The document provides a comprehensive overview of the transport layer in networking, detailing transport services, primitives, and protocols such as TCP and UDP. Key topics include connection establishment and release, multiplexing, crash recovery, and performance issues, demonstrated with examples like socket programming and remote procedure calls. It concludes with references and a discussion on various transport protocol elements and their corresponding headers.

1. The Transport Layer
Chapter 4
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2. The Transport Service
• Services Provided to the Upper Layers
• Transport Service Primitives
• Berkeley Sockets
• An Example of Socket Programming:
– An Internet File Server
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3. Services Provided to the Upper
Layers
The network, transport, and application layers.
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4. Transport Service Primitives
The primitives for a simple transport service.
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5. Transport Service Primitives
The nesting of TPDUs, packets, and frames.
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6. Transport Service Primitives
A state diagram for a simple connection management scheme. Transitions
labeled in italics are caused by packet arrivals. The solid lines show the client's
state sequence. The dashed lines show the server's state sequence.
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7. Berkeley Sockets
The socket primitives for TCP.
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8. Elements of Transport
Protocols
• Addressing
• Connection Establishment
• Connection Release
• Flow Control and Buffering
• Multiplexing
• Crash Recovery
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9. Transport Protocol
(a) Environment of the data link layer.
(b) Environment of the transport layer.
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10. Addressing
TSAPs, NSAPs and transport connections.
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11. Connection Establishment
How a user process in host 1 establishes a connection
with a time-of-day server in host 2.
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12. Connection Establishment
(a) TPDUs may not enter the forbidden region.
(b) The resynchronization problem.
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13. Connection Establishment
Three protocol scenarios for establishing a connection using a
three-way handshake. CR denotes CONNECTION REQUEST.
(a) Normal operation,
(b) Old CONNECTION REQUEST appearing out of nowhere.
(c) Duplicate CONNECTION REQUEST and duplicate ACK.
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14. Connection Release
Abrupt disconnection with loss of data.
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15. Connection Release
The two-army problem.
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16. Connection Release
Four protocol scenarios for releasing a connection. (a) Normal case of a
three-way handshake. (b) final ACK lost.
6-14, a, b
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17. Connection Release
(c) Response lost. (d) Response lost and subsequent DRs lost.
6-14, c,d
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18. Multiplexing
(a) Upward multiplexing. (b) Downward multiplexing.
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19. Crash Recovery
Different combinations of client and server strategy.
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20. A Simple Transport Protocol
• The Example Service Primitives
• The Example Transport Entity
• The Example as a Finite State Machine
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21. The Example Transport Entity
The network layer packets used in our example.
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22. The Example Transport Entity
Each connection is in one of seven states:
1. Idle – Connection not established yet.
2. Waiting – CONNECT has been executed, CALL REQUEST sent.
3. Queued – A CALL REQUEST has arrived; no LISTEN yet.
4. Established – The connection has been established.
5. Sending – The user is waiting for permission to send a packet.
6. Receiving – A RECEIVE has been done.
7. DISCONNECTING – a DISCONNECT has been done locally.
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23. The Internet Transport Protocols:
UDP
• Introduction to UDP
• Remote Procedure Call
• The Real-Time Transport Protocol
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24. Introduction to UDP
The UDP header.
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25. Remote Procedure Call
Steps in making a remote procedure call. The stubs are shaded.
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26. The Real-Time Transport
Protocol
(a) The position of RTP in the protocol stack. (b) Packet nesting.
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27. The Real-Time Transport
Protocol
The RTP header.
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28. The Internet Transport Protocols: TCP
• Introduction to TCP
• The TCP Service Model
• The TCP Protocol
• The TCP Segment Header
• TCP Connection Establishment
• TCP Connection Release
• TCP Connection Management Modeling
• TCP Transmission Policy
• TCP Congestion Control
• TCP Timer Management
• Wireless TCP and UDP
• Transactional TCP
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29. The TCP Service Model
Some assigned ports.
Port Protocol Use
21 FTP File transfer
23 Telnet Remote login
25 SMTP E-mail
69 TFTP Trivial File Transfer Protocol
79 Finger Lookup info about a user
80 HTTP World Wide Web
110 POP-3 Remote e-mail access
119 NNTP USENET news
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30. The TCP Service Model
(a) Four 512-byte segments sent as separate IP datagrams.
(b) The 2048 bytes of data delivered to the application in a single
READ CALL.
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31. The TCP Segment Header
TCP Header.
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32. The TCP Segment Header
The pseudoheader included in the TCP checksum.
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33. TCP Connection Establishment
(a) TCP connection establishment in the normal case.
(b) Call collision.
6-31
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34. TCP Connection Management
Modeling
The states used in the TCP connection management finite state machine.
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35. TCP Transmission Policy
Window management in TCP.
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36. TCP Transmission Policy
Silly window syndrome.
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37. TCP Congestion Control
(a) A fast network feeding a low capacity receiver.
(b) A slow network feeding a high-capacity receiver.
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38. Transitional TCP
(a) RPC using normal TPC.
(b) RPC using T/TCP.
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39. Performance Issues
• Performance Problems in Computer Networks
• Network Performance Measurement
• System Design for Better Performance
• Fast TPDU Processing
• Protocols for Gigabit Networks
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40. References
[1] A. S. Tanenbaum, “Computer Network”, Pearson Education
[2] Forouzen, “Data Communication and Networking”, TMH
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