1Which of the following best defines the primary function of the Network Layer in the OSI model?
A.Framing and physical addressing
B.Node-to-node delivery with error control
C.Process-to-process delivery
D.Routing and logical addressing
Correct Answer: Routing and logical addressing
Explanation:
The Network Layer is responsible for host-to-host delivery, which involves routing packets across networks and managing logical addressing (IP addresses).
Incorrect! Try again.
2In the context of routing algorithms, what does the Optimality Principle state?
A.If router is on the optimal path from router to router , then the optimal path from to also falls along the same route.
B.All routers must use the same operating system to achieve optimality.
C.The optimal path is determined solely by the bandwidth of the links.
D.The shortest path is always the one with the fewest number of hops.
Correct Answer: If router is on the optimal path from router to router , then the optimal path from to also falls along the same route.
Explanation:
The Optimality Principle states that if the best path from to passes through , then the sub-path from to must also be the best path between and .
Incorrect! Try again.
3Which algorithm is commonly used to calculate the shortest path tree in Link State routing protocols like OSPF?
A.Spanning Tree Protocol
B.Dijkstra's Algorithm
C.Bellman-Ford Algorithm
D.Floyd-Warshall Algorithm
Correct Answer: Dijkstra's Algorithm
Explanation:
Link State routing protocols use Dijkstra's algorithm to compute the shortest path from the source node to all other nodes in the network based on a complete topology map.
Incorrect! Try again.
4In Distance Vector Routing, what information does a router send to its neighbors?
A.The status of its own links only
B.Hello packets to discover neighbors
C.The complete topology map of the network
D.Its entire routing table (vectors of distances)
Correct Answer: Its entire routing table (vectors of distances)
Explanation:
In Distance Vector Routing, each router periodically shares its knowledge of the entire network (its routing table containing distances to all destinations) with its immediate neighbors.
Incorrect! Try again.
5The Count-to-Infinity problem is a specific characteristic/drawback of which routing approach?
A.Distance Vector Routing
B.Link State Routing
C.Path Vector Routing
D.Source Routing
Correct Answer: Distance Vector Routing
Explanation:
The Count-to-Infinity problem occurs in Distance Vector Routing when incorrect routing information propagates slowly (slow convergence) after a link failure, causing loops.
Incorrect! Try again.
6Which mechanism prevents the Count-to-Infinity problem by prohibiting a router from advertising a route back onto the interface from which it learned it?
A.Hold-down Timers
B.Triggered Updates
C.Split Horizon
D.Route Poisoning
Correct Answer: Split Horizon
Explanation:
Split Horizon is a technique where a router does not advertise routes back to the neighbor from whom it learned those specific routes, preventing basic loops.
Incorrect! Try again.
7In the Leaky Bucket algorithm, what happens if a packet arrives when the bucket is full?
A.The packet is queued indefinitely.
B.The packet is sent immediately at a higher rate.
C.The bucket expands to accommodate the packet.
D.The packet is discarded (dropped).
Correct Answer: The packet is discarded (dropped).
Explanation:
In the Leaky Bucket algorithm, the bucket has a fixed capacity. If data arrives when the bucket is full, the incoming packets are discarded (dropped).
Incorrect! Try again.
8What is the primary difference between Leaky Bucket and Token Bucket algorithms?
B.Leaky Bucket enforces a constant output rate; Token Bucket allows for bursty traffic.
C.Leaky Bucket is used for routing; Token Bucket is used for error control.
D.There is no functional difference.
Correct Answer: Leaky Bucket enforces a constant output rate; Token Bucket allows for bursty traffic.
Explanation:
A Leaky Bucket smooths traffic to a constant rate (like water leaking from a hole). A Token Bucket accumulates tokens, allowing a burst of data to be sent if enough tokens have accumulated.
Incorrect! Try again.
9Which routing protocol is an Exterior Gateway Protocol (EGP) used for routing between different Autonomous Systems (AS)?
A.EIGRP
B.BGP
C.RIP
D.OSPF
Correct Answer: BGP
Explanation:
Border Gateway Protocol (BGP) is the standard Exterior Gateway Protocol used to exchange routing information between different Autonomous Systems on the Internet.
