SDN Concepts and Algorithms Quiz
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What does the abbreviation 'SDN' stand for?

  • Software Data Network
  • Software Defined Network (correct)
  • System Defined Node
  • System Data Network

    • What is the main advantage of the 'logically centralized control' approach in SDN?

  • Increased network latency
  • Simplified network management (correct)
  • Increased network complexity
  • Reduced network security

    • Which of these is NOT a component of the 'logically centralized control' approach in SDN?

  • Network Interface Card (NIC) (correct)
  • Control Agents (CAs)
  • Network Layer
  • Controller

    • What is the role of the 'match-plus-action' abstraction in SDN?

    <p>Simplifying packet forwarding (B)</p> Signup and view all the answers

    What is the primary purpose of a 'Controller' in SDN?

    <p>To manage and configure network devices (D)</p> Signup and view all the answers

    Why is the 'Control Agent (CA)' crucial in SDN?

    <p>To translate controller instructions into network device actions (C)</p> Signup and view all the answers

    What is the primary advantage of managing the control plane separately from the data plane in SDN?

    <p>Improved network flexibility (A)</p> Signup and view all the answers

    How does a 'generalized match-plus-action' abstraction work within a router?

    <p>It defines rules for packet forwarding based on specific conditions (C)</p> Signup and view all the answers

    When a cost change occurs, the Distance Vector Algorithm uses a "count-to-infinity" process to determine the new cost to a destination. How does this process work?

    <p>Affected routers iteratively update their distance vectors based on the distance vectors received from their neighbors, leading to a potential for increasing distance estimates. (B)</p> Signup and view all the answers

    In the Distance Vector Algorithm, the "bad news travels slow" problem refers to:

    <p>The algorithm's inability to detect and correct routing loops that can arise from link cost changes. (C)</p> Signup and view all the answers

    What is the primary difference between the "good news travels fast" and the "bad news travels slow" scenarios in the Distance Vector Algorithm?

    <p>Good news involves a decrease in the path cost, leading to faster convergence, while bad news involves an increase in the path cost, leading to a slower convergence. (C)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the Distance Vector Algorithm?

    <p>It is a centralized routing algorithm with a single router responsible for maintaining the routing table. (A)</p> Signup and view all the answers

    What is the primary difference between the Link-State (LS) and Distance Vector (DV) routing algorithms?

    <p>LS maintains a complete network topology map, while DV only considers the distance to neighboring routers. (A)</p> Signup and view all the answers

    Which of the following is NOT a goal of routing protocols?

    <p>Determine the path with the least number of hops (B)</p> Signup and view all the answers

    Which of these is NOT a routing protocol type mentioned?

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

    What routing protocol is used for intra-ISP routing?

    <p>OSPF (C)</p> Signup and view all the answers

    What is the primary function of the "Control Plane" in a network?

    <p>Determining the best paths for data packets (A)</p> Signup and view all the answers

    What is the role of Internet Control Message Protocol (ICMP)?

    <p>Providing feedback on network connectivity (C)</p> Signup and view all the answers

    Which of the following is NOT a factor considered when determining the 'cost' of a route?

    <p>Security Level (B)</p> Signup and view all the answers

    What is the primary purpose of the 'Network Layer' in a network?

    <p>Determining the best paths for data to travel (B)</p> Signup and view all the answers

    Which of the following is NOT a challenge of routing?

    <p>Ensuring the integrity of data packets (B)</p> Signup and view all the answers

    What is the purpose of the control plane in a network?

    <p>To manage and control the flow of data traffic in a network. (B)</p> Signup and view all the answers

    What does the 'per-router control plane' refer to?

    <p>A distributed control plane where each router manages its own routing decisions. (D)</p> Signup and view all the answers

    What is the role of the 'routing algorithm' in the network layer?

    <p>To determine the best path for data packets to travel from source to destination. (B)</p> Signup and view all the answers

    What is the purpose of the 'local forwarding table' in a router?

    <p>To store information about the best path for data packets to take to their destination. (B)</p> Signup and view all the answers

    How do routers use forwarding tables to determine the next hop for a data packet?

    <p>By comparing the destination address in the packet header with the addresses in the table. (D)</p> Signup and view all the answers

    What is the relationship between the control plane and the data plane in a network?

    <p>The control plane manages the data plane, determining how data packets are transmitted. (D)</p> Signup and view all the answers

    What was the main reason for the renewed interest in rethinking network control plane around 2005?

    <p>The increasing complexity of networks and the need for more efficient routing protocols. (B)</p> Signup and view all the answers

    What is the main advantage of a per-router control plane?

