Computer Networking: A Top-Down Approach Featuring The .
Computer Networking: A Top-Down ApproachFeaturing the InternetSolutions to Review Questions and ProblemsVersion Date: December 1, 2002This document contains the solutions to review questions and problems for the 2ndedition of Computer Networking: A Top-Down Approach Featuring the Internet by JimKurose and Keith Ross. These solutions are being made available to instructors ONLY.Please do NOT copy or distribute this document to others (even other instructors). We’llbe happy to provide a copy (up-to-date) of this solution manual ourselves to anyone whoasks.All material copyright 1996-2002 by J.F. Kurose and K.W. Ross. All rights reserved
Chapter 1 Review Questions1. There is no difference. Throughout this text, the words “host” and “end system” areused interchangeably. End systems include PCs, workstations, Web servers, mailservers, Internet-connected PDAs, WebTVs, etc.2. Suppose Alice, an ambassador of country A wants to invite Bob, an ambassador ofcountry B, over for dinner. Alice doesn’t simply just call Bob on the phone and say,“come to our dinner table now”. Instead, she calls Bob and suggests a date and time.Bob may respond by saying he’s not available that particular date, but he is availableanother date. Alice and Bob continue to send “messages” back and forth until theyagree on a date and time. Bob then shows up at the embassy on the agreed date,hopefully not more than 15 minutes before or after the agreed time. Diplomaticprotocols also allow for either Alice or Bob to politely cancel the engagement if theyhave reasonable excuses.3. A networking program usually has two programs, each running on a different host,communicating with each other. The program that initiates the communication is theclient. Typically, the client program requests and receives services from the serverprogram.4. The Internet provides its applications a connection-oriented service (TCP) and aconnectionless service (UDP). Each Internet application makes use of one these twoservices. The two services will be discussed in detail in Chapter 3. Some of theprinciple characteristics of the connection-oriented service are: Two end-systems first “handshake” before either starts to send application data tothe other.Provides reliable data transfer, i.e., all application data sent by one side of theconnection arrives at the other side of the connection in order and without anygaps.Provides flow control, i.e., it makes sure that neither end of a connectionoverwhelms the buffers in the other end of the connection by sending to manypackets to fast.Provides congestion control, i.e., regulates the amount of data that an applicationcan send into the network, helping to prevent the Internet from entering a state ofgrid lock.The principle characteristics of connectionless service are: No handshakingNo guarantees of reliable data transferNo flow control or congestion control
5. Flow control and congestion control are two distinct control mechanisms with distinctobjectives. Flow control makes sure that neither end of a connection overwhelms thebuffers in the other end of the connection by sending to many packets to fast.Congestion control regulates the amount of data that an application can send into thenetwork, helping to prevent congestion in the network core (i.e., in the buffers in thenetwork routers).6. The Internet’s connection-oriented service provides reliable data transfer by usingacknowledgements and retransmissions. When one side of the connection doesn’treceive an acknowledgement (from the other side of the connection) for a packet ittransmitted, it retransmits the packet.7. A circuit-switched network can guarantee a certain amount of end-to-end bandwidthfor the duration of a call. Most packet-switched networks today (including theInternet) cannot make any end-to-end guarantees for bandwidth.8. In a packet switched network, the packets from different sources flowing on a link donot follow any fixed, pre-defined pattern. In TDM circuit switching, each host getsthe same slot in a revolving TDM frame.9. At time t0 the sending host begins to transmit. At time t1 L/R1, the sending hostcompletes