1. Part 6 Transport Layer
Transport Level Services
TCP

2. Network, Transport & Application Layers

3. Transport Layer Quality of Service Parameters

4. Primitives for a Simple Transport Layer
services provided to application layer
transport protocol data unit (TPDU)

5. A Transport Protocol - TCP
type of service (connection & datagram)
grade of service (acceptable reliability, delay, throughput, priority)
data transfer
user interface (procedures, data flow, dma)
connection management
expedited delivery
status reporting & security

6. Socket Primitives in TCP

7. TCP/ IP Protocol Suite vs the OSI Model
Heirarchy vs Layering
former allows access to functions of latter, latter restricted to immediate lower layer
separate control & data connections are possible in TCP/ IP
lower level control can be directly used to accomplish higher level functions
multiple entitiy cooperation possible
TCP/ IP supports internetworking directly
TCP/ IP supports connectionless transmission & management functions, OSI is in process of incorporating these

8. TCP/ IP Protocol Architecture
Three Agents: Processes, Hosts & Networks
Processes executing on Hosts communicate via the Network
Four Hierarchical Layers:
Network Access Layer
Internet Layer
Host-Host Layer
Process / Application Layer
The USA DOD Arpanet Design out of which OSI was defined

9. The USA DOD Military Standards
Internet Protocol - IP (MIL-STD-1777) a connectionless datagram service across one or more possibly unrealiable networks
Trans. Control Protocol - TCP (MIL-STD-1778) reliable end-to-end data transfer service(OSI 4)
File Transfer Protocol - FTP (MIL-STD-1780) a process/ application layer service for the transfer of ASCII, EBCDIC & binanry files
SMTP (MIL-STD-1781) a Simple Mail Transfer Protocol
Telnet Protocol (MIL-STD-1782) a simple asynchronous termianl capability

10. Internetworking Example
Applications
TCP IP
NAP 1
Applications
TCP IP
NAP 2
Host A
Host B
Router IP
NAP NAP 2

11. TCP/ IP Frame
Telnet, FTP, SMTP :
User Data
TCPH
User Data
TCP segment :
IP datagram :
IPH
TCPH
User Data
NetH
IPH
TCPH
User Data

12. Example Trace Process 1 of Host A => P2 of B
process 1 hands msg to TCP with dest. P2 of B
TCP may break msg into a number of frames
each frame has Dest Port (ie process P2)
Sequence Number (so can be ordered)
Checksum
TCP hands to IP for sending to B
IP datagram with Dest Host, ie, B, created & sent, possibly via several networks
each IP datagram handed to Network Access layer for 1st, etc, network. contains Dest Subnet address, priorities, etc.

13. USA DOD Protocol Dependancies
FTP
SMTP
TELNET
SNMP
TCP
UDP IP
ARP / RARP
Network Access

14. SMTP - Simple Mail Transfer Protocol
transfers messages among hosts
supports mailing lists, return receipts, forwarding, priorities
does not include message creation, editing
uses local mail packages for mail storing and user notification

15. OSI and the US DOD Model Relationships
7. Application
6. Presentation
5. Session
4. Transport
3. Network
2. Data Link
FTP, SMTP
TELNET
TCP IP
OSI
Model
DOD
Model

16. TCP Header

17. TCP Header Fields
transport services access point (TSAP)
IP address (=NSAP address) + port # are TCP/ IP source & destination addresses
ATM-SAPs (service access points) in ATM
flags
URG=1 if urgent pointer (offset) in use
ACK=1 means ack present, ACK# is expected
PSH=1 means push out to port before assembly
RST for reset, problem has occurred
SYN & ACK for connection request or accepted
FIN to relase connection
window says how many bytes may be open

18. TCP Connection Management States

19. TCP Connection Management Finite State Machine

20. Window Management in TCP (byte based)