Computer Networks · TEE · papers
Q1(a) · TCP/IP network and transport layers
2025-02-19 · 2023-24 / 2024-25
Actual paper; 100 marks attempted. Current-syllabus alignment is stated per question.
Q1(a). Explain the network layer and transport layer protocols of TCP/IP model. [5 marks]
Answer
The TCP/IP model describes the Internet protocol suite in four layers. Many teaching books split the link layer into data link and physical, making a five-layer teaching model; identify the convention before drawing.
Diagram: OSI layers mapped to the four-layer TCP/IP model. Labels: OSI layers mapped to the four-layer TCP/IP model | OSI layers mapped to the four-layer TCP/IP model | 7 Application | 6 Presentation | 5 Session | 4 Transport | 3 Network | 2 Data link | 1 Physical | Application | HTTP, DNS, FTP, SMTP | Transport | Internet | Link / network access | Includes physical access | Some textbooks split link into data link + physical: five layers.
| TCP/IP layer | Function | Examples |
|---|---|---|
| Application | Defines application message formats and exchanges for Web access, naming, email and file transfer; includes presentation/session functions as needed | HTTP, DNS, SMTP, FTP |
| Transport | End-to-end process communication | TCP, UDP, SCTP |
| Internet | IP addressing, routing and best-effort datagrams | IPv4/IPv6 |
| Link/network access | Local delivery and physical access | Ethernet/Wi-Fi and their medium |
| Point | OSI | TCP/IP |
|---|---|---|
| Layer count | Seven | Four here; five-layer teaching variant splits link |
| Upper functions | Application, presentation, session separated | Grouped under application |
| Lower functions | Data link and physical separated | Grouped under link/network access |
| Purpose | General reference architecture | Architecture of deployed Internet protocol family |
| Network service | Reference model can describe different services | Internet layer uses connectionless IP |
| Transport | Conceptual transport service | TCP reliable byte stream; UDP datagrams; SCTP messages |
Yaad rakho: OSI 7; TCP/IP four mein upper three merge, lower two merge.
Internet and transport protocols
| Layer | Protocol | Role |
|---|---|---|
| Internet | IPv4 / IPv6 | Address and deliver best-effort packets across networks |
| Internet | ICMP / ICMPv6 | Report selected IP errors and operational information; used by diagnostic exchanges |
| Transport | TCP | Reliable, ordered byte stream with connection establishment, flow and congestion control |
| Transport | UDP | Connectionless message delivery using ports, without built-in retransmission or ordering |
| Transport | SCTP | Reliable message-oriented association with multiple streams and multihoming support |