Information Technology Reference
In-Depth Information
Summarization of Networks (Continued)
Table 6-15
Binary Address
IP Network
11000111 01100100 00010
100 00000000
199.100.20.0
11000111 01100100 00010
101 00000000
199.100.21.0
11000111 01100100 00010
110 00000000
199.100.22.0
11000111 01100100 00010
111 00000000
199.100.23.0
Transport Layer
The transport layer of the TCP/IP architecture provides two services: one connection-oriented
with TCP and a connectionless service with UDP. This section covers these protocols.
TCP
TCP is a connection-oriented, end-to-end reliable protocol for the communication between host
systems. TCP is specified in RFC 793. TCP assumes unreliable packet delivery service from the
lower layers. TCP is accessed by the IP with protocol number 6. TCP accesses upper-layer
protocols with port numbers. TCP uses several mechanisms for the reliable delivery of data,
including PUSH (PSH) and acknowledgment (ACK) signals, windowing, and multiplexing.
Data in TCP is called
segments
.
TCP Mechanics
This section covers some mechanisms that TCP uses for the reliable delivery of data.
PSH Signal
TCP packages bytes into segments for transmission through the network. TCP decides when
sufficient data has accumulated to form a segment for transmission. The application that uses
TCP can ensure that data is transmitted by indicating that it is pushed to the receiving system.
A PSH pointer indicates how much data is to be sent. The PSH causes the TCP to promptly
forward and deliver data up to the point indicated in the PSH. The data is sent to the receiver,
which is the destination station.
Acknowledgment
TCP must recover damaged, lost, duplicated, or out-of-order data. This is achieved by using
(ACKs) from the receiving system. If an ACK is not received within a timeout interval, the data
is retransmitted.
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