Incorrect! Try again.
10In RIP (Routing Information Protocol), what is the value of the metric that signifies a destination is unreachable (infinity)?
A.100
B.255
C.15
D.16
Correct Answer: 16
Explanation:
RIP uses hop count as a metric. The maximum valid hop count is 15. A hop count of 16 is defined as infinite, meaning the destination is unreachable.
Incorrect! Try again.
11Which packet is sent by a router to the source to signal congestion, effectively telling the source to slow down?
A.Choke Packet
B.Hello Packet
C.Keepalive Packet
D.LSA Packet
Correct Answer: Choke Packet
Explanation:
A Choke Packet is a control packet generated by a congested node and sent back to the source node to restrict the rate of traffic injection.
Incorrect! Try again.
12In Link State Routing, how is the topological information disseminated?
A.By querying the DNS server.
B.By sending path vectors to the central controller.
C.By flooding Link State Packets (LSPs) to all routers in the area.
D.By exchanging routing tables with neighbors only.
Correct Answer: By flooding Link State Packets (LSPs) to all routers in the area.
Explanation:
In Link State Routing, routers flood Link State Packets (LSPs) containing information about their local links to every other router in the network domain.
Incorrect! Try again.
13Congestion control that relies on the receiver sending feedback to the sender is classified as:
A.Closed-loop congestion control
B.Static congestion control
C.Forward error correction
D.Open-loop congestion control
Correct Answer: Closed-loop congestion control
Explanation:
Closed-loop congestion control involves a feedback mechanism where the system monitors the network and reports information back to the source to adjust the transmission rate.
Incorrect! Try again.
14What is the formula for the updating rule in the Bellman-Ford equation used in Distance Vector routing? (Where is the cost from to , and is the cost to neighbor )
A.
B.
C.
D.
Correct Answer:
Explanation:
The Bellman-Ford equation states that the least cost path from to is the minimum of the sum of the cost to a neighbor plus the least cost from that neighbor to the destination , over all neighbors .
Incorrect! Try again.
15Which of the following describes Flooding?
A.A packet received on one line is sent out on all other lines.
B.Packets are sent based on a probability distribution.
C.A packet is sent only to the destination address.
D.Packets are held in a buffer until the line is clear.
Correct Answer: A packet received on one line is sent out on all other lines.
Explanation:
Flooding is a routing technique where every incoming packet is sent out on every outgoing line except the one it arrived on.
Incorrect! Try again.
16OSPF (Open Shortest Path First) divides an Autonomous System into:
A.Segments
B.Areas
C.Zones
D.Clusters
Correct Answer: Areas
Explanation:
OSPF uses a hierarchical structure by dividing the Autonomous System into Areas to limit the flooding of Link State Advertisements and reduce routing table size.
Incorrect! Try again.
17What is Backpressure in the context of congestion control?
A.Prioritizing voice traffic over data traffic.
B.Node-by-node congestion propagation in the reverse direction of data flow.
C.Discarding packets at the tail of the queue.
D.Increasing the window size to push more data.
Correct Answer: Node-by-node congestion propagation in the reverse direction of data flow.
Explanation:
Backpressure is a technique where a congested node stops receiving data from its upstream neighbor, causing the upstream neighbor to eventually become congested, propagating the 'pressure' back to the source.
Incorrect! Try again.
18Which of the following is a Unicast routing protocol?
A.RIP
B.MOSPF
C.PIM
D.DVMRP
Correct Answer: RIP
Explanation:
RIP (Routing Information Protocol) is a unicast routing protocol. The others (DVMRP, PIM, MOSPF) are multicast routing protocols.
Incorrect! Try again.
19The Token Bucket algorithm requires which two parameters?
A.Bucket size and Leak rate
B.Token generation rate and Bucket capacity
C.Hop count and Bandwidth
D.Burst size and Maximum delay
Correct Answer: Token generation rate and Bucket capacity
Explanation:
The Token Bucket is defined by the rate at which tokens are added to the bucket (token generation rate) and the maximum number of tokens the bucket can hold (bucket capacity).
Incorrect! Try again.
20Which mechanism allows a router to randomly drop packets before its queue becomes full to prevent global synchronization of TCP sessions?
