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Chapter 3 Network Technologies

Chapter 3 Network Technologies. Local Area Networks. IEEE 的定義：. A LAN (Local Area Network) is a data communication system allowing a number of independent devices to communicate directly with each other, within a moderately sized geographic

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Chapter 3 Network Technologies

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  1. Chapter 3 Network Technologies Local Area Networks IEEE的定義： A LAN (Local Area Network) is a data communication system allowing a number of independent devices to communicate directly with each other, within a moderately sized geographic area over a physical communication channel of moderate data rates. • 是一個資料(各種形式)通訊系統 • 設備獨立(可以是各種廠牌、各種系統) • 涵蓋範圍不會太大(五公里左右) • 速度不能太慢(大於1Mbps, million bit per second)

  2. Chapter 3 Network Technologies Sharing the Wire An expensive connection ( )

  3. Chapter 3 Network Technologies Sharing the Wire Much cheaper ( )

  4. Chapter 3 Network Technologies Ethernet Protocol CSMA(Carrier Sense Multiple Access) protocols 1-persistent CSMA: the station transmits with a probability of 1 whenever it finds the channel idle, if the channel is busy, it waits until it becomes idle(不忙時就傳，忙時就一直等) non-persistent CSMA: the station transmits if the channel is idle, if the channel is busy, it waits a random time and tries again (不忙時就傳，忙時就回去等一段隨機時間再來)

  5. Chapter 3 Network Technologies Ethernet Protocol CSMA(Carrier Sense Multiple Access) protocols p-persistent CSMA (slotted): the station transmits with a probability of p whenever it finds the channel idle, with a probability of 1-p or if the channel is busy, it waits until the next slot(不忙時有p的機 率傳，有1-p的機率等到下一slot。忙時等到下一slot再重來) CSMA with collision detections (CSMA/CD) 傳後一旦發現碰撞馬上放棄，進入解決碰撞的過程， 可以增加網路的效率。

  6. Chapter 3 Network Technologies Ethernet Protocol IEEE 802.3: 1-persistent CSMA/CD five versions: 10BASE5: Ethernet 10BASE2: Cheapernet(thinnet) 1BASE5: StarLAN 10BASE-T: 10BROAD36 use twisted-pair transmission rate in Mbps segment length in 100m

  7. Chapter 3 Network Technologies Ethernet Protocol Collision Resolution Binary Exponential Backoff 第一次碰撞後 第二次碰撞後 第三次 . . . 隨機選一個slot送

  8. Chapter 3 Network Technologies Ethernet Protocol Protocol layering 資料 連結 層 實體 層 802.2 Logical Link Control LLC 2 MAC 802.3 ~ 802.9, 802.11, 802.12 1 physical (MAC: Medium Access Control) OSI layers

  9. Chapter 3 Network Technologies Ethernet Frame Structure (IEEE 802.2/802.3 Encapsulation) 7 1 6 6 2 4 LLC frame preamble SFD DA SA Len PAD CRC 60 to 1514 bytes synchronize the receiver length of LLC frame Cyclic Redundancy Check start frame delimiter

  10. Chapter 3 Network Technologies Ethernet Frame Structure (Ethernet Encapsulation) 6 2 7 1 6 6 2 4 Data preamble SFD DA SA type CRC 60 to 1514 bytes synchronize the receiver Cyclic Redundancy Check start frame delimiter type 0800: IPv4 datagram 0806: ARP request/reply 8035: RARP request/reply 86DD: IPv6

  11. t0 B A Ａ開始傳送訊框 t0+a-e B A Ｂ開始傳送訊框 衝撞 t0+a B A Ｂ偵測出衝撞 t0+2a B A Ａ偵測出衝撞 Chapter 3 Network Technologies Why do we have a restriction on minimum frame length? 2a=51.2msec

  12. Chapter 3 Network Technologies Ethernet Address Address (48 bits) single address 0 group address multicast (all 1's for broadcast) 1 1 local address proper to network global address one of 246 unique address 0

  13. Chapter 3 Network Technologies The Evolution of Ethernet Technology

  14. Chapter 3 Network Technologies The Evolution of Ethernet Technology

  15. Chapter 3 Network Technologies The Evolution of Ethernet Technology 10Base-T collapses the shared coaxial cable into a small box called the hub.

  16. Chapter 3 Network Technologies The Evolution of Ethernet Technology

  17. Chapter 3 Network Technologies The Evolution of Ethernet Technology

  18. A ... B Chapter 3 Network Technologies The Evolution of Ethernet Technology Architecture of EtherSwitch 交換元件 位址對照表 緩衝 器 工作站埠 A 1 緩衝 器 控制 處理機 C 2 F 3 緩衝 器 G 4 Must have Learning capability 緩衝 器 埠1 埠2 埠3 埠4 衝撞偵測 C G E ... ... ... D H F

  19. Chapter 3 Network Technologies The Evolution of Ethernet Technology: Fast Ethernet • 100 Mbps, IEEE 802.3 CSMA/CD frame format • Medium : Twisted pair -- UTP, STP or 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 with Hub architecture • 100Base4T • Voice-grade Category 3 UTP. Use four pairs of twisted-pair wires. • 100BaseX • Category 5 UTP, STP, or Fiber optic.

  20. Chapter 3 Network Technologies The Evolution of Ethernet Technology: Fast Ethernet The speed is now 10 times faster. What about the minimum frame length? Shorter distance Longer frame Change either or Which change is better?

  21. Chapter 3 Network Technologies The Evolution of Ethernet Technology: Fast Ethernet 100M Hub 100M Hub 10公尺 集線器 集線器 100公尺 100公尺 . . . . . . 工作站與工作站間最多有兩個集線器，要延伸則必須 靠橋接器

  22. Chapter 3 Network Technologies The Evolution of Ethernet Technology: Fast Ethernet 10/100 Fast Ethernet Switch Hub 10M 100M 10M Ethernet 100M Ethernet 10M Hub 100M Hub Hub A Hub B Hub C . . . . . . . . . 10M卡 10M卡 10/100M卡 10/100M卡 100M卡 100M卡

  23. Chapter 3 Network Technologies The Evolution of Ethernet Technology: Gigabit Ethernet • 1000 Mbps, IEEE 802.3 CSMA/CD frame format • Medium : Twisted pair -- UTP cat 5, STP or 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

  24. Chapter 3 Network Technologies The Evolution of Ethernet Technology: Gigabit Ethernet The speed is now 100 times faster. What about the minimum frame length? Shorter distance Longer frame Change either or Distance can not be shortened any more. Frame length can not change for compatibility reason.

  25. Chapter 3 Network Technologies The Evolution of Ethernet Technology: Gigabit Ethernet Solution: Increase the frame length, but the actual data portion remained the same Carrier Extension Slot time=512 bytes 7 2, 6 2, 6 2 46 <= N <= 150 4 0 <= M <= 448 bytes Preamble SFD DA SA LEN LLC PAD FCS Extension 最短訊框尺寸（ >= 64 bytes） 最短訊框尺寸 + 擴充尺寸（>= 512 bytes） FCS 錯誤檢查碼涵蓋範圍 訊框之載波期間

  26. Chapter 3 Network Technologies The Evolution of Ethernet Technology: Gigabit Ethernet Though carrier extension solved the minimum frame length problem, it decreases the efficiency for transmitting short frames. 100 Mbps 1000 Mbps 64 bytes 512 bytes (actual data) (transmitted data) Only 25% increase in efficiency!

  27. 訊爆週期 時槽時間 (512 位元組） 載波 偵測 訊框間隔（96 位元時間） 延伸載波 傳送 訊框 訊框 1 訊框 2 訊框 4 訊框 3 Preamble SFD DA SA LEN LLC PAD FCS Chapter 3 Network Technologies The Evolution of Ethernet Technology: Gigabit Ethernet Frame bursting Burst limit: 65536 bits

  28. Chapter 3 Network Technologies The Evolution of Ethernet Technology ( 曾經有過)100VG-AnyLAN IEEE 802.12之標準 HP和AT&T支持 (give up now) 放棄CSMA/CD，採用新的方法叫需求優先權(Demand Priority) 同時支援Token Ring和Ethernet 須用Category 3, 4, 或5 UTP(Unshielded Twisted Pair) 8蕊線， 或multimode光纖

  29. Chapter 3 Network Technologies The Evolution of Ethernet Technology 100VG-AnyLAN 100VG Hub 100VG Hub 100VG Hub 100VG Hub 100VG Hub

