The document details the functions and characteristics of gateways and routers in network connectivity. Gateways serve as intermediaries connecting users to the internet, while routers forward data packets between networks. It also discusses routing processes, including static and dynamic routing tables, and the algorithms used to determine optimal routes.

1. Figure 21-1
Connecting Devices

2. Gateways
Gateways:
Its a ISP (Internet service provider) that connects
user to the internet. Often acts as a proxy server and
firewall.
The gateway is the computer that routes the traffic
from a workstation to the outside network that is
serving the Web pages.

3. 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 connect.

4. Figure 21-2
Connecting Devices and the OSI Model

5. Figure 21-5
Function of a Repeater

6. Figure 21-11
Routers in an Internet

7. Figure 21-12
A Gateway in the OSI Model

8. Routing

Routing process usually directs forwarding on
basis of routing tables which maintain a record
of routes to various network destination

Most routing algorithms use only one network
path at a time.Multipath routing techniques
enable the use of multiple alternative paths

The following elements are considered in order
to decide which routes are in routing table

Prefix-length(Independent routing )

Metric (Valid within same protocol)

Administrative distance(Valid b/w diff protocol)

9. 
Forwarding
“refers to Internal operation performed by a router
receiving a packet from input link and decides
what output to send to output link interface”

Router
“is a network node connected to two or more
networks that forwards packets fron one
network to another”.

10. Types of routing table

Static routing table
Entries are created manually,updated by
administration

Dynamic routing table.
Entries are updated automatically by dynamic
routing protocols by RIP,OSPF,BGP.