Advanced switching boosts performance

A new breed of intelligent switching technologies that combines application session control with high-speed switching technology could help speed TCP/IP traffic.

These technologies open the door for a range of applications, giving administrators much more control over IP traffic flows and flexibility in deploying network and server resources. One technology that is being deployed in some switch software is policy-based application redirection.

Instead of merely looking at IP or media access control (MAC) address information, switches running application redirection use information from the transport layer - Layer 4 - and identify traffic by TCP port numbers and URLs.

Distributing high-performance processors across switch ports lets switches efficiently implement application redirection while maintaining high levels of resilience and throughput.

By examining information found deep in data packets, more intelligent forwarding decisions can be made about the type of traffic entering the switch and where it should be sent. Packet filters can be applied by TCP source and destination ports, IP source and destination addresses, or protocol types. Administrators then signal the switch to allow, deny or redirect incoming traffic to the appropriate egress port. Filtering rules are applied on a per-port basis, allowing extra control.

For example, filters can be specified to enable or disable caching for specific users and destination sites. Requests for sites that require IP authentication can be forwarded directly to the destination hosts, bypassing cache servers altogether. Traffic from any protocol, port number, IP address or IP address range can be redirected.

Additionally with this technology, switches can examine URL information to determine where it is best to send traffic. This feature gives net administrators new levels of IP traffic control, letting them send traffic directly to servers designed to process specific traffic types.

Identifying and redirecting application traffic within switches solves a growing problem in today's networks. These environments are being increasingly littered with discrete "network appliances," which could be servers designed to perform a specific packet-processing function, such as load balancing, bandwidth management, firewalling or caching.

Appliance products typically examine all packets and determine which are important. Caches, for example, care only about HTTP traffic. Directing only relevant HTTP traffic to caches, as opposed to making them examine all traffic, optimizes the caches.

With application redirection technology, traffic destined for firewalls, caches, virtual private network servers or other appliances could be redirected and load balanced among multiple devices.

Single points of failure are also eliminated because in the event of a failure, traffic of any type can be redirected to other available appliances performing that specific function.

Another example of application redirection involves the Domain Name Service. Proper network operation requires that subscribers' computers be configured with the correct DNS server addresses. A DNS server address that is misconfigured will result in loss of network connectivity and will generate calls to the help desk.

Problems also exist for mobile users who have their local DNS server addresses properly configured but are accessing the network outside their local points of presence. While it's desirable for a mobile subscriber to use the DNS server local to the point of presence (POP) into which they've dialed, that's not where the requests will go. Instead, DNS requests will go to the subscribers' home POP DNS servers, slowing response time.

Application redirection can solve these problems by allowing for the automatic identification and redirection of DNS requests. A mobile user's DNS requests could be intercepted by the switch at each POP and transparently redirected to the closest DNS server. Application redirection also solves the problem of misconfigured DNS addresses by redirecting all DNS requests to the DNS server of the administrator's choice, regardless of where the requests are addressed. If a user's computer has an erroneous DNS server address, it doesn't matter.

Redirection technology can also be used to identify and redirect SMTP traffic to specialized spam filters. The switch can identify SMTP traffic and redirect it to specialized servers designed to filter SMTP traffic. This reduces net bandwidth requirements and provides an automated way to eliminate spam.

ACEdirector 2 overview
Alteon's approach to server load balancing.

Policy Based Networking Technology
How Allot does it.

Williams is the director of marketing at switch vendor Alteon Networks. He can be reached at (408) 360-5500.