1 from IP over SONET/SDH to IP over DWDM
In order to alleviate the Internet as soon as possible the bandwidth of the second half of 1997 pressure, launched IP over SONET/SDH technology that has received many company favor. Like Sprint, GTE Internetworking such as the famous communications company and UUNet and AOL such large isps are announced to establish a nationwide IP over SONET/SDH backbone, the next generation of Internet in the United States are used this technique. But after less than a year, the United States Sprint and Frontier announced in August 1998 to construction of "IP OC - 48", i.e. light DWDM over the Internet. More than 120 members of the scientific research, industry, education in Canada CANARIE) to promote nets (August 15, 1998 composed with bell Canada announced to build the world's first consortium net3 light Internet CA * nationwide. The nets of total investment estimate to more than $120 million. In 1998, the Canadian government budget for the project funding $55m. CA * for Canada net3 early research institutes and universities service to support Canadian high-tech departments, but eventually will be used in Canada all citizens, commercial applications is just a question of time. Participate in the purpose company Cisco by telephone under 0120-2714540 e1_d39 Co. Has Fitel, Newbridge, JDS grow independently Co. And Nortel. The capacity of the net3 because CA * enough to transmit multimedia services, huge, so can carry out many of today's other online cannot carry out education and health, research, commercial applications. The Canadian government has put it as Canada next century development of "digital economy" is an important foundation. CA * net3 is Canada's third generation Internet backbone. The first generation of nets that CA * net3 is Canada's third generation Internet backbone. The first generation of nets that CA * asp.net, in order to upgrade 1994 Canada built a national trial nets, is the world's largest high-speed ATM nets; one Introduced in 1997, the second generation of nets CA * net2 Internet2, as with the United States, the ATM and SONET technology. CA * net3 is directly in light running, canceled ATM and SONET two layers of electrical layer, start from bottom bearing IP business, DWDM fiber to realize wavelength link layer connection. Because it has simple structure, make speed and effciency. CA * net3 adopts 32 wavelength, the highest capacity for 40Gbit/s, more than the world any existing Internet speed, download two and a half hours of film "Titanic" only 1/15s.
Why the second generation nets and only between the third generation nets, less than a year apart? This is mainly because the Internet business, is still in sharp growth of around 10% per month, each growth 6 ~ 9 months, this means to double in 2001 the United States needs to 35Tbit/s network capacity, Canada need 3Tbit/s, at present, some isps have 48IP nets, construction OC - maybe can't use how long will need OC - 192 or OC s209 IP network. For example, America's UUnet company first built in early 1996 - three nets, OC again early 1997 build OC - 12 nets, shall be built at the end of 1998-48 nets, OC late 1999 will build N * OC - 48 nets, every year on a higher level. Users will start the order OC - 12 local loop, such as MCI IP has begun to connect the first batch of OC - 12 users, Microsoft has ordered 3 x OC - 12SONET for Internet access. And the trend of the future that IP business will continue rapid growth, because: with Inetrnet2 and CA * such as net2 (Canada nets), the development of the second generation network appears many new applications. IP phone could develop quickly; New economical optical distributor ADSL possible without the modems like now as popularization, network capacity must increase 100 ~ 1000 times; At present is still in the early stages of the machine to machine applications (such as biological information transmission, IP applications, foreign land backup, Web caching, multicast feed, news feed, batch, database synchronization, E-mail; future applications include distributed human chromosome set sorting, earth - empty database mapping, celestial imaging, database mining etc.) will be proposed to network and bandwidth requirements of further. Expected to 2001, the entire north American data by Internet business volume (mainly constitutes a) will more than voice, by 2005 voice business will only 1% of total business. In this case, obviously, need more high speed, the more simple and more flexible and bandwidth utilization more effective network technology to remove the backbone of pressure.
If, as expected, in the near future, IP business, if a leading business network design optimized for IP business is obviously logical. What is the best technology transfer IP business, industry is a great debate. Communications companies usually tend to use ATM as public network technology, and the Internet is to transmit IP optimal that the network is the best solution, because soon will be laid all application. IP Although the guarantee the quality of service and good business project management perspective, ATM is probably the most appropriate technology. But if the most Internet business is concerned, just required to provide "try to" or "guaranteed" transfer service, so can provide large capacity IP channel technology may be the most appropriate technology. Just in the past year, WDM, gigabit Ethernet, gigabit/than than ZhaoZhao than exchange choose road technology made rapid progress, for the development of light the Internet created a condition. Based on WDM optical Internet is also can put IP over ATM and IP over DWDM these two kinds of solutions into a network structure of technology. So, it was some big companies chosen for a new generation of Internet technology, like a new star is rising.
