Optical Ethernet technology is the integration and development of two mainstream communication technologies: the integration of optical network and Ethernet. It concentrates the advantages of Ethernet and optical networks, such as universal Ethernet applications, low prices, flexible networking, simple management, high reliability and large capacity of optical networks. The high speed and large capacity of optical Ethernet eliminate the bandwidth bottleneck existing between the local area network and the wide area network, and will become a single network structure that integrates voice, data and video in the future. Optical Ethernet technology is one of the mainstream technologies for building broadband metropolitan area optical networks.
1. Proposal of optical Ethernet
Nowadays, enterprises and operators want to reduce costs and increase revenue: (1) For enterprises, the e-commerce environment has brought opportunities for enterprises to meet customer needs and increase revenue. Enterprises can contact customers, partners and suppliers in real time through the network. However, although the demand of enterprises for the network is constantly increasing, the investment in the network has not increased synchronously. Enterprises want to spend less money to get more services, in order to maximize the cost savings of enterprises; (2) For operators, the current network construction mainly considers how to support the existing business while obtaining maximum profits . Problems such as access bandwidth bottlenecks, rate mismatches, and multi-protocol conversion of metropolitan area networks make it difficult for operators to provide the access rates required by enterprise users.
The proposal of the concept of optical Ethernet solves the above-mentioned problems, and at the same time brings revolutionary changes to the construction of broadband metropolitan area networks. The current metropolitan area network is based on the SDH architecture. SDH was originally designed for low-speed, circuit-switched voice services, which guarantees good QoS performance and provides 50 ms of circuit protection switching time; the disadvantage is that SDH equipment is expensive, and it is not flexible and efficient when used for data services. Optical Ethernet is based on the currently widely used and mature Ethernet technology, and strengthens the functions of network management and traffic engineering to meet the data rate and transmission distance requirements of the metropolitan area network. After the operator constructs the optical metropolitan area Ethernet, it can directly provide an Ethernet port at the backbone layer to achieve a seamless connection with the local area network.
2. Advantages of optical Ethernet
The Ethernet technology was proposed by Xerox in 1970, and initially allowed users to share 10 Mbit / s bandwidth through a coaxial cable. Later, Ethernet quickly developed to pass through unshielded twisted pair, and used switches to provide users with 10Mbit / s dedicated line connection. Today, switched Ethernet can transfer 100Mbit / s of dedicated line bandwidth to the desktop, and soon will achieve Gigabit (Gbit / s) to users. Because it is fast, cheap, and easy to use, this "plug and play" technology has become the standard technology for more than 90% of enterprise local area networks (LANs).
Whether it is a private network or a public network, optical Ethernet can be applied. It can be configured as a point-to-point, mesh or ring topology, and can be applied to local area networks, metropolitan area networks, and wide area networks. The advantages brought by the application of optical Ethernet technology are:
(1) Relieve the bandwidth bottleneck Optical Ethernet transmits end-to-end LAN services in its own format and speed, without the need for protocol conversion and without reducing the rate, thus breaking the bandwidth bottleneck existing between the local area network and the wide area network.
(2) Reliability High-optical Ethernet technology combines the robustness of Ethernet proven in LAN with the advantages of well-known optical fiber transmission in MAN and WAN, and can provide five 9-level availability. EthernetoverRPR (EoRPR) can guarantee a protection switching time of 50ms when a catastrophic failure occurs.
(3) Good security Once entering the optical fiber Ethernet network, the end user's Ethernet data frame is encapsulated to protect the transmitted data, and is isolated from other users' business data streams.
(4) Good scalability Because the traffic and bandwidth have been increased, the Ethernet technology standard has also progressed to a higher rate, but it still maintains compatibility with existing network structures.
(5) Low price of ports Because Ethernet has been widely used in enterprises and campus networks, the hardware cost is very low and the technology is very mature, which greatly reduces the network construction costs of operators. For example, the price of the Gigabit Ethernet port is only 1/4 of the ATM and SDH ports, and the price of the upcoming 10Gbit / s Ethernet port is about 1/7 of the SDH port.
