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Questions and Answers

What is the purpose of periodically passing copies of a routing table from router to router?

  • To communicate topology changes immediately (correct)
  • To update the routing tables with new information
  • To reduce the number of hops in the subnet
  • To increase the time delay in milliseconds

    • What is another name for the distance vector routing algorithm?

  • The Link State algorithm
  • Dijkstra's algorithm
  • The distributed Bellman-Ford routing algorithm (correct)
  • The Path Vector algorithm

    • What is contained in each entry of a routing table in distance vector routing?

  • The metric used and the number of hops to the destination
  • The IP address of the destination and the metric used
  • The preferred outgoing line and an estimate of the time or distance to that destination (correct)
  • The preferred outgoing line and the IP address of the destination

    • What is one of the metrics that can be used in distance vector routing?

    <p>Number of hops</p> Signup and view all the answers

    How does a router measure the delay in milliseconds if the metric is delay?

    <p>By sending ECHO packets that the receiver just time-stamps and sends them back</p> Signup and view all the answers

    What is the name of the algorithm used in the Internet under the name RIP?

    <p>Distance vector routing algorithm</p> Signup and view all the answers

    What is the name of the researchers who developed the distance vector routing algorithm?

    <p>Bellman and Fulkerson</p> Signup and view all the answers

    What was the original routing algorithm used in ARPANET?

    <p>Distance vector routing algorithm</p> Signup and view all the answers

    What is the main limitation of static routing in large or complex networks?

    <p>It requires a lot of time to define and maintain static route table entries</p> Signup and view all the answers

    What is the primary function of a default route?

    <p>To forward packets to a last resort outlet</p> Signup and view all the answers

    What is the primary function of a HELLO packet in link-state routing?

    <p>To learn who its neighbors are and their network addresses</p> Signup and view all the answers

    What happens to static routes in the routing table if a destination is down?

    <p>The static route remains in the routing table</p> Signup and view all the answers

    What type of network topologies were Distance Vector Protocols mainly designed for?

    <p>Small</p> Signup and view all the answers

    What is the main problem with the Distance Vector Routing algorithm?

    <p>It does not take line bandwidth into account when choosing routes</p> Signup and view all the answers

    What is the term 'Distance Vector' derived from?

    <p>The fact that the protocol includes a vector of distances (hop counts)</p> Signup and view all the answers

    What is the main difference between static and dynamic routing?

    <p>Static routing is manual, while dynamic routing is automatic</p> Signup and view all the answers

    What is the purpose of step 3 in the link-state routing process?

    <p>To construct a packet telling all that has just been learnt</p> Signup and view all the answers

    How do Distance Vector Protocols treat low speed links and high-speed links?

    <p>They treat low speed links equally or sometimes prefer them over high-speed links</p> Signup and view all the answers

    Why was the Distance Vector algorithm replaced?

    <p>It did not take line bandwidth into account and took too long to converge</p> Signup and view all the answers

    What is the purpose of a default outlet router?

    <p>To act as a last resort outlet for unknown destinations</p> Signup and view all the answers

    What type of algorithm is link-state routing also known as?

    <p>Shortest Path First (SPF) algorithm</p> Signup and view all the answers

    What is the finite limit of hops in Distance Vector Protocols after which a route is considered unreachable?

    <p>15</p> Signup and view all the answers

    What happens to dynamic routes in the routing table if a destination is down?

    <p>The dynamic route is removed from the routing table</p> Signup and view all the answers

    What is one deficiency of Distance Vector Protocols?

    <p>They rely on hop counts</p> Signup and view all the answers

    What is the primary advantage of default routing?

    <p>It is used for networks with a single exit point</p> Signup and view all the answers

    What is placed in a router's routing table when it learns about other networks?

    <p>Each of the other network entries learnt from the other router</p> Signup and view all the answers

    How do routers exchange network numbers in Distance Vector Protocols?

    <p>Via periodic broadcasts of the entire routing table</p> Signup and view all the answers

    What is the first task of a router when it is booted?

    <p>To learn who its neighbors are and their network addresses</p> Signup and view all the answers

    What is the main characteristic of dynamic routing?

    <p>It is automatic and dependent on the network state</p> Signup and view all the answers

    What happens when a route exceeds the finite limit of hops in Distance Vector Protocols?

    <p>The route is considered unreachable</p> Signup and view all the answers

    What is the outcome of the 5-step process in link-state routing?

    <p>A complex database of topology information</p> Signup and view all the answers

    What is a consequence of the reliance on hop counts in Distance Vector Protocols?

