With Net Guard's AC200 and AC300 hardware-based bandwidth allocation products, Allot Communications uses some slightly different approaches. (The AC200 supports throughput rates as high as 1.544Mbits/sec, while the AC300 can support throughput rates as high as 45Mbits/sec.)

The products use an algorithm called class-based weighted fair queuing to establish multiple queues. Instead of performing TCP rate control, these products act as a TCP proxy. Apparently, a TCP proxy terminates the TCP connection on one side and initiates another connection on the other side, which Allot claims is a more effective approach than intercepting and modifying TCP packets in transit (the approach used by Packeteer). An add-on module can provide server load balancing. The AC200 retails for $ 7,000, while the AC300 sells for $ 13,000.

Future Directions With prices for T1 connections in the $ 1,000 to $ 1,500 range, and with T3 connections costing perhaps 20 times as much, it would be easy to justify installing bandwidth managers even if they did nothing more than save you from adding new lines. If, in fact, they serve to align the use of existing WAN connectivity with the valuable activities of your organization, their appeal is practically irresistible--even to a CFO with a diamond stick-pin where his heart ought to be.

It's worth elaborating on an idea that only Ukiah Software has implemented--tying bandwidth management policies to enterprise wide directory services. The Internet or WAN access point is the locus of many critical services, including VPNS, firewalls, proxy servers, network address translation, and load balancing. User profiles, group definitions, authentication information, digital certificates, MAC and IP addresses, and priority ratings are just a few of the obvious directory-storable items that could be applied to security, performance, and other important policies.

Software developers and users have put off the full use of directory services for years, but the opportunities are too great for any more procrastination. Just as a rich directory service can make setting up bandwidth management products easy, directories will soon be so easy to justify that it will seem foolish not to take advantage of them.

It has become clear in recent years that TCP and IP do not lend themselves to precise service guarantees. ATM was designed to handle multiple types of traffic flows gracefully, but it seems unlikely that it will ever compose a large fraction of endpoint-to-endpoint networks, and it introduces some problems of its own.

Today's bandwidth management products can do an effective job of increasing the efficiency of costly WAN resources, and forthcoming standards that make use of the TOP type of service byte, among other developments, will allow these relatively rough tools to approach the ideal of guaranteed service levels.