    <p>Improved scalability and flexibility in managing routing decisions. (A)</p> Signup and view all the answers

    What is the purpose of the 'flow-removed' message from the controller to a switch?

    <p>To instruct the switch to delete a specific flow entry from its flow table. (D)</p> Signup and view all the answers

    What is a key challenge in hardening the control plane of an SDN network?

    <p>All of the above. (D)</p> Signup and view all the answers

    What is a potential advantage of using SDN-computed congestion control over traditional routing protocols?

    <p>SDN-computed congestion control can react more quickly to changes in network traffic. (B)</p> Signup and view all the answers

    Which of the following is NOT a traditional network layer protocol discussed in the text?

    <p>NETCONF/YANG (C)</p> Signup and view all the answers

    What information does an ICMP echo reply (ping) message provide?

    <p>The latency between the sender and the destination. (A)</p> Signup and view all the answers

    What is the main function of the 'port status' OpenFlow message?

    <p>To inform the controller of a change in the status of a port on the switch. (A)</p> Signup and view all the answers

    How are SDN-computed forwarding tables different from router-computed forwarding tables ?

    <p>SDN-computed forwarding tables are more flexible and adaptable to changing network conditions. (A)</p> Signup and view all the answers

    What is the main reason why network operators do not typically create or send OpenFlow messages directly?

    <p>Higher-level abstractions provide a more user-friendly way to manage SDN networks. (B)</p> Signup and view all the answers

    Which of the following are not routing protocols mentioned in the content as being used within the Internet?

    <p>OpenFlow (B), RIP (C)</p> Signup and view all the answers

    What is the primary function of the network layer's data plane?

    <p>Moving packets from a router's input to its appropriate output (C)</p> Signup and view all the answers

    Which of the following options provides a logically centralized approach to managing the network's control plane?

    <p>Software Defined Networking (B)</p> Signup and view all the answers

    Identify the protocol that is not directly associated with network management and configuration?

    <p>BGP (D)</p> Signup and view all the answers

    Traditional routing algorithms are typically part of which network control plane approach?

    <p>Per-router control (A)</p> Signup and view all the answers

    Which two routing protocols are primarily used to manage routing within the Internet?

    <p>BGP and OSPF (B)</p> Signup and view all the answers

    Which protocol is not directly mentioned in the content as being used in the Internet's network management?

    <p>OSPF (D)</p> Signup and view all the answers

    Which of the following routing protocols is a link-state protocol?

    <p>OSPF (A)</p> Signup and view all the answers

    Flashcards

    Network Control Plane

    The part of a network responsible for routing and managing network traffic.

    Routing Protocols

    Protocols that determine how routers communicate and share information about network destinations.

    OSPF

    Open Shortest Path First; a link-state routing protocol for intra-ISP routing.

    BGP

    Border Gateway Protocol; a protocol used for routing between different ISPs.

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    Forwarding

    The process of moving packets from the input to the appropriate output of a router.

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    Routing

    Determining the path packets take from their source to destination.

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    Per-Router Control

    Traditional method of structuring network control where each router makes independent decisions.

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    Software Defined Networking (SDN)

    A modern approach to network management that centralizes control for better efficiency and flexibility.

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    Logically Centralized Control

    A network management approach where control is coordinated from a single, central entity.

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    SDN

    Software-Defined Networking, a networking paradigm that separates data forwarding from control functions.

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    Generalized Match-plus-Action Abstraction

    A framework in SDN where routers match incoming data to actions based on various criteria.

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    Router

    A device that forwards data packets between computer networks.

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    IP Forwarding

    The process of sending packets from one host to another using Internet Protocol.

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    Control Agents (CAs)

    Local entities that communicate with a central controller to manage network operations.

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    Network Layer

    The layer in the OSI model responsible for data transfer between devices, using logical addressing.

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    Central Controller

    A distinct, typically remote system that oversees local Control Agents in a network.

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    Control Plane

    The component of a network responsible for making decisions about how data packets are routed.

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    Data Plane

    The part of the network that forwards data packets based on the control plane's decisions.

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    Routing Algorithm

    A set of rules that determine the path data packets take through the network.

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    Forwarding Table

    A table used by routers to determine the next hop for data packets based on their destination addresses.

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    Per-Router Control Plane

    An architecture where each router independently runs its own control algorithms.

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    Local Forwarding Table

    The specific forwarding table located within a router that guides packet forwarding decisions locally.

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    Packet Header

    Information at the start of a data packet that contains addressing and control information.

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    Interaction of Components

    The process by which routing algorithm components in the control plane communicate to update forwarding tables.

