CS6250 Computer Networks Practice Exam 1 Guide 2026, Exams of Computer Networks

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CS6250 Computer Networks Practice Exam 1 Guide 2026

a | Ds ce eee ee ee es CS6250 Computer Networks Practice Exam 1 Guide 2026 How did Licklider and his team in the early 1960s experiment with a precursor to the internet? - CORRECT AINSWWERE Connecting two computers over a dial-up telephone line What is the Domain Name System (DNS) designed to do primarily? - CORRECTING WER) Translate domain names into IP addresses Whar is the architectural design of the Internet protocol stack based on? - SORRECIAINGIVER! Layers T/F: Both the data link and transports layer protocols may provide error correction - CORRECT ANSWER - True What allows for communication between the applications layer and the transport layer - SORRECT ANSWER-S ockets Which of the following protocols belong to the application layer? [etherneYDNS/UDP/IP] - SOREL ANSMERE DNs Which two protocols belong to the transport layer? [IP/TCP/UDP/HTTP] - GORREGRANSWERLTCP, UDP When an application sends a packet of information across the network, this packet travels down the IP stack aud undergoes what proces CORRECT ANSWER Encapsulation bua ee ee ee ee eee ee ee ee ee eee eee eee “1 I I I I I I I I I I I I I I I I I I I I I I I I al According to the end-to-end principle, where should most of the Internet's functionality/intelligence be implemented? - CORRECT ANSWER -At the edges of the network What is the difference between hubs, bridges, and routers? - CORRECT ANSWER -They operate on different layers of the IP stack T/F: the UDP and TCP protocols have a large overlap of functionality - CORRECT ANSWER -false T/F; the transport layer protocols offer a logical connection between processes, only if the hosts reside in the sme network CORRECTS T/F; a sender host receives a message from the application layer it encapsulates it with the transport layer header before passing it down to the neowork layer - GORRECIANSIVER!- true T/F: an application running on a host can bind to multiple sockets simultaneously - SORRECHANS WER true T/F: a host cannot maintain a TCP socket and a UDP socket simulcaneously - GORRECMANSWVER false ‘T/F: the identifier of a UDP socket is a tuple of destination IP address and port - SORRECIMANSWERI- true T/F: the identifier of a TCP socket is a cuple of source IP address and port - SORRECIANSWERI false T/F: UDP is considered more lightweight than TCP - CORRECT ANSWER -true r I I I I I I I I I I I I I I I I I I I I I I I I L “1 I I I I I I I I I I I I I I I I I I I I I I I I al a) a timeout occurs b) a triple duplicate acknowledgement occurs - GORRECMAINSWER false T/F; consider a TCP connection and a diagram that shows the congestion as it progresses over time, From the diagram, when we observe the congestion window to drop to its initial value, we infer chat a packet loss T/F: consider a TCP connection and a diagram that shows how the congestion window progresses over time. from the diagram we can identify the time periods of slow start when the congestion window increases by 1 cret RTT -SRRECTIANSIAERE ss T/F: TCP cubic was designed for better network utilization - CORRECT ANSWER -true T/F: TCP cubic congestion window growth function is designed not to overflow the receiver's buffer - CORRECT ANSWER Fil T/F: TCP cubic uses a cubic function to increase the congestion window - CORRECT ANSWER -true T/F: TCP cubic increases the congestion window in every RTT - CORRECTING WER false UDP and TCP use port numbers to identify the sending application and destination application; why don't UDP and TCP just use process IDs rather than define port numbers? - SORRECHANSWERI process IDs are specific to an os, making the protocol operating system dependent ~a single process can set up multiple channels of communications, so couldn't properly demultiplex - having processes run on well known ports is an important convention why does UDP take 1's complement of the checksum instead of just the sum? r I I I I I I I I I I I I I I I I I I I I I I I I L “1 I I I I I I I I I I I I I I I I I I I I I I I I al how does the receiver compute and detect errors? using 1's complement, us it possible chat a 1-bit or 2-bit error will go undetected? - CORRECT ANSWER - to detect errors, the receiver adds the four words (three original and checksum); if the sum contains a zero, receiver knows there was an error; all 1-bit errors will be detected, but 2-bit errors may be undetected TCP uses additive increase multiplicative decrease (AIMD) policy for fairness; would AIAD, MIAD, or MIMD converge? how would their convergence behavior differ from AIMD? - GORRECIANSWERI- MIAD will converge; AIAD and MIMD will oscillate over the full bandwidth utilization line, but will not converge; the other policies are not as stable, decrease policy in AIAD/MIAD is not as aggressive to address congestion control, and increase policy in MIAD and MIMD is too aggressive AINSIVER in cubic, the window growth only depends on the time between two consecutive congestion explain how in TCP cubic the congestion window growth becomes independent of RTTs events; one congestion event is the time when TCP undergoes fast recovery, allowing cubic flows competing in the same bottleneck to have approx. same size window independent of RTTs, achieving good RTT fairness (based on time since last loss event, not RTTs or acks) T/F: “routing” and “forwarding” are interchangeable terms - CORRECT ANSWER -false ‘TF: consider a source and destination host; before packets leave the source host, the host needs to define the path over which che packers will travel co reach the destination host - GORRBCMANSIWERI-false T/F: intra-domain routing refers to routing that takes place among routers that belong to the same administrative domain. in contrast, when routers belong to different administrative domains, we refer to routing as inter-domain routing - CORRECT ANSWER -true ‘T/F: consider the link-state routing protocol; the link costs are known to all nodes - CORRECT ANSWER - true r I I I I I I I I I I I I I I I I I I I I I I I I L “1 I I I I I I I I I I I I I I I I I I I I I I I I al T/F: the poison reverse technique solves the count-to-infinity problem for all network topologies - CORRECT ANSWER Fis T/F: the routing information protocol (RIP) is based on the distance vector