Looked from the network development tendency that, user the demand growth which interlocks to the network is bigger than to the tradition telecommunication service demand growth, simultaneously the operation business own equipment network management system gradually completely will transfer based on TCP/IP realizes The ethernet already is at present applies the most widespread local area network transmission mode, realized the 10M/100M even higher speed rate network transmission through the twisted pair line and the transmission facility, the application extremely widespread, the technology quite was also mature The ethernet by its tenth background, the network management simple, is easy to promote but took realizes the first choice plan which the IP data transmission and turns on to obtain the universal approval This point by the general operations business approval, spokesman Tian Suning which the net passed once explicitly was also indicated that, In China, the ethernet is the outlet which the wide band turns on in The Chinese telecommunication while vigorously is promoting which ADSL turns on also to realize the importance which the ethernet turns on, positively advances the ethernet to turn on the technology And realizes through the many kinds of ways, also respectively had the characteristic but all simultaneously to bring their inevitable some insufficiencies: ATM (local area network emulation) provides the ethernet connection through LANE, this plan support many kinds of services and guaranteed
QoS, but network system structure complex, transmission efficiency low, the expenses lose big (may reach above 25%) SDH (Packet OverSDH) or EOS (Ethernet Over SDH) provide the ethernet connection through POS, has made up the above plan insufficiency in the certain degree, specially really makes when the new net because it saves among the more complex ATM level but presently to be succinct However has had to provide the ethernet service to the economic construction good network to turn on, these technologies appear complex and the cost too are high, simultaneously also increased the network management complex degree The ethernet optical fiber transceiver may directly turn on the ethernet through the newly built optical fiber, however brings the optical fiber waste and the transmitting range is limited How therefore uses the existing rich E1 resources to pass on the ethernet is concisely realizes one kind which the ethernet turns on, the low cost plan

The ready-made transmission technology actually also has the correlation the realization method: The traditional data networking (E1 to V.35) and comes through the protocol converter the router to the E1 connection indirectly to realize transmits IP with E1 (like chart 1), like this increased the network route to jump the number (HOP), each router also needed a legitimate IP address, let the network change extremely complex, greatly increases the operation business investment, reduced the network construction progress Therefore has the necessity directly to complete the ethernet in the data link layer to the E1 transformation, to this comes the full use existing E1 resources, to realize the network simple, the network construction maintenance facilitates and constructs the expense to be low and so on the merit Therefore we need only is an ethernet to the E1 connection switch, E1 transmits the platform through PDH or SDH to be allowed very easily to surmount the area, the compatible different technology and the standard, realize between LAN and between the WAN interconnection or several LAN long-distance range interconnection, so may substitute for the partial VPN router and the edge router, reduces the network the route to jump the number (HOP), enormously reduces when the network extends, lets be distanced the very far several LAN company to become identical LAN, the user passable on-line neighbor has visited the far-end user, quite simple convenience (like chart 2).

The ethernet technology is based on the IEEE802.3, core is CSMA/CD; E1 based on suggestion and so on ITU-T G.703, in the transmission process must establish the empty electric circuit (VC) In order to guarantee these two kind of different communication the speed and the construction of data match and the transmission transparency, has all adopted two levels of buffers structures the common ethernet to the E1 transformation technology The first level of buffer by the internal pair of mouth RAM constitution, mainly uses in the speed match, receives FIFO, MII including ethernet MII transmits FIFO, E1 receives FIFO, E1 transmits FIFO; The second level of buffer by the piece outside SRAM constitution, mainly uses in E1 and the MAC frame formation, including transmission formation and receive formation

The ethernet transfers the E1 technology the main difficulty to concentrate in the MII connection, the E1 connection and in the buffer data exchange Because the ethernet MII connection clock is 2.5MHz, but the E1 work clock is 2.048MHz, during each module data exchange is an asynchronous process, for the guarantee data exchange accuracy, must use shakes hand the mechanism to realize module synchronization and to avoid to the buffer visit conflict How in has solved the problem which transmits after the single-channel E1 economy convenience realization ethernet, another question actually follows on somebody's heels: The band width and the new service appearance always has the characteristic which the benign interaction grows, therefore, in and turns on to the ethernet transmission the network construction also will have to give dual attention to the existing band width handling ability and the future expansion ability, will be able unceasingly to grow in the demand will manifest the service smooth promotion and the equipment investment safeguard advantage List E1 turns on the ethernet such way not to be able to meet the above need, therefore we have the necessity to let the user according to need nimbly to come, the convenient disposition E1 quantity to transmit the ethernet, like this both can satisfy the different user to the band width different demand, and can meet the needs which the later network will promote, moreover because will be causes the band width the use factor high based on the E1 granularity, also the network management will be simple Therefore with can nimbly dispose the E1 number the protocol converter to realize the ethernet transmission no matter or tomorrow will want the band width in today list E1 to promote all is necessary and is reasonable to multi- E1

In realizes with the multichannel E1 transmission ethernet service, and in the actual project installment, the debugging and the maintenance must be simpler, this request protocol converter has the ethernet MAC frame data on many E1 electric circuit which wilfully disposes is analyzing with the assembly ability However current distributes in the network E1 is quite complex: The different way, the different medium, between different operation business E1 inevitably exists when extends the difference, therefore the request protocol converter also must solve when during different E1 exists extends when the difference must be able the correct reorganization MAC frame, to guarantee the data transmission the reliability