An Investigation into Transport Protocols and Data Transport ...

4.2. Protocol Description 52
TCP Segment
0 4 10 16
32 bits
Source Port
Sequence Number
Destination Port
Data
Offset
TOS
Checksum
Acknowledgement Number
Control Flags
Receiver Window
Urgent Pointer
TCP Options (variable)
Padding (variable)
Data (variable)
Figure 4.2: TCP header format.
and satellite communications, technological development has increased the
size of the Internet by orders of magnitude in terms of size, speed, load and
connectivity - and all this in the last couple of decades [CO01, CO99]. Even
with the wide range of network conditions present on the Internet, TCP has
been able to utilise and effectively share network resources between Internet
Users. More importantly, it is generally believed to have prevented severe
congestion collapse during this time [FF99, Nag84].
4.2 Protocol Description
The TCP header is shown in Figure 4.2. The source and destination ports
allow the hosts to identify multiple concurrent TCP flows at once. The
sequence and acknowledgment numbers facilitate reliable transport (See Section
4.2.2). The Receiver Window field is used for flow control (See Section
4.2.3). The Data Offset field provides a pointer to the start of the Data
field as TCP Options [Pos81b] are variable in size. The size of the Data field