameters, such as caller ID, time of day and called party. Personal Assistant is straightforward to install and use, and adds a new dimension to enterprise telephony. This is particularly true of the rules-based follow-me feature, which traditionally is administered by the corporate PBX operator. Personal Assistant extends its configuration interface to the end user via the Web, letting any user define very specific rules for forwarding calls in a follow-me application.

Overall, the voice features of the Catalyst 4224 are merely icing on the cake. Branch-office customers seeking to future-proof their network designs for VoIP have a great option for rolling out VoIP support without a significant capital investment. The combination of a high-performance 24-port switch with a full-featured branch-office router would in itself be a great deal. The addition of powerful voice features and expansion options makes the Catalyst 4224 a killer platform for branch-office connectivity.

A former senior technology editor of Network Computing, Joel Conover is a senior analyst at tactical competitive response solutions firm Current Analysis. Send your comments on this article to him at jec@currentanalysis.com.

Got VoIP? Then Get the Book!

For many enterprise IT managers, IP telephony may be as foreign to them as Greek. A new book from Cisco Press, Cisco CallManager Fundamentals: A Cisco AVVID Solution, helps sort out the mysteries of IP telephony in a language that any IT manager can understand. From the basics of PBX functionality through the configuration of site-to-site and PSTN connections, CallManager Fundamentals gives IT administrators access to the technology involved in IP telephony.

To coincide with the release of CallManager 3.1 -- the call-processing component of Cisco's IP telephony solution -- CallManager Fundamentals conveniently covers all of the features in the new release, including personal voice-mail options such as call forwarding and caller recognition, implementing music on hold, and advanced fault-tolerance features. With extensive examples and down-to-earth discussions regarding complex telephony subjects, this book is a must-read for any IT administrator considering or evaluating the deployment of IP telephony software.

Book Info:
Cisco CallManager Fundamentals: A Cisco AVVID Solution
By John Alexander, Chris Pearce, Anne Smith, Delon Whetten 720 pages 1st edition (July 31, 2001) Cisco Press
ISBN: 1587050080