10/27/ Data Link Layer - Lin 1 CPET/ECET Data Link Layer Data Communications and Networking Fall 2004 Professor Paul I-Hai Lin Electrical and Computer Engineering Technology Indiana University-Purdue University Fort Wayne

10/27/ Data Link Layer - Lin 2 Data Link Layer Packetizing Flow Control Media Access Control Addressing Error Control

10/27/ Data Link Layer - Lin 3 Data Link Layer IEEE LAN Standards  CSMA/CD  Token Bus  Token Ring  DQDB  Wireless Data Link Layer (Internet Model)  Medium Access Layer  Logical Link Control

10/27/ Data Link Layer - Lin 4 Data Link Layer Ch 10 – Error Detection and Correction Ch 11 – Data Link Control and Protocols Ch 12 – Point-to-Point Access: PPP Ch 13 – Multiple Access Ch 14 – Local Area Networks: Ethernet Ch 15 – Wireless LANs

10/27/ Data Link Layer - Lin 5 Data Link Layer Ch 16 – Connecting LANs, Backbone Networks, and Virtual LANs Ch 17 – Cellular Telephone and Satellite Networks Ch 18 – Virtual Circuit Switching: Frame Relay and ATM

10/27/ Data Link Layer - Lin 6 Error Detection and Correction 10.1 Types of Errors  Single-Bit Error  Burst Error 10.2 Detection  Redundancy  Parity Check  Cyclic Redundancy Check (CRC)  Checksum

10/27/ Data Link Layer - Lin 7 Error Detection and Correction 10.3 Error Correction  Retransmission  Forward Error Correction  Hamming Code  Burst Error Correction

10/27/ Data Link Layer - Lin Types of Errors  Single-Bit Error  One bit error  Happen often in parallel communications From p. 244, Figure 10.1 of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin Types of Errors  Burst Error  2 or more bits affected by noise  Not necessarily in consecutive bits From p. 244, Figure 10.2 of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin Detection  Redundancy From p. 245, Figure 10.3 of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin Detection  Parity Checking (based on addition)  Even parity  Odd parity  Performance  Check all single bit errors  Detect burst errors with a total number of bits changed is ODD (1, 3, 5, etc)

10/27/ Data Link Layer - Lin Detection  Even Parity Check From p. 246, Figure 10.5 of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin Detection  Two-Dimensional Parity Check From p. 248, Figure 10.6 of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin 14 Two-Dimensional Parity Check  Method  Calculate parity bit for each data unit (row)  Calculate parity bit for each column to create a new parity row  Add parity row to the end of the data stream for transmitting  Performance  Can detect a burst errors of n bits  Cannot detect one pattern of errors: 2 bit in one data unit is damaged and another 2 bit in exactly the same positions in another data unit is also damaged

10/27/ Data Link Layer - Lin Detection  CRC Generator and Checker  Based on binary division (remainder) From p. 250, Figure 10.7 of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin 16 CRC Generator  Binary Division (modulo-2)  C code, (VHDL)  Assembly language From p. 251, Figure 10.8 of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin 17 CRC Checker  Binary Division – CRC Cheker From p. 252, Figure 10.9 of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin 18 CRC - Polynomial  Polynomial selecting criteria  It should not be divisible by x -> all burst errors of a length equal to the degree of the polynomial are detected  It should be divisible by x + 1 -> all burst errors affecting an ODD number of bits are detected From p. 252, Figure of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin Detection  Standard Polynomials From p. 253, Table 10.1 of Data Communications and Networking, Forouzan, McGrawHill NamePolynomialApplicationCRC-8x 8 + x 2 + x + 1ATM header CRC-10x 10 + x 9 + x 5 + x 4 + x 2 + 1ATM AAL ITU-16x 16 + x 12 + x 5 + 1HDLC ITU-32 x 32 + x 26 + x 23 + x 22 + x 16 + x 12 + x 11 + x 10 + x 8 + x 7 + x 5 + x 4 + x 2 + x + 1 LANs

10/27/ Data Link Layer - Lin Detection  Checksum From p. 254, Figure of Data Communications and Networking, Forouzan, McGrawHill

10/27/ Data Link Layer - Lin 21 Summary Questions?