Download Lecture 3 unit 1 - Dr. Rajiv Srivastava

Lecture 3
unit 1
Router
• A router is a device that forwards data packets
along networks. A router is connected to at least
two networks, commonly two LANs or WANs or a
LAN and its ISP's network. Routers are located at
gateways, the places where two or more
networks are connected.
• Routers use headers and forwarding tables to
determine the best path for forwarding the
packets, and they use protocols such as BGP,
OSPF, ICMP to communicate with each other and
configure the best route between any two hosts.
• A router normally supports multiple protocol
routing.
Gateways
• Gateways are also called protocol converters
& can operate at any network layer. The
activities of a gateway are more complex
than that of the router or switch as it
communicates using more than one
protocol.
• A gateway is a network point that acts as an
entrance to another network.
• It connects two independent network. A
gateway is a protocol converter.
• It adjust the data rate, size and data format.
Types of Gateways
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Host Gateways
LAN Gateways
Electronic Mail Gateways
Firewall
Proxy servers
NAT (Network Address Translation)
Voice/Media Gateways
Payment gateway
Switches
• A switch is a device which provides bridging
functionally with greater efficiency. A switch acts
as a multiport bridge to connect devices or
segments in a LAN.
• Switch enables dedicated access
• Eliminates collisions and increases capacity
• Supports multiple conversations at the same time
• The switch has a buffer for each link to which it is
connected. When it receives a packet, it stores
the packet in the buffer of the receiving link and
checks the address to find the outgoing link.
• If the outgoing link is free, the switch sends the
frame to that particular link.
• Switches are of two types :
1. Store and forward switch
2. Cut – through switch
• A store – and – forward switch stores the
frame in the input buffer until the whole
packet has arrived.
• A cut-through switch, forwards the packet to
the output buffer as soon as the destination
address is received.
Line Configuration
Computer networks can transmit data by two
method –
1. Point to point network.
2. Multi point network.
Point to point network.
• A point-to-point line configuration provides a
dedicated link between two devices. The
entire capacity of the channel is reserved for
transmission between those two devices.
Most point-to-point line configurations use an
actual length of wire or cable to connect the
two ends.
Point-to-Point Line Configuration
Multi point network.
• A multipoint line configuration is one in which
more than two specific devices share a single
device share a single link.
• In a multipoint environment, the capacity of
the capacity of the channel is shared, either
spatially or temporally. If several devices can
use the link simultaneously, it is a spatially
shared line configuration. If users must take
turns, it is a time shared line configuration.
Multipoint Line Configuration