Fast Ethernet - 1 Fast Ethernet and Gigabit Ethernet  All rights reserved. No part of this publication and file may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written permission of Professor Nen-Fu Huang (

Fast Ethernet - 2 Fast Ethernet  The goal of the Fast Ethernet is to obtain an order of magnitude increase in speed over 10BaseT Ethernet (IEEE 802.3) while retaining the same wiring systems, MAC method, and frame formats.  In IEEE 802.3, the longest distance between two stations is 2.5km, with a slot time of 51.2us (512 bits for 10Mbps).  One way to increase the speed is to shorten the distance.  In Hub architecture, the distance between station and Hub is at most 100m and the round-trip distance between two stations is 400m.  A faster speed can be used to transmit frames under CSMA/CD protocol while keeping the minimum frame size as 512 bits.  In the standard, the speed is 100Mbps and denoted as 100BaseT.

Fast Ethernet - 3 Fast Ethernet Characteristics  100 Mbps  IEEE CSMA/CD frame format  Medium Twisted pair -- UTP, STP fiber  CSMA/CD Protocol, do not support priority scheme  Do not support guaranteed delay service Frames collision  Bandwidth utilization is not guaranteed to be fair  Low bandwidth utilization under heavy load  Suitable for multimedia communications under moderate load  Good fault tolerance Hub architecture  100Base4T Voice-grade Category 3 UTP. Use four pairs of twisted-pair wires.  100BaseX Category 5 UTP, STP, or Fiber optic.

Fast Ethernet - 4 Communication Architecture  The Convergence Sublayer (CS) provides the interface between CSMA/CD MAC sublayer and PMD layer IEEE LLC IEEE CSMA/CD MAC ANSI X3T9.5 MAC ANSI X3T9.5 PHY IEEE PLS ANSI X3T9.5 PMD CS IEEE MAU Coaxial Cable Fiber STP/UTP Fiber STP/UTP 實體層 鏈結層

Fast Ethernet - 5 MII Interface Signalling  To support different transmission medium, a Media Independent Interface (MII) is defined between CS and PMD.  The major functions of the CS Convert the transmit and receive serial data streams at the MAC sublayer interface into and from 4-bit nibbles for transfer across the MII. Relay the carrier sense and collision detection signals generated by the PMD sublayer to the MAC sublayer Transmit clock(TxClk) Transmit data (TxD{0..3}) Transmit enable (TxEn) Carrier Sense (CRS) Collision detect (CD) Receive clock(RxClk) Receive data (RxD{0..3}) Receive data enable (RDv) Receive error (RErr) Transmit data Transmit enable Carrier Sense Collision detect Receive data Receive error MAC CS PMD CSMA/CD 次層界面 MII 界面

Fast Ethernet Base4T  Category 3 UTP cable contains 4 separate twisted-pair wires.  To reduce the bit rate used in each wire, all four wire pairs are used in 100Base4T.  For each direction of transmission, 3 pairs are used to transmit the frame and the other pair is used for carrier sensing and collision detecting (if any). 載波感測 衝撞偵測 載波感測 衝撞偵測 第一對雙絞線 第二對雙絞線 第三對雙絞線 第四對雙絞線 工作站至集線器 集線器至工作站 工作站 集線器

Fast Ethernet Base4T -- Line Coding  The bit rate on each pair of wires needs only be Mbps.  The Manchester encoding used in Ethernet is not used due to a bit rate of Mbps requires a clock rate of MHz which exceeds the 30MHz limit set for use with such cables.  To reduce the clock rate, a 3-level (ternary) code is used instead of straight (2- level) binary coding.  8B6T encoding: prior to transmission, each set of 8 binary bits is converted into 6 ternary (3-level) symbols. A symbol signaling rate of (100x6/8)/3 = 25 MHz. 8 位元 符號 字碼

Fast Ethernet Base4T -- Line Coding  The three signal levels used are +V, 0, -V (+,0,-).  The codewords are selected such that the line is d.c. balanced (the line signal is zero).  The 6 ternary symbols have 729 (3 6 ) possible codewords.  To represent complete set of 8-bit byte combination, 256 codewords are needed.  The selection rules are To achieve DC balance To ensure all codewords that have at least two signal transitions within them (for the purpose of synchronization)  For the first case, only those codewords with a combined weight of 0 or +1 are selected. 267 codewords meet this condition.  For the second case, those codewords with fewer than two transitions (5 codes) and those staring or ending with four consecutive zeros (6 codes) are eliminated.  = 256.

