Connectionless QoS, Part 2

Last time, we looked at how IEEE 802.1p solved some quality-of-service issues. This time, we'll look at IEEE 802.1Q.

IEEE 802.1Q established a new method for setting up virtual LANs across shared media by defining a new frame type called a " tagged frame. " The tagged frame provides a way to maintain priority information across a LAN.

Before 802.1Q, virtual LANs (VLAN) were vendor-proprietary solutions that could be established only on a per-switch basis. By contrast, the new standard set up a method for logically defining VLANs within a port that could be shared across multiple vendor platforms. The new application introduced by IEEE 802.1Q defined a VLAN registration protocol for propagating registration across the network by tagging frames with a VLAN ID, allowing the tags to be sent to multiple switches. This VLAN technique was especially important in limiting broadcast traffic, since broadcast traffic wastes bandwidth. By eliminating the need for all traffic to be broadcast to everyone on the network, this approach also increased user security because it introduced a " virtual private tunnel. "

Another important feature of 802.1Q was the added ability to share multiple subnets across a high-speed link. This capability not only reduced the number of lower speed links needed for physical separation, but it also allowed for asymmetrical traffic management so that different speed links could be managed more easily.

With IEEE 802.1p and 802.1Q, we saw the introduction of some important concepts that have been carried forward for further QoS development. These 802.1 features also can be mapped into higher layer protocols like IP and ATM. We'll talk about some more of these QoS solutions and how they are addressed at the IP layer in the coming weeks.

Steve Taylor is President of Distributed Networking Associates and Publisher/Editor-in-Chief of Webtorials.Com. For more detailed information on most of the topics discussed in this newsletter, connect to Webtorials.Com, the first Web site dedicated exclusively to market studies and technology tutorials in the Broadband Packet areas of Frame Relay, ATM, and IP.

Larry Hettick is an independent consultant, with 19 years of experience in telecommunications and data communications marketing and product management for service providers and equipment vendors. He can be reached at larry@larryhettick.com

You can reach the authors at taylor@webtorials.com or larry@larryhettick.com.

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