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Prb#5
- 1. Name:Ahmed Osama Osman IDnumber :11010214464 Date: November 19th 2014 Problem # 5 Solutions Q1. In this question, we consider some of the pros and cons of virtual-circuit and datagram networks. a.) Suppose that routers were subjected to conditions that might cause them to fail fairly often. Would this argue in favor of a VC or datagram architecture? Why? b.) Suppose that a source node and a destination require that a fixed amount of capacity always be available at all routers on the path between the source and destination node, for the exclusive use of traffic flowing between this source and destination node. Would this argue in favor of a VC or datagram architecture? Why? c.) Suppose that the links and routers in the network never fail and that routing paths used between all source/destination pairs remains constant. In this
- 2. scenario, does aVC or datagram architecture have more control traffic overhead? Why? Solution: a) Datagram: In the case of connection-oriented network, every router failure will involvethe routing of that connection. At a minimum, this will require the router that is upstreamfrom the failed router to establish a new downstream part of the path to the destinationnode, with all of the requisite signaling involved in setting up a path. Moreover, all of therouters on the initial path that are downstream from the failed node must take down thefailed connection, with all of the requisite signaling involved to do this. Whereas in thecase of connectionless datagram network, no signaling is required to either set up a newdownstream path or take down the old downstream path. b) VC: In this case in order for a router to maintain an available fixed amount of capacity onthe path between the source and destination node for that source-destination pair, it wouldneed to know the characteristics of the traffic from all sessions passing through that link.That is, the router must have per-session state in the router. This is possible in aconnection-oriented network, but not with a connectionless network. Thus, a connection-oriented VC network would be preferable.
- 3. c) In this scenario,datagram architecture has more control traffic overhead. This is due tothe various packet headers needed to route the datagrams through the network. But in VC Reference : http://www.scribd.com/doc/221350919/Assignment-Chap-4#scribd Q2. Consider the network below. a.) Suppose that this network is a datagram network. Show the forwarding table in router A, such that all traffic destined to host H3 is forwarded through interface 3. b.) Suppose that this network is a11001000 10010001 01010001 01010101 11100001 01000000 11000011 00111100 11100001 10000000 00010001 01110111 datagram network. Can you write down a forwarding table in router A, such that all traffic from H1 destined to host H3 is forwarded through interface 3, while all traffic from H2 destined to host H3 is forwarded through interface 4? (Hint: this is a trick question.) c.) Now suppose that this network is a virtual circuit network and that there is one ongoing call between H1
- 4. and H3, andanother ongoing call between H2 and H3. Write down a forwarding table in router A, such that all traffic from H1 destined to host H3 is forwarded through interface 3, while all traffic from H2 destined to host H3 is forwarded through interface 4. d.) Assuming the same scenario as (c), write down the forwarding tables in nodes B, C, and D. Solution: a. Destination Address H3 Link Interfac 3 b. No, because forwarding rule is only based on destination address. c.Incoming interface Incoming VC Outgoing Interface 1 12 3 2 63 4 outgoing vc 22 18
- 5. refrences: file:///C:/Users/A/Downloads/CS132_EECS148_ProblemSet3_Solution.pdf Q3. Consider a datagramnetwork using 32-bit host addresses. Suppose a router has four links, numbered 0 through 3, and packets are to be forwarded to the link interfaces as follows: Destination Address Range Link Interface 11100000 00000000 00000000 00000000 Through 0 11100000 00111111 11111111 11111111 11100000 01000000 00000000 00000000 Through 1 11100000 01000000 11111111 11111111 11100000 01000001 00000000 00000000 Through 2 11100001 01111111 11111111 11111111 Otherwise 3
- 6. a.) Provide aforwarding table that has five entries, uses longest prefix matching, and forwards packets to the correct link interfaces. Prefix Match Link Interface 11100000 00 0 11100000 01000000 1 11100001 2 11100000 01000001 2 Otherwise 3 Reference : http://www.scribd.com/doc/221350919/Assignment-Chap-4#scribd b.) Describe how your forwarding table determines the appropriate link interface for datagram’s with destination addresses: 11001000 10010001 01010001 01010101 11100001 01000000 11000011 00111100 11100001 10000000 00010001 01110111 Solution: a) 0 1 2 3 b)
- 7. Address Short Answer 11001000 1001000101010001 01010101 11100001 01000000 11000011 00111100 11100001 10000000 00010001 01110111 Q4. Consider a router that interconnects three subnets: Subnet 1, Subnet 2, and Subnet 3. Suppose all of the interfaces in each of these three subnets are required to have the prefix 223.1.17/24. Also suppose that Subnet 1 is required to support at least 60 interfaces, Subnet 2 is to support at least 90 interfaces, and Subnet 3 is to support at least 12 interfaces. Provide three network addresses (of the form a.b.c.d/x) that satisfy these constraints. Solution: 223.1.17/24 (Network ID) 11011111 00000001 00010001 ???????? Subnet 1 11011111 00000001 00010001 0??????? Subnet 2 11011111 00000001 00010001 10?????? Subnet 3 11011111 00000001 00010001 11?????? All 223.1.17/24 Subnet 1 223.1.17.0/25
- 8. Subnet 2 223.1.17.128/26 Subnet3 223.1.17.192/26 Reference: https://uniteng.com/wiki/lib/exe/fetch.php?media=classlog:computernetwork:hw4_report.pdf Q5. Consider a subnet with prefix 128.119.40.128/26. Give an example of one IP address (of form xxx.xxx.xxx.xxx) that can be assigned to this network. Suppose an ISP owns the block of addresses of the form 128.119.40.64/26. Suppose it wants to create four subnets from this block, with each block having the same number of IP addresses. What are the prefixes (of form a.b.c.d/x) for the four subnets? Solution: IP address range: 128.119.40.128 ‐ 128.119.40.191 Note: 128.119.40.128(last 8 bits: 10000000, reserved address), 128.119.40.191(last 8 bits: 10111111, reserved address, broadcast) Four subnets: 128.119.40.64/28 128.119.40.80/28 128.119.40.96/28 128.119.40.112/28
- 9. Reference: https://uniteng.com/wiki/lib/exe/fetch.php?media=classlog:computernetwork:hw4_report.pdf Q6. Use the whoisservice at the American Registry for Internet Numbers(http://www.arin.net/whois) to determine the IP address blocks for three universities. Can the whois services be used to determine with certainty the geographical location of a specific IP address? Use www.maxmind.com to determine the locations of the Web servers at each of these universities. Solution: Geographic locations of where these IP addresses are not tracked and provided by arin’s whois service since this service only give contact and registration information, autonomous system numbers (ASN), organizations or customers that are associated with these resources, and related Points of Contact (POC). 1. Arizona State University. 2. University of Arizona. 3. Franklin W. Olin College of Engineering Reference: https://uniteng.com/wiki/lib/exe/fetch.php?media=classlog:computernetwork:hw4_report.pdf