(6) High network efficiency The traditional telecommunications network uses a complex multi-layer architecture (such as IPoverATM, IPoverSONET, and IPoverDWDM, etc.). The disadvantages of this architecture are: On the one hand, ATM and SDH equipment are very expensive, which increases the operator ’s Cost; on the other hand, when data is transferred between the local area network and the wide area network, complex protocol conversion is required through the router, which will increase network overhead, reduce transmission efficiency, and also bring delay and jitter. Optical Ethernet is an end-to-end Ethernet. Data transfer between LAN and WAN does not require protocol conversion, so it can greatly improve transmission efficiency.
(7) Interoperability Strong optical Ethernet is a well-defined public technology. It enables devices of multiple manufacturers to have interoperability in LAN, MAN and WAN, which is conducive to end-to-end compatibility.
(8) Bandwidth management Optical Ethernet can implement bandwidth management at the packet level without having to designate a specific port. Operators can allocate different bandwidths according to different services, adjustable from 1 to 1000 Mbit / s (in increments of 1 Mbit / s). Enterprises can replace multiple E1 or E3 WAN connections with a single 10/100 / 1000Mbit / s Ethernet port.
(9) New business opportunities Optical Ethernet can provide two important types of services: services that operators provide directly to end users and services that operators provide to other operators.
At present, the access methods that users can choose are basically various access methods based on copper wire, and the rate is between kbit / s and Mbit / s. It has been unable to meet the increasing needs of users. In terms of individual users, users are not only satisfied with the slow browsing of the Internet, but also applications such as VOD and Internet TV, which have higher bandwidth requirements, also attract users and content providers.
On the other hand, more than 95% of users use Ethernet to connect to their internal networks, and the current access network forces users to purchase expensive routers to connect to the telecommunications access network. The conversion of the protocol also brings a lot of additional overhead. Operators choose ATM and SDH / SONET to transmit IP services mainly considering network scalability, reliability and technology maturity. Although these methods have many advantages, they have obvious shortcomings in the management of the bandwidth that maps layer 2 data to layer 1. From the perspective of transmission, they need to determine the bandwidth required for transmission based on the "dedicated line" method. The data entering the backbone network follows the rules of the traditional TDM network. Even higher. These methods result in a waste of optical transmission bandwidth.
(2) Metro optical Ethernet solution
Optical Ethernet technology extends the superiority of Ethernet to metropolitan area networks, providing end-to-end Ethernet connectivity without the need for multi-protocol conversion. Optical Ethernet can solve the above problems faced by the metropolitan area network, and build a new generation of broadband metropolitan area network for operators to meet the huge market demand for bandwidth.
Optical Ethernet can use different types of Ethernet transmission, including: bare fiber Ethernet (EthernetOverFiber), flexible packet ring Ethernet (EthernetOverRPR) and DWDM Ethernet (EthernetOverDWDM). No matter what type of transmission network is deployed, the simplicity and economy of Ethernet can be used to provide efficient services.
EOF
EoF (Ethernetoverfiber) is a common and convenient optical Ethernet mode, which can support the rate of 10Mbps ~ 10Gbps, and supports point-to-point and mesh network connection. EOF is a very cost-effective and high-performance optical Ethernet solution with a transmission distance of up to 70 kilometers.
EORPR
RPR (Resilient Packet Ring) is a new type of optical fiber ring transmission technology suitable for multi-service packet transmission. It has the characteristics of dual-ring structure, dynamic bandwidth allocation, statistical multiplexing, service level support and fair access. It is the current data transmission on optical networks. An optimization technique for packages. The IEEE802.17 working group is currently standardizing RPR. The proposed standard stems from the need for high-efficiency and low-cost transmission of multi-service packet streams in broadband metropolitan area networks. The basic idea of ​​the standard formulation is to combine the advantages of the traditional telecommunication network SDH and computer Ethernet, and to design a fiber transmission technology with reliability (elasticity) comparable to SDH, packet-oriented rather than circuit-oriented, and higher bandwidth utilization.
The traditional Ethernet uses a "best effort" transmission mechanism, which can well adapt to the sudden transmission requirements of data services and has good scalability; the disadvantage is that there is no QOS guarantee and the protection switching capability is poor. SDH equipment has a protection switching time of less than 50ms, and has good QOS performance, but SDH uses voice-oriented. TDM transmission mode is not efficient when transmitting data services. EORPR combines the economics of Gigabit Ethernet, SDH has the advantages of strict guarantee for delay and jitter, reliable clock and 50ms ring protection and recovery. The RPR network is a ring structure composed of packet switching nodes, and adjacent nodes are connected by a pair of optical fibers. The links between nodes are based on optical fiber and can be expanded using WDM.
