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

Nine, the basic technology and scheme of building broadband metropolitan area Network

There are three basic technologies and schemes for building broadband metropolitan Area network: The metropolitan Area Network scheme based on SDH, 10GE-based metropolitan area Network scheme and ATM-based metropolitan Area Network scheme.

1, the metropolitan area network based on SDH technology

The early SONET/SDH was for traditional telecom services, and it was not suitable for transmitting IP packets. With the development of technology, based on the next generation of

The SONET/SDH technology's multi-service transmission platform (MULTI-SERVICETRANSPORTPLATFORM,MSTP) replaces the single-function splitter multiplexer (add-

DROPMULTIPLEXER,ADM) and the Digital crossover system (DIGITALCROSS-CONNECTSYSTEM,DCS) make the IPOVERSONET/SDH scheme more feasible.

2, broadband metropolitan area network based on 10GEthernet technology

Using the vast bandwidth resources of optical fiber, as well as the mature and widely used Ethernet technology, provide operators with technical support for building a new generation of broadband metropolitan area Network

Hold. The emergence of optical Ethernet fundamentally changed the planning, construction and management of broadband metropolitan area network. Optical Ethernet for Broadband metropolitan area Network can have a variety of real

Two of the most important: 10GE-based technology and resilient packet-ring technology.

The devices and lines that can operate optical Ethernet must meet the high operational reliability of the telecom network 99.999%. It has to overcome the shortcomings of traditional Ethernet, with

The following features:

1) can allocate the bandwidth according to the actual application demand of the end user, ensure the full and reasonable application of the bandwidth resources.

2) with authentication and authorization function, the user access network resources must be authenticated and authorized to ensure the security and lawful use of users and network resources;

3) Provide billing functions, timely access to the user's Internet time record and traffic records, support by Internet time, user traffic, or monthly billing method.

Support real-time billing;

4) Support VPN and firewall, can effectively guarantee the network security;

5) Support MPLS, with certain service quality assurance, provide sub-level QoS Network service;

6) Easy, fast and flexible use of user and business extensions.

Because optical Ethernet is the product of the combination of Ethernet and DWDM technology, it has obvious advantages in the operation of broadband metropolitan area network.

The technical advantages of 10GBPS optical Ethernet are mainly shown in the following aspects:

1) Ethernet and DMDW technology are very mature, and have been widely used. After estimating, a similar

The scale of the broadband metropolitan Area Network, the cost of optical Ethernet is 1/5 of SONET, is 1/10 of ATM.

2) IEEE has standardized Ethernet technology for rates from 10Mbps, 100Mbps, 1Gbps to 10Gbps, and the Ethernet technology standard for 100Gbps

is under study. It can cover the core layer of the broadband Metropolitan Network, the aggregation layer to the access layer of the various requirements, so Ethernet technology in the broadband metropolitan area Network to provide

The potential benefits of multiple end-to-end scenarios.

3) If a broadband metropolitan area network can use the same technology at all levels, then the network in the design, formation, operation, management and personnel training are

Very convenient and effective.

3, the metropolitan area network based on the elastic packet ring RPR Technology

The elastic Packet Ring (RESILIENTPACKETRING,RPR) is a transmission technology that transmits IP packets directly on the fiber, and its work is based on

Cisco Corporation proposes dynamic packet Transfer (DYNAMICPACKETTRANSPORT,DPT) technology. Study on the IEEE802.17 of elastic packet ring RPR standard

Group was established in January 2001 with the aim of providing high-speed, viable ring network technology for IP and other packet switching networks.

The elastic packet ring RPR uses a double-loop structure, which is the same as the FDDI structure. Maximum length of bare fiber between two RPR nodes in the RPR ring

can reach 100km. RPR will be a clockwise transmission of the fiber called the outer ring, will be transmitted counterclockwise in the optical fiber called the Inner ring. The inner ring and the elastic packet ring RPR

The outer ring can transmit the IP packet by the method of statistic multiplexing, and can realize the function of "self-healing ring". Both the inner and outer rings of RPR can transmit data groups and

control grouping. Each node can communicate with adjacent nodes using two-directional fibers. This is done in addition to the efficient use of fibre bandwidth,

One purpose is to speed up the control packet transmission, improve the reliability of the ring, implement "ring self-healing" function, to ensure the system reliability and service quality of the metropolitan area network.

