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Layers four and five of the Internet protocol stack are implemented in the end systems but not in the routers in the network core.
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With ADSL, each subscriber gets more downstream bandwidth than upstream bandwidth.
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Twisted-pair cooper wire is no longer present in computer networks.
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Two packets A and B are sent in that order through a connection-oriented communication network. They could arrive at the destination:
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in any order, after having traversed the same route.
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only in the order A-B, after possibly having traversed different routes.
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in any order, after possibly having traversed different routes.
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only in the order A-B, after having traversed the same route.
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Two packets A and B are sent in that order through a connectionless communication network. They will arrive at the destination:
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in any order, after possibly having traversed different routes.
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in the order A-B, after having traversed the same route.
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in any order, after having traversed the same route.
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in the order A-B, after possibly having traversed different routes.
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The Internet received its name in the 1980s because:
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it was an interim (temporary) design of what it later became, but the name stuck.
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it was meant to be a network internal to the United States Department of Defense.
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it consisted of many interconnected networks.
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it achieved international scope with the addition of the City University of London.
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DNS lookups often involve a combination of recursive and iterative queries.
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The Date: header in the HTTP response message indicates when the object in the response was last modified.
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Skype relay nodes are typically peers under the control of Skype users.
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The process that sends messages into, and receives messages from, the network through a software interface is called a socket.
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In a P2P File Distribution architecture, the server must sequentially send (upload) file copies.
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to transfer messages from one mail server to another.
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to transfer messages from mail server to a user agent.
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to define the format of message headers.
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all of the above.
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Suppose a DNS resource record has Type=MX. Then:
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Value is the hostname of the DNS server that is authoritative for Name.
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Value is the IP address of the mail server that has the alias hostname Name.
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Value is the hostname of the mail server that has the alias hostname Name.
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none of the above.
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Local DNS name servers:
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cache resource records, but discard them after a period of time that is on the order of a few days.
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cache resource records and never discard them.
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obtain resource records from Web caches.
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never cache resource records.
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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.
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The size of the TCP RcvWindow never changes throughout the duration of the connection.
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When a TCP segment arrives to a host, the socket to which the segment is directed depends on
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UDP has which of the following characteristics:
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When a UDP segment arrives to a host, in order to direct the segment to the appropriate socket, the OS uses:
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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:
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404 Not Found.
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200 OK.
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304 Not Modified.
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none of the above.
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Streams are not needed in which of the following programs:
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TCPserver.
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UDPserver
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TCPclient
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UDPclient
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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
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approximately 100 seconds.
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approximately 10 seconds.
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approximately 1 second.
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approximately 1000 seconds.
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For BitTorrent, which of the following is true:
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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.
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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.
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Among the chunks that a peer does not have, the peer will request chunks that appear to be relatively rare in the torrent.
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All of the above.
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Consider the latency model for dynamic congestion windows. Which of the following components contribute to latency?
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TCP applies fast retransmit to a segment when:
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it estimates unusually large RTTs.
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it receives three ACKs for an earlier segment.
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the segment's timer expires.
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none of the above.
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Nmap is often used to:
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do port scans over a range of ports at a target host.
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measure throughput between hosts.
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measure round-trip times between hosts.
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decipher encrypted traffic.
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With SYN cookies, when a server receives a SYN segment, it returns a SYNACK with:
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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).
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initial sequence number 1.
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a randomly chosen initial sequence number.
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none of the above.
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Before sending a packet into a datagram network, the source must determine all of the links that packet will traverse between source and destination.
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The primary role of a router is to forward datagrams from input links to output links.
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Forwarding involves transferring a packet from the router’s input link to the appropriate output link.
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A forwarding table is:
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a. Used to find the proper interface to which the input interface should forward a packet.
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b. Configured using a centralized routing algorithm.
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c. Configured through routing protocol messages received by router.
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A and C.
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B and C.
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How are routing paths calculated?
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The full route is mapped out in the datagram’s header.
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Paths are calculated by routing algorithms.
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Datagrams always flow on the same path and don’t need to be calculated.
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The path is calculated based on available network bandwidth.
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Guaranteed Delivery:
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Guarantees that the packet will eventually arrive at its destination
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Guarantees the amount of time between the transmission of two successive packets at the sender is equal to the amount of time between their receipt at the destination.