    <p>Inefficient routing behavior may occur</p> Signup and view all the answers

    What happens to the routing table in large networks?

    <p>It becomes very hard to maintain</p> Signup and view all the answers

    What is a characteristic of D-V protocols?

    <p>They are flat and lack hierarchy</p> Signup and view all the answers

    What do routers exchange in Link State protocols?

    <p>Link states</p> Signup and view all the answers

    What do routers build in Link State protocols?

    <p>Their own routing tables</p> Signup and view all the answers

    What is the purpose of IP Routing protocols?

    <p>To determine the path that data follows</p> Signup and view all the answers

    What is the role of routers in IP Routing?

    <p>They perform traffic directing functions</p> Signup and view all the answers

    What is the term for the set of protocols that determine the path that data follows?

    <p>IP Routing</p> Signup and view all the answers

    What is the purpose of a routing protocol?

    <p>To specify how routers communicate with each other to distribute information</p> Signup and view all the answers

    What is the main benefit of planning an addressing scheme in a network?

    <p>Easier addition of routers in the future</p> Signup and view all the answers

    What is a characteristic of routed protocols?

    <p>They define the format and use of fields within a packet</p> Signup and view all the answers

    What is the purpose of a routing protocol?

    <p>To provide mechanisms for sharing routing information</p> Signup and view all the answers

    What is an example of a routed protocol?

    <p>IP</p> Signup and view all the answers

    Why do networks tend to use hierarchical routing as they grow in size?

    <p>Because it becomes impossible to have every router keep an entry of every other router</p> Signup and view all the answers

    What is static routing?

    <p>A method of routing that is set up manually in the router</p> Signup and view all the answers

    Why is centralised addressing authority important?

    <p>To prevent address conflicts</p> Signup and view all the answers

    What is the main goal of routing protocols in IP routing?

    <p>To select the least-cost path to the destination</p> Signup and view all the answers

    What is a major disadvantage of dynamic routing?

    <p>It tries to force dynamic routing on situations that do not really need it, wasting bandwidth and effort</p> Signup and view all the answers

    What is the benefit of designing an addressing scheme that will work with routing?

    <p>It allows for easier addition of routers in the future</p> Signup and view all the answers

    What is the main difference between routing and bridging?

    <p>Routing is used at the IP level, while bridging is used at the Data Link Layer</p> Signup and view all the answers

    What is the primary function of routing algorithms and protocols?

    <p>To make decisions about network paths</p> Signup and view all the answers

    Why are static routing configurations considered stable?

    <p>Because they are less prone to changes</p> Signup and view all the answers

    What happens as networks keep on growing in size?

    <p>Routing tables grow proportionately</p> Signup and view all the answers

    What is similar to how routing is done in a telephone network?

    <p>Hierarchical routing</p> Signup and view all the answers

    Why is dynamic routing not always the best option?

    <p>It tries to force dynamic routing on situations that do not really need it</p> Signup and view all the answers

    What is the term often referred to as the process of neighbour notification?

    <p>Neighbour notification</p> Signup and view all the answers

    What do routers transmit on the network in link-state routing?

    <p>Link State Packets (LSPs)</p> Signup and view all the answers

    What is constructed by routers in link-state routing?

    <p>Topological databases</p> Signup and view all the answers

    What algorithm is used by routers to construct the logical topology of shortest paths?

    <p>Dijkstra algorithm</p> Signup and view all the answers

    What is the purpose of the routing table in link-state routing?

    <p>To switch packet traffic</p> Signup and view all the answers

    What is compared in several key areas in Table 1?

    <p>Link-state routing and distance vector routing</p> Signup and view all the answers

    What do routers use to determine the shortest path to each other network?

    <p>SPF algorithm</p> Signup and view all the answers

    What is the outcome of the link-state routing process?

    <p>Switching of packet traffic</p> Signup and view all the answers

    What is the primary difference between link-state routing algorithms and distance vector routing algorithms?

    <p>The knowledge of distant routers and their interconnections</p> Signup and view all the answers

    What is the purpose of link-state network discovery mechanisms?

    <p>To create a common picture of the entire internetwork</p> Signup and view all the answers

    What do routers learn about in the first step of link-state network discovery?

    <p>Their neighbours and directly connected networks</p> Signup and view all the answers

    Which of the following protocols uses a link-state algorithm?

    <p>OSPF</p> Signup and view all the answers

    What is the main advantage of link-state routing algorithms?

