CS254 Network Technologies · 2006. 9. 27. · 16.2 Backbone Networks Bus Backbone Star Backbone...
Transcript of CS254 Network Technologies · 2006. 9. 27. · 16.2 Backbone Networks Bus Backbone Star Backbone...
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CS254 Network Technologies
Lecture 5: Ethernet networks & devices
Dr Nikos AntonopoulosDepartment of Computing
University of SurreyAutumn 2006
Figure 14.1 Three generations of Ethernet
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14.1 Traditional Ethernet
MAC Sublayer
Physical Layer
Switched Ethernet
Full-Duplex Ethernet
Figure 14.2 802.3 MAC frame
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Figure 14.3 Minimum and maximum length
Figure 14.4 Ethernet addresses in hexadecimal notation
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Figure 14.5 Unicast and multicast addresses
Figure 14.6 Physical layer
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Figure 14.10 Categories of traditional Ethernet
Figure 14.13 Connection of stations to the medium using 10Base-T
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Figure 14.18 Switched Ethernet
Figure 14.19 Full-duplex switched Ethernet
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16.1 Connecting Devices
Repeaters
Hubs
Bridges
Two-Layer Switches
Figure 16.1 Connecting devices
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Figure 16.2 Repeater
A repeater connects segments of a LAN.
Note:
A repeater is a regenerator, not an amplifier.
A repeater forwards every frame; it has no filtering capability.
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Figure 16.3 Function of a repeater
Figure 16.4 Hubs
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A bridge has a table used in filtering decisions.
Note:
Bridge functionality
� Every bridge has a routing table which is used for routing frames from one network to another
� There are two main algorithms:��������� ��������� ��������� �������������� �!�"�#��$�%�������&��
� A bridge which implements the learning algo rithm o nly is called learning o r t rans p arent b rid ge
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Figure 16.5 Bridge
Learning algorithm
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Figure 16.6 Learning bridge
A Bridge problem
� If two or more transparent bridges are connected with each other forming a loop then there is the problem of livelock
� Livelock: A frame propagates infinitely through the bridges without ever reaching its destination
� Solution: Each bridge implements the spanning tree algorithm on start-up
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Figure 16.7 Loop problem
Spanning tree algorithm concepts� Each bridge is given a unique ID� Aim: Remove any loops among bridges by
transforming the logical organization of the bridges into a tree
� Concept 1: Each bridge exchanges messages with the other bridges to determine the shortest path from itself to the root bridge
� Concept 2: The bridge with the smallest ID number becomes the root bridge of the network
� Concept 3: Initially each bridge assumes to be the root bridge (selfish bridges)
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Figure 16.8 Prior to spanning tree application
Figure 16.10 Forwarding ports and blocking ports
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16.2 Backbone Networks
Bus Backbone
Star Backbone
Connecting Remote LANs
Figure 16.11 Bus backbone
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Figure 16.12 Star backbone
Figure 16.13 Connecting remote LANs
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16.3 Virtual LANs
Membership
Configuration
IEEE Standard
Advantages
Figure 16.14 A switch connecting three LANs
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Figure 16.15 A switch using VLAN software