  30. Chapter 3 Network Technologies The Evolution of Ethernet Technology 100VG-AnyLAN 需求優先權協定(Demand Priority Protocol) 當工作站要送資料時先送一個Request-to-send的信號給 集線器，如果集線器認為一切都正常則回一個 Acknowledge-to-send的信號給工作站，然後工作站就 可送資料出去給集線器，集線器再負責將資料送達目 的地，如此可避免資料碰撞的問題，也很容易可以分 出不同的優先等級。

  31. Chapter 3 Network Technologies The Evolution of Ethernet Technology 100VG-AnyLAN 缺點: 因協定不同，網路管理資料庫(Management Information Base)須重寫。 10/100M的網路卡須支持兩種不同協定，成本必較昂貴。

  32. Chapter 3 Network Technologies Other LAN Technologies: Token Ring

  33. Chapter 3 Network Technologies Other LAN Technologies: Fiber Distributed Data Interface

  34. Chapter 3 Network Technologies Other LAN Technologies: Fiber Distributed Data Interface

  35. 本站 前站 後站 Chapter 3 Network Technologies Other LAN Technologies: Token Bus 50 40 60 20 50 60 30 邏輯環 網路（Ｂus） 10 20 30 30 60 50 20

  36. Chapter 3 Network Technologies Other LAN Technologies: Distributed Queue Dual Bus HOB A 訊槽(Slot) Bus A 訊槽 產生器 ... 工作站n-1 工作站n 工作站1 工作站2 訊槽 產生器 Bus B HOB B 訊槽(Slot) HOB: Head of Bus

  37. Chapter 3 Network Technologies Integrated Services Digital Networks: Narrowband ISDN

  38. Chapter 3 Network Technologies Integrated Services Digital Networks: Narrowband ISDN TCP/IP traffic travels in Unnumbered Information (UI) frames, in which the control field has a value of 3.

  39. Chapter 3 Network Technologies Integrated Services Digital Networks: Narrowband ISDN Stop-and-wait protocol or alternating bit protocol (not efficient for long-delay network)

  40. Chapter 3 Network Technologies Integrated Services Digital Networks: Narrowband ISDN Go-back-N protocol (in contrast to select-repeat protocol) modifier

  41. Chapter 3 Network Technologies Integrated Services Digital Networks: Narrowband ISDN Never allow more than 128 frames to be outstanding without an acknowledgement.

  42. Chapter 3 Network Technologies The Point-to-Point Protocol (PPP) Protocol layering TCP/IP PPP Dialup Modem ISDN High speed leased line

  43. Chapter 3 Network Technologies The Point-to-Point Protocol (PPP) Link Control Protocol LCP establishes and maintains each point to point link. It has three major tasks: 1. Set up the link in an orderly manner 2. Negotiate configuration for the link’s operation ensure that the termination of the link is graceful

  44. Chapter 3 Network Technologies The Point-to-Point Protocol (PPP) Link Control Protocol: Authentication protocols PAP: password authentication protocol Username, password OK May be intercepted

  45. Chapter 3 Network Technologies The Point-to-Point Protocol (PPP) Link Control Protocol: Authentication protocols

  46. Chapter 3 Network Technologies The Point-to-Point Protocol (PPP) Network Control Protocol Just as LCP coordinates the operation of a link, PPP has several network control protocols to coordinate the operation of various network protocols over that link. IPv4’s NCP allows the two systems to negotiate particular compression protocols, and it lets a system asks its peer for an IPv4 address.

  47. Chapter 3 Network Technologies The Point-to-Point Protocol (PPP)

  48. Chapter 3 Network Technologies High-Speed Wide Area Networks

  49. Chapter 3 Network Technologies Frame Relay • An upgrade to X.25, making it efficient enough to support higher speeds • simple enough to be implemented almost entirely in hardware • eliminated nearly all the processing required in network switches, including error recovery and sophisticated flow control • speed limited only by the bandwidth of the links connecting the switches

  50. Chapter 3 Network Technologies Frame Relay At the interface between a host or router and a frame relay switch, the protocol is quite simple. It is the same protocol as in ISDN, LAPD. However, the only frame exchanged is unnumbered information (UI) frame.

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