Page 761 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

acknowledge packet is sent is known as the transmission window.
Data flow is controlled through a mechanism called sliding windows.

TCP is able to use different sizes of windows (in other words, a
different number of transmitted packets) before sending an
acknowledgment. Larger windows allow for faster data transmission,
but they should be used only on reliable connections where lost or
corrupted data is minimal. Smaller windows should be used when the
communication connection is unreliable. TCP should be employed
when the delivery of data is required. Sliding windows allow this size

to vary dynamically because the reliability of the TCP session changes
while in use. In the event that all packets of a transmission window
were not received, no acknowledgment is sent. After a timeout period,
the sender will resend the entire transmission window set of packets
again.

The TCP header is relatively complex when compared to the other
common Transport layer protocol, UDP. A TCP header is 20 to 60

bytes long. This header is divided into several sections, or fields, as
detailed in Table 11.1.

TABLE 11.1 TCP header construction (ordered from
beginning of header to end)

Size in bits Field

16 Source port

16 Destination port
32 Sequence number

4 Data offset

4 Reserved for future use

8 Flags (see Table 11.2)

16 Window size
16 Checksum

16 Urgent pointer

Variable Various options; must be a multiple of 32 bits

All of these fields have unique parameters and requirements, most of