A.Tail Drop
B.Leaky Bucket
C.Priority Queuing
D.RED (Random Early Detection)
Correct Answer: RED (Random Early Detection)
Explanation:
RED monitors the average queue size and drops packets probabilistically before the buffer overflows, signaling congestion early to TCP sources so they reduce their window size desynchronized.
Incorrect! Try again.
21BGP uses which type of routing algorithm?
A.Link State
B.Distance Vector
C.Shortest Path First
D.Path Vector
Correct Answer: Path Vector
Explanation:
BGP is a Path Vector protocol. It is similar to Distance Vector but stores the entire path (sequence of AS numbers) to a destination to prevent loops and enforce policy.
Incorrect! Try again.
22In Hierarchical Routing, routers are grouped into:
A.Subnets only
B.Regions or Clusters
C.Datagrams
D.Vectors
Correct Answer: Regions or Clusters
Explanation:
Hierarchical routing scales to large networks by organizing routers into groups (regions/clusters), where routers only know the details of their own group and summaries of others.
Incorrect! Try again.
23Which of the following is a symptom of severe congestion?
A.Increased bandwidth
B.Low latency
C.High throughput
D.Packet loss and increased delay
Correct Answer: Packet loss and increased delay
Explanation:
When a network is congested, router buffers fill up, leading to queuing delays and eventually packet drops (loss) when buffers overflow.
Incorrect! Try again.
24In the TCP Congestion Control mechanism (often discussed in network layer contexts regarding flow interaction), what happens during the 'Slow Start' phase?
A.The sender stops sending packets.
B.The congestion window increases linearly.
C.The congestion window remains constant.
D.The congestion window increases exponentially.
Correct Answer: The congestion window increases exponentially.
Explanation:
In Slow Start, the congestion window size doubles every Round Trip Time (RTT), resulting in exponential growth until the threshold (ssthresh) is reached.
Incorrect! Try again.
25What is the 'Poison Reverse' technique?
A.Flooding bad packets to clear the buffer.
B.A security attack on routing tables.
C.Reversing the path of the packet to the source.
D.A variation of Split Horizon where the route is advertised with a cost of infinity.
Correct Answer: A variation of Split Horizon where the route is advertised with a cost of infinity.
Explanation:
Poison Reverse extends Split Horizon. Instead of not advertising the route back to the source, the router advertises it with an infinite metric (unreachable) to explicitly break loops.
Incorrect! Try again.
26Which routing algorithm requires a global knowledge of the network topology?
A.Distance Vector
B.Random Walk
C.Flooding
D.Link State
Correct Answer: Link State
Explanation:
Link State routing (like OSPF) requires every router to have the full map (topology) of the network to calculate the shortest paths.
Incorrect! Try again.
27What is the standard administrative distance (trustworthiness) order for these protocols (Lowest to Highest implies Most to Least trusted)?
A.Connected Interface < OSPF < RIP
B.RIP < OSPF < Connected Interface
C.OSPF < Connected Interface < RIP
D.RIP < Connected Interface < OSPF
Correct Answer: Connected Interface < OSPF < RIP
Explanation:
Directly connected interfaces are most trusted. OSPF (usually AD 110) is trusted more than RIP (usually AD 120).
Incorrect! Try again.
28Which concept refers to the maximum amount of data that the network can transmit per unit of time?
A.Jitter
B.Packet Delay
C.Throughput
D.Latency
Correct Answer: Throughput
Explanation:
Throughput is the actual rate at which data is successfully delivered over a communication channel.
Incorrect! Try again.
29In the context of Quality of Service (QoS), Jitter refers to:
A.The size of the packet header.
B.The total time taken for a packet to reach the destination.
C.The number of packets lost.
D.The variation in packet arrival times.
Correct Answer: The variation in packet arrival times.
Explanation:
Jitter is the variation in the delay (latency) of received packets. High jitter degrades real-time applications like VoIP.
Incorrect! Try again.
30In Congestion Control, what is Load Shedding?
A.Dropping packets when routers cannot process them fast enough.
B.Adding more routers to the network.
C.Compressing data to reduce size.
D.Distributing traffic equally among all links.