2 what is light the Internet
Light the Internet also called IP nets or IP over DWDM. In short, direct light in running on the Internet is light to the Internet. In optical Internet net, high-performance router through ADM or WDM optical coupler direct connect to WDM optical fiber, optical fiber in the wavelength is link layer interconnection. High-performance router instead of traditional circuit-switched concept based on the ATM and SONET/SDH electricity exchange and reuse equipment (see chart 1), become a key multiplexing equipment, used as a major exchange/choose road equipment, by its wavelength access, exchange, control choose road and protection. Therefore, light the Internet is a real link layer data networks, can make bypass or designated wavelength by direct connection, network service engineering (agriculture engineering) can only finish the IP layer. Using the specified wavelength, more flexible in structure, and has the will to optical switching and QuanGuangXuan road structure shift possible. Dense WDM systems so that we can use to telecom business recovery, part of wavelengths are designated for high bandwidth IP optical network, namely IP over, it may be used for high WDM volume "try to" transmission machine to machine operations; Another part of the wavelengths are designated for ATM optical network, namely IP over ATM it may to support VPN and execute important tasks IP nets; And part of the wavelength is designated for the traditional SONET/SDH business, namely IP over SONET/SDH, it may be used to concentrate and transmit the traditional IP network business. The attractions with nets revival telecommunications company based on the user's specific requirement can provide a complete service to users and agreement.
The nets yuan constitutes a light Internet including: fiber, laser, EDFA, optical coupler, electricity regeneration Repeaters, repeater, light points inserted multiplex, cross connectors and switch. The zero dispersion migration NZDSF) the most appropriate fiber (for its chromaticity dispersion WDM, the nonlinear effect is small. High-performance laser is WDM systems expensive devices. The majority were broadband EDFA can simultaneously amplification WDM, all due to wavelength, so demanding, plain gain after six or so after optical amplifier amplification need an electricity. So, in OC - 48 rate, light span can reach 400km, in OC - 192 can reach 250km. Optical coupler is used to put together and each wavelength apart, play decompose the role of reuse, and to reuse. On the long WDM systems need electricity regeneration Repeaters, and then divide level 3: R1, R2, R3. R1 regeneration is data transparent, and the pulse to forming; R2 regeneration to pulse, the clock to forming redefine; R3 now born to data packet re-form format. Forwarder used to transform from router or other devices, and produce the light signal to insert the right wavelength optical coupler optical signals. Light points inserted multiplex, light in long-distance WDM cross connection equipment is widely used in the system. Light switches can make ADM and crossing connection equipment dynamic configuration.
Light is the basic structure of the Internet. Optical fiber optical coupler, direct connect the various wavelengths coupler separately or combination, the input and output are simple optical connectors, within the original wavelength of data sent SONET/SDH equipment or high-performance router. Light the Internet is one of the advantages of biggest can adapt IP data business asymmetry, the data on the different wavelengths different rate. Another characteristic is on both sides of the fiber optic ring, can use can obtain full bandwidth, routing in when he handed big unexpected data don't need cache, also won't have packet loss, only when the fiber at fracture occurs packet loss. In optical fiber and protection work net, protect the idle optical fiber in business peak bandwidth usable also to preach the data, not introducing dithering, delay or packet loss. Recovery efforts in IP layer and not finish in the physical. In fiber fracture of dithering and delay sensitive, real-time business can give high priority. Use fiber optical fiber and protection work another advantage is may establish a "direct" or "bypass" wavelength.
Due to the high cost of long-distance WDM systems in portfolio, so it can be used before reach a high enough to save the Internet, mixed light cost. Big business in the light of the data link delivered in the data, small portfolio ATM PVC or SONET/SDH OC - x ceiling. Or between the two centers node volume data in WDM wavelength ceiling, ATM PVC or SONET/SDH OC - x is used for optical fiber fracture of business when recovery.
3 light the benefits of the Internet
First, the light of the Internet and the ATM, ATM network compared various business in comprehensive transmission is optimal, but to IP business speaking, ATM is not optimal. ATM in network engineering design had high flexibility, easy to support VPN and various service category; ATM in business engineering have a good ability, it allows us to different business types of establishing "clear" according to the business channel, load, the congestion and other condition offer various link, but costs is complexity. ATM's another disadvantage is long and established because SVC lost bandwidth utilization rate. For the establishment of an SVC long time than network adapter, in its time to build on in SVC data transmitted to SVC is constructed to cache, reason in this period even online capacity, also can't used to send data. As bandwidth, the more time to establish an SVC on behalf of idle bandwidth is bigger also, even more than the original to preach the volume of data.
