Network Layer

Internetworking

A collection of networks to provide data delivery of host-to-host.

H# are hosts

R# are routers

IP and Routing

Internet Protocol (IP)

Governs the transmission of data over the internet.

Responsible for Routing data packets.

• Sender

  • Encapsulates segments into datagrams and sends them from the sending host to the receiving host

• Receiver

  • Datagrams are delivered to the transport layer

• Every host and router

  • Network layer protocols that operate at the network, data link, and physical layers

• A router examines the header fields in all IP datagrams that pass through it

Network Layer

Encapsulation

segment

datagram

frame

• Routing Protocols

  • RIP, OSPF, BGP

• IP Protocol

  • Address

  • Datagram Format

  • Packet handling

• ICMP Protocol

  • Error reports

  • Router Signals

• Forwarding Table

Internet network Layer (disassembled) 

Router Architecture

datagrams journey

The concept of net neutrality is based on the idea that the internet should be an open and level playing field, where all users have equal access to information and online resources, regardless of their location, financial resources, or the type of device they use to access the internet.

If network neutrality is not enforced, ISPs could prioritize or block certain types of internet traffic, including specific websites, applications, or services. This could have significant implications for how routers function and how data is transmitted over the internet.

https://www.youtube.com/watch?v=fpbOEoRrHyU

https://worldpopulationreview.com/country-rankings/countries-without-net-neutrality

Network Neutrality

• Buffering, classification, and scheduling

  • Help routers efficiently manage network traffic, ensure data integrity, and optimize network performance.

• Throughput

  • Maximising throughput within the whole network.

• Delay

  • Minimizing the mean packet to send traffic through the network effectively.

Routing

Routing algorithms

Routing algorithms for internet

Dynamic Routing Protocol Overview

RIP protocol was updated to RIPv2 to accommodate growth in the network environment
     RIPv2 does not scale to current larger network implementations 

Routing Protocols developed to meet the need of larger networks include:
     Open Shortest Path First (OSPF)
     Intermediate System-to-Intermediate System (IS-IS).
     Enhanced IGRP (EIGRP)

Border Gateway Protocol (BGP) is used between Internet service providers (ISPs)

• Each node constructs a one-dimensional array (a vector) containing the "distances" (costs) to all other nodes and distributes that vector to its immediate neighbours.

• The starting assumption for distance-vector routing is that each node knows the cost of the link to each of its directly connected neighbours.

• These costs may be provided when the router is configured by a network manager. A link that is down is assigned an infinite cost.

RIP (Routing Information Protocol)

• Routers send their advertisements every 30 seconds;

• A router also sends an update message whenever an update from another router causes it to change its routing table.

• One point of interest is that it supports multiple address families, not just IP. RIP version 2 (RIPv2) also introduced the subnet masks, whereas RIP version 1 worked with the old classful addresses of IP.

• All link costs are equal to 1, just as in our example. Thus, it always tries to find the minimum hop route. Valid distances are 1 through 15, with 16 representing infinity. This also limits RIP to running on fairly small networks—those with no paths longer than 15 hops.

RIP (Routing Information Protocol)

• Starting Assumptions

  • Each node is assumed to be capable of finding out the state of the link to its neighbours and the cost of each link.

• Aim

  •  Each node to know the least-cost path to any destination.

• Mechanism 1

  • A solid and reliable way to provide link-state information to all nodes in the network.

• Mechanism 2

  • To be able to calculate the routes from the sum of all the accumulated link-state knowledge.

OUR SERVICES

Link State Routing (Routing Table)

Link State Request Packet

Link State Acknowledgement Packet

Example of Building a route table for Link State Routing

Authentication of Routing Messages

Open Shortest Path First Protocol (OSPF)

Additional Hierarchy

Load Balancing

Multiple Cost Metrics

Send information from one node to many other nodes, and the entire network can thus be impacted by bad information from one node. For this reason authenticating routing messages has become very important.

OSPF introduces another layer of hierarchy into routing by allowing a domain to be partitioned into areas. A router within a domain only needs to know how to get to the right area reducing the amount of information in the routing table.

Allows multiple routes to the same place to be assigned the same cost and will cause traffic to be distributed evenly over those routes, thus making better use of the available network throughput.

For each link, multiple cost metrics for different Types of Services (ToS) (e.g., satellite link cost (more delay involved) set low for best effort ToS; high for real-time ToS)