Correct Answer: Dropping packets when routers cannot process them fast enough.
Explanation:
Load Shedding is a strategy where routers simply discard (shed) packets when their buffers get too full to handle the load.
Incorrect! Try again.
31Which BGP attribute is used to detect loops in routing paths?
A.Next Hop
B.MED
C.Local Preference
D.AS_PATH
Correct Answer: AS_PATH
Explanation:
The AS_PATH attribute contains the list of Autonomous Systems the route has traversed. If a BGP router sees its own AS number in the AS_PATH, it rejects the route to prevent a loop.
Incorrect! Try again.
32What happens in the Congestion Avoidance phase of TCP (AIMD)?
A.Window size doubles every RTT.
B.Window size is cut to zero.
C.Window size grows exponentially.
D.Window size increases by 1 segment (MSS) every RTT.
Correct Answer: Window size increases by 1 segment (MSS) every RTT.
Explanation:
In Congestion Avoidance, TCP uses Additive Increase. The congestion window is incremented linearly (usually +1 MSS per RTT) to probe for bandwidth carefully.
Incorrect! Try again.
33ECN (Explicit Congestion Notification) allows routers to:
A.Drop packets immediately.
B.Mark packets to signal impending congestion to endpoints without dropping them.
C.Increase the bandwidth of the link.
D.Reroute packets to a faster path.
Correct Answer: Mark packets to signal impending congestion to endpoints without dropping them.
Explanation:
ECN allows routers to set a bit in the IP header to signal congestion. The receiver echoes this to the sender, who reduces the transmission rate, avoiding packet drops.
Incorrect! Try again.
34The Knee in the throughput vs. load graph represents:
A.The point where throughput stops increasing linearly and delay starts increasing rapidly.
B.The point of zero latency.
C.The maximum capacity of the link.
D.The point where throughput drops to zero.
Correct Answer: The point where throughput stops increasing linearly and delay starts increasing rapidly.
Explanation:
The knee is the point where the load reaches the capacity where queues start building up. Throughput growth slows down and delay shoots up. This is the ideal operating point.
Incorrect! Try again.
35Which of the following is true for Static Routing?
A.It is suitable for very large, changing networks.
B.It uses complex algorithms like Dijkstra.
C.Routes are manually configured by the administrator.
D.Routes are updated automatically when topology changes.
Correct Answer: Routes are manually configured by the administrator.
Explanation:
Static routing involves the manual entry of routes into the routing table. It does not adapt automatically to network changes.
Incorrect! Try again.
36In OSPF, the Backbone Area is numbered as:
A.Area 1
B.Area 255
C.Area 100
D.Area 0
Correct Answer: Area 0
Explanation:
In OSPF, Area 0 is reserved for the backbone area. All other areas must connect to Area 0.
Incorrect! Try again.
37Which variable tracks the available capacity in a Token Bucket algorithm?
A.Counter
B.Sequence Number
C.TTL
D.Window Size
Correct Answer: Counter
Explanation:
The Token Bucket uses a counter (representing tokens). The counter increments periodically and decrements when a packet is sent.
Incorrect! Try again.
38What is the main disadvantage of Flooding?
A.It is not robust.
B.It requires complex routing tables.
C.It always finds the longest path.
D.It generates a vast number of duplicate packets, wasting bandwidth.
Correct Answer: It generates a vast number of duplicate packets, wasting bandwidth.
Explanation:
Because flooding sends every packet out every line, the total number of packets in the network grows exponentially, consuming immense bandwidth.
Incorrect! Try again.
39RIP updates are sent periodically every:
A.60 seconds
B.30 seconds
C.90 seconds
D.10 seconds
Correct Answer: 30 seconds
Explanation:
RIP routers broadcast their routing tables to neighbors every 30 seconds by default.
Incorrect! Try again.
40Traffic Shaping is about:
A.Encrypting the payload.
B.Compressing headers.
C.Controlling the rate of traffic sent to the network to comply with a profile.
D.Dropping packets that exceed limits.
Correct Answer: Controlling the rate of traffic sent to the network to comply with a profile.
Explanation:
Traffic shaping buffers excess packets and releases them at a controlled rate to smooth out bursts, whereas policing/dropping would simply discard them.
