With the recent development of Internet, IP networks will become an important future application platform for communications networks. Major communications operators to transmit voice business has been laid by SDH / SONET technology, the huge network of fiber-optic communications infrastructure. Communication network to reunification - IP network evolution process, the protection of existing investments became the first major communications carriers to consider. Service providers need some affordable solutions, by their existing in the SDH / SONET network transmission of Ethernet services. CCOM introduced based on the EOS (Ethernet over SDH / SONET) technology products, it will be the existing communication network in the two technologies: the Ethernet and SDH / SONET technology are organically combined, thereby protecting the general users and investment in telecommunications operators, it is convenient to the existing network can open new IP services.
Second, NIF-EOS technical background
EOS equipment is a basic stand-alone channel service unit / digital service unit (Channel Service Unit / Digital Service Unit, CSU / DSU). It receives the Ethernet frame, using EOS protocol to compress these frames will be mapped to the SONET on them, after processing, send a complete SONET frame. The receiving side, it performs the opposite operation, extracting the Ethernet from the SONET frame, and then send out.
EOS SONET equipment can be completed in the time slot insertion / removal (ADM), in their existing TDM channels, to provide Ethernet slip. This is easy to telecom companies in the existing TDM platform for their customers Ethernet interface.
Ethernet: Ethernet is by the Xerox Corporation's Palo Alto Research Center (PARC) in the 70's developed a kind of LAN technology, is now the most popular local area network standard.
100Base-TX: 100Base-TX Fast Ethernet is a standard, using standard CAT5 or higher twisted pair cable, the speed reached 100Mbps.
SDH / SONET: SONET / SDH is a transmission in fiber-optic information transmission system technology. It defines the data operations of the optical signal multiplexing and synchronous frame structure. SONET / SDH, there are two implementation: ANSI (American National Standards Institute) issued a SONET (Synchronous Optical Network) standard, ITU-T (International Telecommunications Union) to the European standard called SDH (Synchronous Digital Hierarchy). SONET / SDH is mainly used for replacement of outdated, low-rate PDH (Plesyocronous Digital Hierarchy) technology, and SONET and SDH is compatible global standard. SONET signals are integer multiples of 51.84Mbps, and SDH signal is 3x51.84Mbps multiple of the two signals can be interoperable.
EOS agreement: LAPS
Ethernet over LAPS (Link Access Procedure-SDH) by the ITU-T X.86 standard definition, is similar to HDLC (High Data Link Control) is a connectionless protocol, will become SONET load. LAPS frame of the first two bytes are for compatibility with HDLC address and control constants (namely 0x04 and 0x03). SAPI (service access point identifier) will be pointed out that the load type, this time with 0xfe01 Ethernet MAC frame will be constant. Then followed by MAC frame, a 32 bit LAPS FCS (CRC) and an end mark. When the link closed set, it will send the space between the frame byte, they mark the end of the same.
All data will be through a X 43 +1 self-synchronous code converter, and then inserted into the SONET will load in order to avoid the harmful impact of the packet.
Align byte HDLC-type protocol has a feature that some bytes are lost, but from the sequence of bytes to replace. Therefore, when some of the Ethernet frame contains a number 0x7d and 0x7e bytes, the link efficiency will decline.
EOS agreement: GFP
GFP is the general frame program (Generic Framing Procedure), which is based on SDL (Simple Data Link), is still at the drafting stage.
GFP is a complete agreement, with three marking options, and two load the corresponding options. In addition to Ethernet outside, it also corresponds to PPP,
Fibre Channel and IBM-owned fiber-optic connection (FICON) and Enterprise Systems Connection (ESCON).
GFP frames are 2-3 in the logo position, load and 32-bit FCS option. Each logo has a 16-bit CRC bit protection. The first is the core identity, which by the load length indicator (PLI) to indicate frame length. Next is the type of identification, including the type of compression load code. Extension of identity is as a selective heading, it can handle logical link, the service category, and source / destination address. In a simple point to point applications may be omitted this identification. Finally, the load data and a 32-bit FCS option (CRC). Addition to the core identity of all other fields, must be through X 43 +1 self-synchronous code converter to ensure that the impact will not be harmful packets.
If there is no data to send, will be sent home closed frame. Is a closed set the length of the frame identifies the core identity is set to 0. GFP has a good nature, it is not lost character. Link will depend on the output of the number of loads, rather than loading the value contained in bytes. This also means that recipients must complete a search process to identify the effective core identity, and after they find to be locked.
NIF-EOS can be applied to Ethernet interconnection, by providing 100Base-TX Fast Ethernet interface to STM-1 optical interface conversion between the use of SDH / SONET network to connect two Fast Ethernet, use of existing TDM resources to achieve low-cost way to bridge IP networking.
NIF-EOS of the STM-1 optical interface to a rate of 155Mbps, use the interface for the SC single-mode optical fiber, wavelength 1310nm or 1550nm, the system gain greater than 12dB. It's Fast Ethernet interface complies 802.3u 100Base-TX standard, using RJ45 interface, and works in full duplex state. The device has 220VAC and-48VDC power supply means optional, also used the power redundancy to ensure that the user time when the overall stability of using the device.
NIF-EOS also offers a wealth of alarm functions. Not only can the device LED indicator light to show the link status, and full duplex mode send and receive state information, also provides the voice alarm function, so users can more easily perceive by hearing to equipment failure, thereby greatly enhancing the device security. In addition, the device also offers a D-type 9 pin female interface, can easily alarm information output device to device easier to carry out centralized management.
In addition, NIF-EOS is also very easy to use environment at a temperature of 0 鈩?~ 40 鈩? relative humidity 5% ~ 90% (no condensation) of the environment can work well.
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