CSC 344: Cmputer Netwrks Review Questins 1. Select the crrect answer amng the chices by placing a checkmark next t the right statement. (i). ARP (Address Reslutin Prtcl) is used t btain IP address fr a MAC address ARP (Address Reslutin Prtcl) is used t btain MAC address fr an IP address (ii). (iii). IP datagram packet is paylad f a TCP segment TCP segment is paylad f an IP datagram In the TCP flw cntrl is dne t ensure that there is n packet lss. In the TCP flw cntrl is dne t ensure the receiver buffer des nt ver flw. (iv). If a TCP server were t supprt 100 simultaneus cnnectins, each frm a different client, hw many sckets wuld the TCP server have? 100 sckets 200 sckets 101 sckets (v). DNS (dmain name service) uses TCP prtcl fr the transprt layer t enquire the IP address frm a server UDP prtcl fr the transprt layer t enquire the IP address frm a server (vi). The length f MAC address (in number f bits) is? Varies frm 32 bits t 64 bits 8 bits 16 bits 32 bits 48 bits 64 bits (vii). Which f the fllwing statement is true. All hsts n the same subnet are cnfigured with the same subnet mask. Each hst has its wn distinct mask
(viii). The maximum length f an Ethernet frame (in number f bytes) is? 100 bytes 1000 bytes 1500 bytes (ix). In the Netwrk Layer Prtcl IPv4, the IP datagram has a TTL (time t-live) field. The value f this field is? the length f time after which the datagram is destryed. The length f time recrd is maintained in the DNS server The number f hps after which the datagram is destryed (x). In DHCP, the field TTL (time t-live) field is? The length f time fr which the IP address is valid. The length f time recrd is maintained in the DNS server The number f hps after which the datagram is destryed (x). In DNS, the field TTL (time t-live) field is? The length f time fr which the IP address is valid. The length f time recrd is maintained in the DNS server The number f hps after which the datagram is destryed (xii). If an IP address is 123.1.1.0/24 then hw many hsts can there be within the subnet? 32 64 128 256 512 (xiii). NAT enabled ruters are used fr. Ethernet cnnectin within a small Netwrk Masquerading multiple devices behind a single IP address Ruting IP datagrams in internet
(xiv). In a Ethernet, the hsts which are cnnected by a switch, Share the cllisin dmain D nt share the cllisin dmain (xv). In case f TCP prtcl, errr in a TCP segment is detected by the sender which f the fllwing The sender receives a duplicate psitive acknwledgement The sender receives a negative acknwledgement The sender des nt receive any acknwledgement within the time ut interval 2. In the CSMA/CD: Ethernet multiple access prtcl whenever there is a cllisin the adapter waits fr K.512 bit times after a cllisin. Fr K = 20 hw lng des an adapter wait until returning t sense the channel fr retransmissin in a 10Mbps Ethernet? 3. Cnsider an IP subnet with prefix 129.17.129.97/25. Prvide the range f IP addresses (f the frm xxx.xxx.xxx.xxx t yyy.yyy.yyy.yyy) that can be assigned t hsts in the subnet. 4. Fur hsts A, B, C, and D are cnnected by an Ethernet. In the fllwing space-time diagram, identify the times (place an x mark and identify the time n time axis similar t t0 and t1) when the ndes A, B, C and D detect cllisin.
5. Hst A and B are directly cnnected with a 100 Mbps link. There is ne TCP cnnectin between tw hsts, and A is sending t B an enrmus file ver this cnnectin. Hst A can send int its TCP cnnectin at a rate f 80 Mbps, but hst B can read ut f it s receive buffer at a maximum rate f 40 Mbps. Which f the tw mechanisms in TCP will g int effect? (place a checkmark )
Flw Cntrl Cngestin Cntrl 6. T cntrl Cngestin in TCP tw variables cwnd, rwnd and are used by sender. The variable cwnd refers t the size f cngestin windw, and rwnd is the size f receiver windw, then which f the fllwing inequality is true. LastByteSent LastByteAcked <= min{cwnd, rwnd} LastByteSent LastByteAcked <= max{cwnd, rwnd} LastByteSent LastByteReceived <= min{cwnd, rwnd} LastByteSent LastByteReceived <= max{cwnd, rwnd} 7. Cnsider a 1 Gbps Ethernet. T have an efficiency f 80% what is the maximum distance between tw ndes? Efficiency f Ethernet is given by the fllwing Frmula: Efficiency = 1 1 + 5d prp dtrans Assume a frame length f 1500 bytes and that there are n repeaters. Als assume the prpagatin speed f 2 10 8 m/sec 8. Suppse users share a 1 Mbps link. Als suppse each user requires 500 kbps when transmitting, but each user transmits nly 10 percent f the time. (See the discussin n Packet switching Versus Circuit Switching in textbk page 30). When circuit switching is used hw many users can be supprted. Fr the remainder f the questin assume packet switching is used. Why will there be n queueing delay if tw r fewer users transmit simultaneusly? What is the prbability that a user is transmitting? Suppse there are three users what is the prbability that at any given time all three users are transmitting. Suppse that there are five users, what is the prbability that three f them are transmitting. (use prperty f binmial prbability) Suppse that there are five users, what is the prbability that less than three f them are transmitting. (use prperty f binmial prbability)
Suppse that there are five users, what is the prbability that mre than three f them are transmitting. (use prperty f binmial prbability) 9. Suppse within yur Web brwser yu click n a link t btain a Web page. Suppse that the IP address f the URL is cached in yur lcal hst, s that DNS lk up is nt necessary. Dente RTT as the rund trip time between the lcal hst and the server cntaining the Web page. Assume the Web page cnsists f a base html file and three small images. Assume the transmissin time fr all the bjects is negligible in cmparisn with the RTT. Hw much time elapses (in terms f RTTs) frm the time user clicks n the link until the client receives the entire Web page fr each f the fllwing? Nn-persistent HTTP with n parallel cnnectin. Nn-persistent HTTP with up t five parallel cnnectin. Persistent HTTP with pipelining. 10. Figure 3.53 is cpied belw, Fr each f the TCP Tahe and TCP Ren prtcls experiencing the behavir shwn, answer the fllwing questins. Give ne line justifying yur answer. a. Identify the intervals f time when TCP slw start is perating. b. Identify the intervals f time when TCP cngestin avidance is perating. c. Identify the Transmissin rund when triple duplicate ACK event ccurs. d. What is the initial value f at the first transmissin rund? e. What is the initial value f at the 10th transmissin rund?