Incorrect! Try again.
41In the context of routing, what is Convergence?
A.The merging of two distinct packets.
B.The process of combining two networks.
C.The compression of routing tables.
D.The state where all routers share a consistent view of the network.
Correct Answer: The state where all routers share a consistent view of the network.
Explanation:
Convergence is the time it takes for all routers in a network to agree on the optimal routes after a change in topology.
Incorrect! Try again.
42What type of graph search does the Distance Vector algorithm effectively perform?
A.Breadth-First Search
B.Depth-First Search
C.Minimum Spanning Tree
D.Distributed Bellman-Ford
Correct Answer: Distributed Bellman-Ford
Explanation:
Distance Vector routing is essentially a distributed implementation of the Bellman-Ford shortest path algorithm.
Incorrect! Try again.
43Which field in the IP header is used to prevent infinite looping of packets?
A.Checksum
B.Fragment Offset
C.Time to Live (TTL)
D.Version
Correct Answer: Time to Live (TTL)
Explanation:
The TTL field is decremented by 1 at each router. If it reaches 0, the packet is discarded, preventing it from circulating forever.
Incorrect! Try again.
44In a Datagram network (Connectionless), routing decisions are made:
A.Only at the source node.
B.Only at the destination node.
C.For every individual packet.
D.Only once at the connection setup.
Correct Answer: For every individual packet.
Explanation:
In a datagram (packet-switched) network, each packet is treated independently, and the router makes a forwarding decision for each packet based on the current routing table.
Incorrect! Try again.
45If a router receives a packet with a destination address that is not in its routing table, and no default route exists, what does it usually do?
A.Broadcasts the packet to all ports.
B.Sends the packet back to the sender.
C.Discards the packet and sends an ICMP Destination Unreachable message.
D.Holds the packet until a route appears.
Correct Answer: Discards the packet and sends an ICMP Destination Unreachable message.
Explanation:
If a specific route and a default route are missing, the router drops the packet and typically informs the source via ICMP.
Incorrect! Try again.
46The Cliff in the Load vs. Throughput/Delay graph signifies:
A.The point where congestion begins.
B.The start of the slow start phase.
C.The point where throughput collapses heavily due to extreme congestion.
D.The ideal operating point.
Correct Answer: The point where throughput collapses heavily due to extreme congestion.
Explanation:
The 'Cliff' is the point of congestion collapse where the load is so high that throughput drops drastically (packets are dropped, retransmissions increase load further).
Incorrect! Try again.
47RSVP (Resource Reservation Protocol) is used primarily for:
A.Detecting link failures.
B.Assigning IP addresses.
C.Reserving resources (bandwidth/buffers) for QoS flows.
D.Routing table updates.
Correct Answer: Reserving resources (bandwidth/buffers) for QoS flows.
Explanation:
RSVP is a signaling protocol used to reserve resources across a network for Integrated Services (IntServ) QoS.
Incorrect! Try again.
48In Dijkstra's algorithm, which data structure is typically used to select the node with the smallest tentative distance?
A.Queue
B.Linked List
C.Priority Queue
D.Stack
Correct Answer: Priority Queue
Explanation:
A Priority Queue (often implemented as a Min-Heap) is used to efficiently select the unvisited node with the smallest calculated distance from the source.
Incorrect! Try again.
49What is the primary metric used by OSPF to calculate cost?
A.Bandwidth
B.Delay
C.Load
D.Hop Count
Correct Answer: Bandwidth
Explanation:
OSPF uses a reference bandwidth (usually 100 Mbps) divided by the interface bandwidth to calculate cost (Cost = Reference BW / Interface BW). Higher bandwidth implies lower cost.
Incorrect! Try again.
50Which of the following describes Multipath Routing?
A.Distributing traffic load over multiple available paths to the same destination.
B.Sending the same packet over multiple paths for redundancy.
C.Routing all traffic through a single best path.
D.Routing based on multiple metrics like delay and cost combined.
Correct Answer: Distributing traffic load over multiple available paths to the same destination.
Explanation:
Multipath routing allows the use of multiple paths to a destination simultaneously to increase aggregate bandwidth and fault tolerance.