Connectionless QoS, Part 1
 
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Several weeks ago (before we replied to the flurry of ATM and CBR reader questions), we introduced some basics about TCP/IP. We would now like to begin a series on one of the big issues facing IP as a convergence protocol - its ability to support quality of service (QoS).
As our readers will recall, IP is a connectionless protocol, and connectionless protocols do not support sequential or prioritized delivery without special handling. This special handling was first addressed in an IEEE standard for Ethernet as a shared network media in the IEEE 802.1 specification, approved for use in December 1998.
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The 802.1 specification was the first to address priority issues associated with connectionless protocols. The specification provides a standard way to add traffic management across a shared network using bridged technology in 802.1p and across virtual LANs in 802.1Q. As a subset of IEEE 802.1Q, specification 802.1p provides a way to expedite traffic based on a traffic class by providing frameworks for registration protocols and multicast filtering.
The registration protocol, called Generic Attribute Registration Protocol (GARP), provides a method for passing information to other GARP participants, including rules registering and de-registering timing criteria across the network. GARP Multicast registration protocol (GMRP) allows devices to declare membership in a multicast group.
By creating a multiple queue - one for each class of traffic - higher priority traffic was able to get through faster than lower priority traffic. When the shared Ethernet's bridged media became congested, lower priority frames were discarded, assuming a higher layer protocol would request retransmission.
The 802.1p specification presented a major milestone in standardized traffic management. Next time, we'll look at how 802.1Q added additional QoS features for the VLAN.
RELATED LINKS
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.
Convergence archive
Past newsletters.
TCP/IP basics, Part 1
Network World Convergence Newsletter, 10/22/01
TCP/IP basics, Part 2
Network World Convergence Newsletter, 10/24/01
3Com looks to change face of network
Network World, 11/19/01
NEC lets companies dive into VoIP
Network World, 11/19/01
