What Is Internetworking?

Network interconnection means that two or more communication networks are connected to each other with one or more network communication devices through a certain method to form a larger network system. The purpose of network interconnection is to enable users in different networks to communicate with each other and share software and data.

Chinese name: Network interconnection
Foreign name: Internetworking

Purpose: Different network users communicate with each other
Related concepts: Internet, LAN, MAN, WAN

The purpose of network interconnection

The purpose of connecting different networks to each other is to allow users in any one network to communicate with users in other networks and also allow users in any one network to access data in other networks. ^[1]

Network interconnection type

The types of network interconnection mainly include:

LAN and LAN
LAN and WAN
LAN and WAN and LAN
WAN and WAN

How Internet Networks Are Connected

Networks can be connected to each other through different devices.

At the physical layer, networks can be connected through repeaters or hubs. They usually simply move data from one network to another network of the same type.

At the data link layer, bridges and switches can be used for network connections. They can receive frames, check MAC addresses, and forward these frames to a different network.

At the network layer, routers can be used to connect two networks.

At the transport layer, a transport gateway is used. A transport gateway is the interface between two transport layer connections.

At the application layer, the application gateway can translate the semantics of the message. ^[1]

Network interconnection reference model

OSI and TCP / IP are two important network architectures. The OSI reference model and the TCP / IP reference model have the same thing in that they both adopt a layered idea and use the concept of a protocol stack at the same layer, but they are very different in layer division and function design. ^[2]

Network interconnection open system interconnection reference model

OSI (Open System interconnection) Open System Interconnection Reference Model

Network interconnection physical layer

Mechanical properties: the shape, size of the interface, the number and arrangement of pins, etc.

Electrical performance: The voltage, current, impedance, waveform, rate, and balance characteristics of the signal specified by the interface.

Engineering specifications: the meaning, characteristics, and standards of the interface pins.

Working mode: Determine the transmission mode of the data bit stream, such as: simplex, half duplex, or full duplex.

The physical layer protocols are:

Network interconnection

American Electronics Industry Association (EIA) RS232, RS422, RS423, RS485, etc .;

X.25, X.21, etc. of the International Telegraph and Telephone Advisory Committee (CCITT);

The data unit of the physical layer is bits (BIT), and the typical device is a hub HUB.

Network Interconnect Link Layer

The link layer shields the physical characteristics of the transmission medium, enabling data to be transmitted reliably.

Contents include media access control, connection control, sequence control, flow control, error control, and arbitration protocols.

The link layer protocols are:

The protocols are character-oriented communication protocol (PPP) and bit-oriented communication protocol (HDLC).

Arbitration agreement: 802.3, 802.4, 802.5, namely:

CSMA / CD (CarrierSenseMultipleAccesswithCollisionDetection), Token

Bus, TokenRing

The data unit of the link layer is a frame, which realizes access to the MAC address. A typical device is a switch.

Internetwork layer

The network layer manages connection methods and routing.

Connection method: Virtual Circuits and Datagram services.

A virtual circuit is a route for connection-oriented data communication.

path.

Datagrams are connectionless-oriented, and each datagram has routing capabilities.

The data unit of the network layer is a packet, which uses an IP address. A typical device is a router.

This layer can be used for flow control, but the flow control is more used in the second or fourth layer.

Internetwork transport layer

Provide end-to-end services. Can realize flow control and load balancing.

Transport layer information includes ports, control words, and checksums.

The transport layer protocols are mainly TCP and UDP.

The transport layer is located in the fourth layer of OSI. The equipment used in this layer is the host itself.

Internetworking session layer

The main content of the session layer is authentication, session management, and determining the communication method through the session.

Once the connection is established, the task of the session layer is to manage the session.

Network interconnection presentation layer

The presentation layer mainly explains the meaning of communication data, such as code conversion and format conversion, so that different terminals can be represented.

It also includes encryption and decryption, compression and decompression.

Network interconnection application layer

The application layer should be directly-oriented programs or services, including system programs and user programs.

For example, www, FTP, DNS, POP3, and SMTP are all application layer services.

When sending data, it is a process of packaging data from the application layer to the physical layer.

When receiving, it is a process of unpacking data from the physical layer to the application layer.

From the functional perspective, it can be divided into three groups. Layers 1 and 2 solve network channel problems, layers 3 and 4 solve transmission problems, and layers 5, 6, and 7

Manage access to application processes.

From the control perspective, it can be divided into two groups. Layers 1, 2, and 3 are communication subnet layers, and layers 4, 5, 6, and 7 are host control layers.