transmission and the entire packet is received at the router (no propagationdelay). Because the router has the entire packet at time t1, it can begin to transmit thepacket to the receiving host at time t1. At time t2 t1 L/R2, the router completestransmission and the entire packet is received at the receiving host (again, nopropagation delay). Thus, the end-to-end delay is L/R1 L/R2.10. In a VC network, each packet switch in the network core maintains connection stateinformation for each VC passing through it. Some of this connection stateinformation is maintained to a VC-number translation table. (See page 25)11. The cons of VCs include (i) the need to have a signaling protocol to set-up and teardown the VCs; (ii) the need to maintain connection state in the packet switches. Forthe pros, some researchers and engineers argue that it is easier to provide QoSservices - such as services that guarantee a minimum transmission rate or servicesthat guarantee maximum end-to-end packet delay – when VCs are used.12. One advantage of message segmentation is that it allows for pipelined transmissionover a series of links, as discussed in the text. (See also online Java applet.) Imaginethe store-and-forward delays in sending an MP3 or a DVD video as a single message!Another advantage is that without it, small messages can get stuck behind largemessages in router buffers.13. 1. Dial-up modem over telephone line: residential; 2. DSL over telephone line:residential or small office; 3. Cable to HFC: residential; 4. 100 Mbps switched
Etherent: company; 5. Wireless LAN: mobile; 6. Cellular mobile access (for example,WAP): mobile14. A tier-1 ISP connects to all other tier-1 ISPs; a tier-2 ISP connects to only a few ofthe tier-1 ISPs. Also, a tier-2 ISP is a customer of one or more tier-115. A POP is a group of one or more routers in an ISPs network at which routers in otherISPs can connect. NAPs are localized networks at which many ISPs (tier-1, tier-2 andlower-tier ISPs) can interconnect.16. HFC bandwidth is shared among the users. On the downstream channel, all packetsemanate from a single source, namely, the head end. Thus, there are no collisions inthe downstream channel.17. Ethernet LANs have transmission rates of 10 Mbps, 100 Mbps, 1 Gbps and 10 Gbps.For an X Mbps Ethernet (where X 10, 100, 1,000 or 10,000), a user cancontinuously transmit at the rate X Mbps if that user is the only person sending data.If there are more than one active user, then each user cannot continuously transmit atX Mbps.18. Ethernet most commonly runs over twisted-pair copper wire and “thin” coaxial cable.It also can run over fibers optic links and thick coaxial cable.19. Dial up modems: up to 56 Kbps, bandwidth is dedicated; ISDN: up to 128 kbps,bandwidth is dedicated; ADSL: downstream channel is .5-8 Mbps, upstream channelis up to 1 Mbps, bandwidth is dedicated; HFC, downstream channel is 10-30 Mbpsand upstream channel is usually less than a few Mbps, bandwidth is shared.20. The delay components are processing delays, transmission delays, propagationdelays, and queuing delays. All of these delays are fixed, except for the queuingdelays, which are variable.21. Five generic tasks are error control, flow control, segmentation and reassembly,multiplexing, and connection setup. Yes, these tasks can be duplicated at differentlayers. For example, error control is often provided at more than one layer.22. The five layers in the Internet protocol stack are – from top to bottom – theapplication layer, the transport layer, the network layer, the link layer, and thephysical layer. The principal responsibilities are outlined in Section 1.7.2.23. Routers process layers 1 through 3. (This is a little bit of a white lie, as modernrouters sometimes act as firewalls or caching components, and process layer four aswell.)Chapter 1 Problems