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Guarantees delivery within a specified host-to-host delay bound.
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Guaranteed Delivery with Bounded Delay
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Guarantees delivery within a specified host-to-host delay bound
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Guarantees a packet will arrive at its destination.
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Guarantees the amount of time between the transmission of two successive packets at the sender is equal to the amount of time between their receipt at the destination.
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Guaranteed Maximum Jitter
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Guarantees the amount of time between the transmission of two successive packets at the sender is equal to the amount of time between their receipt at the destination
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Guarantees a packet will arrive at its destination.
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Guarantees delivery within a specified host-to-host delay bound.
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All link layer protocols that support IP have the same frame structure (i.e., length of frame, number and length of header fields).
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CRC error detection, as used in Ethernet, is always able to detect whether there is an error in a frame.
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The even parity bit scheme can correct single bit errors.
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With CDMA, each sender uses the same code, cm, m=1,...,M.
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Each LAN adapter has a unique LAN address.
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A channel partitioning protocol has which of the following characteristics forwarding table is:
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In slotted ALOHA with N active nodes, the probability that no node transmits in a given slot is
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An ARP query packet is encapsulated in
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Ethernet provides which of the following services to the network layer
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error detection.
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flow control.
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reliable data transfer.
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all of the above.
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For Ethernet, if an adapter determines that a frame it has just received is addressed to a different adapter
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it discards the frame without sending an error message to the network layer.
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it discards the frame and sends an error message to the network layer.
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it sends a NACK (not acknowledged frame) to the sending host.
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it delivers the frame to the network layer, and lets the network layer decide what to do.
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A typical "infrastructure network" wireless network includes base stations.
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In CDMA, the chipping rate is typically the same as the original data rate.
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The 11 channels in the 802.11 are non-overlapping.
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If you enter an Internet café and more than one AP is present, then the packets your host sends are forwarded into the Internet by both APs.
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During the 802.11 association handshake protocol, the wireless host gets assigned an IP address.
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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:
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multiples Ym with the sum of the M code values.
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multiplies each Ym with the corresponding cm, sums the resulting values and divides by M.
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simply declares Ym as the sent value.
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none of the above.
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A beacon frame sent by an AP includes
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The 802.11 protocol does not implement collision detection because (Click all that apply)
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collision detection was found to be useless in wired Ethernet.
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the adapter would still not be able to detect all collisions due to hidden terminals.
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it is costly to build wireless hardware that detects collisions.
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all of the above.
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Packets sent by two stations in 802.11 can collide because
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at a given time, the random backoff values of the two stations are the same.
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the packets are sent to different APs but on the same channel.
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the two stations could be hidden from each other.
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all of the above.
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An 802.11 frame includes:
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In IP spoofing, the attacker interchanges the source and destination addresses in the sender's IP datagram.
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Nonce's are often used to combat the playback attack.
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Two parties often use public-key encryption to agree on a shared one-time symmetric session key.
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For public-key certification, PGP uses certification authorities.
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The AH protocol provides secrecy at the network layer.
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Which of the following statements best describes the purpose of the SNMP protocol?
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The SNMP protocol specifies the actions a network manager should take in response to a specific set of network fault conditions.
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The SNMP protocol is a tool for gathering data about network conditions and executing remote actions at remote managed devices.
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The SNMP protocol is used by the network manager to provision resources, such as bandwidth, server capacity and other computational/communication resources needed to meet the mission-specific needs of an enterprise.
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Suppose a network manager wanted to query the value of the number of TCP segments received by a host running the Microsoft Windows 2000 operating system in a US-based company. What would be the prefix (leading digits) of the MIB variable that should be queried?
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1.2.840.11356
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1.2.840
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1.3.6.1.2.1.1
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What is the maximum number of received UDP datagrams that can be counted (without overflow) in the MIB-2 UDP module?
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2**32 - 1
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2**64 -1
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2**16 - 1
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2**31 - 1
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What is the purpose of a presentation service?
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To allow a client to inform a server that it (the client) is present and ready to receive data.
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To encode, transmit, and translate data from one machine-specific format to another.
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To display data in a format specified by a user.
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None of the above.
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Filtering in a firewall can be based on: