2. Consider a slotted TDM hierarchical network in which there are 8 computers sharing a 10 Mbps channel to a router R1, sending packets to R1 which must all be forwarded by R1 over an outgoing link (called the MAN link), as shown in Figure 1. Computers A-H always have packets waiting to be sent, so no timeslot on the shared LAN is idle. Ignore the propagation delay on the LAN. The MAN link outgoing from R1 is a 100 Mbps link. The network layer protocol in use has a PDU with exactly 40 bytes of header and exactly 200 bytes of payload (SDU). The DLC layer protocol in use on the LAN has a PDU with exactly 40 bytes of header and 20 bytes of trailer. The DLC layer protocol in use on the outgoing link from R1 has a PDU with 40 bytes of header and no trailer. The physical layer does not impose any bit overhead in either channel. Use 1 Mbps = 1000000 bps.

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
Question
2. Consider a slotted TDM hierarchical network in which there are 8 computers sharing a
10 Mbps channel to a router R1, sending packets to R1 which must all be forwarded by
R1 over an outgoing link (called the MAN link), as shown in Figure 1. Computers A-H
always have packets waiting to be sent, so no timeslot on the shared LAN is idle. Ignore
the propagation delay on the LAN. The MAN link outgoing from R1 is a 100 Mbps link.
The network layer protocol in use has a PDU with exactly 40 bytes of header and exactly
200 bytes of payload (SDU). The DLC layer protocol in use on the LAN has a PDU with
exactly 40 bytes of header and 20 bytes of trailer. The DLC layer protocol in use on the
outgoing link from R1 has a PDU with 40 bytes of header and no trailer. The physical
layer does not impose any bit overhead in either channel. Use 1 Mbps = 1000000 bps.
B
D
E
F
G
H
R1
R2
Figure 1
(a) What is the transmission delay of a bit for Computer A?
(b) What is the transmission delay of a DLC PDU for Computer A?
(c) The TDM slotting of Computers A-H is at the individual PDU level, i.e. a PDU
transmission from Computer A on the LAN is followed by one from Computer B, and so
on. In the LAN, each network layer PDU is encapsulated in one DLC PDU. If the
outgoing link from R1 follows the same discipline, what is the width of a DLC PDU on
the MAN link? (The transmission time of a bit or group of bits is sometimes referred to
as their "width" on the line.)
(d) R forwards each packet as soon as it is completely received. Ignore processing and
queueing time at R1, if any. What is the delay between the instant when a packet first
starts transmission at Computer A and the instant when the same packet starts
transmission at R1?
(e) What is the amount of time between two successive PDU transmissions are seen on
the MAN link?
(f) What is the bitrate perceived by the network layer of Computer A?
Transcribed Image Text:2. Consider a slotted TDM hierarchical network in which there are 8 computers sharing a 10 Mbps channel to a router R1, sending packets to R1 which must all be forwarded by R1 over an outgoing link (called the MAN link), as shown in Figure 1. Computers A-H always have packets waiting to be sent, so no timeslot on the shared LAN is idle. Ignore the propagation delay on the LAN. The MAN link outgoing from R1 is a 100 Mbps link. The network layer protocol in use has a PDU with exactly 40 bytes of header and exactly 200 bytes of payload (SDU). The DLC layer protocol in use on the LAN has a PDU with exactly 40 bytes of header and 20 bytes of trailer. The DLC layer protocol in use on the outgoing link from R1 has a PDU with 40 bytes of header and no trailer. The physical layer does not impose any bit overhead in either channel. Use 1 Mbps = 1000000 bps. B D E F G H R1 R2 Figure 1 (a) What is the transmission delay of a bit for Computer A? (b) What is the transmission delay of a DLC PDU for Computer A? (c) The TDM slotting of Computers A-H is at the individual PDU level, i.e. a PDU transmission from Computer A on the LAN is followed by one from Computer B, and so on. In the LAN, each network layer PDU is encapsulated in one DLC PDU. If the outgoing link from R1 follows the same discipline, what is the width of a DLC PDU on the MAN link? (The transmission time of a bit or group of bits is sometimes referred to as their "width" on the line.) (d) R forwards each packet as soon as it is completely received. Ignore processing and queueing time at R1, if any. What is the delay between the instant when a packet first starts transmission at Computer A and the instant when the same packet starts transmission at R1? (e) What is the amount of time between two successive PDU transmissions are seen on the MAN link? (f) What is the bitrate perceived by the network layer of Computer A?
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