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Recent questions tagged peterson-davie

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Peterson and Davie
Suppose that forwarding tables are all established and then C-E link fails. Question : What update will be there in the C and E tables after failure and which tables information will be exchanged? what will be the table of A after C and E have reported the news?

prasoon raghav asked in Computer Networks May 13, 2017

by prasoon raghav

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Peterson Davie Q.15,17
Graph links are given as A-C=3,A-D=8,B-E=2,C-F=6,C-E=1,D-E=2 (A)Give global distance vector table (B)Routing table at node D by Link State algorithm (C) Suppose the forwarding tables are all established as in (A) and then the C–E ... have reported the news. (ii) The tables of A and D after their next mutual exchange. (iii) The table of C after A exchanges with it.

Archies09 asked in Computer Networks Jun 23, 2016

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Peterson Davie 3.38c
Suppose an $IP$ packet is fragmented into $10$ fragments, each with a $1$% (independent) probability of loss. To a reasonable approximation, this means there is a $10$% chance of losing the whole packet due to loss of a fragment. What is the ... loss of the whole packet if the packet is transmitted twice, (c) Explain how use of the Ident field might be applicable here.

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.38b
Suppose an $IP$ packet is fragmented into $10$ fragments, each with a $1$% (independent) probability of loss. To a reasonable approximation, this means there is a $10$% chance of losing the whole packet due to loss of a fragment. What is ... loss of the whole packet if the packet is transmitted twice, (b) Assuming any given fragment may have been part of either transmission?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.38a
Suppose an $IP$ packet is fragmented into $10$ fragments, each with a $1$% (independent) probability of loss. To a reasonable approximation, this means there is a $10$% chance of losing the whole packet due to loss of a fragment. What is ... of the whole packet if the packet is transmitted twice, (a) Assuming all fragments received must have been part of the same transmission?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.37
Path $MTU$ is the smallest $MTU$ of any link on the current path (route) between two hosts. Assume we could discover the path $MTU$ of the path used in the previous exercise, and that we use this value as the $MTU$ for all the path segments. Give the sizes and offsets of the sequence of fragments delivered to the network layer at the destination host.

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.36
Suppose a $TCP$ message that contains $1024$ bytes of data and $20$ bytes of $TCP$ header is passed to $IP$ for delivery across two networks interconnected by a router (i.e., it travels from the source host to a router to the destination host) ... offsets of the sequence of fragments delivered to the network layer at the destination host. Assume all $IP$ headers are $20$ bytes.

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.35
Some signalling errors can cause entire ranges of bits in a packet to be overwritten by all $0$s or all $1$s. Suppose all the bits in the packet, including the Internet checksum, are overwritten. Could a packet with all $0$s or all $1$s be a legal $IPv4$ packet? Will the Internet checksum catch that error? Why or why not?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.34
Why does the Offset field in the $IP$ header measure the offset in $8$-byte units? (Hint: Recall that the Offset field is $13$ bits long.)

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.33
What aspect of $IP$ addresses makes it necessary to have one address per network interface, rather than just one per host? In light of your answer, why does $IP$ tolerate point-to-point interfaces that have nonunique addresses or no addresses?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.32b
Suppose a $10$-Mbps Ethernet hub (repeater) is replaced by a $10$-Mbps switch, in an environment where all traffic is between a single server and $N$ "clients." Because all traffic must still traverse the server-switch link, nominally there is no improvement in bandwidth. (b) What other advantages and drawbacks might a switch offer versus a hub?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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12

Peterson Davie 3.32a
Suppose a $10$-Mbps Ethernet hub (repeater) is replaced by a $10$-Mbps switch, in an environment where all traffic is between a single server and $N$ "clients. "Because all traffic must still traverse the server switch link, nominally there is no improvement in bandwidth. (a) Would you expect any improvement in bandwidth? If so, why?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.30
A stage of an $n \times n$ banyan network consists of $(n/2) 2 \times 2$ switching elements. The first stage directs packets to the correct half of the network, the next stage to the correct quarter, and so on, until the packet is routed to the correct output ... of $2 \times 2$ switching elements needed to make an $n \times n$ banyan network. Verify your answer for $n = 8$.

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.29c
Suppose that a switch is designed to have both input and output $FIFO$ buffering. As packets arrive on an input port they are inserted at the tail of the $FIFO$. The switch then tries to forward the packets at the head of each $FIFO$ ... buffering memory can be redistributed freely. Suggest a reshuffling of the buffers that avoids the above problem, and explain why it does so.

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.29c
Suppose that a switch is designed to have both input and output $FIFO$ buffering. As packets arrive on an input port they are inserted at the tail of the $FIFO$. The switch then tries to forward the packets at the head of each $FIFO$ ... buffering memory can be redistributed freely. Suggest a reshuffling of the buffers that avoids the above problem, and explain why it does so.