The EORPR solution solves the problem of wasted bandwidth resources of traditional SDH rings. Because in EORPR, the bandwidth resources in both directions on the SDH ring are fully utilized. At the same time, SDH uses space reuse and statistical multiplexing technologies to further improve bandwidth utilization. The RPR ring can be extended to thousands of kilometers, and can provide flexible and multi-service optical Ethernet applications.
EODWDM
EODWDM uses DWDM as the transmission carrier to improve the transmission capacity of single-beam optical fiber through wavelength multiplexing. EODWDM adopts Ethernet frame format, which can be connected through end-to-end, ring or mesh. EODWDM is particularly effective in the context of high bandwidth and high efficiency, such as information storage solutions and data center interconnection. The current commercial DWDM system can support up to 32 wavelengths (each wavelength is equivalent to an OC48 or OC192 channel), and the network capacity is increased to 320 Gbit / s. This system can work on conventional fiber or non-zero dispersion-shifted fiber, and is suitable for metropolitan area networks and wide area networks.
EODWDM has the following advantages:
Make full use of the bandwidth resources of the optical fiber, greatly improving the transmission rate.
The DWDM system has good interconnection ability with Ethernet or SONET and SDH networks. The configuration is simple and convenient. It does not make much adjustment to the existing network structure. It supports future broadband business networks and network upgrades, and is expandable. Sex, high survivability and other characteristics.
Regardless of the signal rate, it can easily introduce new services such as broadband and data, and is compatible with devices of different systems and different manufacturers.
(3) Application status of Metro Ethernet
Optical Ethernet is first used in North America. In recent years, a number of metro Ethernet operators (MECs) have appeared in North America, such as Yipes, Cogent, and Telseon. Take Yipes as an example. Currently, public Ethernet access services are provided in about 20 major cities in the United States. A large number of G-bit Ethernet switches are used in the network to provide Internet access and transparent LAN interconnection (TLS) for users through optical fibers to the building Business, its main customers are ISP, WEB-based enterprises and other commercial users and schools.
The construction of the domestic broadband IP metropolitan area network began in 1999. Unlike North America, the domestic Ethernet access business is first aimed at residential users, because most Chinese urban residents are concentrated in various communities. In order to provide Internet access to their users, some cable TV stations in some provinces and cities choose Ethernet to build a city broadband network. The Ethernet / HFC hybrid method is used to provide Ethernet to users in some communities and Ethernet to others. In the cell, CableModem provides services to users. Since 2000, telecommunications companies around the country have begun to build broadband metropolitan area networks, mainly using Ethernet to users, and ADSL as a supplement.
Metro Ethernet is well used in the United States and Japan. The main reason is that Metro Ethernet can obtain larger bandwidth at a lower cost. In foreign countries, Metro Ethernet service has been recognized as the mainstream development trend. The current and planned optical Ethernet equipment is based on Layer 2 LAN switches, Layer 3 LAN switches, SONET equipment and DWDM. For example, Nortel uses three methods to build fiber-optic Ethernet, including Layer 2/3 LAN switches-Passport 8600; OPTera add / drop multiplexer, which is a RPR solution and OPTera packet edge system that can pass Nortel (OPTeraPacketEdgeSystem) Collaborated SONET fiber optic equipment; there is also a direct Ethernet connection on its DWDM products.
(1) Perfect user management User management is the foundation of all services. In the initial stage of network construction, in order to adapt to market demand and quickly launch user access services, each operator generally adopts a monthly subscription system. Simple monthly tariffs do have the advantages of being simple and fast, but in the long run, this over-single tariff policy will not only cause operators to lose a lot of customers and waste a lot of network resources, but also make broadband network operations lack Efficient and flexible management methods make operators in a disadvantaged position in the future market competition. Therefore, building a broadband network operation support platform has become an urgent demand of current broadband operators.
