ROUTER—
•Routers are both hardware and software
•The purpose of router to connect two or more networks
•Routers work under network layer of OSI model
•A router contains routing table as well as routing protocols
•Router uses address, i.e. the combination of network numbers and node address.
Protocols for Routers:
•Routing Information Protocol (RIP): This routing protocol is used by several network operating systems for routing the packets from source to destination.
•Each router maintains a table of each destination and the file table is frequently updated by routing information protocol broadcast message
•They also maintain the total number of hop(the movement of data from one network device to another) in routing table to select the shortest path to the destination.
Exterior Gateway Routing Protocol (ERGP):
This is the enhance form of RIP.
It also manages there problems.
There are frequently arising with RIP.
It works like default routing protocol across the internet.
It uses up to five conditions to select the best route.
Open Shortest Path First (OSPF): It might be possible that there are several path between one router to another but main responsibility of this protocol is to select shortest path they use.
•Routing means finding route or the next hop for A packet.
•A device called router does the routing function.
•It uses a table called routing table to find the route to the packet’s final destination.
•Routing tables contain information about the potential paths that a data packet should take to travel through the internet work and reach its destination.
•Router will read the header of each packet that arrives and extract the destination address of the packet.
•The router then sends the packet out on the appropriate transmission path based on a calculation of the optimum route to that destination.
•So routing involves two main functions:-
•1) Forwarding Function: when packets need to be sent to a host or hosts on another network, they are forwarded to a router that is connected to that particular local network.
•The router to which the packet is forwarded will then check its routing tables to determine the path with the lowest cost value or metric.
•The routing metric mainly includes the following :
•Hop Count: The number of intermediate router between a given network and the local route.
•Latency : The time delay in processing a packet through the router or over a given route.
•Congestion : The length of the packet queue at the incoming port of the router.
•Load : The processor use at the router or the number of packets per second that it is currently processing.
•Load : The processor use at the router or the number of packets per second that it is currently processing.
•Bandwidth : the available capacity of a route to support network traffic, decreases as network traffic increases.
•Reliability : The relative amount of downtime that a particular router might experience because of malfunctions.
•Maximum Transmission Unit (MTU): The largest packet size that the router can forward without needing to fragment the packet.
•2) Filtering Function : Filtering is the process of controlling the flow of packets based on attributes such as source.
•Filtering is done to protect the network from unauthorized traffic.
•Network administrators can create rules for filtering out unwanted packets.
•A packet that satisfies all the rules is allowed to be transmitted.
•While a packet that violates any of the rules is dropped.
BASIC PACKET FILTERING
PACKET FILTERING :
•Static Filtering : In Static filtering, ports are configured as either permanently open or permanently closed.
•For example, to deny outside packets access the company’s intranet server on port 80 .
•One can configure the router to block all incoming packets directed towards port 80.
•Dynamic Filtering : In Dynamic Filtering, selected ports can be opened for authorized access and closed for others.
•Theses ports are opened at the start of a legitimate session and then closed at the end of the session to secure the port against unauthorized attempts.
•One can configure rules in the router to read the incoming packets, dynamically open the two ports to allow a session to be started,
•Monitor the flow of packets to ensure that no attempts is made to hijack the session by an unauthorized user and close the randomly assigned ports when the session ends.
ROUTING METHODS :
1.Static Routing :
•In static routing method, routing tables are manually configured by the network administrator.
•Static routing is generally used in smaller networks that contain only a smaller number of routers or where security is a major concern.
•Routers that use static routing are called static routers.
•Each static router must be configured and maintained separately because static routers do not exchange routing information with each other.
•Static routes use less bandwidth than dynamic routes
Dynamic Routing :
•Dynamic Routing is a routing mechanism which is handled by a routing protocol.
•These protocols dynamically exchange routing information among routers on an internet work, Dynamic Router.
•A routing protocol is installed on each Dynamic Router.
•The routers periodically exchange their routing information so that if the internet work is reconfigured or a router goes down, the routing tables of each router are modified accordingly.
Protocols for Routers:
•Routing Information Protocol (RIP): This routing protocol is used by several network operating systems for routing the packets from source to destination.
•Each router maintains a table of each destination and the file table is frequently updated by routing information protocol broadcast message
•They also maintain the total number of hop(the movement of data from one network device to another) in routing table to select the shortest path to the destination.
Exterior Gateway Routing Protocol (ERGP):
This is the enhance form of RIP.
It also manages there problems.
There are frequently arising with RIP.
It works like default routing protocol across the internet.
It uses up to five conditions to select the best route.
Open Shortest Path First (OSPF): It might be possible that there are several path between one router to another but main responsibility of this protocol is to select shortest path they use.
•Dynamic routers are less secure because routing tables can be hampered by hackers.
•If the network is reconfigured or a router goes down, it takes time for this information to propagate between the various routers on the network.
•Routing protocols also create additional network traffic.
