Network Routing Explained

Routing Explained

• Network routing is the process of selecting a path across networks.
• Routing communication is essential due to increased internet connectivity.
• Routing determines the route for Internet Protocol (IP) packets from source to destination in packet-switching networks.

Routers: The Traffic Directors

• Routers are specialized hardware devices which make judgments while internet routing.
• Routers forward data packets between networks and direct traffic using the destination IP address.
• Routers operate at Layer 3 (network layer) of the OSI Model.
• Responsible for finding the optimal path for data across networks.

The Routing Process

• Routing directs data packets from one node to another.
• Note: a node refers to a network device called a 'Router'.
• Routing involves decisions for reliable and efficient data packet delivery across LAN, WAN, or MAN networks, which ensure data is transmitted from one location to another.
• Aims to find the shortest path using routing metrics.
• Involves analyzing the destination IP Address of the data packet.
• The source node sends a data packet with its IP address embedded in the header.
• The nearest router receives the data packet and routes it based on specific metrics to other routers.
• This process repeats until the data packet reaches its intended destination.
• There's a limit to hop counts, exceeding which the packet is considered lost.

Types of Routing

• Routing is classified into three types: static, default, and dynamic.

Static Routing

• Static routing is "non-adaptive" routing configured manually by network admins
• Administrators must manually input routing information based on their assessment of all routes
• Static routing is advantageous because of lower CPU overhead, enhanced security, and zero bandwidth usage between routers

Disadvantages of Static Routing

• It is hard for administrators to manually input each route for large networks
• Administrators require extensive knowledge of network topology, else there may be difficulty adding each route manually

Static Routing Configuration

• Includes manual configuration of routes on routers
• Routers R1, R2, and R3 require specific IP address configurations on their interfaces.
• Commands used to configure static routes for routers R1, R2, and R3.
• Configuring the route for the 192.168.10.0 network on router R3 specifies the network ID and next-hop addresses.

Default Routing

• This method involves configuring the router to send all packets to a single router or next hop
• Commonly used with stub routers: routers with only one way to reach other networks

Advantages of Default Routing

• Provides a "last resort" route for unmatched packets, ensuring delivery.
• Simplifies network configuration by reducing complex routing tables.
• Improves network reliability decreasing packet loss.

Disadvantages of Default Routing

• Sole reliance on default routes is inefficient due to lack of specific path consideration
• Introduces additional network latency
• Can be used during dynamic routing configurations
• The same topology used for static routing can also be used

Implementing Default Routing

• R1 and R2 are stub routers and are configured for default routing
• Specific commands are shown for configuring default routing for R1 and R2

Dynamic Routing

• Dynamic routing automatically adjusts routes based on network conditions.
• It discovers destinations and routes using protocols like RIP and OSPF.
• Routers must run the same dynamic protocol to exchange routes
• Routers advertise topology changes to each other.

Advantages of Dynamic Routing

• Easy to configure.
• Selects the most effective route to a remote network and discovers remote networks

Disadvantages of Dynamic Routing

• Consumes more bandwidth for communication.
• Less secure than static routing.

Routing Conclusions

• Routing enables every network device to share data.
• Routing employs algorithms to select the shortest data packet path via metrics (hop count, delay, bandwidth).
• Routing tables are logical data structures for storing routes.
• Static routing involves manual route addition.
• Dynamic routing transmits packets using shortest path algorithms.
• Default Routing configures a router to send packets to a default route if no specific path exists.

Working Principle of Routing

• Routing finds the shortest path from source to destination node over a network.

Step 1: Communication Initiation

• A node (client/server) starts communication using HTTP.

Step 2: Data Packets

• The source divides data into small packets for transmission via de-assembling and encapsulating.
• Each data packet carries the destination node's IP address.

Step 3: Routing Table

• The routing table stores IP addresses and information about the nearest routes.
• The source node consults the table to identify nodes that transmit packets to the destination.
• It then selects the shortest path using a shortest path algorithm.
• Routing tables reside on a router, to help determine the shortest path.

Step 4: Hopping Procedure

• Involves the packet undergoing multiple hops within the network to reach its final destination.
• Hop count is defined as the number of nodes required to reach the destination node.
• Packets have a hop limit, upon exceeding it they are considered lost and are retransmitted.

Step 5: Reaching the Destination Node

• Data packets re-assemble and transform into complete information at the destination, verifying the data packet authenticity through error-checking mechanisms.
• The data packet is transmitted over the least hop-count path and the path on which there is less traffic in order to avoid packet loss.

Routing Components

• Sender.
• Receiver.
• Routers.
• The shortest path is the path with the least hop count.

Routing Protocols

• RIP (Routing Information Protocol) is a distance-vector protocol that utilizes hop count as a metric.
• OSPF (Open Shortest Path First) is a link-state protocol using Dijkstra's algorithm.
• EIGRP (Enhanced Interior Gateway Routing Protocol) is a hybrid protocol, using link-state and distance-vector features.
• BGP (Border Gateway Protocol) is a path-vector protocol used for routing between autonomous systems.
• IS-IS (Intermediate System to Intermediate System) is a link-state protocol used in ISPs.

Varying Routing Metrics

• The goal of routing protocols is to find available paths for routing packets, creating routing tables, and making choices based on metrics.
• There are two types of routing protocols

Distance Vector Routing

• Nodes advertise their routing table to adjacent nodes at regular intervals.
• Routers need to be updated frequently to have an accurate network view.
• Uses fixed length sub-net, which is not suitable for scaling.
• Uses the Bellman-Ford Algorithm to find the shortest path.

Link State Routing

• Routers send their updated tables if there are additions.
• Uses bandwidth effectively.
• All routers exchange data on different links (cost, hop) count and look for the possible best path.
• Uses a highly scalable variable length sub-net mask that allows addressing properly.
• Uses Dijkstra's Algorithm to find the shortest path.

Metrics for Measuring Travel Cost

• Hop Count refers to the number of nodes a data packet passes to get to its destination, minimize hop count and find shortest path.
• Bandwidth Consumption: measured in Kbps, Mbps, or Gbps, it relates to the ability of a network to send data.
• Delay: is the time is takes to send a data packet from node to node.

Other types of delays include

• Propagation delay.
• Transmission delay.
• Queuing delay.
• Load: is the network traffic on a path
• Packets route to path with less load so they come in given time.
• Reliability: is the packet being delivered, despite other conditions.

Routing Advantages

• Routing can be done in many ways, it's useful to know needs and choose the correct one
• Automated routing is favored for the routing being done by set algorithms, manually configurations give more control

Routing Scalability

• Large-scale enterprise networks sharing sensitive information that must be organized.

Load Balancing Considerations

• Data routes are taken from general paths that could be at risk of loss

Routing Disadvantages

• Disadvantages differ in routing types.
• Static routing is only for smaller networks with a good view and knowledge of the network topology
• Else security concerns and complex configurations may occur.
• Dynamic routing gives less algorithm control is computationally expensive and consumes bandwidth
• Default routing is difficult for paths that will be sent, but can be configured if defined easily.

Conclusion

• Routing allows network devices to share data across the internet (algorithms select the path when routing based on metrics).

What is Routing FAQs

• Traffic systems example, the drive chooses the shortest path.
• Routes check the IP of every packet and send it to the router on any metrics.
• Default gateway is a router that lets the hosts connect with networks outside their LAN.