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Technology Stocks : The New QLogic (ANCR)
QLGC 16.070.0%Aug 24 5:00 PM EST
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To: Craig Stevenson who wrote (14423)2/19/1998 12:05:00 AM
From: George Dawson  Read Replies (1) of 29386
 
Craig,

Dr. Benner on class 4 service (explained as a discussion of the address identifiers):

"x'FF FFF9': reserved for future usage as Quality-of Service Facilitator for future Class 4 Service. When implemented Extended Link Service commands sent to this address will be used to request a set of Quality-of-Service parameters for a Class 4 Virtual Service. A Class 4 Virtual Circuit is an extension of Class 1 Service which allows reservation of some fraction of the available link bandwidth and/or allows guarantee of maximum delivery latency, with Quality-of Service for these parameters negotiated between the requestor and the Quality of Service Facilitator."

AND

"Class 4 is a new Class of service, which is intended to incorporate the advantages of a Class 1 Dedicated Connection without reserving the entire link bandwidth and without preventing multiplexing over circuits with guaranteed service levels."

He goes on to point out that a Class 4 connection is a typical bidirectional FC connection with QoS parameters to guarantee a percentage of link bandwidth and/or latency. There can be 254 simultaneously active multiplexed class 4 connections per N_Port. Frames are delivered in order at the negotiated rate."

As you know Ancor offers intermix as an option to class 1. My understanding is that all elements of the connection need to support intermix or complicated things happen. It would seem to me that class 4 would be a natural extension of Ancor's technology - instead of muxing class 2 and 3 frames in intermix, reserving specific portions of available bandwidth for class 1.

George D.

Ref: Benner AF. Fibre Channel: Gigabit Communications and I/O for Computer Networks. McGraw-Hill, 1996.
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