RPR technology mainly has the following characteristics:

1) High utilization of bandwidth

In traditional SDH networks, 50% of the ring bandwidth is redundant, and RPR uses a double-loop structure to transmit data grouping and control grouping. The traditional FDDI ring network

, when the source node succeeds in sending a data frame to the destination node, the data frame is retracted from the loop by the source node, while the RPR ring limit data frame is only

The fiber segment between the source node and the destination node is transmitted, and when the source node succeeds in sending a data frame, the data frame is collected from the loop by the destination node.

Back. In this way, the data frame will no longer occupy the loop bandwidth of the downstream segment and improve the utilization of the ring bandwidth.

2) Fair sex is good
Fairness is a major guarantee that network operators must provide. When two data frames have the same priority, the RPR ring can provide them with the same

The access capability of the loop channel, each node in the RPR loop executes the SRP fairness algorithm, which enables equal bandwidth between nodes to prevent individual nodes from

The traffic is large and the ring congestion is caused. The RPR ring also supports weighted fairness rules and ingress and egress peak rate limits to guarantee the bandwidth purchased by the user

Provide the appropriate services.

3) strong fast protection and recovery capability

The fast protection and recovery capabilities of the RPR ring make it a carrier-grade technology, and the RPR uses a self-healing ring design concept that can be used in 50ms

Time, isolate faulty nodes and fiber segments, provide SDH-level fly protection and recovery without the need for dedicated bandwidth like SDH

Therefore, the utilization of the ring bandwidth is further improved.

4) guarantee the quality of service

to ensure the quality of service (QoS) of the network, the RPR ring assigns different priorities to different business data to ensure reliable transmission of high-priority information loss.

Ten, network access technology and methods

1, at present, can be used as a user access network, there are three main categories: computer networks, telecommunications networks and radio and television networks.

2, at present, from the point of view of technology, access networks are mainly divided into five categories: terrestrial wired communications networks, wireless communications and mobile networks, health

Star Pass Networks , cable networks and terrestrial radio and television networks. Here, the computer LAN is classified as a terrestrial wired communication system. People visually call them

User five lanes of the pickup information highway.

3, the future of information network construction should be divided services and construction, the establishment of a tiered service model and unified standards, so that the original belong to different industries of the network

Network System a nationwide network, providing a high-performance service platform for the development of new applications, allowing more households, businesses and institutions to

Counting Machine more convenient access to the Internet. This application demand leads to the development and change of access network technology, which will lead to computer network, telecommunication network and electric

View-through The emergence of the "triple network Convergence" of the letter network.

4, basic types of broadband access technology

Types of access technologies for different application environments and related standards:

From the user access point of view, can be divided into Access technology and access mode, access to the user's working environment and demand.

Access technology can be divided into two types of wired access and wireless access, access to the user's environment and needs, it can be broadly divided into home access, campus

Access, institutions and enterprise access.

From the perspective of implementation technology, the current broadband access technology is mainly the following: Digital subscriber line xDSL, optical fiber coaxial cable mixed network HFC technology, optical fiber

Access technology, wireless access technology and LAN access technology. Wireless access can be divided into wireless LAN access, wireless metropolitan area Network access and wireless Adhoc connection

Into.

5, the characteristics of various access technologies

(1) Digital subscriber Line xDSL Access technology

Most telephone companies tend to push digital subscriber line xDSL (digitalsubscriberline) applications. Digital Subscriber Line xDSL is also called the Digital subscriber ring

Lu. The digital subscriber line is a pair of copper twisted-pair wires from the user to the local telephone exchange center, which is also called the central office. xDSL is the US Bell Pass

In 1989, the Institute developed a high-speed transmission technology based on the user telephone copper twisted-pair wire for the video-on-demand (VIDEO-ON-DEMOND,VOD) service.

Postoperative

Compared with other broadband access technologies, the advantages of XDSL technology are mainly shown in:

1) to provide sufficient bandwidth to meet people's needs for multimedia network applications;

2) The performance and reliability have obvious advantages;

3) The use of existing telephone copper twisted pair, can be smoothly connected with the existing network of people, is one of the more economical access schemes.

xDSL technology is divided into rate symmetric and rate asymmetric two according to the rate of upstream (user to Exchange) and downlink (switching to user)

Two Depending on the rate and distance of the signal transmission, and the difference between the upstream rate and the downstream rate, the main digital subscriber line xDSL can be divided into:

1) Asymmetric Digital subscriber Line (ASYMMETRICDIGITALSUBSCRIBERLINE,ADSL)

2) High bit Rate Digital subscriber line (HIGHBITERATEDSL,HDSL)

3) Rate Adaptive Digital Subscriber Line (RATEADAPTIVEDSL,RADSL)

4) Very high bit Rate Digital subscriber line (VERYHIGHBITERATEDSL,VDSL)

The following table shows the upstream and downstream rate parameters of the main xDSL technology:

The main technical features of ASDL are shown in:

1) It can be used on existing telephone copper twisted-pair lines to overlap and not interfere with the traditional analog telephone service, that is, the ordinary telephone service pots, to provide high

Fast Digital services. As a result, ASDL allows users to retain the analog phone service they have applied for, and can support the user's new

Broadband services. The new broadband service can be internet online access, remote office, VOD and so on video VOD.

