Design Of GFP Encapsulation And De-encapsulation Module In EoS

Along with fast development of Ethernet operation, mapping Ethernet into SDH network is a bottle neck of MAN (Metropolitan Area Network). Before mapped into SDH backbone network, Ethernet frame should be encapsulated so that the conflict between the constant data rate of backbone network and the variable transmission of Ethernet can be settled properly. GFP (Generic Framing Procedure) is a kind of data encapsulation technology settling such conflict. GFP is a kind of advanced data adapting and mapping technology. By GFP, kinds of upper layer data can be encapsulated and transmitted efficiently in present network.As a kind of Link Layer protocol, GFP (G.7041) defines an easy and flexible data adaption manner. When transmitted in byte synchronized network, not only is GFP able to carry Packet-Oriented data with variable length, also it can carry Block-Coded data with fixed length. GFP provides a kind of general mechanism to adapt upper layer client data into SDH network. Client data stream involves data packet with variable length, such as IP/PPP and Ethernet MAC Frame, and data stream with fixed length, such as Fiber Channel and ESCON. Besides, compared with other encapsulation protocols, such as PPP/HDLC and LAPS, characteristics of GFP are as follow: GFP introduces the same delineation mechanism as ATM, reducing the delineation overhead and preventing the efficiency of transmission from transmission information; GFP exceeds the limitation that Link Layer Protocol can only support Point-to-Point topology and realizes the support to different topology; by introducing concept of the multiple service level, GFP is able to realize the simple bandwidth control. As a result, GFP can provide higher encapsulation efficiency, higher standardization, greater transimission reliability and wider utilization.This paper does research on FPGA design of GFP in EoS system. First of all, the paper analyzes the background of EoS and introduces three encapsulation technologies in EoS system. After analysis of the three technologies, the paper concludes the advantages of GFP in Ethernet encapsulation. After the comparision of FPGA design and ASIC design, the paper works out the FPGA design scheme and introduces the FPGA design flow. Then, this paper details the module partition and design of GFP in EoS system and provides the simulation waveforms of top module and submodule. Constraints and logic synthesis are completed in the ISE environment of Xilinx Corp. At last, the paper summarizes the work and defect and describes the future of NGN.The design is completed with Verilog HDL and simulation is processed with Modelsim produced by Mentor Graphics Corp. The design programming, Test Bench generation, utilization of IP core, user constraints and logic synthesis are completed in the ISE produced by Xilinx Corp.The merits of the paper are as follow: the research and analysis of the three current Ethernet encapsulation technologies are completed, and detailed partition and design of GFP in EoS are performed. Thereinto, the paper adapts the parallel data processing technology and pipelining technology to speed the data process. And, to reduce the area of design, the module reuse technology is used in the design of some modules. Besides, the paper makes some innovation in several key modules, such as single bit error detection and correction module, the Look-Up-Table methodology applied in place of traditional logic design.