At present, the most common 10 / 100M Ethernet is obviously insufficient as the bandwidth of the metropolitan backbone network. Even if multiple Fast Ethernet links are bundled and used, the need to meet multimedia and other large-bandwidth services is still overwhelming. With the standardization of Gigabit Ethernet and the widespread application in production practice, Ethernet technology has gradually extended to the convergence layer of the metropolitan area network. However, in the current environment of 10 / 100M broadband users, the Gigabit Ethernet link is also reluctant as a convergence, and it is beyond its ability as a backbone. Although Ethernet multi-link aggregation technology has been standardized, multiple gigabit links can be bundled and used. However, considering fiber resources and wavelength resources, link bundling is generally only used in POP points or short-distance application environments.
Transmission distance is also a major obstacle to Ethernet's inability to serve as a convergence / backbone link technology for metropolitan data networks. Whether it is 10 / 100M or Gigabit Ethernet, due to signal-to-noise ratio, collision detection, available bandwidth, etc., the transmission distance of Category 5 lines is difficult to break through the 100-meter limit. Restricted by the synchronization mechanism. Obviously, the 5km transmission distance of Gigabit Ethernet is still far from being within the metropolitan area.
In summary, the main reason why Ethernet technology is not suitable for use in the backbone / aggregation layer of the metropolitan area network is bandwidth and transmission distance. The new 10 Gigabit Ethernet standard has taken into account the metro backbone network requirements at the beginning of the design. First, the bandwidth of 10G is sufficient to meet the bandwidth requirements of the metro backbone network at this stage and for a period of time in the future. The transmission distance of the network can be up to 40km, and can be used with 10G transmission channels (up to thousands of kilometers using the WAN SONET package), which can fully meet the application range of the metropolitan area network / WAN. In other words, with the emergence of 10 Gigabit Ethernet technology, the above two problems have been basically solved.
Ethernet uses CSMA / CD mechanism, that is, carrier sense multiple access with collision detection. 10 Gigabit Ethernet technology is similar to Gigabit Ethernet, and still retains the Ethernet frame structure. Provide 10Gbps transmission speed through different coding methods or wavelength division multiplexing.
10 Gigabit Ethernet and the traditional Ethernet standard are completely different on the physical layer (providing 10Gbit / s transmission speed through different coding methods or wavelength division multiplexing), and the data link layer has also undergone major changes. First of all, because the 10 Gigabit Ethernet interface is basically applied to point-to-point links and does not need to share bandwidth, collision detection, carrier monitoring and multiple access mechanisms are no longer important, so it seems that it is not so important for the implementation of the CSMA / CD mechanism. ; Secondly, in order to achieve a high rate of 10Gbps, it is likely to use the OC-192 frame format for encapsulation, which requires the mapping function of Ethernet frames to OC-192 frame format at the physical sublayer; LAN-oriented, the network management function is relatively weak, the transmission distance is short and there is no physical line protection measures. When applied to the wide area network, the network management system, signal frequency phase jitter and signal synchronization all need to be carefully designed.
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