Chapter 3 Slides Prepared By Kaif Jamal Gilani

Chapter 3 Slides Prepared By: Kaif Jamal Gilani (Course Coordinator) Mohammad Rafeek Khan (Course Teacher) Department of CNET Faculty of CS&IS Jazan University

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Extended Address To increase the range of DLCIs, the Frame Relay address has been extended from the original 2 -byte address to 3 -or 4 - byte addresses. Figure shows the different addresses. Note that the EA field defines the number of bytes ; it is 1 in the last byte of the address , and it is a in the other bytes. Note that in the 3 -and 4 -byte formats, the bit Before the last bit is set to O.

Figure Of DLCI

EXERCISE ON FRAME RELAY

Exercise-1 The address field of a Frame Relay frame is 1011000000010111. What is the DLCI (in decimal)?

Solution-1 We first need to look at the EA bits. In each byte, the EA bit is the last bit (the eight bit from the left). If EA bit is 0, the address ends at the current byte; if it 1, the address continues to the next byte. Address → 10110000 00010111 The first EA bit is 0 and the second is 1. This means that the address is only two bytes (no address extension). DLCI is only 10 bits, bits 1 to 6 and 9 to 12 (from left). Address → 10110000 00010111 DLCI → 1011000001 → 705

Excercise-2 The address field of a Frame Relay frame is 101100000101001. Is this valid ? Solution 2: Not Valid , because address field of frame relay is 15 bit , it should be 16 bit.

Exercise-3 Find the DLCI value if the first 3 bytes received is 7 C 74 El in hexadecimal.

Solution-3 We first need to look at the EA bits. In each byte, the EA bit is the last bit (the eight bit from the left). If the EA bit is 0, the address ends at the current byte; if it 1, the address continues to the next byte. Address → 0 x 7 C 74 E 1 → 011111000111010011100001 The first two EA bit are 0 s and the last is 1. This means that the address is three bytes (address extension). DLCI is 16 bits, bits 1 to 6, 9 to 12, and 17 to 22. Address → 01111100 01110100 111000 DLCI → 0111111000 → 32248

Exercise-4 Find the value of the 2 -byte address field in hexadecimal of Frame Relay if the DLCI is 178. Assume no congestion.

Solution-4

Exercise-5 In Figure a virtual connection is established between A and B. Show the DLCI for each link. Figure

Solution-5

Exercise-6 In Figure a virtual connection is established between A and B. Show the corresponding entries in the tables of each switch.

Solution-6 In