    <p>They provide a more accurate view of the network</p> Signup and view all the answers

    What is the primary function of a router in the distance vector routing algorithm?

    <p>To receive routing tables from its neighbouring routers</p> Signup and view all the answers

    What is the relationship between link-state routers in a network?

    <p>They share a common view of the entire internetwork</p> Signup and view all the answers

    What is the primary characteristic of the distance vector routing algorithm?

    <p>It accumulates network distances to maintain a database of network topology</p> Signup and view all the answers

    What is the main limitation of the distance vector routing algorithm?

    <p>It does not allow routers to know the exact topology of an internetwork</p> Signup and view all the answers

    What is the outcome of link-state network discovery?

    <p>A common picture of the entire internetwork is created</p> Signup and view all the answers

    What is the purpose of adding a distance vector number to the routing table?

    <p>To increase the distance vector, thereby increasing the hop count</p> Signup and view all the answers

    What is a characteristic of link-state routing protocols?

    <p>They are widely used in actual networks</p> Signup and view all the answers

    What is the similarity between distance vector information and highway signs?

    <p>Both indicate the distance to the destination</p> Signup and view all the answers

    What is the outcome of the step-by-step process of distance vector routing updates?

    <p>The algorithm accumulates network distances to maintain a database of network topology</p> Signup and view all the answers

    What happens when a router receives a routing table from its neighbouring router?

    <p>It adds a distance vector number to the routing table and passes it to its other neighbouring router</p> Signup and view all the answers

    What is the primary role of distance vector routing updates?

    <p>To maintain a database of network topology information</p> Signup and view all the answers

    What is the primary function of Router 1 when a packet destined for network 100.1.0.0 arrives?

    <p>To pass the packet to the best network along the path</p> Signup and view all the answers

    What is represented as a direction to a destination network by a router?

    <p>The best network along the path</p> Signup and view all the answers

    What is the function of interface S0 in Router 1?

    <p>To connect to network 100.1.0.0</p> Signup and view all the answers

    What is the next hop for a packet destined for network 100.4.0.0 in Router 1?

    <p>Router 2 through interface S2</p> Signup and view all the answers

    What is the purpose of a router in a network?

    <p>To connect multiple networks together</p> Signup and view all the answers

    What is the result when a packet arrives at a router and the best path is determined?

    <p>The packet is sent to the next hop along the path</p> Signup and view all the answers

    What is the role of a router when a packet is destined for a network that is not directly connected?

    <p>To send the packet to the next hop along the path</p> Signup and view all the answers

    What is the primary function of router configuration?

    <p>To determine the best path for packet forwarding</p> Signup and view all the answers

    What is a key assumption of routing in IP networks?

    <p>Addresses convey partial information about a host's location</p> Signup and view all the answers

    What is the primary goal of subnetting?

    <p>To reduce the size of routing tables</p> Signup and view all the answers

    Which of the following is NOT a design plan for addressing in IP networks?

    <p>Dynamic Host Configuration Protocol (DHCP)</p> Signup and view all the answers

    What is the main limitation of static routing in large networks as mentioned in the content?

    <p>It is not scalable</p> Signup and view all the answers

    What happens to the routing table in large networks?

    <p>It grows proportionately</p> Signup and view all the answers

    What is a key benefit of using subnetting in IP networks?

    <p>Greater flexibility in network design</p> Signup and view all the answers

    Why do networks tend to use hierarchical routing as they grow in size?

    <p>To make routing more efficient</p> Signup and view all the answers

    What is the primary function of a router in IP networks?

    <p>To forward packets based on destination addresses</p> Signup and view all the answers

    Which of the following is a characteristic of IP Address Classes?

    <p>Hierarchical addressing structure</p> Signup and view all the answers

    What is the primary function of a routing protocol?

    <p>To determine the best path for data to follow</p> Signup and view all the answers

    What is the primary advantage of using CIDR?

    <p>Increased scalability and flexibility in network design</p> Signup and view all the answers

    What is the purpose of IP routing protocols?

    <p>To determine the best path for data to follow</p> Signup and view all the answers

    What is a key requirement for implementing routing in IP networks?

    <p>A centralised addressing authority</p> Signup and view all the answers

    What happens when a network grows in size?

    <p>Routing tables grow proportionately</p> Signup and view all the answers

    What is the benefit of designing an addressing scheme that will work with routing?

    <p>It makes routing more efficient</p> Signup and view all the answers

    What is a major disadvantage of dynamic routing?