2) This technology has little to do with the actual parameters of the local loop, and it has nothing to do with the characteristics of the user phone's copper twisted pair, so the user does not need

The door is re-laying the cable for the ASDL service.

3) ASDL provides non-wideband characteristics, upstream rate at 64kbps~640kbps, downlink rate in 500kbps~7mbps. Users can select as needed

Upstream and downstream rates.

(2) Basic concept of HFC for fiber coaxial cable hybrid network

The basic structure of HFC in fiber coaxial cable hybrid network

From the user access point of view, optical fiber coaxial cable hybrid network (HYBRIDFIBERCOAX,HFC) is a two-way transformation of the CATV network, is the user

An important way to access the Internet via cable TV broadband.

Classification of cable modem Cablemodem

The cable modem Cablemodem is designed specifically for data transmission using a cable TV network. At the sending end, it modulates the data and

After using the cable television network (CATV) coaxial cable to allow the frequency to send out, at the receiving end, the modulated signal is demodulated, the data is restored.
The Cablemodem connects the user computer to the cable TV coaxial cable. It contains not only the modulation and demodulation part, but also the encryption and decryption and protocol adaptation.

Part of the functionality with bridges, routers, and hubs. Cablemodem uses the Frequency division multiplexing method, divides the bidirectional channel into: From the computer terminal to the network side

The direction referred to as the upstream channel, from the network to the computer terminal is called the downlink channel. The uplink channel uses the carrier frequency range in the 5mhz~42mhz, uplink channel

Bandwidth is generally 200kbps~10mbps. Downlink, the channel uses the carrier frequency generally in the 450mhz~750mhz, the channel bandwidth generally can reach 36Mbps.

Cablemodem can be divided into the following types:

A) from the transmission mode, the Cablemodem can be divided into two kinds of bidirectional symmetric transmission and asymmetric transmission. The symmetric transfer rate is 2mbps~4mbps,

Up to 10Mbps. The asymmetric downlink rate is 30Mbps and the upstream rate is 500kbps~2.56mbps.

b) from the direction of data transmission, cablemodem can be divided into unidirectional, bidirectional two categories.

c) from the synchronous mode, Cablemodem can be divided into two types: synchronous and asynchronous Exchange. Synchronous interchanges are similar to Ethernet, and asynchronous interchanges are similar to ATM

Technology.

D) from the point of Access, Cablemodem can be divided into personal cablemodem and broadband multiuser cablemodem. Broadband modems can have a network

The function of the bridge, can be a computer LAN access.

e) From the interface point of view, Cablemodem can be divided into external, built-in and interactive set-top box three kinds. External Cablemodem via NIC connection

Count computer, so the connection cablemodem need to add a network card, which is the disadvantage of external cablemodem. But external

Cablemodem can support simultaneous access of multiple computers on the LAN. The interactive set-top box is also a cablemodem that allows users to directly

On-screen access to the network or email.

(3) Optical fiber access Technology

The vast majority of network operators believe that the ideal broadband access network will be based on fiber-optic network. Optical access technology has a broad application prospects. Especially

Passive optical Network (PASSIVEOPTICALNETWORK,PON) technology, and ATM-based wideband passive optical Network (APON) technology. Due to the use

Fiber as a medium, the bandwidth has been greatly improved. Because Apon is a passive system, the installation, opening and maintenance of operating costs can be further

Continue to decrease. In the long run, Apon is an ideal long-term response to the increasing pressure of multimedia services and fast-growing IP services.

Far-away solution.

The passive fiber network PON is the ITU SG15 Research Group in g.983 recommended "high-speed fiber access system based on passive fiber network" to standardize. The recommendation

is divided into two parts:

a) symmetric business of oc-3,155.520mbps.

b) Upstream oc-3,155.520mbps, downlink oc-12,622.080mbps asymmetric business.

According to g.983 recommendations, the transmission medium can be one or two single-mode fiber. Bidirectional transmission is achieved by wavelength Division multiplexing WDM (one or two fiber).