Therefore, as compared with ZhaoZhao than router, ATM overly complex, and no special in throughput in large-scale backbone improvement, and then in IP over ATM over WDM is no advantage. If the dominant business is IP, then ATM nets can only increase complexity, making the network providers in management increase costs. However, the router and WDM fiber directly connected to the Internet has become more favorable light.
The light of the Internet and the SONET/SDH, SONET/SDH compared the big advantage is its restore ability, but need complex link management. In optical Internet, SONET/SDH layer's complex link management is not necessarily require. Because protect and restore ability is the Internet inherent distributed survivability part, so if IP layer can alone bear survivability, they don't need to set up in the Internet under a layer structure of survival ability again. In addition, development SONET/SDH network was one of the original intention is to make the whole network synchronization, more stable. Now use GPS can also economic inaccessible synchronism purpose. And with the penetration of IP technology, network is becoming more and more tolerant, so the timing errors can save SONET/SDH this layer. In optical Internet, let routers connected directly with WDM wavelength a great advantage, namely the router can be in fiber optic ring on both sides use several wavelength, business, load sharing IP might make the Internet link bandwidth utilization, and increase costs double little. In case of optical fiber breaker, can put the IP business put on a can of fiber up to send, or into another completely different path up to choose way. As the Internet data has self-similarity, so the consequences of optical fiber fracture under the environment in data networks in traditional telecommunication network environment than serious, can pass flow control, cache and to choose road and other technologies to compensate for.
In addition, in light of the Internet, the router can establish asymmetry, to balance the transceiver wavelength out network service. SONET/SDH network in design is always thinking of sending and receiving business is balanced, so the asymmetry of traffic it not optimal.
And based on circuit switching WDM optical switching compared, in the light of the Internet, the router in network edge, rather than in the core of optical switching equipment network will be grouped to choose road and the main intelligence exchange equipment. So the future when introducing optical switching need not use too complicated exchange technology, can shorten the light circuit settling time, network management is relatively simple.
4 the frame structure light the Internet
Light Internet either by SONET/SDH frame structure, also can use gigabit Ethernet frame structure than. Because long WDM wavelength 200km ~ 500km needed every electric regeneration, most once renewable equipment use SONET/SDH frame structure. If the network inside and use SONET/SDH reclamation equipment and the repeater, then from router IP packet must be stowed SONET/SDH frame.
SONET/SDH frame structure is one of the great strengths in its header carrying signaling and network management in information. Network management information for long-distance WDM systems are very important, especially if there are a lot of electricity and light regenerators, it can make us quickly to network fault diagnosis and positioning, but spending is also big. If put these functions into IP choose road equipment, spending can decrease.
SONET/SDH frame has its limitations. SONET/SDH frame is based on 8kHz voice synchronous sampling and contains header information. In addition, IP packet can be mapped to two or more a SONET/SDH frame, can also multiple IP packet mapped to a SONET/SDH frame, depending on the size of the IP packet. Therefore, in a router interface SONET/SDH frame of SAR (Segmentation Assembly and Reassembly) processing is very time-consuming, make throughput and performance affected. Many companies are enacted a new frame structure standard, called "Fast - IP" or "Slim SONET/SDH", it provides SONET/SDH frames, but many of the functions and how to make the header position frame size and group size matching newer technology use in. SONET/SDH frame structure of the biggest drawback is SONET/SDH forwarders and regenerator is expensive.
Another choice is to use gigabit Ethernet frame structure than. It is not as much as SONET/SDH network state information, but it costs low, most computer LAN are using this frame, reason is very attractive. Because of using "induction" agreement, so the timing jitter and not to like SONET/SDH so sensitive, as long as the control well, there would be no obvious packet loss.
Using gigabit Ethernet frame than another advantage is that it ends the frame structure with the same host, he doesn't need the data remapping to other transfer protocol (such as SONET/SDH or ATM), so in a router interface also need not SAR and bit into the operation to send data frame and transmit frame alignment. In addition, gigabit Ethernet shunts than the equipment cost is low.
At present than Ethernet transceiver two-way gigabit bandwidth was 2.5 Gbit cumulative/s, currently 5Gbit/s and formulated 10Gbit/s standards.
5 closing
Judging from the above analysis, light to carry large amounts IP business Internet is ideal. It not only networking is simple, high speed, high efficiency, and bandwidth flexible, more important is the economy is very considerable. According to a Canadian CANARIE study think: the light Internet adopted WDM, and depriving the ATM and SONET, can reduce bandwidth costs provided 95%. However, because of high quality business router itself transmit limitations, now it looks, the most likely solution is first construction mix network and allows IP over ATM and IP over WDM etc coexist, meet the user's various needs.
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