IP Communication

Networks and Cyber Security Course Overview

• Instructor: Alireza Esfahani, BSc, MSc, PhD, FHEA, M IEEE, M ECSO

• Position: Senior Lecturer in Cyber Security, Cyber Security Course Leader

• Institution: School of Engineering and Computing, University of West London

Module Content and Schedule

• Week 1: (12 Feb) - Networking Fundamentals

• Week 2: (19 Feb) - Network and Internet Protocol

• Week 3: (26 Feb) - IP Communication

• Week 4: (5 Mar) - Internet Layer

• Week 5: (12 Mar) - Internet Layer - Routing

• Week 6: (19 Mar) - Transport Layer

• Week 7: (26 Mar) - Security Protocols, Firewalls

• Week 8: (9 Apr) - VPN (Virtual Private Network), and IDS (Intrusion Detection Systems)

• Week 9: (16 Apr) - Wireless and Mobile Networks

• Week 10: (23 Apr) - Complementary session (IoT - Internet of Things)

• Week 11: (30 Apr) - Revision

• Week 12: (7 May) - In-class Test

Week 3 - IP Communication

Agenda

1. Network Topology & Internet Structure

2. IP Class

Network Topology

• Definition: To install a network effectively, one must understand how all components (computers, cables, peripherals) connect.

• Types of Network Topologies:

  • Physical Topology:

  • Describes the actual physical layout of the network, showing how devices are connected (physically, via cables or wirelessly).

  • Logical Topology:

  • Illustrates how data flows through the network, irrespective of physical connections.

  • Physical and logical topologies may differ significantly.

Standard Topologies Overview

1. Bus Topology:

   • All computers connect along a single cable segment.

   • Signals travel along the cable; if not terminated, they bounce back.

   • Considered obsolete.

2. Star Topology:

   • All devices connect through a central switch.

   • Each workstation has a direct connection to the switch, making it popular for modern networks.

   • Advantages:

     • Easy to add new devices.

     • Cable breaks affect only single nodes.

     • Centralized management simplifies network administration.

   • Disadvantages:

     • Switch failure leads to total system failure, though troubleshooting is manageable.

     • Higher cost due to cabling and switch devices.

3. Ring Topology:

   • Devices are connected to form a continuous loop.

   • Signals travel in one direction and are regenerated by each device in turn.

   • Obsolete due to operational limitations.

4. Extended Star:

   • Multiple star topologies interconnected.

5. Mesh Topology:

   • Every workstation connects to every other workstation.

   • Rarely used due to high costs and complexity.

6. Tree Topology:

   • Combines characteristics of star and bus topologies.

   • Heavy cabling leads to higher cost and complexity in maintenance.

Internet Structure

Packet Transmission

• Host Functionality:

  • Hosts split application messages into packets of length L bits.

  • Transmits packets into access networks at transmission rate R.

• Transmission Delay:

  • Time to transmit L-bit packet can be calculated as $ext{Transmission delay} = \frac{L}{R}$.

Network Core

• Defined as a mesh of interconnected routers that forwards packets from one to another through links.

• Packet Switching Principle:

  • Messages are broken down into packets that transfer at the link's full capacity.

Packet-Switching: Store-and-Forward

• Entire packet must arrive at the router before onward transmission.

• One-Hop Transmission Delay Example:

  • Given: L = 7.5 Mbits, R = 1.5 Mbps, transmission time is $\frac{L}{R} = 5 ext{ seconds}$.

Queuing Delay and Loss

• If the arrival rate to a link exceeds its transmission rate (
  R), packets will queue and may be dropped if buffers fill up.

Packet Scheduling

• Determines the sequence in which packets are sent via links:

  • Options can include first-come, first-served, priority, or round-robin.

IP Address Classes

IPv4 and IPv6 Overview

• IPv4:

  • 32 bits, allows for 4,294,967,296 addresses.

  • Addresses formatted as four numbers (0-255) separated by periods.

  • Can be assigned either statically or dynamically.

• IPv6:

  • 128 bits, supports 340,282,366,920,938,463,374,607,431,768,211,456 addresses.

  • Uses geographic region for address allocation.

  • Structured as eight 4-digit hexadecimal numbers separated by colons (e.g., 1080:0:0:0:0:800:0:417A).

IP Addressing Structure

• Class A:

  • First octet = Network, remaining three = Subnets/Hosts.

  • Range = 1.0.0.0 to 126.255.255.255.

• Class B:

  • First two octets = Network, last two = Subnets/Hosts.

  • Range = 128.0.0.0 to 191.255.255.255.

• Class C:

  • First three octets = Network, last one = Subnets/Hosts.

  • Range = 192.0.0.0 to 223.255.255.255.

Classful Addressing vs. CIDR

• Classful Addressing:

  • Rigid structure, requiring specific bytes for different classes.

  • Inefficiencies noted (e.g., Class B large for small organizations).

• CIDR (Classless Inter-Domain Routing):

  • Flexible network portion of arbitrary length using format a.b.c.d/x, where x is bits in network part.

  • E.g., classless form allows for a more efficient use of IP address space.

Benefits of CIDR

• More efficient distribution and utilization of IP address space, reducing wastage of addresses.

• Allows for subnetting by logically grouping hosts, leading to improved security and performance in data handling.

Subnetting

• Definition: Logical subdivision of an IP network, improving security and performance.

• Each subnet identified by a range of IP addresses; for example: 223.1.1.1 - 223.1.1.254.

• Subnet Mask: Distinguishes network and node portions, with defaults being:

  • Class A: 255.0.0.0

  • Class B: 255.255.0.0

  • Class C: 255.255.255.0

• How to Determine Subnet Addresses:

  • Calculate network requirements, and establish subnet masks and ranges accordingly.

Conclusion

• Topics Covered:

  • Internet Connection

  • IP Classes

  • Subnetting

• Final Notes: Students are welcome to ask questions to further clarify any points discussed today.