    <p>It consumes a lot of bandwidth and memory</p> Signup and view all the answers

    What is the primary function of a network switch?

    <p>To appear as part of the wire and introduce no resistance, no attenuation, no delay</p> Signup and view all the answers

    How do routers determine the next-hop address to which a packet should be delivered?

    <p>By consulting a routing table to determine the next-hop address</p> Signup and view all the answers

    What is the key difference between a layer 2 switch and a layer 3 switch?

    <p>Layer 2 switches bridge, while layer 3 switches route</p> Signup and view all the answers

    What is the benefit of using special silicon chips in network switches?

    <p>They reduce the packet processing time and increase network efficiency</p> Signup and view all the answers

    What is the primary objective of IP routing?

    <p>To examine the destination IP address of a packet and determine the next-hop address</p> Signup and view all the answers

    What is the role of routers in IP routing?

    <p>To forward packets from one network to another based on routing tables</p> Signup and view all the answers

    What is the key difference between static and dynamic routing?

    <p>Static routing is manual, while dynamic routing is automatic</p> Signup and view all the answers

    What is the primary goal of routing in a network?

    <p>To select the most optimal path for packet transmission</p> Signup and view all the answers

    What is the primary advantage of IP routing?

    <p>It allows for efficient routing of packets between networks</p> Signup and view all the answers

    What are the two basic functions employed by a router to relay a packet?

    <p>Path determination and switching</p> Signup and view all the answers

    What is the main limitation of routing techniques that prioritize packets between adjacent stations?

    <p>Lack of fairness to distant stations</p> Signup and view all the answers

    What is the primary function of a routing table in a router?

    <p>To determine the most optimal path for packet transmission</p> Signup and view all the answers

    What is the main goal of optimizing routing in a network?

    <p>To minimize overhead processing required</p> Signup and view all the answers

    What is the primary advantage of using routing techniques that prioritize packets between adjacent stations?

    <p>Increased throughput between adjacent stations</p> Signup and view all the answers

    What is the primary role of a router in IP routing?

    <p>To forward packets based on network layer addresses</p> Signup and view all the answers

    What is the main consequence of relying on hop counts in routing techniques?

    <p>Limited network scalability</p> Signup and view all the answers

    Study Notes

    Network Reachability and Routing

    • Network reachability in static routing is not dependent on the existence and state of the network itself.

    Static Routing

    • Static routes remain in the routing table regardless of the destination's state (up or down).
    • Traffic is still sent towards the destination even if it's down.
    • Static routing is not suitable for large or complex networks due to the time required to define and maintain static route table entries.

    Default Routing

    • Default routing is a "last resort" outlet for traffic to destinations unknown to the local router.
    • A default route is a path on which a router should forward a packet if it does not have specific knowledge about the packet's destination.

    Dynamic Routing

    • Dynamic routing refers to routes being learned via an internal or external routing protocol.
    • Network reachability is dependent on the existence and state of the network.
    • If a destination is down, the route disappears from the routing table, and traffic is not sent towards the destination.
    • Dynamic routing enables routers to build their routing tables automatically and make appropriate forwarding decisions.

    Distance Vector Routing

    • Each router maintains a routing table containing one entry for each router in the subnet.
    • The entry consists of two parts: the preferred outgoing line/port to use for that destination and an estimate of the time or distance to that destination.
    • The metric used might be the number of hops, time delay in milliseconds, total number of packets queued along the path, or something similar.
    • Link State Routing replaced Distance Vector Routing in 1979.
    • The algorithm involves 5 steps: discovering neighbors, measuring delay or cost, constructing a packet, sending the packet to other routers, and computing the shortest path to every other router.
    • Link-state routing algorithms maintain a complex database of topology information.

    Distance Vector Protocols

    • Distance Vector Protocols, such as RIP Version 1, were designed for small network topologies.
    • The protocol includes a vector of distances (hop counts) in its routing updates.
    • Low-speed links are treated equally or sometimes preferred over high-speed links, depending on the calculated hop count.
    • Distance Vector Protocols have a finite limit of hops (15) after which a route is considered unreachable.
    • The reliance on hop counts is one deficiency of distance vector protocols.
    • Routing information gets updated through periodic broadcasts of the entire routing table, which can be inefficient in large networks.
    • Link State Protocols work on the basis that routers exchange information elements called link states, which carry information about links and nodes.
    • Routers do not exchange routing tables; instead, each router builds its own routing table using the exchanged link states.