Fast Ethernet - 9 8B6T Code Mapping Table A A A A B B B B C C C C D D D D E E E E F F F F A A A A B B B B C C C C D D D D E E E E F F F F 資料 位元組 字碼 資料 位元組 字碼 資料 位元組 字碼 資料 位元組 字碼 資料 位元組 字碼 資料 位元組 字碼 資料 位元組 字碼 資料 位元組 字碼 A C E A C E A C E A C E A C E A C E A C E A C E A C E A C E A AA CA EA B AB CB EB C AC CC EC D AD CD ED E AE CE EE F AF CF EF B D F B D F B D F B D F B D F B D F B D F B D F B D F B D F A BA DA FA B BB DB FB C BC DC FC D BD DD FD E BE DE FE F BF DF FF

Fast Ethernet B6T Coding Scheme  DC Balance: All the codewords selected have a combined weight of either 0 or +1. If a string of codewords each of weight +1 is transmitted, then the mean signal level at the receiver will move away rapidly from the zero level, causing the signal to be misinterpreted. This is known as DC Wander.  To overcome this, whenever a string of codewords with a weight of +1 is to be sent, the symbols in alternate codewords are inverted prior to transmission.  For example: => , , , ,...  State Machine: 總和 = 0 總和 = 1 比重 = 1, 字碼不變 比重 = 1, 字碼反相 比重 = 0 字碼不變 比重 = 0 字碼不變 開始

Fast Ethernet B6T Coding Scheme  To reduce the latency during the decoding process, six ternary symbols corresponding to each encoded byte are transmitted on three wire pairs A1(w=1) B1(w=1) C1(w=0) A2(w=1) B2(w=0) C2(w=0) A1(w=1)A2(w=1) B1(w=1) B2(w=0) C1(w=0) C2(w=0) IEEE 位元串 6 符號字碼 傳送至三條 雙絞線上 雙絞線

Fast Ethernet B6T Coding Scheme  The transmission procedure adopted enables further error checking to be added to the basic CRC. At the end of each frame transmission (after the four CRC bytes have been transmitted) one of two different End-Of- Stream (EOS) codes is transmitted on each of the three pairs. 雙絞線 CRC-3 CRC-4 E E E E3 E2 總和 = 0 總和 = 1 E EOS 功能結束 線路重新 達成平衡

Fast Ethernet - 13 Collision Detection  A DTE detects a collision by detecting a signal on pair 2 while it is transmitting. The hub detects a collision by the presence of a signal on pair 1.  The strong signals transmitted on pairs 1, 3, and 4 from the DTE side each induce a signal into the collision detect wire (pair 2). This is known as Near- End CrossTalk (NEXT) which is interpreted by the DTE as a collision signal being received from the hub. 載波感測 衝撞偵測 載波感測 衝撞偵測 第一對雙絞線 第二對雙絞線 第三對雙絞線 第四對雙絞線 工作站 集線器 NEXT

Fast Ethernet - 14 Collision Detection  To minimize NEXT the preamble at the start of each frame is encoded as a string of 2-level (as opposed to 3-level) symbols. This increases the signal-level amplitude variations which helps the DTE/hub to distinguish between an induced NEXT signal and the preamble of a colliding frame.  The preamble pattern: Start-of-Stream (SOS) is made up to two 2-level codewords, SOS-1 and SFD. 第二對雙絞線 SOS-1 SFD 資料 SOS-1 SFD 資料 SOS-1 SFD 資料 第三對雙絞線 第四對雙絞線 工作站 集線器

Fast Ethernet - 15 Ether-Switch  To speed up the transmission rate of Ethernet Hub without changing the interface cards on stations.  Ether-Switch Architecture  Each pair of Ethernets can have a transmission simultaneously.  For example, (Ethernet 1 - Ethernet 4) and (Ethernet 2 - Ethernet 3) Ether- Switch A B... C D E F G H Ethernet 4 (10Mbps) Ethernet 3 (10Mbps) Ethernet 2 (10Mbps) Ethernet 1 (10Mbps)

Fast Ethernet - 16 Ether-Switch Block Diagram 埠 4埠 4 埠 3埠 3 埠 2埠 2 控制 處理機 工作站 埠 埠 1埠 1 A B... C D E F G H 交換元件 緩衝 器 緩衝 器 緩衝 器 緩衝 器 衝撞偵測 A 1 C 2 F 3 G 4 位址對照表

Fast Ethernet - 17 Gigabit Ethernet Network Structure PCS PMA PMD Reconcilation Medium PCS PMA PMD Reconcilation Medium PLS Reconcilation Medium PMA PLS Medium PMA MAC MAC Control (Option) LLC Higher Layers MDI AUI MII GMII 1Mbps, 10Mbps 10 Mbps 100 Mbps 1000 Mbps PHYSICAL DATA LINK NETWORK TRANSPORT SESSION PRESENTAION APPLICATION PHY MAU

Fast Ethernet - 18 Frame Format (Carrier Extension) Preamble SFD DA SA LEN LLC PAD FCS Extension 7 1 2, 6 2, <= N <= <= M <= 448 位元組 最短訊框尺寸（ >= 64 位元組） 最短訊框尺寸 + 擴充尺寸（ >= 512 位元組） FCS 錯誤檢查碼涵蓋範圍 訊框之載波期間

Fast Ethernet - 19 Frame Bursting Example 訊爆週期 時槽時間 (512 位元組） 載波 偵測 傳送 訊框 訊框 1 訊框 2 訊框 3 訊框 4 訊框間隔（ 96 位元時間） 延伸載波 Preamble SFD DA SA LEN LLC PAD FCS

