Mar14 - CSE398: Network Systems Design Instructor: Dr....

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CSE398: Network Systems Design Instructor: Dr. Liang Cheng Department of Computer Science and Engineering Lehigh University March 14, 2005
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Instructor: Dr. Liang Cheng CSE398: Network Systems Design 03/14/05 Outline ± ± Switching fabrics (Chapter 10) ± Summary and homework
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Instructor: Dr. Liang Cheng CSE398: Network Systems Design 03/14/05 Recall: Packet Demultiplexing ± Used with layered protocols ± Packet proceeds through one layer at a time (inefficient) ± On input, software in each layer chooses module at next higher layer ± On output, type field in each header specifies encapsulation ± Inefficient b/c sequential processing among layers
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Instructor: Dr. Liang Cheng CSE398: Network Systems Design 03/14/05 Packet Classification ± Alternative to demultiplexing for higher speed ± Considers all layers at the same time ± Linear in number of fields ± Two possible implementations ± Software ± Hardware
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Instructor: Dr. Liang Cheng CSE398: Network Systems Design 03/14/05 Example Classification ± Classify Ethernet frames carrying traffic to Web server ± Specify exact header contents in rule set ± Example ± Ethernet type field specifies IP: ± IP type field specifies TCP: 2-octet IP type is 6 ± TCP destination port specifies Web server: 2-octet TCP destination port is 80
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Instructor: Dr. Liang Cheng CSE398: Network Systems Design 03/14/05 Illustration of Encapsulated Headers
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Instructor: Dr. Liang Cheng CSE398: Network Systems Design 03/14/05 Software Implementation of Classification ± Compare values in header fields ± Conceptually a logical and of all field comparisons ± Example if ( (frame type == 0x0800) && (IP type == 6) && (TCP port == 80) ) declare the packet matches the classification; else declare the packet does not match the classification; Optimization?
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Instructor: Dr. Liang Cheng CSE398: Network Systems Design 03/14/05 Optimizing Software Classification ± Comparisons performed sequentially reorder comparisons to minimize effort ± Assume ± 95.0% of all frames have frame type 0800 16 ± 87.4% of all frames have IP type 6 ± 74.3% of all frames have TCP port 80 ± Values 6 and 80 do not occur in corresponding positions in non-IP packet headers ± Reordering tests can optimize processing time declare the packet matches the classification;
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This note was uploaded on 08/06/2008 for the course CSE 398 taught by Professor Cheng during the Spring '05 term at Lehigh University .

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Mar14 - CSE398: Network Systems Design Instructor: Dr....

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