Homework 3 assignment for ECE671 Posted: 03/01/18 Due: 03/08/18

Transcription

1 ECE67: Homework Homework assignment for ECE67 Posted: //8 Due: /8/8 Note: In all written assignments, please show as much of your work as you can. Even if you get a wrong answer, you can get partial credit if you show your work. If you make a mistake, it will also help the grader show you where you made a mistake. Problem ( Points): Consider the single switch VLAN in Figure, and assume an external router is connected to switch port. Assign IP addresses to the EE and CS hosts and router interface. Trace the steps taken at both the network layer and the link layer to transfer an IP datagram from an EE host to a CS host. Figure For this problem, keep the following in mind: Assume the IP addressing scheme for the EE and CS nodes follows the one indicated in Figure. Assume that the EE VLAN has ID and the CS VLAN has ID. The first figure at the following link gives you an idea of the logical setup for such a scenario: a. Assign IP addresses to the three nodes in the EE VLAN and to the three nodes in the CS VLAN. b. Describe how the router interface has to be set up. What 8.q VLAN ID will be added to a frame that comes from subnet../4? What 8.q VLAN ID will be added to a frame that comes from subnet../4? c. Suppose that host A in EE department would like to send an IP datagram to host B in CS department. What would be the steps taken at both the network layer and the link layer?

2 Figure a. The IP addresses for those three computers (from left to right) in EE department are:...,...,... The subnet mask is../4. b. The IP addresses for those three computers (from left to right) in CS department are:...,...,... The subnet mask is../4. The router s interface card that connects to port can be configured to contain two sub-interface IP addresses:... and... The first one is for the subnet of EE department, and the second one is for the subnet of CS department. Each IP address is associated with a VLAN ID. Suppose... is associated with VLAN, and... is associated with VLAN. This means that each frame that comes from subnet../4 will be added an 8.q tag with VLAN ID, and each frame that comes from../4 will be added an 8.q tag with VLAN ID. c. Suppose that host A in EE department with IP address... would like to send an IP datagram to host B (...) in CS department. Host A first encapsulates the IP datagram (destined to...) into a frame with a destination MAC address equal to the MAC address of the router s interface card that connects to port of the switch. Once the router receives the frame, then it passes it up to IP layer, which decides that the IP datagram should be forwarded to subnet../4 via sub-interface... Then the router encapsulates the IP datagram into a frame and sends it to port. Note that this frame has an 8.q tag VLAN ID. Once the switch receives the frame on port, it knows that this frame is destined to VLAN with ID, so the switch will send the frame to Host B which is in CS department. Once Host B receives this frame, it will remove the 8.q tag. Problem ( Points): a. In general, explain the purpose of the receiver-advertised window in TCP. b. Assume a TCP sender transmits 4 TCP segments with respective sequence numbers, 4, 6, 48. The sender receives four acknowledgements with the following sequence numbers, 4, 4, 4, 4. Complete Figure to show what TCP segments are exchanged between sender and receiver.

3 ECE67: Homework Seq #: Figure

4 Seq #: Seq #:6 X Seq #:48 duplicate s Resend 4 Seq #:6 Problem ( Points): Consider the following network. With the indicated link costs, use Djikstra s shortestpath algorithm to compute the shortest path from x to all network nodes. Show how the algorithm works by computing a table below.

5 ECE67: Homework 5 z 8 x 6 y 5 7 v 4 t 5 5 w 4 u Step N D(t),p(t) D(u),p(u) D(v),p(v) D(w),p(w) D(y),p(y) D(z),p(z) x,x 5,x 6,x 8,x Step N D(t),p(t) D(u),p(u) D(v),p(v) D(w),p(w) D(y),p(y) D(z),p(z) x,x 5,x 6,x 8,x xv 7,v 8,v - 5,x 6,x 8,x xvw 7,v 8,v - - 6,x 8,x xvwy 7,v 8,v ,x 4 xvwyz 7,v 8,v xvwyzt - 8,v xvwyztu Problem 4 ( Points): Consider the network shown below, and assume that each node initially knows the cost to each of its neighbors. Consider the distance-vector algorithm and show the distance table entries at node z. (Please show the intermediate steps until convergence is reached!)

6 u v 6 z y x v From x z 6 v From x z 6 v 6 From x z 7 5 5

7 ECE67: Homework 7 v 5 From x 4 z v 5 From x 4 z Problem 5 (5 Points): a. Consider a datagram network using 8-bit host address. Suppose a router uses longest prefix matching and has the following forwarding table: Prefix Match Interface For each of the four interfaces, give the associated range of destination host addresses and the number of addresses in the range. b. In the following classful IP addresses, find the class of each address: a. b c c. In the classless IP address, what is the network address if one of it s address is: /7 a. Destination Address Range Link Interface

8 number of addresses for interface = 6 =64 number of addresses for interface = 5 = number of addresses for interface = =+64 =96 number of addresses for interface = 6 =64 b. The leading bit is, Class A The first byte is 7, which falls between 4 to 9, Class D The first byte is 4, which falls between to 7, Class A c. The prefix length is 7 -> keep the first 7 bits as is and change the remaining 5 bits to s. The last 5 bits affect only the last byte. The last byte is. By setting the last 5 bits to s, we get =64 So network address is : /7 Problem 5 (5 Points): a. Given the following forwarding table, create a binary tree that allows longest prefix match lookup. Interface Prefix A / (F) B /4 (D) C / (E) D / (C) E / (A) F /4 (B) b. In that binary graph you created show how a search for the appropriate interface for address would be performed. Please indicate the individual steps in the correct order. c. Create a tree in which always two bits per step are looked up (Trie).

9 ECE67: Homework 9 a. st E nd D A F X 5 th B C b. see a.) c. A F E E E D B C C