(2) Higher network reliability mainly includes the following aspects: link / path protection and fault recovery, congestion control, routing and flow control. The existing Ethernet technology has defects in these aspects. For example, in the MAN network, loops often occur. Although SpanningTree can be used to eliminate loops, not only the bandwidth cannot be effectively used, but also when the link fails, the reconstruction of the spanning tree requires more Up to ten seconds. Compared with traditional SDH, this is unacceptable. In order to solve the above problems, IEEE established the 802.17 working group, devoted to the research of ring structured Ethernet technology Resilient Packet Ring (RPR), with a view to greatly improving the reliability of the network.
(3) Improve the security mechanism, including strict isolation at layer 2, controlled access at layer 3, host protection, and network security.
(4) Abundant service provision capabilities, which can provide high-speed Ethernet Internet access, multicast / broadcast, VoIP, broadband Internet access card, VPN, VPDN, bandwidth rental and wholesale and other business types.
(5) Flexible and diverse accounting support, which can not only support remote RADIUS authentication and accounting, but also support the accounting of local phone bill regular backup.
(6) Good operation and maintenance capabilities.
5. Construction of optical Ethernet
Optical Ethernet is first used in North America. In recent years, a number of metro Ethernet operators (MECs) have appeared in North America, such as Yipes, Cogent, Telseon, etc. Taking Yipes as an example, he currently provides public Ethernet access services in about 20 major cities in the United States. A large number of Gigabit Ethernet switches are used in his network to provide users with Internet access and transparent LAN interconnection through optical fibers to the building TLS) business, the main customers are business users and schools such as ISPs, law firms, and Web-based enterprises.
Unlike North America, China's Ethernet access business first targets residential users. Private homes in North America are very dispersed. The fiber-to-road approach is adopted. The number of users covered by each pair of fiber is very small. Therefore, it is more economical to use ADSL and CableModem in North America. The situation in China is completely different. The residents of the city are concentrated in various types of communities, and the number of houses in the community is between 300 and 2000. It is very economical and practical for operators to use fiber-to-cell methods. According to estimates, the cost of Ethernet access users (excluding fiber and twisted pair) is about 30 to 60 US dollars, much lower than ADSL and CableModem.
In China, the construction of broadband IP metropolitan area networks began in 1999. In order to provide Internet access services to their cable TV users, some cable TV stations in some provinces and cities choose Ethernet technology to build urban broadband networks, and use a hybrid Ethernet / HFC method to provide Ethernet to users in some communities and in other communities. Provide services from Ethernet to the cell and CableModem to the user. Since 2000, telecommunications companies around the country have begun to build broadband metropolitan area networks, mainly Ethernet to users, and ADSL as a supplement.
The construction of a broadband metropolitan area network can be basically divided into three stages. The main goal of the first phase is to seize the market. Operators fully realize that the market is the company's lifeline, so including China Telecom, China Unicom, Netcom, and cable TV companies have made rapid access to commercial buildings and residential communities the first priority. At this stage, everyone has adopted the existing various Ethernet switches to quickly build up the network architecture, and the main business provided is the monthly Internet access service.
In the second phase, operators re-examine their own broadband MANs from the perspective of public operation networks and optimize them from various perspectives to improve the reliability and manageability of the network and consider adopting new technologies. The application of Ethernet in metropolitan area networks also poses challenges to the industry and equipment manufacturers. Since Ethernet products are currently mainly used in enterprise network environments, there are weaknesses in equipment reliability and network reliability. In addition, the development of Ethernet-based networking technology, user management, bandwidth management, and billing systems has become the main task. Therefore, the main task of the second phase is to optimize the broadband metropolitan area network into a real public telecommunications network.
After the first phase of network construction is completed, the focus of operators will shift to business. The main task of the third phase is to develop more business that attracts users based on the existing network and bring more business income To maximize the value of its investment on the Internet. At present, the main business of the broadband metropolitan area network is Internet access, and we can expand the business in several ways.
6. Conclusion
The optical network is penetrating from the wide area network and the metropolitan area network to the local network, and the Ethernet is also extending from the local area network to the metropolitan area network and the wide area network. Optical Ethernet is a fusion of optical network and Ethernet, which combines the advantages of both, such as the universal application of Ethernet, low price, flexible networking and simple management, and high reliability and large capacity of optical network. Metro Optical Ethernet greatly saves the cost of network construction, eliminates the bandwidth bottleneck existing between LAN and WAN, and will surely become an excellent solution for the construction of next-generation IP metro networks that integrate voice, data and video in the future.
