Layers four and five of the Internet protocol stack are implemented in the end systems but not in the routers in the network core.
True
False
With ADSL, each subscriber gets more downstream bandwidth than upstream bandwidth.
Twisted-pair cooper wire is no longer present in computer networks.
4. Two packets A and B are sent in that order through a connection-oriented communication network. They could arrive at the destination:
a. in any order, after having traversed the same route.
b. only in the order A-B, after possibly having traversed different routes.
c. in any order, after possibly having traversed different routes.
d. only in the order A-B, after having traversed the same route.
5. Two packets A and B are sent in that order through a connectionless communication network. They will arrive at the destination:
a. in any order, after possibly having traversed different routes.
b. in the order A-B, after having traversed the same route.
c. in any order, after having traversed the same route.
d. in the order A-B, after possibly having traversed different routes.
6. The Internet received its name in the 1980s because:
a. it was an interim (temporary) design of what it later became, but the name stuck.
b. it was meant to be a network internal to the United States Department of Defense.
c. it consisted of many interconnected networks.
d. it achieved international scope with the addition of the City University of London.
DNS lookups often involve a combination of recursive and iterative queries.
The Date: header in the HTTP response message indicates when the object in the response was last modified.
Skype relay nodes are typically peers under the control of Skype users.
The process that sends messages into, and receives messages from, the network through a software interface is called a socket.
In a P2P File Distribution architecture, the server must sequentially send (upload) file copies.
12. SMTP is used to:
a. to transfer messages from one mail server to another.
b. to transfer messages from mail server to a user agent.
c. to define the format of message headers.
d. all of the above.
13. Suppose a DNS resource record has Type=MX. Then:
a. Value is the hostname of the DNS server that is authoritative for Name.
Value is the IP address of the mail server that has the alias hostname Name.
c. Value is the hostname of the mail server that has the alias hostname Name.
d. none of the above.
14. Local DNS name servers:
a. cache resource records, but discard them after a period of time that is on the order of a few days.
b. cache resource records and never discard them.
c. obtain resource records from Web caches.
d. never cache resource records.
Consider an HTTP Web server using persistent connections. Suppose the server spawns a separate process for each client that connects to the server. Then each of these spawned processes will have different server port numbers.
The size of the TCP RcvWindow never changes throughout the duration of the connection.
17. When a TCP segment arrives to a host, the socket to which the segment is directed depends on
a. the source IP address of the datagram that encapsulated the segment.
b. the destination port number.
c. the source port number.
18. UDP has which of the following characteristics:
a. regulated send rate.
b. connection state at the server.
c. three-way hand shake for connection establishment.
19. When a UDP segment arrives to a host, in order to direct the segment to the appropriate socket, the OS uses:
a. the source port number.
b. the source IP address.
c. the destination port number.
20. Suppose a client sends an HTTP request message with the If-modified-since: header. Suppose the object in a server has not changed since the last time a client retrieved the object. Then the server will send a response message with the status code:
a. 404 Not Found.
b. 200 OK.
c. 304 Not Modified.
21. Streams are not needed in which of the following programs:
a. TCPserver.
b. UDPserver.
c. TCPclient.
d. UDPclient.
22. Consider the minimum time for P2P file distribution, as discussed in Section 2.6. Suppose the upload rate of the server is10 Mbps, the upload rates of all peers is 1 Mbps, and the download rates of all peers is 10 Mbps. Further suppose that there are 100 peers and the file is 100 million bits. The minimum distribution time is
a. approximately 100 seconds.
b. approximately 10 seconds.
c. approximately 1 second.
d. approximately 1000 seconds.
For BitTorrent, which of the following is true:
a. Although a peer may have 50 concurrent TCP connections with other peers, at any given instant of time it sends data to less than 10 other peers.
b. At a given instant of time, a peer A may upload to a peer B, even if peer B is not sending anything to A.
c. Among the chunks that a peer does not have, the peer will request chunks that appear to be relatively rare in the torrent.
d. All of the above.
