A - B
Understanding TCP/IP
Most of people think that TCP/IP is a protocol, in fact
it is a suite of protocols under one roof and here is a list of most important protocols
in the TCP/IP suite:
- Internet Protocol (IP)
- Transmission Control Protocol (TCP)
- File Transfer Protocol (FTP)
- Simple Mail Transport Protocol (SMTP)
- HyperText Transport Protocol (HTTP)
- Network News Transport Protocol (NNTP)
These Protocols were defined in the Basic
Concepts Section.
The Structure of an IP Address
From the structure of an
IP datagram you knew that datagram includes the the source IP address and the destination
IP address.
IP address is a 32-bit value given
to every computer connected to the Internet assigned by the network administrator,
example :
1100110111010000111000100000010
It's hard to work with these
numbers in this shape, so in order to make it easier to work with TCP/IP,we change their
form to another one called dotted-decimal notation.This notation
divides the 32 bit of the IP address into 4 groups of 8 bits (each group called quad
), then converted to decimal equivalent, and separated by dots.
11001101 |
11010000 |
11100010 |
0000010 |
205 |
208 |
113 |
2 |
You
can use scientific calculator to convert from 32-bit shape to the decimal but check that
the Bin is selected, enter the appropriate 1's and 0's, and select the Dec
option.
The Structure of an IP Datagram
The network data is broken into packets
these packets don't only contain the the data but also the header information
that specifies items like destination address. The data is transmitted in form of packets
these packets called datagram.
The datagram header can be from 160 to 512
bits in length, the address of the host that send the datagram and the address of the host
the supposed to receive the the datagram are included in the datagram header. Here is the
format of a datagram header.
| Field |
Bits |
Description |
| Version |
0 to 3
|
Specifies the format of the header |
| Internet Header Length |
4 to 7 |
The length of the header. |
| Type of Service |
8 to 15 |
Specifies the quality of the service desired . |
| Total Length |
16 to 31 |
The length of the datagram, including the header and data. |
| Identification |
32 to 47 |
An identify value that lets the destination reassembles a fragmented
datagram. |
| Flags |
48 to 50 |
One flag specifies whether a datagram can be fragmented. If it can't, and
the host can't handle the datagram, it discards the datagram. If the datagram can be
fragmented, another flag indicates whether this is the last fragmented. |
| Fragment Offset |
51 to 63 |
This field specifies the position in the datagram of this fragment
if the datagram is fragmented. |
| Time to Live |
64 to 71 |
Shows the maximum number of hosts through which the datagram can be
routed. |
| Protocol |
72 to 79 |
Represent the session layer of protocol like HTTP or NNTP |
| Header Checksum |
80 to 95 |
Used to check the integrity of the header. |
| Source Address |
96 to 127 |
Shows the IP address of the host that sent the datagram. |
| Destination Address |
128 to 159 |
Shows the IP address of the host that supposed to receive the datagram. |
| Options |
160 and over |
This field specifies extra options like security. |
| The rest of the datagram is
used by the data that supposed to be transmitted to the destination host. |
|