Problem 1.There is no single right answer to this question. Many protocols would do the trick.Here's a simple answer below:Messages from ATM machine to ServerMsg name-------HELO userid PASSWD passwd BALANCEWITHDRAWL amount BYEpurpose------Let server know that there is a card in theATM machineATM card transmits user ID to ServerUser enters PIN, which is sent to serverUser requests balanceUser asks to withdraw moneyuser all doneMessages from Server to ATM machine (display)Msg name-------PASSWDOKERRAMOUNT amt BYEpurpose------Ask user for PIN (password)last requested operation (PASSWD, WITHDRAWL)OKlast requested operation (PASSWD, WITHDRAWL)in ERRORsent in response to BALANCE requestuser done, display welcome screen at ATMCorrect operation:clientserverHELO (userid)-------------- ------------PASSWD passwd -------------- ------------BALANCE-------------- ------------WITHDRAWL amt -------------- (check if valid userid)PASSWD(check password)OK (password is OK)AMOUNT amt check if enough to coverwithdrawlOK ------------ATM dispenses BYE-------------- ------------- BYEIn situation when there's not enough money:HELO (userid)-------------- (check if valid userid) ------------- PASSWDPASSWD passwd -------------- (check password)
------------- OK (password is OK)-------------- ------------- AMOUNT amt WITHDRAWL amt -------------- check if enough towithdrawl ------------- ERR (not enough funds)error msg displayedno given outBYE-------------- ------------- BYEBALANCEcoverProblem 2.a) A circuit-switched network would be well suited to the application described, becausethe application involves long sessions with predictable smooth bandwidth requirements.Since the transmission rate is known and not bursty, bandwidth can be reserved for eachapplication session circuit with no significant waste. In addition, we need not worrygreatly about the overhead costs of setting up and tearing down a circuit connection,which are amortized over the lengthy duration of a typical application session.b) Given such generous link capacities, the network needs no congestion controlmechanism. In the worst (most potentially congested) case, all the applicationssimultaneously transmit over one or more particular network links. However, since eachlink offers sufficient bandwidth to handle the sum of all of the applications' data rates, nocongestion (very little queueing) will occur.Problem 3.a) We can n connections between each of the four pairs of adjacent switches. This givesa maximum of 4n connections.b) We can n connections passing through the switch in the upper-right-hand corner andanother n connections passing through the switch in the lower-left-hand corner,giving a total of 2n connections.Problem 4.Tollbooths are 100 km apart, and the cars propagate at 100km/hr. A tollbooth services acar at a rate of one car every 12 seconds.(a) There are ten cars. It takes 120 seconds, ortwo minutes, for the first tollbooth to service the 10 cars. Each of these cars have apropagation delay of 60 minutes before arriving at the second tollbooth. Thus, all the carsare lined up before the second tollbooth after 62 minutes. The whole process repeats itselffor traveling between the second and third tollbooths. Thus the total delay is 124 minutes.(b) Delay between tollbooths is 7*12 seconds plus 60 minutes, i.e., 61 minutes and 24seconds. The total delay is twice this amount, i.e., 122 minutes and 48 seconds.Problem 5.
a) The time to transmit one packet onto a link is ( L h ) / R . The time to deliver the firstof the M packets to the destination is Q ( L h ) / R . Every ( L h ) / R seconds a newpacket from the M 1 remaining packets arrives at the destination. Thus the total latencyist s (Q M 1)( L h ) / R .b) (Q M 1)( L 2h ) / Rc) The time required to transmit the message over one link is ( LM 2h ) / R . The timerequired to transmit the message over Q links is Q ( LM 2h ) / R .d) Because there is no store-and-forward delays at the links, the total delay ist s ( h ML ) / R .Problem 7.First assume that F / S is an integer. The delay isFh 1 S h F, 1 F S h S R S R where h 40.If F / S is not an integer, then the delay is F F S h1 S h F F S F S 2h h . 1 RR R S S In general, the delay is1 F F h S h R S which is approximately equal to1 hF .F h S R S Taking the derivative of S hFand setting to 0 givesSS min Fh .Problem 8.a) d prop m / s seconds.b) d trans L / R seconds.c) d end to end (m / s L / R ) seconds.d) The bit is just leaving Host A.e) The first bit is in the link and has not reached Host B.
