The basic principle of network system structure and design (i.)

One, the classification of the computer network

The computer network can be divided into three types of local area network (LAN), Metro (man) and wide area networks (WAN) according to its geographical coverage.

The technical characteristics of 1,lan are mainly shown in:

1) LAN covers a limited geographical range, it adapts to institutions, campuses, factories and other limited range of computers, terminals and all kinds of information processing equipment network needs.

2) LAN provides high data transfer efficiency (10mbps~10gbps), low bit error rate and high quality data transmission environment.

3) LAN generally belongs to one unit all, easy to establish, maintain and expand.

From the perspective of media access method, LAN can be divided into shared media LAN and switched LAN, from the point of view of the type of transmission media used, the LAN can be divided into wired media and wireless LAN using wireless communication channel.

2,man

The city area network is referred to as the city domain net. Man is a high-speed network between a WAN and a LAN. Man's design goal is to meet the needs of a large number of enterprises, agencies, and companies in the dozens of km range of interconnected LAN interconnection requirements to achieve a large number of users of data, voice, graphics and video and other information transmission.

3,wan

The WAN, also known as the remote network, covers a geographical range from dozens of km to thousands of km. The communication subnets of the WAN can use the common packet switching network, the satellite communication network and the wireless packet switching network to interconnect the computer systems distributed in different regions in order to achieve the purpose of resource sharing.

Distinction: The Internet is the largest of the WAN, but the WAN is not the Internet.

Second, the characteristics of computer network structure

The typical computer network can be divided into logical functions: resource subnets and communication subnets.

1) resource subnet consists of main computer system, terminal, terminal Controller, network external device, various software resources and information resources. The resource subnet is responsible for the data processing business of the whole network, and is responsible for providing various network resources and network services to network users.

2) Communication sub-network consists of communication control processor, communication line and other communication equipment, complete network data transmission, forwarding and other communications processing business. The communication control processor is called the network node in the network topology structure.

The user's computer can be connected via LAN, or the telephone switching network (PSTN), the limited TV network (CATV), Wman or WLAN are all connected to the man as the regional backbone. The man is also connected to the WAN as a national or regional backbone network through routers and fibre optics. Multiple WAN interconnects form an Internet system that covers the world.

Third, LAN technology

Ethernet is the most widely used in LAN technology. In recent years, the development of Ethernet technology has roughly three directions:

1) Increase the data transfer rate of Ethernet.

2) A large LAN is hung into multiple networks connected by bridges or routers.

3) Change the shared media mode to swap mode. A virtual local area network (VLAN) appears on the basis of a switched LAN.

Four, Man Technology

The IEEE802 Commission's definition of man is based on a summary of the characteristics of FDDI technology, which is generated relative to the WAN and LAN. The early man was the optical fiber as the transmission medium, the preferred technology is the fiber ring network, the typical technology is the fiber Distributed Data Interface (FDDI). FDDI is designed to achieve high-speed, high-reliability and wide-range LAN interconnection. FDDI supports a dual loop structure with fast ring self-healing capability.

Five, WAN technology

1,wan is a public data network (PDN).

The focus of 2,wan technology research is the long-distance, service-wide broadband core switching technology.

3, typical network types and technologies used in the WAN mainly include:

1) Public Switched Telephone Network (PSTN)

2) Integrated Services Digital Network (ISDN)

3) Digital data Network (DDN)

4) X. Packet switching network

5) Frame Relay Network (FR)

6) Asynchronous Transfer Mode Network (ATM)

7) GE and 10GE Optical Ethernet

Six, the structure of broadband metropolitan area Network

1, the design of a broadband metropolitan area network will involve "three platforms and one export", that is, the network platform, business platform, management platform and urban broadband export issues.

The overall structure of the broadband metropolitan area network:

2, the hierarchical structure of the network platform

Logically speaking, the hierarchical structure of broadband metropolitan network platform can be further divided into: The core Exchange layer is also called the core layer, edge aggregation Also

Called the aggregation layer, the user access layer is also called the access layer.

The core layer mainly undertakes the function of high-speed data exchange, the aggregation layer mainly undertakes the function of routing and traffic aggregation, and the access layer mainly undertakes the user access and the

to the function of flow control.

Using the advantages of hierarchy structure, the location of functional entities between layers is clear, the interface is open, standard specification, easy to assemble and manage.