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.29b
Suppose that a switch is designed to have both input and output $FIFO$ buffering. As packets arrive on an input port they are inserted at the tail of the $FIFO$. The switch then tries to forward the packets at the head of each $FIFO$ to the tail of the appropriate output $FIFO$. (b) What is this behavior called?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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17

Peterson Davie 3.29a
Suppose that a switch is designed to have both input and output $FIFO$ buffering. As packets arrive on an input port they are inserted at the tail of the $FIFO$. The switch then tries to forward the packets at the head of each $FIFO$ to the tail of ... $FIFO$. (a) Explain under what circumstances such a switch can lose a packet destined for an output port whose $FIFO$ is empty

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.28
Suppose a switch is built using a computer workstation and that it can forward packets at a rate of $500,000$ packets per second, regardless (within limits) of size. Assume the workstation uses direct memory access $(DMA)$ to move data in and out of its main ... the $I/O$ bus has a bandwidth of $1$ Gbps. At what packet size would the bus bandwidth become the limiting factor?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.27
Suppose a workstation has an $I/O$ bus speed of $1$ Gbps and memory bandwidth of $2$ Gbps. Assuming $DMA$ is used to move data in and out of main memory, how many interfaces to $100$-Mbps Ethernet links could a switch based on this workstation handle?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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20

Peterson Davie 3.26
Suppose a workstation has an $I/O$ bus speed of $800$ Mbps and memory bandwidth of $2$ Gbps. Assuming direct memory access (DMA) is used to move data in and out of main memory, how many interfaces to $100$-Mbps Ethernet links could a switch based on this workstation handle?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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21

Peterson Davie 3.25
Cell switching methods (like $ATM$) essentially always use virtual circuit switching rather than datagram forwarding. Give a specific argument why this is so (consider the preceding question).

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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Peterson Davie 3.24
What percentage of an $ATM$ link's total bandwidth is consumed by the $ATM$ cell headers? Ignore padding to fill cells or $ATM$ adaptation layer headers.

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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23

Peterson Davie 3.23
Suppose a bridge has two of its ports on the same network. How might the bridge detect and correct this?

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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24

Peterson Davie 3.4
Give forwarding tables for switches $S1$ to $S4$ in Figure 3.46. Each switch should have a default routing entry, chosen to forward packets with unrecognized destination addresses toward OUT. Any specific destination table entries duplicated by the default entry should then be eliminated.

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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25

Peterson Davie 3.3
For the network given in Figure 3.45, give the datagram forwarding table for each node. The links are labeled with relative costs; your tables should forward each packet via the lowest-cost path to its destination.

makhdoom ghaya asked in Computer Networks Apr 24, 2016

by makhdoom ghaya

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26

Peterson Davie 2.44c
Suppose the Ethernet transmission algorithm is modified as follows: After each successful transmission attempt, a host waits one or two slot times before attempting to transmit again, and otherwise backs off the usual way. (c) Suppose the Ethernet transmission ... a host waits one or two slot times before attempting to transmit again, and otherwise backs off the usual way.

makhdoom ghaya asked in Computer Networks Apr 23, 2016

by makhdoom ghaya

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27

Peterson Davie 2.44b
Suppose the Ethernet transmission algorithm is modified as follows: After each successful transmission attempt, a host waits one or two slot times before attempting to transmit again, and otherwise backs off the usual way. (b) Show how the strategy above can now lead to a pair of hosts capturing the Ethernet, alternating transmissions, and locking out a third.

makhdoom ghaya asked in Computer Networks Apr 23, 2016

by makhdoom ghaya

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28

Peterson Davie 2.44a
Suppose the Ethernet transmission algorithm is modified as follows: After each successful transmission attempt, a host waits one or two slot times before attempting to transmit again, and otherwise backs off the usual way. (a) Explain why the capture effect of the previous exercise is now much less likely.

makhdoom ghaya asked in Computer Networks Apr 23, 2016

by makhdoom ghaya

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29

Peterson Davie 2.42c
Suppose the round-trip propagation delay for Ethernet is $46.4 \mu s$. This yields a minimum packet size of $512$ bits ($464$ bits corresponding to propagation delay $+48$ bits of jam signal). (c) If compatibility were not an issue, how might the specifications be written so as to permit a smaller minimum packet size?

makhdoom ghaya asked in Computer Networks Apr 23, 2016

by makhdoom ghaya

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30

Peterson Davie 2.42b
Suppose the round-trip propagation delay for Ethernet is $46.4 \mu s$. This yields a minimum packet size of $512$ bits ($464$ bits corresponding to propagation delay $+48$ bits of jam signal). (b) What are the drawbacks to so large a minimum packet size?

makhdoom ghaya asked in Computer Networks Apr 23, 2016

by makhdoom ghaya

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Recent questions tagged peterson-davie