11 switches

Switches Reading: Section 3.2 COS 461: Computer Networks Spring 2006 (MW 1:30-2:50 in Friend 109) Jennifer Rexford Teaching Assistant: Mike Wawrzoniak http://www.cs.princeton.edu/courses/archive/spring06/cos461/

Midterm Exam ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Goals of Today’s Lecture ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Shuttling Data at Different Layers ,[object Object],[object Object],[object Object],[object Object],Application gateway Transport gateway Router Bridge, switch Repeater, hub Frame header Packet header TCP header User data

Physical Layer: Repeaters ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Physical Layer: Hubs ,[object Object],[object Object],[object Object],[object Object],[object Object],hub hub hub hub

Limitations of Repeaters and Hubs ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Link Layer: Bridges ,[object Object],[object Object],[object Object],[object Object],[object Object],host host host host host host host host host host host host Bridge

Link Layer: Switches ,[object Object],[object Object],[object Object],[object Object],[object Object],switch A B C D

Dedicated Access and Full Duplex ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Bridges/Switches: Traffic Isolation ,[object Object],[object Object],[object Object],[object Object],hub hub hub switch/bridge collision domain collision domain collision domain

Advantages Over Hubs/Repeaters ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Disadvantages Over Hubs/Repeaters ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Motivation For Cut-Through Switching ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],A B switches

Cut-Through Switching ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],A B switches

Motivation For Self Learning ,[object Object],[object Object],[object Object],[object Object],[object Object],switch A B C D

Self Learning: Building the Table ,[object Object],[object Object],[object Object],[object Object],[object Object],A B C D Switch learns how to reach A.

Self Learning: Handling Misses ,[object Object],[object Object],[object Object],[object Object],A B C D When in doubt, shout!

Switch Filtering/Forwarding ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],forward on all but the interface on which the frame arrived

Flooding Can Lead to Loops ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Solution: Spanning Trees ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Constructing a Spanning Tree ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],root One hop Three hops

Steps in Spanning Tree Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Example From Switch #4’s Viewpoint ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],1 2 3 4 5 6 7

Example From Switch #4’s Viewpoint ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],1 2 3 4 5 6 7

Robust Spanning Tree Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],See Section 3.2.2 in the textbook for details and another example

Evolution Toward Virtual LANs ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Group users based on organizational structure, rather than the physical layout of the building.

Why Group by Organizational Structure? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

People Move, and Roles Change ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Example: Two Virtual LANs Red VLAN and Orange VLAN Bridges forward traffic as needed R R O R O O R O

Example: Two Virtual LANs Red VLAN and Orange VLAN Switches forward traffic as needed R O R O R R R O O O R O R R R O O O

Making VLANs Work ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Moving From Switches to Routers ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Comparing Hubs, Switches, & Routers

Conclusion ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

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