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CS 118 Spring 2008 : Problems
Problem 1
Problem 1
Suppose nodes A and B are on the same 10Mbps Ethernet bus, and the propagation delay between the
two nodes is 255 bit times.
Suppose node A begins transmitting a frame and, before it finishes, node B
begins transmitting a frame.
Can A finish transmitting before it detects that B has transmitted?
Why
or why not?
If the answer is yes, then A incorrectly believes that its frame was successfully transmitted
without a collision.
Hint:
Suppose at time
t
= 0 bit time, A begins transmitting a frame.
In the worst
case, A transmits a minimum-sized frame of 512+64 bit times. So A would finish transmitting the frame at
t
= 512 + 64 bit times. Thus, the answer is no, if B’s signal reaches A before bit time
t
= 512 + 64 bits. In
the worst case, when does B’s signal reach A?
Problem 2
Consider a 100 Mbps 100BASE-T Ethernet with all nodes directly connected to a hub. To have an efficiency
of 0.50, what should be the maximum distance between a node and the hub? Assume a frame length of 64
bytes and that there are no repeaters. Does this maximum distance also ensure that a transmitting node A
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- Spring '08
- CHU
- Networking, IP address, Fast Ethernet, 64 bit, 0 bit, 1,000 bytes
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