Cambridge IGCSE 0478 · Topic 2 · 2.1d

Client-Server, P2P &
Network Addresses

Client-Server · Peer-to-Peer · IP Addresses · MAC Addresses

CSZoneCambridge IGCSE Computer Science 0478

Client-Server Networks

Dedicated Servers & Clients

In a client-server network, one or more powerful servers provide resources and services. Clients (workstations) request those services. The server is always on and centrally manages everything.

Advantages: centralised backups and security; easy to manage user accounts and access rights; resources are always available from a central point

Disadvantages: if the server fails, all clients lose access; requires expensive dedicated server hardware and a network administrator to manage it

Used in: schools, businesses, hospitals — anywhere needing centralised control and security

Peer-to-Peer (P2P) Networks

All Devices Are Equal

In a peer-to-peer network, every device (peer) is equal — each can act as both client and server, sharing files and resources directly with other peers.

Advantages: no expensive server needed; cheaper and easier to set up; no single point of failure — if one peer fails, others continue

Disadvantages: each device manages its own security (inconsistent); performance degrades as more peers join; difficult to manage for large networks

Examples: home networks, small offices, file-sharing applications

Comparison

Client-Server vs P2P

Security: Client-server wins — server controls all user accounts and access rights centrally. P2P: each device controls its own security, making it inconsistent.

Cost: P2P wins — no dedicated server hardware needed. Client-server requires expensive server and ongoing IT administration.

Reliability: Client-server: if server goes down, clients lose all services. P2P: no single point of failure — network continues if one peer fails.

Scalability: Client-server scales well for large organisations. P2P becomes hard to manage as more devices join.

IP Addresses

Logical Addressing for Routing

An IP address is a logical address assigned to a device on a network. It is used to identify the device and enable routing — directing packets across networks to reach the correct destination.

IPv4: 32-bit address written as four decimal numbers separated by dots — e.g. 192.168.1.1. Provides ~4.3 billion unique addresses (now exhausted)

IPv6: 128-bit address written in hexadecimal — e.g. 2001:0db8:85a3::8a2e:0370:7334. Provides a virtually unlimited number of addresses

IP addresses can be static (fixed, manually set — used for servers) or dynamic (automatically assigned by a DHCP server each time a device connects)

MAC Addresses

Physical Hardware Addresses

A MAC (Media Access Control) address is a hardware address permanently burned into a device's Network Interface Card (NIC) by the manufacturer. It uniquely identifies the NIC at the hardware level.

Format: 48-bit address written as 6 pairs of hexadecimal digits — e.g. A3:B7:4F:12:CC:01

Used for communication within a local network (LAN) — the Link layer of TCP/IP uses MAC addresses to deliver frames between devices on the same network

IP vs MAC: IP address = logical, can change, used for routing between networks. MAC address = physical, permanent, used within the local network

MAC addresses can be used for network filtering — only allowing known MAC addresses to connect to a wireless network

Exam Practice

Have a go at this question

Cambridge IGCSE 0478 style

A school network uses a client-server model. Give two advantages and one disadvantage of using a client-server network compared to a peer-to-peer network for a school.

3 marks

Advantage — any two from: centralised backups mean student work is always saved and recoverable [1]; user accounts and access rights are managed in one place (easier to control who can access what) [1]; security is consistent across all devices [1]. Disadvantage: if the server fails/is offline, students cannot access files or services [1].

Key Takeaways

What to Remember

Client-server: centralised server controls resources; secure, manageable, but expensive and single point of failure

P2P: all devices equal; cheap, no single failure point, but inconsistent security and hard to manage at scale

IP address: logical, used for routing between networks; IPv4 (32-bit) or IPv6 (128-bit)

MAC address: physical hardware address burned into NIC; 48-bit hex; used within the local network