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    Link State Protocol

    A routing protocol that maintains a complete view of the network by exchanging link state information.

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    Distance Vector Protocol

    A routing protocol that determines the best path based on distance to each node's neighbors.

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    Good Path

    A path in routing that is the least costly, fastest, or least congested.

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    Routing Challenge

    The significant task of ensuring efficient and effective data routing in a network.

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    Flow-Removed Message

    Message indicating deletion of a flow table entry at a switch.

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    Port Status Message

    Notification to the controller about a change in a port's state.

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    Control Plane Hardening

    Improving stability and security of the network control system.

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    Internet Scaling

    Extending network operations beyond a single Autonomous System (AS).

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    SDN in 5G

    The role of Software Defined Networking in enhancing 5G cellular networks.

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    SDN Congestion Control

    Using SDN to manage data flow by regulating sender rates based on congestion feedback.

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    ICMP

    Internet Control Message Protocol, for diagnostic and error messages.

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    Echo Reply

    An ICMP message type that responds to a ping request.

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    Distance Vector (DV) Protocol

    A routing protocol where routers share information about the distance to various network destinations.

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    Count-to-Infinity Problem

    A situation in distance vector routing where incorrect routing information can circulate, causing incorrect paths and looping updates.

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    Link Cost Change

    A change in the cost of a network link that affects routing decisions and distance vectors of routers.

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    Message Complexity in LS vs. DV

    In link-state (LS) algorithms, messages grow quadratically with routers, whereas distance vector (DV) is less complex but slower.

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    Robustness of Routing Protocols

    The ability of a routing protocol to handle failures or compromised routers and still maintain accurate routing information.

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    Study Notes

    Chapter 5: Network Layer: Control Plane

    • This chapter provides a note on the use of these PowerPoint slides for faculty, students, and readers, which are available in PowerPoint form to demonstrate animations.
    • These slides can be adapted freely to fit individual needs.
    • If the slides are used in a class, the source should be mentioned.
    • If the slides are posted on a website, the adaptation from the original slides should be acknowledged, along with the copyright information.
    • For any revision history, refer to the slide notes.
    • The material is copyright 1996-2020 and J.F Kurose and K.W. Ross hold all rights reserved.

    Network Layer Control Plane: Our Goals

    • Understanding the principles behind the network control plane.
    • Traditional routing algorithms.
    • SDN (Software Defined Networking) controllers.
    • Network management and configuration.
    • Internet Control Message Protocol (ICMP).

    Network Layer: "Control Plane" Roadmap

    • The study roadmap for the network control plane
    • Routing protocols
    • Link state
    • Distance vector
    • Intra-ISP routing: OSPF
    • Routing among ISPs: BGP
    • SDN control plane
    • Internet Control Message Protocol (ICMP)
    • Network management, configuration
    • SNMP
    • NETCONF/YANG (not included)

    Network-Layer Functions

    • Forwarding: moving packets from a router's input to its output.
    • Routing: determining the route taken by packets from source to destination.
    • Two approaches to structuring network control plane: per-router control (traditional), and logically centralized control (software defined networking).

    Introduction

    • The forwarding and flow tables are the key elements that link the network layer's data plane and control plane.
    • Generalized forwarding includes forwarding a packet to a router's output port, dropping a packet, or replicating a packet.
    • Two routing control approaches: per-router control, (OSPF and BGP) and logically centralized control (SDN).

    Introduction: Two Approaches

    • Per-router control (OSPF and BGP).
    • Logically centralized control (SDN)

    Routing Protocols

    • Determining the best paths (routes) from source hosts to receiving hosts through a network of routers.
    • Path: sequence of routers packets traverse to reach destination host.
    • "Good" routing: least cost, fastest, least congested.
    • Graph Abstraction: representing the network.
    • N: the set of routers (e.g., u, v, w, x, y, z).
    • E: the set of links (e.g., (u,v), (u,x), etc.).
    • Link costs (ca,b) determined by the network operator: can be a constant (1), inversely related to bandwidth, inversely related to congestion.

    Routing Algorithm Classification

    • Static: routes change slowly over time.
    • Dynamic: routes change more quickly, responding to link cost changes.
    • Global algorithms: all routers have complete topology and link cost information.
    • Decentralized algorithms: iterative process where routers exchange info with neighbors (distance vector algorithms).
    • Centralized: network topology and link costs known to all nodes via link state broadcast
    • All nodes have the same information.
    • Computes least-cost paths from one node (source) to all other nodes, creating a forwarding table for the source node.
    • Iterative approach: after k iterations, the least-cost path to k destinations are known.