Fast Ethernet - 20 Gigabit Ethernet Repeater Set MAC MAC Control (Option) LLC Higher Layers 1000 Mbps Link Segment PHYSICAL DATA LINK NETWORK TRANSPORT SESSION PRESENTAION APPLICATION PHY PCS PMA PMD Medium MDI GMII PCS PMA PMD Reconcilation Medium MDI GMII PHY PCS PMA PMD MDI GMII PHY 1000 Mbps 基頻集線器 1000 Mbps Link Segment 1000 Mbps 基頻集線器組 ISO 參考模式 CSMA/CD 網路

Fast Ethernet - 21 Gigabit Ethernet Communication Structure 1000BASE-LX nm 光傳送接收器 1000BASE-SX nm 光傳送接收器 1000BASE-CX STP 傳送接收器 1000BASE-T 4-Pair 傳送接收器 SMF MMF 50 um MMF 62.5 um Balance Shielded Copper Cat-5 UTP 3 km 550m 550m 300m 25m 100m 8B/10B 編碼 / 解碼 1000BASE-T 編碼 / 解碼 Gigabit Media Independent Interface (GMII) Media Access Control (MAC) Logical Link Control (LLC) Ethernet Upper Layers

Fast Ethernet - 22 Gigabit Ethernet Applications-- Multi-port Bridge (Single bandwidth) 集線器 (Repeater) 工作站 (DTE) 工作站 (DTE) 工作站 (DTE) 工作站 (DTE) 集線器 (Repeater) 工作站 (DTE) 工作站 (DTE) 工作站 (DTE) 工作站 (DTE) 集線器 (Repeater) 工作站 (DTE) 工作站 (DTE) 工作站 (DTE) 工作站 (DTE) 多埠橋接器 (Multi-port Bridge) 衝撞網域 1 衝撞網域 2 衝撞網域 3

Fast Ethernet Mbps 專屬線路 工作站 (DTE) 工作站 (DTE) 100BASE-T 集線器 工作站 (DTE) 工作站 (DTE) 工作站 (DTE) 多埠橋接器 (Multi-port Bridge) 100 Mbps 分享網路 100 Mbps 1000 Mbps 專屬線路 1000 Mbps 1000BASE-T 集線器 工作站 (DTE) 工作站 (DTE) 工作站 (DTE) 1000 Mbps 分享網路 1000 Mbps 10 Mbps 專屬線路 工作站 (DTE) 工作站 (DTE) 100 Mbps 專屬線路 10 Mbps 100 Mbps Gigabit Ethernet Applications-- Multi-port Bridge (Multiple Bandwidth)

Fast Ethernet - 24  CSMA/CD 網路的實際大小受限於各個網路元件的特性。這些特 性包括：  傳輸媒介（線路）長度及其傳遞延遲。  集線器元件延遲（啟動，穩定，結束）。  MAUs 及 PHYs 延遲（啟動，穩定，結束）。  集線器所造成的訊框間隔萎縮。  DTEs 執行 CSMA/CD 演算法的延遲。  MAUs 及 PHYs 的衝撞偵測延遲。

Fast Ethernet Mbps 網路區段時間延遲

Fast Ethernet - 26 Transmission System Model (TSM -1 ) 集線器組 工作站 (DTE) 工作站 (DTE) A+B = 衝撞網域直徑 工作站 (DTE) 工作站 (DTE) A B

Fast Ethernet - 27 Transmission System Model (TSM -2 ) 集線器 工作站 (DTE) 工作站 (DTE) PHY

Fast Ethernet B/10B Encoding B/10B 編碼器 a b c d e i f g h j H G F E D C B A 10 8+Control GMII (125 Mbytes/s) 編碼器輸入 編碼器輸出 PMA 服務界面 (125 M code_groups/s) PMD 服務界面 (1250 Mbps) 位元 0 先傳送 tx_code_group B/10B 解碼器 a b c d e i f g h j H G F E D C B A 10 8+Control x x x GMII (125 Mbytes/s) 解碼器輸入 解碼器輸出 PMA 服務界面 (125 M code_groups/s) PMD 服務界面 (1250 Mbps) 位元 0 先接收 rx_code_group Comma + Symbol 對齊 PCS 編碼功能 PCS 解碼功能 TXD RXD

Fast Ethernet - 29 子區塊偏差值的計算方式  子區塊偏差值的計算方式如下： 任何一個子區塊後的偏差值為正，如果該子區塊包含 ”1” 的數量大於 “0” 的 數量。如果是在一個值為 的六位元子區塊後，則偏差值仍然為正。 相同的，如果是在一個值為 0011 的四位元子區塊後，則偏差值仍然為正。 任何一個子區塊後的偏差值為負，如果該子區塊包含 ”1” 的數量小於 “0” 的 數量。如果是在一個值為 的六位元子區塊後，則偏差值仍然為負。 相同的，如果是在一個值為 1100 的四位元子區塊後，則偏差值仍然為負。 在其他狀況下（包含 ”1” 的數量等於 “0” 的數量），則偏差值保持不變。

Fast Ethernet - 30 偏差值計算與錯誤偵測範例（一）

Fast Ethernet - 31 偏差值計算與錯誤偵測範例（二）

Fast Ethernet - 32 偏差值計算與錯誤偵測範例（三）