1. Proposal of optical Ethernet
Nowadays, enterprises and operators want to reduce costs and increase revenue: (1) For enterprises, the e-commerce environment has brought opportunities for enterprises to meet customer needs and increase revenue. Enterprises can contact customers, partners and suppliers in real time through the network. However, although the demand of enterprises for the network is constantly increasing, the investment in the network has not increased synchronously. Enterprises want to spend less money to get more services, in order to maximize the cost savings of enterprises; (2) For operators, the current network construction mainly considers how to support the existing business while obtaining maximum profits . Problems such as access bandwidth bottlenecks, rate mismatches, and multi-protocol conversion of metropolitan area networks make it difficult for operators to provide the access rates required by enterprise users.
The proposal of the concept of optical Ethernet solves the above-mentioned problems, and at the same time brings revolutionary changes to the construction of broadband metropolitan area networks. The current metropolitan area network is based on the SDH architecture. SDH was originally designed for low-speed, circuit-switched voice services, which guarantees good QoS performance and provides 50 ms of circuit protection switching time; the disadvantage is that SDH equipment is expensive, and it is not flexible and efficient when used for data services. Optical Ethernet is based on the currently widely used and mature Ethernet technology, and strengthens the functions of network management and traffic engineering to meet the data rate and transmission distance requirements of the metropolitan area network. After the operator constructs the optical metropolitan area Ethernet, it can directly provide an Ethernet port at the backbone layer to achieve a seamless connection with the local area network.
2. Advantages of optical Ethernet
The Ethernet technology was proposed by Xerox in 1970, and initially allowed users to share 10 Mbit / s bandwidth through a coaxial cable. Later, Ethernet quickly developed to pass through unshielded twisted pair, and used switches to provide users with 10Mbit / s dedicated line connection. Today, switched Ethernet can transfer 100Mbit / s of dedicated line bandwidth to the desktop, and soon will achieve Gigabit (Gbit / s) to users. Because it is fast, cheap, and easy to use, this "plug and play" technology has become the standard technology for more than 90% of enterprise local area networks (LANs).
Whether it is a private network or a public network, optical Ethernet can be applied. It can be configured as a point-to-point, mesh or ring topology, and can be applied to local area networks, metropolitan area networks, and wide area networks. The advantages brought by the application of optical Ethernet technology are:
(1) Relieve the bandwidth bottleneck Optical Ethernet transmits end-to-end LAN services in its own format and speed, without the need for protocol conversion and without reducing the rate, thus breaking the bandwidth bottleneck existing between the local area network and the wide area network.
(2) Reliability High-optical Ethernet technology combines the robustness of Ethernet proven in LAN with the advantages of well-known optical fiber transmission in MAN and WAN, and can provide five 9-level availability. EthernetoverRPR (EoRPR) can guarantee a protection switching time of 50ms when a catastrophic failure occurs.
(3) Good security Once entering the optical fiber Ethernet network, the end user's Ethernet data frame is encapsulated to protect the transmitted data, and is isolated from other users' business data streams.
(4) Good scalability Because the traffic and bandwidth have been increased, the Ethernet technology standard has also progressed to a higher rate, but it still maintains compatibility with existing network structures.
(5) Low price of ports Because Ethernet has been widely used in enterprises and campus networks, the hardware cost is very low and the technology is very mature, which greatly reduces the network construction costs of operators. For example, the price of the Gigabit Ethernet port is only 1/4 of the ATM and SDH ports, and the price of the upcoming 10Gbit / s Ethernet port is about 1/7 of the SDH port.
(6) High network efficiency The traditional telecommunications network uses a complex multi-layer architecture (such as IPoverATM, IPoverSONET, and IPoverDWDM, etc.). The disadvantages of this architecture are: On the one hand, ATM and SDH equipment are very expensive, which increases the operator ’s Cost; on the other hand, when data is transferred between the local area network and the wide area network, complex protocol conversion is required through the router, which will increase network overhead, reduce transmission efficiency, and also bring delay and jitter. Optical Ethernet is an end-to-end Ethernet. Data transfer between LAN and WAN does not require protocol conversion, so it can greatly improve transmission efficiency.
