IP is the primary network protocol used on the Internet, developed in the 1970s.
A D V E R T I S E M E N T
On the Internet and many other networks, IP is often used together with the Transport Control Protocol (TCP) and referred to interchangeably as TCP/IP.
IP supports unique addressing for computers on a network. Most networks use the IP version 4 (IPv4) standard that features IP addresses four bytes (32 bits) in length. The newer IP version 6 (IPv6) standard features addresses 16 bytes (128 bits) in length.
Type of service specification.
Fragmentation and re-assembly.
IP Message Format
IP is defined by RFC 791.
Version (4 bits) - The IP protocol version, currently 4 or 6.
Header length (4 bits) - The number of 32 bit words in the
Type of service (TOS) (8 bits) - Only 4 bits are used which are
minimize delay, maximize throughput, maximize reliability, and
minimize monetary cost. Only one of these bits can be on. If all
bits are off, the service is normal. Some networks allow a set
precedences to control priority of messages the bits are as follows:
Bits 0-2 - Precedence.
111 - Network Control
110 - Internetwork Control
101 - CRITIC/ECP
100 - Flash Override
011 - Flash
010 - Immediate
001 - Priority
000 - Routine
Bit 3 - A value of 0 means normal delay. A value of 1 means
Bit 4 - Sets throughput. A value of 0 means normal and a 1
means high throughput.
Bit 5 - A value of 0 means normal reliability and a 1 means
Bit 6-7 are reserved for future use.
Total length of the IP data message in bytes (16 bits)
Identification (16 bits) - Uniquely identifies each datagram.
This is used to re-assemble the datagram. Each fragment of the
datagram contains this same unique number.
flags (3 bits) - One bit is the more fragments bit
Bit 0 - reserved.
Bit 1 - The fragment bit. A value of 0 means the packet may
be fragmented while a 1 means it cannot be fragmented. If this
value is set and the packet needs further fragmentation, an ICMP
error message is generated.
Bit 2 - This value is set on all fragments except the last
one since a value of 0 means this is the last fragment.
Fragment offset (13 bits) - The offset in 8 byte units of this
fragment from the beginning of the original datagram.
Time to live (TTL) (8 bits) - Limits the number of routers the
datagram can pass through. Usually set to 32 or 64. Every time the
datagram passes through a router this value is decremented by a
value of one or more. This is to keep the datagram from circulating
in an infinite loop forever.
Protocol (8 bits) - It identifies which protocol is encapsulated
in the next data area. This is may be one or more of TCP(6),
UDP(17), ICMP(1), IGMP(2), or OSPF(89). A list of these protocols
and their associated numbers may be found in the /etc/protocols file
on Unix or Linux systems.
Header checksum (16 bits) - For the IP header, not including the
options and data.
Source IP address (32 bits) - The IP address of the card sending
Destination IP address (32 bits) - The IP address of the network
card the data is intended for.
Options - Options are:
Security and handling restrictions
Record route - Each router records its IP address
Time stamp - Each router records its IP address and time
Loose source routing - Specifies a set of IP addresses the
datagram must go through.
Strict source routing - The datagram can go through only the
IP addresses specified.
Data - Encapsulated hardware data such as ethernet data.
The message order of bits transmitted is 0-7, then 8-15, in network byte
order. Fragmentation is handled at the IP network layer and the messages are
reassembled when they reach their final destination. If one fragment of a
datagram is lost, the entire datagram must be retransmitted. This is why
fragmentation is avoided by TCP. The data on the last line, item 14, is ethernet
data, or data depending on the type of physical network.
Share And Enjoy:These icons link to social bookmarking sites where readers can share and discover new web pages.
Internet Protocol, Networking Tutorial, Networking tutorial pdf, history of Networking, basic Networking, syntax use in Networking, networking training courses, networking tool kit, networking switch.