f) The first bit has reached Host B.g) Want100L(2.5 108 ) 893 km.m S 28 10 3RProblem 9.Consider the first bit in a packet. Before this bit can be transmitted, all of the bits in thepacket must be generated. This requires48 8sec 6msec.64 10 3The time required to transmit the packet is48 8sec 384 µ sec.1 10 6Propagation delay 2 msec.The delay until decoding is6msec 384 µ sec 2msec 8.384msecA similar analysis shows that all bits experience a delay of 8.384 msec.Problem 10.a) 10 users can be supported because each user requires one tenth of the bandwidth.b) p 0.1 . 40 40 nc) p n (1 p ) . n 9 40 40 nd) 1 p n (1 p ).n 0 n We use the central limit theorem to approximate this probability. Let X j be independentrandom variables such that P (X j 1) p .P ( “11 or more users” 40 P X j 10 j 1 40 j 1 ) 1 P X j 10 40 X j 4j 1 P 40 0.1 0.9 6 40 0.1 0.9
6 P Z P (Z 3.16)3.6 0.999when Z is a standard normal r.v. Thus P ( “10 or more users” ) 0.001 .Problem 11.a) 10,000M M M nb) p n (1 p )n N 1 n Problem 12.It takes LN / R seconds to transmit the N packets. Thus, the buffer is empty when abatch of N packets arrive.The first of the N packets has no queueing delay. The 2nd packet has a queueing delayof L / R seconds. The n th packet has a delay of ( n 1) L / R seconds.The average delay isL 11 N( n 1) L / R N n 1RNN 1L 1 ( N 1) N L ( N 1). 22R n R Nn 0Problem 13.a) The transmission delay is L / R . The total delay isILL L/R R(1 I ) R 1 Ib) Let x L / R .xTotal delay 1 axProblem 14.qa) There are Q nodes (the source host and the N 1 routers). Let d procdenote theprocessing delay at the q th node. Let R q be the transmission rate of the q th link and letqqd trans L / R q . Let d propbe the propagation delay across the q th link. ThenQ[]qqqd end to end d proc d trans d prop.q 1
qb) Let d queuedenote the average queueing delay at node q . ThenQ[]qqqqd end to end d proc d trans d prop d queue.q 1Problem 15.The command:traceroute -q 20 www.eurecom.frwill get 20 delay measurements from the issuing host to the host, www.eurecom.fr. Theaverage and standard deviation of these 20 measurements can then be collected. Do yousee any differences in your answers as a function of time of day?Problem 16.a) 40,000 bitsb) 40,000 bitsc) the bandwidth-delay product of a link is the maximum number of bits that can be inthe linkd) 1 bit is 250 meters long, which is longer than a football fielde) s/RProblem 17.25 bpsProblem 18.a) 40,000,000 bitsb) 400,000 bitsc) .25 metersProblem 19.a) ttrans tprop 400 msec 40 msec 440 msecb) 10 * (ttrans 2 tprop) 10*(40 msec 80 msec) 1.2 secProblem 20.a) 150 msecb) 1,500,000 bitsc) 600,000,000 bitsProblem 21.
Let’s suppose the passenger and his/her bags correspond to the data unit arriving to thetop of the protocol stack. When the passenger checks in, his/her bags are checked, and atag is attached to the bags and ticket. This is additional information added in theBaggage layer if Figure 1.20 that allows the Baggage layer to implement the service orseparating the passengers and baggage on the sending side, and then reuniting them(hopefully!) on the destination side. When a passenger then passes through security, andadditional stamp is often added to his/her ticket, indicating the at the passenger haspassed through a security check. This information is used to ensure (e.g., by later checksfor the security information) secure transfer of people.
Chapter 2 Review Questions1. The Web: HTTP; file transfer: FTP; remote login: Telnet; Network News: NNTP; email: SMTP.2. The host that initiates the communication session is the client.3. The IP address of the destination hosts and the port numbers of the destination socket.4. You probably use a browser and a mail reader on a daily basis. You may also use anFTP user agent, a Telnet user agent, an audio/video player user agent (such as a RealNetworks player), an instant messaging agent, a P2P file-sharing agent, etc.6. A protocol uses handshaking if the two communicating entities first exchange controlpackets before sending data to each other. SMTP uses handshaking at the applicationlayer whereas HTTP does not.7. The applications that use those protocols require that all application data is receivedin the correct order and without gaps. TCP provides this service whereas UDP doesnot.8. In both cases, the site must keep a database record for the user. With HTTPauthentication, the user first registers with the site. During each subsequent visit, theuser provides a username and password, which allows the site to identify the user andupdate the user’s record. With cookies, the user does not explicitly provide ausername and password each time it visits the site. However, browser identifies theuser by sending the user’s cookie number each time the user accesses the site.10. In persistent HTTP without pipelining, the browser first waits to receive a HTTPresponse from the server before issuing a new HTTP request. In persistent HTTP withpipelining, the browser