3, core switch layer, Edge aggregation layer and user access layer's main function

Basic functions of the core Exchange layer

The core exchange layer of broadband metropolitan area Network mainly has the following basic functions:

1) The core Exchange layer connects multiple aggregation tiers to provide high-speed packet forwarding for the network of the aggregation layer, providing a high-speed, secure and

with the data transmission environment with QoS guarantee capability.

2) The core Exchange layer realizes the interconnection with the backbone network, provides the city's broadband IP exit.

3) The core Exchange layer provides access to the Internet for users of broadband metropolitan area networks. Core Exchange layer structure design is focused on its possible

by Scalability and openness.

Basic functions of the aggregation layer:

The aggregation layer is at the edge of the core exchange layer of the broadband metropolitan Area Network, and its basic functions are:

1) aggregation, forwarding and exchange of data packet transmission by aggregating the user traffic of the access layer.

2) based on the user traffic of the access layer, local routing, filtering, traffic equalization, QoS priority management, security control, IP address translation, streaming

Amount of plastic processing.

3) The user traffic is forwarded to the core switch layer or local route processing according to the processing result.

Basic functions of the access layer:

The access layer solves the "last kilometer" problem. It is connected to the end user through various access technologies, providing access to the users within its reach

Internet and other information services.

It is important to note that the core layer, the aggregation layer and the access layer of the broadband metropolitan Area Network are a complete works. In practical applications, it can be based on the coverage of a city

Scope, network size, number of users, and the hosted business to determine whether to use a subset of it. For example, in designing a broadband metropolitan area network that covers large cities

, the complete core layer, the switching layer and the three-layer structure of the aggregation layer are usually used. When designing a broadband metropolitan area network covering small and medium-sized cities, it may be early

Phase only need to adopt the core layer and the aggregation layer structure of the two-layer structure, and the aggregation layer and access layer to consider, of course, it may be a bit of the city can be nuclear

The heart layer is combined with the aggregation layer to consider. Operators can be fully based on their network size, number of users, business distribution and development stages and other factors, consider the wide

With the structure and level of the metropolitan area network.

Seven, the basic principle of the establishment of broadband metropolitan area Network

to build and successfully operate a broadband metropolitan area network The basic principles to follow are: the operational, manageability, and scalability of a standard network.

The established broadband metropolitan area network must be manageable. As a practical operation of the broadband metropolitan Area Network, it is different from the provision of broadband services to the public LAN,

and need to have enough network management ability. This capability is manifested in carrier-grade access management, business management, network security, billing capabilities, IP address assignment,

QoS assurance and other aspects.
1) The telecom level access management of the broadband metropolitan Area Network includes the protection of the user's account opening, the client and the user's rights.

The broadband metropolitan area Network device must support the user's identity authentication, the use authority authentication and the billing function. Business management to support multi-ISP, IP-based virtual special

Network VPN and many other value-added services. Network security to ensure that the system, equipment security and user security.

2) Broadband metropolitan Area Network must provide the use of time, traffic, business and other means of billing, support for fixed users and mobile users of the billing hand

Paragraph Broadband metropolitan area Network must have IP address assignment ability, can support dynamic and static address assignment, support network address translation NAT function.

3) Broadband metropolitan area Network must be able to provide users with bandwidth assurance, to achieve traffic engineering, to provide personalized user

QoS assurance for the policy. Therefore, broadband metropolitan area network must be able to provide equipment management and network management, can provide users with business-based management, such as virtual

Dedicated network VPN management, finally achieve sub-level, sub-authority and sub-regional network management.

Eight, the key technology of managing and operating broadband metropolitan area Network

The key technologies for the management and operation of broadband metropolitan area Network are: Bandwidth service, QoS, network management, user management, multi-service access, statistics

and billing, IP address allocation and address translation, network security, and so on.

At present, broadband metropolitan area Network to ensure the quality of service QoS requirements of the main technologies are: Resource Reservation (RSVP). Differentiated Services (DIFFSERV) and multiprotocol switching

Mpls.

The use of traditional telecommunications networks for network management is called "in-band", while the use of IP networks and protocols for network management is called "out-of-band".

In-band network management refers to the use of data Communication Network (DCN) or public Switched Telephone network (PSTN) dialing, network equipment to configure data. Out-of-band

Network management refers to the establishment of network management system using Network Management Protocol (SNMP).

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The basic principle of network system structure and design (i.)