- Switch
- A switch
is an interconnection device
that connects
multiple networks
that uses
the same network protocol:
Another name for a switch:
- A switch is also known as: "Multi-way Bridge"
- A switch
is an interconnection device
that connects
multiple networks
that uses
the same network protocol:
- Networking Babel:
- Switch =
a device that
connect (multiple)
networks of the
same type
- A switch operates at the Data Link layer level
- Router =
a device that connect
networks of the different type
- A router
operates (= processes)
at the
Network layer level
- A router (See: click here )
- A router
operates (= processes)
at the
Network layer level
- Switch =
a device that
connect (multiple)
networks of the
same type
- Note:
- some textbooks
will call
device that connect
networks
of the different type:
- A switch..... (instead of a router)
- some textbooks
will call
device that connect
networks
of the different type:
- Forwarding table:
- Each port
of the switch, has an associated
forwarding table :
Forwarding table contains:
- Node addresses of nodes that reside on the network segment
- Each port
of the switch, has an associated
forwarding table :
- Learning:
(adding entries to the
forwarding table)
- When the switch
receives a
frame from
a node on
port P:
The switch will:
if ( source address ∉ Forwarding Table(P) ) { Insert source address into Forwarding Table(P); } Reset expiration timer for source address;
Note:
- The learned entries can expire
- Expired entries are deleted
- When the switch
receives a
frame from
a node on
port P:
- Forwarding Operation of a
switch:
- Suppose an Ethernet switch
receives an Ethernet frame
on some port P:
if ( Destination Addr ∈ Forwarding Table(Q (≠ P)) ) { Forward frame on port Q;
}
else if ( Destination Addr ∈ Forwarding Table(P) )
{
Discard frame;
}
else
{
Forward frame on all other port except port P;
(This operation is called: broadcasting)
}
- Suppose an Ethernet switch
receives an Ethernet frame
on some port P: