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General questions about ATM networks

1. ATM networks use a token bucket scheme to regulate traffic (traffic shaping). A new token is put into the bucket every 1 usec so ATM cells can be sent during this period. The data payload of ATM cells is 48 bytes.
What is the maximum sustainable net (or effective) data rate?

2. A bridge between an 802.3 LAN and an 802.4 LAN has a problem with intermittent memory errors. Can this problem cause undetected errors with transmitted frames, or will these all be caught by the frame checksum?

3. A virtual circuit is newly set up in an ATM network. Between the source and destination hosts lie 3 ATM switches. How many messages (including acknowledgments) will be sent to establish the circuit (or connection)?

4. When a 1024-bytes message is sent with AAL 3 / 4, what is the efficiency achieved? In other words, what fraction of the bits transmitted are useful data bits? Repeat for AAL 5.

5. A CPU executes instructions at the rate of 100MIPS. Data can be copied 64 bits at a time, with each word copied costing 4 instructions. If an incoming packet has to be copied twice, can this system handle a 10-Gbps line? For simplicity, assume that all instructions, including those instructions that read or write memory, run at the full 100 MIPS rate.

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1) ATM networks use a token bucket scheme to regulate traffic (traffic shaping). A new token is put into the bucket every 1 usec so ATM cells can be sent during this period. The data payload of ATM cells is 48 bytes.
What is the maximum sustainable net (or effective) data rate?

ATM payload = 48 bytes = 48*8 = 384 bits
An ATM cell may be sent every time a new token is placed into the Token Bucket, which occurs every 1 microseconds.

So the maximum sustainable data rate = 384 bits/ 1x10-6
= 384 Mbps

2) A bridge between an 802.3 LAN and an 802.4 LAN has a problem with intermittent memory errors. Can this problem cause undetected errors with transmitted frames, or will these all be caught by the frame checksum?

When going between dissimilar LANs, the checksum must be recomputed by the bridge. If the bridge memory is bad, the checksum ...

Solution Summary

General questions about ATM networks are determined. The maximum sustainable net data rates are provided.

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