networking and internetworking devices. repeater
TRANSCRIPT
Networking and internetworking devices
Repeater
Hub
Function of a bridge
Regenerate and filter traffic
Check destination address
Forwards the new copy to the segment towhich the address belongs
Multiport bridge
Connecting LAN segments in two buildings
Router
Gateway
Gateway is a protocol converter
IBM
Novell
Switch
Backbone
Routing algorithms
• Calculate the shortest path between two routers– Distance vector routing– Link state routing
In distance vector routing, each router periodically shares its knowledge about the
entire network with its neighbors
Network ID Cost Next Hop(ID of the next router)
The cost is base on hop count1= No hop
Routing table
14 155 1 + 1 hop
14 2 B55 2 B
14 1 14 2 B23 1 55 2 B78 114 1 23 1 55 2 B78 1
A’s new table
Final routing table
In link state routing, each router shares its knowledge of its neighborhood with all
routers in the internetwork• Flooding router sends its info.
to all of its neighbors, each neighbor sends the packet to all of its neighbors, and so on.
• Link state packet (LSP)Advertiser IDDestination network IDCostNeighbor ID
Initialization• Each router sends a short
greeting packet to its neighbor• Prepare an LSP, Floods the
network• Every router receivers every
LSP , Puts the info. Into a Link state
database
Flooding of A’s LSP
Every router has the same Link state database
Dijkstra’s Algorithm
• finds shortest paths from given source node s to all other nodes
• by developing paths in order of increasing path length
• algorithm runs in stages. each time adding node with next shortest path
• algorithm terminates when all nodes processed by algorithm
Link state routing table for router A โดยใช้� Dijkstra Algorithm
Link state routing table for router A
Bellman-Ford Algorithm
• find shortest paths from given node subject to constraint that paths contain at most one link
• find the shortest paths with a constraint of paths of at most two links
• and so on
Example of Bellman-Ford Algorithm