/ 5 1 (error control) (flow control) / 5 2
Layer 1 gateway: repeater ( ) Layer 2 gateway: bridge ( ) Layer 3 gateway: router (datalink frame) / 5 3 Data link control (error detection / correction) (flow control) Addressing Logical link control (MAC) / 5 4
1970 X25(HDLC) 1980 LAN Ethernet Token Ring FDDI Wireless Ethernet 1990 LAN Frame Relay ATM SONET and POS Wireless Ethernet LAN Fast Ethernet Gigabit Ethernet / 5 5 Ethernet families (IEEE802.3) Wireless Ethernet (IEEE802.11) ATM SONET xdsl (ADSL, VDSL, ) ISDN LAP-B, X.25 PPP / 5 6
2 Point-to-Point connection CCITT X.25 (HDLC/LAPB) ISDN ITU-T Broadcast Channel (LAN) IEEE 802 (ISO 8802) LLC (Logical Link Control) MAC (Media Access Control) Ethernet, FDDI, Token Ring IEEE802 ISO8802 / 5 7 (2) Network Layer ISO/OSI Local Area Network Definitions (8802) CCITT Datalink Layer Definition Data link Layer Logical Link Control Sublayer Media Access Control Sublayer 8802/3 CSMA/CD 8802/2 LLC 8802/4 Token Bus 8802/5 Token Ring CCITT X.25 (HDLC/LAPB) Physical Layer / 5 8
(propagation delay) (errors) IEEE802.2 IEEE802.x / 5 9 Unacknowledged Connectionless Service Acknowledged Connectionoriented Service LAN, real-time traffic (voice/speech) Unacknowledged Connectionoriented Service Acknowledged connectionless Service (acknowledge) / 5 10
(frame)»» / 5 11 (1) CCITT X.21 8bit ASCII(IA5) STX, ETX DLE (DataLink Escape) character stuffing / 5 12
(2) Original Data B DLE A Transmission Sequence ETX DLE B DLE DLE A STX DLE transmission data frame character stuffing / 5 13 (3) bit stuffing 01111110 1 0 1 0 / 5 14
(4) Original Data Transmission Sequence end bit pattern start bit pattern transmission bit stuffing / 5 15 (1) Unacknowledged Connectionless Service LAN, real-time traffic (voice/speech) Acknowledged connectionless Service (acknowledge) / 5 16
(2) Connection-oriented Service / 5 17 Error Control (Error Correction Code) (Error Detection Code) (timer) (retransmission) / 5 18
(parity) ASCII 7 even parity: CRC (Cyclic Redundancy odd parity: Check code) FEC (Forwarded Error Correction) / 5 19 CRC (1) CRC (a n-1,.., a 1, a 0 ) a i 0 1 F(x)=a n-1 x n-1 + +a 2 x 2 +a 1 x+a 0 modulo 2 (exclusive OR) / 5 20
CRC (2) CRC G(x) r (r < m) m M(x) ( m-1) r 0 x r M(x) x r M(x) G(x) R(x) F(x) F(x) = x r M(x) + R(x) / 5 21 CRC (3) F(x)G(x) r G(x) / 5 22
CRC (1) CRC-12 x 12 +x 11 +x 3 +x 2 +x+1 CRC-16 x 16 +x 15 +x 2 +1 CRC-CCITT x 16 +x 12 +x 5 +1 CRC / 5 23 CRC (2) CRC-12 CRC-16 CRC-CCITT (CRC-16 CRC-CCITT) 99.997% 99.998% / 5 24
Error Correction Code (hamming code) aa+1 b2b+1 1 1 b a / 5 25 retransmission ARQ (Automatic Repeat request) Stop-and-wait Go-back-N Selective -repeat / 5 26
Stop-and-wait Protocol (1) Sender t 1 t 5 t 4 t 1 t 2 t 3 Receiver t 1 : t 2 : t 3 : t 4 : t 5 : / 5 27 Stop-and-wait Protocol (2) 2t 1 +t 2 +t 3 +t 4 / 5 28
Go-back-N Protocol (1) Stop-and-Wait Protocol / 5 29 Go-back-N Protocol (2)!! 1 2 3 4 5 3 4 5 6 1 2 4 5 3 4 5 6 / 5 30
Go-back-N Protocol (3) Go-back-N N (on-the-fly frame ) / 5 31 Selective-repeat Protocol (1) Go-back-N Go-back-N / 5 32
Selective-Repeat Protocol (2)!! 1 2 3 4 5 3 6 7 8 1 2 4 5 3 6 7 8 / 5 33 Stop-and-Wait, Go-back-N Selective-Repeat (flow control) / 5 34
Window Flow Control W (1) (2) Nr Nr < W sliding window flow control / 5 35 (error control) (flow control) / 5 36