(7) Interoperability Strong optical Ethernet is a well-defined public technology. It enables devices of multiple manufacturers to have interoperability in LAN, MAN and WAN, which is conducive to end-to-end compatibility.
(8) Bandwidth management Optical Ethernet can implement bandwidth management at the packet level without having to designate a specific port. Operators can allocate different bandwidths according to different services, adjustable from 1 to 1000 Mbit / s (in increments of 1 Mbit / s). Enterprises can replace multiple E1 or E3 WAN connections with a single 10/100 / 1000Mbit / s Ethernet port.
(9) New business opportunities Optical Ethernet can provide two important types of services: services that operators provide directly to end users and services that operators provide to other operators.
At present, the access methods that users can choose are basically various access methods based on copper wire, and the rate is between kbit / s and Mbit / s. It has been unable to meet the increasing needs of users. In terms of individual users, users are not only satisfied with the slow browsing of the Internet, but also applications such as VOD and Internet TV, which have higher bandwidth requirements, also attract users and content providers.
On the other hand, more than 95% of users use Ethernet to connect to their internal networks, and the current access network forces users to purchase expensive routers to connect to the telecommunications access network. The conversion of the protocol also brings a lot of additional overhead. Operators choose ATM and SDH / SONET to transmit IP services mainly considering network scalability, reliability and technology maturity. Although these methods have many advantages, they have obvious shortcomings in the management of the bandwidth that maps layer 2 data to layer 1. From the perspective of transmission, they need to determine the bandwidth required for transmission based on the "dedicated line" method. The data entering the backbone network follows the rules of the traditional TDM network. Even higher. These methods result in a waste of optical transmission bandwidth.
(2) Metro optical Ethernet solution
Optical Ethernet technology extends the superiority of Ethernet to metropolitan area networks, providing end-to-end Ethernet connectivity without the need for multi-protocol conversion. Optical Ethernet can solve the above problems faced by the metropolitan area network, and build a new generation of broadband metropolitan area network for operators to meet the huge market demand for bandwidth.
Optical Ethernet can use different types of Ethernet transmission, including: bare fiber Ethernet (EthernetOverFiber), flexible packet ring Ethernet (EthernetOverRPR) and DWDM Ethernet (EthernetOverDWDM). No matter what type of transmission network is deployed, the simplicity and economy of Ethernet can be used to provide efficient services.
EOF
EoF (Ethernetoverfiber) is a common and convenient optical Ethernet mode, which can support the rate of 10Mbps ~ 10Gbps, and supports point-to-point and mesh network connection. EOF is a very cost-effective and high-performance optical Ethernet solution with a transmission distance of up to 70 kilometers.
EORPR
RPR (Resilient Packet Ring) is a new type of optical fiber ring transmission technology suitable for multi-service packet transmission. It has the characteristics of dual-ring structure, dynamic bandwidth allocation, statistical multiplexing, service level support and fair access. It is the current data transmission on optical networks. An optimization technique for packages. The IEEE802.17 working group is currently standardizing RPR. The proposed standard stems from the need for high-efficiency and low-cost transmission of multi-service packet streams in broadband metropolitan area networks. The basic idea of ​​the standard formulation is to combine the advantages of the traditional telecommunication network SDH and computer Ethernet, and to design a fiber transmission technology with reliability (elasticity) comparable to SDH, packet-oriented rather than circuit-oriented, and higher bandwidth utilization.
The traditional Ethernet uses a "best effort" transmission mechanism, which can well adapt to the sudden transmission requirements of data services and has good scalability; the disadvantage is that there is no QOS guarantee and the protection switching capability is poor. SDH equipment has a protection switching time of less than 50ms, and has good QOS performance, but SDH uses voice-oriented. TDM transmission mode is not efficient when transmitting data services. EORPR combines the economics of Gigabit Ethernet, SDH has the advantages of strict guarantee for delay and jitter, reliable clock and 50ms ring protection and recovery. The RPR network is a ring structure composed of packet switching nodes, and adjacent nodes are connected by a pair of optical fibers. The links between nodes are based on optical fiber and can be expanded using WDM.