The passive optical network pon technology is a good transition way for the existing network, and for the future b-isdn. However, in order to flexibly raise

For broadband multimedia services, ATM-based wideband passive optical networks (apon) may be a more appropriate approach. This approach is on the PON network, and the real

The ATM transmission based on cell is now, which allows multiple users in the access network to share the entire bandwidth. Because the system combines ATM and PON technology, it is said

It is Apon (atm+pon).

The Apon system is the product of the combination of PON and ATM. PON provides inexpensive shared transport media for multiple users, while ATM technology is low-to-

High-speed media services provide a reliable interface, Apon combines the advantages of both, and other access methods compared with the following advantages:

A) stable and reliable system;

b) can be different bandwidth, transmission quality of demand;

c) compared to the cable television network, each user can occupy independent bandwidth without congestion; d) the access distance can reach 20km~30km.

(4) Broadband wireless access Technology

Wireless access Technology mainly includes: 802.11 standard wireless LAN (WLAN) access, 802.16 standard wireless metropolitan area network (WMAN) Access,

And the Adhoc access technology being developed.

802.16 standard and wireless metropolitan area network Wman

The main goal of IEEE802.16 standard system is to develop the physical layer and media access control Mac sub-layer of wireless access system working in 2~66mhz Band

Specification. 802.16 is 802.16 is a point-to-multipoint standard in terms of sight, for large data volume access. 802.16A adds non-visual range and wireless network

Grid (support for WIRELESSMESHNETWORK,WMN structures. 802.16 and 802.16A after the revised unified name of 802.16D, in May 2004

Officially announced.
Wireless networks established according to the 802.16 standard may cover parts of a city at the same time due to the fixed location of the building, it needs to be in each building

Built-up Stand -by station, the base station uses the full duplex, the wideband communication way work. And each 802.16 wireless network access to the number of users, often more than 802.11

Wireless the number of users on the LAN. It is the 802.16 standard to ensure that the wireless network to access users of the quality of service, it needs more bandwidth, so 802.16 standard

quasi-regulation The wireless network uses a higher frequency of the 10~66ghz band. This band uses millimeter waves.

In 802.16 the standard was added two physical layer standard 802.16d with 802.16e. 802.16d is mainly for fixed wireless network deployment, 802.16e needle

Fire standard problem of wireless communication for mobile objects such as cars and automobiles.

The Forum organization corresponding to the IEEE802.16 standard Working Group is WiMAX. Similar to the Wi-Fi Alliance, which is dedicated to WLAN application, industry members

attend WiMAX Forum is committed to the promotion and application of IEEE802.16 wireless network standards.

802.11 standard with wireless LAN WLAN

802.11 the Wireless LAN standard is defined using infrared, FM spread spectrum and direct sequence spread spectrum technology, data transmission rate is 1Mbps or 2Mbps.

802.11B defines a wireless LAN standard that uses a direct sequence spread spectrum technology with a transmission rate of 1Mbps, 2Mbps, 5.5Mbps, and 11Mbps. 802.11A will

the transfer rate is increased to 54Mbps. WLAN is a hot issue in current network research, the 802.11 standard has been developed from 802.11, 802.11a

At 802.11j, the physical layer, MAC layer, wireless bridge, and QoS management, security and identity authentication of wireless transmission technology of various frequency bands have been made a series

set forth.

WMN Technology of wireless grid grid

At present, Adhoc Technology has two development direction: first, the development and application of the adviser and the specific industry, on this basis, the wireless sensor network WSN is generated;

One is to the wireless Civil access network development, there is no wire mesh grid wmn. Wireless Grid wmn appeared in the mid 1990s, in 2000

began to attract people's attention.

The direct power to promote the development of wireless grid WMN is the application demand of Internet access. Wireless access in one area can be used in cellular mobile communication systems

Unified or Wireless LAN. Cellular mobile communication and WLAN have their limitations from the angle of application. From the perspective of investment income, cellular mobile communication and non -

Line Bureau domain networks are more suitable for densely populated areas with a defined user base. For the user mobility is relatively large, not suitable for the construction of high-power base station application site to

and a temporary communication needs,ADHOC technology has been developing in parallel with cellular mobile communication technology . However, due to the limitations of military use, Adhoc technology

Surgery in no progress has been made in the civil field for quite some time. In this context, people began to consider whether Adhoc technology and cellular mobile technology,

Wireless The combination of LAN technology is applied to the wireless Broadband access network, which provides users with ubiquitous connection.

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