24. Consider the latency model for dynamic congestion windows. Which of the following components contribute to latency?
a. the sum of all the stalled times.
b. round trip time, RTT.
c. the transmission time of the object, O/R.
25. TCP applies fast retransmit to a segment when:
a. it estimates unusually large RTTs.
b. it receives three ACKs for an earlier segment.
c. the segment's timer expires.
26. Nmap is often used to:
a. do port scans over a range of ports at a target host.
b. measure throughput between hosts.
c. measure round-trip times between hosts.
d. decipher encrypted traffic.
27. With SYN cookies, when a server receives a SYN segment, it returns a SYNACK with:
a. an initial sequence number that is a hash of the IP addresses and port numbers in the SYN segment (as well as of other things).
b. initial sequence number 1.
c. a randomly chosen initial sequence number.
Before sending a packet into a datagram network, the source must determine all of the links that packet will traverse between source and destination.
The primary role of a router is to forward datagrams from input links to output links.
Forwarding involves transferring a packet from the router’s input link to the appropriate output link.
All link layer protocols that support IP have the same frame structure (i.e., length of frame, number and length of header fields).
CRC error detection, as used in Ethernet, is always able to detect whether there is an error in a frame.
The even parity bit scheme can correct single bit errors.
With CDMA, each sender uses the same code, cm, m=1,...,M.
Each LAN adapter has a unique LAN address.
41. A channel partitioning protocol has which of the following characteristics forwarding table is:
a. it does not generate collisions.
b. all transmitting nodes get the same amount of bandwidth.
there is no master node.
42. In slotted ALOHA with N active nodes, the probability that no node transmits in a given slot is
a. (1-p)N
b. (1-p)N
c. pN
d. 1-p
43. An ARP query packet is encapsulated in
a. an IP datagram.
a link-layer frame addressed to a specific adapter.
a link-layer broadcast frame.
none of the above.
Ethernet provides which of the following services to the network layer
a. error detection.
flow control.
reliable data transfer.
all of the above.
45. For Ethernet, if an adapter determines that a frame it has just received is addressed to a different adapter
a. it discards the frame without sending an error message to the network layer.
it discards the frame and sends an error message to the network layer.
it sends a NACK (not acknowledged frame) to the sending host.
it delivers the frame to the network layer, and lets the network layer decide what to do.
A typical "infrastructure network" wireless network includes base stations.
In CDMA, the chipping rate is typically the same as the original data rate.
The 11 channels in the 802.11 are non-overlapping.
If you enter an Internet café and more than one AP is present, then the packets your host
During the 802.11 association handshake protocol, the wireless host gets assigned an IP address.
51. In CDMA, let Ym be the received value in the mth mini-slot for some slot i. Let cm, m=1,...,M, be the sender's M code values. To determine the bit value the sender sent, the receiver:
a. multiples Ym with the sum of the M code values.
b. multiplies each Ym with the corresponding cm, sums the resulting values and divides by M.
simply declares Ym as the sent value.
52. A beacon frame sent by an AP includes
a. the AP's SSID.
b. the AP's MAC address.
c. both the AP's MAC address and SSID.
53. The 802.11 protocol does not implement collision detection because (Click all that apply)
a. collision detection was found to be useless in wired Ethernet.
b. the adapter would still not be able to detect all collisions due to hidden terminals. c. it is costly to build wireless hardware that detects collisions.
c. it is costly to build wireless hardware that detects collisions.
54. Packets sent by two stations in 802.11 can collide because
a. at a given time, the random backoff values of the two stations are the same.
b. the packets are sent to different APs but on the same channel.
c. the two stations could be hidden from each other.
An 802.11 frame includes:
a. an acknowledgement field.
b. a sequence number field.
c. four address fields.
In IP spoofing, the attacker interchanges the source and destination addresses in the sender's IP datagram.
Nonce's are often used to combat the playback attack.
65. Filtering in a firewall can be based on:
a. source and destination IP addresses
b. TCP ACK bits
c. source and destination port numbers
d. all of the above