protocol - CORRECT ANSWER -true T/F: open shortest path first (OSPF) is based on the link state routing algorithm - CORRECT ANSWER - true s points that a network has is upper bounded - GORRECTANS WER false T/F; the number of egre T/F: consider a network with multiple egress points. further consider that these egress points offer different paths to the same external conditions. then these paths must have different costs - CORRECT ANSWER - false T/F; according to the hot potato routing technique it is in a network's best interest to route the traffic so that it exits the network at the router geographically closest to the one form which it entered the network - CORRECT ANSWER ilk T/F:; assume a source and destination host. as packets travel over a path from the source co the destination host the packets are handled by multiple routers over that path. if these routers belong to different administrative domains, they. need to run the same intra-domain routing algorithm, since they are on the CORRECT ANSWER Fis same path for that pair of hosts a packet is when it is moved from a router's input link to the appropriate link - SORRECHANSWER -forwarded which action is network-wide? (involving multiple routers) - GORRECMANSWER routing r I I I I I I I I I I I I I I I I I I I I I I I I L “1 I I I I I I I I I I I I I I I I I I I I I I I I al ‘T/F: incra-domain routing involves multiple administrative domains - SORRECIAINGWER T/F; upon termination of Dijkstra's algorithm, all nodes in a network are aware of the entire network topology select the terms describing the distance vector algorithm: - distributed ~ centralized - iterative - asynchronous nchronous - non-terminating - GORRECTANSWER -discribuced, iterative, asynchronous what can cause the count-to-infinity problem? - GORRECTANS WER outi ng loops Dijkstra's algorithm is a algorithm, also referred to as a algorithm - CORRECT ANSWER - global, link-state the bellman-ford equation is used by the algorithm. the Routing Information Protocol (RIP) is an example of: -a link-state algorithm -a distance-vector algorithm - poison reverse - an inter-domain routing algorithm r I I I I I I I I I I I I I I I I I I I I I I I I L “1 I I I I I I I I I I I I I I I I I I I I I I I I al ‘T/F: a customer-provider relationship between ASes is based on a financial settlement, which determines how much the customer will pay the provider; the provider takes care of connecting the customer network with destinations found in the provider's routing table; the customer pays regardless of the direction of traffic - T/F; there is no incentive for smaller ISPs to peer with each other - CORRECT ANSWER. T/F: provider ASes have a financial incentive to forward as much of their customers’ traffic as possible - what is the correct order for an AS to import its routes based on their incentive CORRECT ANSWER. rouces are learned from: customers --> peers -> providers what is the difference between iBGP and eBGP? disseminating external routes CORRECT ANSWER. both flavors take care of - an eBGP session is established between two border routers that belong to different ASes - an iBGP session is established between routers that belong to the same AS - once a router hears about a route that is learned from eBGP, then it disseminates that route to other internal routers in the same AS, using iBGP what is the difference between iBGP and IGP? - CORRECT ANSWER - IGP-ike protocols are used to establish paths between the internal routers of an AS based on specific costs within the AS - iBGP is only used to disseminate external routes within the AS T/F: a router within the AS decides which route to export by first applying import policies to exclude routes entirely from further consideration - true y the LocalPref attribute is used to prefer routes learned through a specific AS over other ASes for traffic - CORREGHANSWERE ou:bousc r I I I I I I I I I I I I I I I I I I I I I I I I L a | assume AS_X learns of a route to the same destination DEST_A via AS_Y and AS_Z; if AS_X prefers to route its traffic through AS_Z due to peering or business, it can assign a LocalPref value to routes it learns from AS_Z, and thus using LocalPref, AS_X can control where traffic exits the AS - CORRECT ANSWER - higher the MED (multi-exit discriminator) value is used by ASes connected by multiple links to designate which of those links are preferred for traffic - CORRECT ANSWER. inbound assume that AS_X prefers routes advertised to AS_Y to go through RI instead of R2; for AS_Y to be influenced to choose RI to forward traffic to AS_X, R1 must have a MED value, assuming that all ote attributes are equal CORRECT ANSWER - lower one of the services offered by IXPs is protection against attacks - GORRECTANSWERDDos T/F: participation of an AS in an IXP is free - CORRECT ANSWER -false T/F: IXPs handle large volumes of traffic - CORRECT ANSWER -true T/F: one of the reasons why networks choose to peer at IXPs is because critical players in today's internet ecosystem often “incentivize" other networks at IXPs - CORRECT ANSWER +truc T/P: private peering Pls do not use che IXPs public peering infrastructure - CORRECIANSWER ccuc T/F: [XP's users may use route servers for an additional cost - CORRECT ANSWER -false T/F: route servers keep track of the BGP sessions they maintain with each participant AS through RIBs - bua ee ee ee ee eee ee ee ee ee eee eee eee Ds ce eee ee ee es “1 I I I I I I I I I I I I I I I I I I I I I I I I al T/F: when a large provider or CDN joins an IXP, this can act as an incentive for other networks to join as «lt- SORRECHANSTERE T/F: at an IXP, the members have the choice to peer privately or publicly - CORRECT ANSWER -true T/F: IXPs leading incentive to establish route servers was to charge the participants for using it BSW T/F: an IXP route server does not need to run the BGP protocol to facilitate the establishment of multi-lateral pectng sessions - RRS TBR ‘T/F: for multi-lateral BGP peering sessions at an IXP, the participants have the choice to advertise routes, either directly to other participants, or to the route server - CORRECT ANSWER. false the data plane functions of a traditional router are implemented in - GORRECTANSWER hardware the control plane functions of a traditional router are implemented in - CORRECT ANSWER - software which plane operates on a shorter timescale? - CORREGISANSSTERE