The EORPR solution solves the problem of wasted bandwidth resources of traditional SDH rings. Because in EORPR, the bandwidth resources in both directions on the SDH ring are fully utilized. At the same time, SDH uses space reuse and statistical multiplexing technologies to further improve bandwidth utilization. The RPR ring can be extended to thousands of kilometers, and can provide flexible and multi-service optical Ethernet applications.
EODWDM
EODWDM uses DWDM as the transmission carrier to improve the transmission capacity of single-beam optical fiber through wavelength multiplexing. EODWDM adopts Ethernet frame format, which can be connected through end-to-end, ring or mesh. EODWDM is particularly effective in the context of high bandwidth and high efficiency, such as information storage solutions and data center interconnection. The current commercial DWDM system can support up to 32 wavelengths (each wavelength is equivalent to an OC48 or OC192 channel), and the network capacity is increased to 320 Gbit / s. This system can work on conventional fiber or non-zero dispersion-shifted fiber, and is suitable for metropolitan area networks and wide area networks.
EODWDM has the following advantages:
Make full use of the bandwidth resources of the optical fiber, greatly improving the transmission rate.
The DWDM system has good interconnection ability with Ethernet or SONET and SDH networks. The configuration is simple and convenient. It does not make much adjustment to the existing network structure. It supports future broadband business networks and network upgrades, and is expandable. Sex, high survivability and other characteristics.
Regardless of the signal rate, it can easily introduce new services such as broadband and data, and is compatible with devices of different systems and different manufacturers.
(3) Application status of Metro Ethernet
Optical Ethernet is first used in North America. In recent years, a number of metro Ethernet operators (MECs) have appeared in North America, such as Yipes, Cogent, and Telseon. Take Yipes as an example. Currently, public Ethernet access services are provided in about 20 major cities in the United States. A large number of G-bit Ethernet switches are used in the network to provide Internet access and transparent LAN interconnection (TLS) for users through optical fibers to the building Business, its main customers are ISP, WEB-based enterprises and other commercial users and schools.
The construction of the domestic broadband IP metropolitan area network began in 1999. Unlike North America, the domestic Ethernet access business is first aimed at residential users, because most Chinese urban residents are concentrated in various communities. In order to provide Internet access to their users, some cable TV stations in some provinces and cities choose Ethernet to build a city broadband network. The Ethernet / HFC hybrid method is used to provide Ethernet to users in some communities and Ethernet to others. In the cell, CableModem provides services to users. Since 2000, telecommunications companies around the country have begun to build broadband metropolitan area networks, mainly using Ethernet to users, and ADSL as a supplement.
Metro Ethernet is well used in the United States and Japan. The main reason is that Metro Ethernet can obtain larger bandwidth at a lower cost. In foreign countries, Metro Ethernet service has been recognized as the mainstream development trend. The current and planned optical Ethernet equipment is based on Layer 2 LAN switches, Layer 3 LAN switches, SONET equipment and DWDM. For example, Nortel uses three methods to build fiber-optic Ethernet, including Layer 2/3 LAN switches-Passport 8600; OPTera add / drop multiplexer, which is a RPR solution and OPTera packet edge system that can pass Nortel (OPTeraPacketEdgeSystem) Collaborated SONET fiber optic equipment; there is also a direct Ethernet connection on its DWDM products.
(1) Perfect user management User management is the foundation of all services. In the initial stage of network construction, in order to adapt to market demand and quickly launch user access services, each operator generally adopts a monthly subscription system. Simple monthly tariffs do have the advantages of being simple and fast, but in the long run, this over-single tariff policy will not only cause operators to lose a lot of customers and waste a lot of network resources, but also make broadband network operations lack Efficient and flexible management methods make operators in a disadvantaged position in the future market competition. Therefore, building a broadband network operation support platform has become an urgent demand of current broadband operators.
(2) Higher network reliability mainly includes the following aspects: link / path protection and fault recovery, congestion control, routing and flow control. The existing Ethernet technology has defects in these aspects. For example, in the MAN network, loops often occur. Although SpanningTree can be used to eliminate loops, not only the bandwidth cannot be effectively used, but also when the link fails, the reconstruction of the spanning tree requires more Up to ten seconds. Compared with traditional SDH, this is unacceptable. In order to solve the above problems, IEEE established the 802.17 working group, devoted to the research of ring structured Ethernet technology Resilient Packet Ring (RPR), with a view to greatly improving the reliability of the network.
