IP protocol family of computer network

Internet Protocol IP

There are also three protocols that are used with the IP protocol:

Address Resolution Protocol ARP (Address Resolution Protocol)

Inter-network Control Message Protocol ICMP (Internet Control Message Protocol)

Internet Group Management Protocol IGMP (Internet Group Management Protocol)

Connect the networks to each other to use some intermediate devices , also known as intermediate systems or trunking (relay) systems. Depending on the level at which the intermediary device resides, there are several different intermediate devices available:

Physical Layer Relay System: transponder (repeater).

Data Link Layer relay system: Bridge or bridge .

Network Layer relay System: router (router).

A mixture of bridges and routers: the bridge (brouter).

Trunking system above the network layer: Gateway .

Format of IP datagrams

An IP datagram consists of a header and a data component.

The first part of the header is a fixed length, a total of 20 bytes , which all IP datagrams must have.

The fixed part of the header is followed by some optional fields whose length is variable.

Address Resolution Protocol ARP

Regardless of the protocol used by the network layer, the hardware address must eventually be used when transferring data frames on the actual network link. This needs to solve a problem, how to find its corresponding physical address according to the IP address of a machine, or in turn, how to find its corresponding IP address according to the physical address. Address Resolution Protocol ARP and Inverse Address Resolution Protocol Rarp is used to solve such problems.

Each host has an ARP cache (Arpcache) with the IP address of each host and router on the local area network to the Hardware Address mapping table, which is also frequently updated dynamically.

When host a wants to send an IP datagram to a host B on the local area network, it first looks at the IP address of Host B in its ARP cache. If so, you can find out its corresponding hardware address, then write this hardware address to Mac frame, and then send the Mac frame to this hardware address over the LAN.

If the IP address of Host B is not found, host a broadcasts a packet of ARP requests on the local area network, and all hosts on the local area network receive this ARP request packet, but only Host B returns an ARP response packet, which is written to the mapping table when host a receives it.

Inter-Network Control Message Protocol ICMP

In order to improve the chances of successful IP datagram delivery, Internet Control Message Protocol ICMP (Controlmessage Protocol) was used at the internetwork. ICMP allows the host or router to report error conditions and provide reports about anomalies .

ICMP is not a high-level protocol, but an IP-layer protocol. The ICMP packet is the data of the IP layer datagram, plus the header of the datagram, which makes up the IP datagram sent out.

There are two types of ICMP packets, the ICMP error Reporting message and the ICMP inquiry message .

There are 5 types of ICMP Error Reporting messages:

(1) The end point is not reached

(2) Source point suppression (Sourcequench)

(3) Time exceeded

(4) Parameter problems

(5) Change route (redirect) (Redirect)

There are two types of ICMP inquiry messages:

(1) Echo Request and reply message

(2) Timestamp request and reply message

An important application of ICMP is the packet-inter-network detection ping(Packet intenet Groper), which is used to test connectivity between two hosts. Ping is an example of using the network layer ICMP directly by the application layer. It, does not pass the transport layer of TCP or UDP.

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IP protocol family of computer network