    IP Routing

    • IP Routing is an umbrella term for the set of protocols that determine the path data follows across multiple networks from its source to its destination.
    • IP Routing protocols enable routers to build up a forwarding table that correlates final destinations with next-hop addresses.
    • A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between nodes on a computer network.

    Enforcement of IP Addressing

    • A plan for IP addressing must be enforced, and addressing authority must be centralized.
    • A design is useless unless addresses are assigned in accordance with it.
    • Planning for routing is essential, even if it's not used initially, to ensure a scalable and organized addressing scheme.

    Routed Protocols

    • A routed protocol is a protocol that contains sufficient network-layer addressing information for user traffic to be directed from one network to another.
    • Routed protocols define the format and use of the fields within a packet.
    • Examples of routed protocols include IP and Novell's IPX.

    Routing Protocols

    • A routing protocol provides mechanisms for sharing routing information.
    • Routing protocol messages move between routers, allowing them to communicate with other routers to update and maintain routing tables.
    • Routing protocol messages do not carry end-user traffic from network to network.

    Types of Routing

    • There are three types of routing: static, default, and dynamic.

    Static Routing

    • Static routing refers to routes to destinations being set up manually in the router.
    • It is a stable but not very flexible configuration.
    • Static and default routing are not necessarily outdated and can be useful in certain situations.

    Dynamic Routing

    • Dynamic routing is a more flexible and scalable approach, but it can be more complex and resource-intensive.
    • It is not necessary to use dynamic routing in all situations, and it can be a waste of bandwidth, effort, and money.

    Routing Algorithms

    • Routing algorithms and protocols form the core of the internet, as they make decisions about routing.
    • Network engineers assign costs to network paths, and routing protocols select the least-cost path to the destination.
    • Examples of routing algorithms include distance vector and link-state routing.

    Distance Vector Routing

    • Distance vector routing algorithms do not allow a router to know the exact topology of an internetwork.
    • Distance vector information is similar to the information found on signs at a highway intersection.
    • Examples of distance vector routing protocols include RIP.
    • Link-state routing algorithms maintain full knowledge of distant routers and how they interconnect.
    • Examples of link-state routing protocols include NLSP, OSPF, and IS-IS.
    • Link-state routing is widely used in actual networks.
    • Link-state network discovery mechanisms are used to create a common picture of the entire internetwork.
    • All routers employing the link-state routing algorithm share this common view of the internetwork.
    • Link-state network discovery proceeds through neighbor notification, transmission of LSPs, and construction of topological databases.
    • Distance vector routing can be compared to link-state routing in several key areas, including:
      • Complexity and scalability
      • Convergence time
      • Network topology knowledge
      • Reaction to network changes

    IP Routing Principles

    • IP Routing is a process that sends packets from a host on one network to another host on a different remote network.
    • It helps to examine the destination IP address of a packet, determine the next-hop address, and forward it.

    Routing and Network Layer Addresses

    • Routers relay a packet from one data link to another using two basic functions: path determination and switching functions.
    • Path determination function enables the router to select the most appropriate interface for forwarding a packet.
    • Switching function enables a router to accept a packet on one interface and forward it on a second interface.
    • Routing assumes that addresses have been assigned to network elements to facilitate data delivery.

    Routing Table

    • Routing tables are used by routers to determine the next-hop address to which the packet should be delivered.
    • The routing table consists of a list of network addresses and corresponding interface numbers.

    Routing Algorithms

    • Routing algorithms and protocols form the core of the Internet, as they make all the decisions.
    • Network engineers assign costs to network paths, and routing protocols select the least-cost path to the destination.

    Types of Routing

    • Static routing: a plan must exist by which addresses are assigned, and the design plan must be implemented in switching nodes.
    • Dynamic routing: routers use dynamic routing to update their routing tables, and it is more flexible than static routing.
    • Default routing: it is not as flexible as dynamic routing, but it is more stable.

    Switching

    • A networking switch is designed to behave like a wire when relaying data signals.
    • Switches must implement a normal path selection algorithm, and they can forward packets directly from source to destination without passing through RAM buffers.
    • Switches are faster than normal bridges and routers, and they use special silicon chips to forward packets.

    Learning Objectives

    • Understand the concept of switching and routing.
    • Understand routed and routing protocols.
    • Identify types of routing: static, default, dynamic.
    • Understand routing algorithms.
    • Understand distance vector and link state routing.

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    ch1.pdf

    Description

    Learn about static routing in computer networks, its advantages and limitations, and how it differs from dynamic routing. Test your understanding of static route tables and their maintenance.

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