(3) Improve the security mechanism, including strict isolation at layer 2, controlled access at layer 3, host protection, and network security.
(4) Abundant service provision capabilities, which can provide high-speed Ethernet Internet access, multicast / broadcast, VoIP, broadband Internet access card, VPN, VPDN, bandwidth rental and wholesale and other business types.
(5) Flexible and diverse accounting support, which can not only support remote RADIUS authentication and accounting, but also support the accounting of local phone bill regular backup.
(6) Good operation and maintenance capabilities.
5. Construction of optical Ethernet
Optical Ethernet is first used in North America. In recent years, a number of metro Ethernet operators (MECs) have appeared in North America, such as Yipes, Cogent, Telseon, etc. Taking Yipes as an example, he currently provides public Ethernet access services in about 20 major cities in the United States. A large number of Gigabit Ethernet switches are used in his network to provide users with Internet access and transparent LAN interconnection through optical fibers to the building TLS) business, the main customers are business users and schools such as ISPs, law firms, and Web-based enterprises.
Unlike North America, China's Ethernet access business first targets residential users. Private homes in North America are very dispersed. The fiber-to-road approach is adopted. The number of users covered by each pair of fiber is very small. Therefore, it is more economical to use ADSL and CableModem in North America. The situation in China is completely different. The residents of the city are concentrated in various types of communities, and the number of houses in the community is between 300 and 2000. It is very economical and practical for operators to use fiber-to-cell methods. According to estimates, the cost of Ethernet access users (excluding fiber and twisted pair) is about 30 to 60 US dollars, much lower than ADSL and CableModem.
In China, the construction of broadband IP metropolitan area networks began in 1999. In order to provide Internet access services to their cable TV users, some cable TV stations in some provinces and cities choose Ethernet technology to build urban broadband networks, and use a hybrid Ethernet / HFC method to provide Ethernet to users in some communities and in other communities. Provide services from Ethernet to the cell and CableModem to the user. Since 2000, telecommunications companies around the country have begun to build broadband metropolitan area networks, mainly Ethernet to users, and ADSL as a supplement.
The construction of a broadband metropolitan area network can be basically divided into three stages. The main goal of the first phase is to seize the market. Operators fully realize that the market is the company's lifeline, so including China Telecom, China Unicom, Netcom, and cable TV companies have made rapid access to commercial buildings and residential communities the first priority. At this stage, everyone has adopted the existing various Ethernet switches to quickly build up the network architecture, and the main business provided is the monthly Internet access service.
In the second phase, operators re-examine their own broadband MANs from the perspective of public operation networks and optimize them from various perspectives to improve the reliability and manageability of the network and consider adopting new technologies. The application of Ethernet in metropolitan area networks also poses challenges to the industry and equipment manufacturers. Since Ethernet products are currently mainly used in enterprise network environments, there are weaknesses in equipment reliability and network reliability. In addition, the development of Ethernet-based networking technology, user management, bandwidth management, and billing systems has become the main task. Therefore, the main task of the second phase is to optimize the broadband metropolitan area network into a real public telecommunications network.
After the first phase of network construction is completed, the focus of operators will shift to business. The main task of the third phase is to develop more business that attracts users based on the existing network and bring more business income To maximize the value of its investment on the Internet. At present, the main business of the broadband metropolitan area network is Internet access, and we can expand the business in several ways.
6. Conclusion
The optical network is penetrating from the wide area network and the metropolitan area network to the local network, and the Ethernet is also extending from the local area network to the metropolitan area network and the wide area network. Optical Ethernet is a fusion of optical network and Ethernet, which combines the advantages of both, such as the universal application of Ethernet, low price, flexible networking and simple management, and high reliability and large capacity of optical network. Metro Optical Ethernet greatly saves the cost of network construction, eliminates the bandwidth bottleneck existing between LAN and WAN, and will surely become an excellent solution for the construction of next-generation IP metro networks that integrate voice, data and video in the future.
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