issues requests as soon as it has a need to do so, withoutwaiting for response messages from the server.11. FTP uses two parallel TCP connections, one connection for sending controlinformation (such as a request to transfer a file) and another connection for actuallytransferring the file. Because the control information is not sent over the sameconnection that the file is sent over, FTP sends control information out of band.12. Message is sent from Alice’s host to her mail server over HTTP. Alice’s mail serverthen sends the message to Bob’s mail server over SMTP. Bob then transfers themessage from his mail server to his host over POP3.13. Will contain the header line Content-Type: application/msexcel .15. With download and delete, after a user retrieves its messages from a POP server, themessages are deleted. This poses a problem for the nomadic user, who may want to
access the messages from many different machines (office PC, home PC, etc.). In thedownload and keep configuration, messages are not deleted after the user retrievesthe messages. This can also be inconvenient, as each time the user retrieves the storedmessages from a new machine, all of non-deleted messages will be transferred to thenew machine (including very old messages).16. See online Java applet.17. A host’s authoritative name server provides the “official” translation of a hostname toan IP address (among other things). A host’s local name server is a proxy to the DNSsystem: the host first queries its local name server for a mapping; the local nameserver then obtains the mapping on the behalf of the querying host.18. Yes an organization’s mail server and Web server can have the same alias for a hostname. The MX record is used to map the mail server’s host name to its IP address.19. You can find a link to nslookup at the online site.20. With the UDP server, there is no welcoming socket, and all data from different clientsenters the server through this one socket. With the TCP server, there is a welcomingsocket, and each time a client initiates
Computer Networking: A Top-Down Approach Featuring the Internet Solutions to Review Questions and Problems Version Date: December 1, 2002 This document contains the solutions to review questions and problems for the 2nd edition of Computer Networking: A Top-Down Approach Featuring the Internet by Jim Kurose and Keith Ross.
9788177584752 Halsall / Kulkarni Computer Networking and the Internet, 5e 5 909.00 2006 9788131711453 Keshav An Engineering Approach to Computer Networking 1 959.00 2007 9789332585492 Kurose Computer Networking: A Top-Down Approach, 6/e 6 879.00 2017 9788131709351 Stallings Computer N
Dell EMC Networking S4148F-ON 2.2 Dell EMC Networking S4248FB-ON The Dell EMC Networking S4248FB-ON is a 1-RU, multilayer switch with forty 10GbE ports, two 40GbE ports, and six 10/25/40/50/100GbE ports. Two S4248FB-ON switches are used as leaf switches in the examples in this guide. Dell EMC Networking S4248FB-ON 2.3 Dell EMC Networking Z9100-ON
Networking Fundamentals » Volume 5, TCP/IP Networking Page 3 SECTIoN 2 Networking Models The OSI model and the TCP/IP model are the prevalent methods to describe the interdependency of networking protocols. Both of these are conceptual models only and simply describe, not prescribe how networking
Networking 101 . Agenda Introduction Networking Defined Purpose of Networking Types of Networking Meet & Greets Recap Disney Agenda . Did You Know? Approximately 70 percent of all jobs are found through networking Most people you meet have at least 250 contacts
Docker Networking with Linux Guillaume Urvoy-Keller Reference Scenario Basic tools: bridges, VETH Basic tools 2: Networking in namespaces Minilab : Anatomy of a docker container networking environment (45 min) Docker (host-level) Networking Docker Networking Model Docker Swarm Docker Network Overlay Sources documents Laurent Bernaille blog .
1.2 Advantages of computer networking Basically, Networking is a connection between two or more computers. The main purpose of a network is to share the information among different users. Figure 1.1 shows the networking of two computers: Fig 1.1 Computer in network Computer network consist of the following:
of Computer Networking: A Top-Down Approach by Jim Kurose and Keith Ross. These solutions are being made available to instructors ONLY. Please do NOT copy or distribute this document to others (even other instructors). Please do not post any solutions on a publicly-available Web site. We’ll be happy to provide a copy (up-to-date) of this solution
Banking on Cloud A discussion paper by the BBA and Pinsent Masons Outside of banking, public cloud computing has proven to be a driver of innovation, enabling new competitors, products and more flexible business models. By comparison, banks have been understandably slower in migrating products and services and leveraging the benefits of the public cloud, taking time first to focus on assessing .