    Dijkstra's Algorithm: An Example

    • Detailed steps of calculating least cost paths, using a table to illustrate node states, predecessors, and least cost.

    Dijkstra's Algorithm: Another Example

    • Illustrative example of Dijkstra's algorithm with a different network topology, showing the process of computing least-cost paths, tables, and predecessor nodes.

    Exercise 5.0

    • Constructing a table to calculate the least cost paths in a network.

    Exercise 5.1-5.3

    • Similar exercise questions on calculating the least cost paths in networks.

    Distance Vector Algorithm

    • Based on the Bellman-Ford Equation, considering the cost of the least-cost path from x to y as Dx(y).
    • Estimated least cost path from x to y can be calculated using each neighbor v's cost from v to y (Dv(y) + cx,v).

    Distance Vector Algorithm: Key Idea

    • Each node periodically sends its distance vector to its neighbors.
    • Node updates its distance vector using the algorithm given the new estimates received by its neighbors.
    • Under minimal, normal conditions, the estimate converges at the actual least cost.

    Distance Vector Algorithm: Examples

    • Illustrative examples showing calculations for different nodes and network situations.
    • The impact of link cost changes on a distance vector (DV) algorithm calculation.

    Comparison of LS and DV Algorithms

    • Comparing link state (LS) and distance vector (DV) routing algorithms.
    • The complexity of messages sent, speed of convergence, and robustness to failures (e.g., malfunctions or compromised routers).

    Exercise 5.9

    • Calculations based on the figure and constructed table using the Bellman-Ford algorithm.

    Network Layer: "Control Plane" Roadmap

    Illustrative examples (figures and tables) for calculations.

    • Routing protocols, including intra-ISP routing (OSPF), inter-ISP routing (BGP).
    • SDN control plane.
    • Network management and configuration(SNMP, NETCONF/YANG).
    • Internet Control Message Protocol (ICMP).

    Making Routing Scalable

    • Issues encountered in scaling up routing in large networks (e.g, billions of destinations).
    • Large routing tables and routing table exchange traffic.

    Internet Approach to Scalable Routing

    • Aggregation of routers into Autonomous Systems (ASes), or domains.
    • Distinguish intra-AS (within a single Autonomous System / network) and inter-AS (among Autonomous Systems) routing.

    Interconnected ASes

    • Intra-AS and inter-AS routing for forwarding tables to include internal and external destinations.

    Inter-AS Routing: A Role in Intradomain Forwarding

    • As1 (autonomous system 1) learning which destinations (other Autonomous Systems) are reachable.
    • Propagating this reachability information to all routers in AS1.

    Intra-AS Routing: Routing Within an AS

    • Interior Gateway Protocols (IGPs) protocols including RIP, IGRP/EIGRP, OSPF, and IS-IS.

    OSPF (Open Shortest Path First) Routing

    • Publicly available routing system based on link-state.
    • Full network topology known to all routers.
    • Dijkstra's algorithm to compute forwarding tables.
    • All OSPF messages are authenticated for security

    Hierarchical OSPF

    • Hierarchical structure for OSPF, dividing the network into areas with summarized information between backbone and area border routers.
    • Local routers compute routing within their area, and forward packets outside to area border routers.

    Internet Inter-AS Routing: BGP

    • Border Gateway Protocol (BGP) is the de facto inter-domain routing protocol.
    • The glue that holds the Internet together, with each AS advertising reachability information to other neighboring ASes, using internal (iBGP) and external (eBGP) routing.

    Why Different Intra-, Inter-AS Routing

    • Policy: control over how traffic is routed within and between ASes is more important in inter-AS than intra-AS.
    • Scale: hierarchical AS structure to reduce the scale of routing tables.
    • Performance: Intra-AS routing optimization, while inter-AS routing performance is controlled by policy.

    Software Defined Networking (SDN)

    • Distributed, per-router control approach to network control plane.
    • SDN has a central controller (network OS) that manages and installs forwarding tables in the network switches.
    • Separate control and data planes.

    SDN: Selected Challenges

    • Hardening the control plane for dependability, reliability, and performance.
    • Robustness to failures.
    • Distributed system for dependability and security.
    • Meeting specific requirements (e.g., real-time, ultra-reliable, ultra-secure).
    • Internet-scaling.
    • 5G cellular networks use SDN.

    SDN and the Future of Traditional Network Protocols

    • SDN computing versus traditional router computing: (table creation).
    • SDN computing congestion control.

    Network Layer: "Control Plane" Roadmap

    ICMP: Internet Control Message Protocol

    • Used by hosts and routers for communicatiing network-level information.
    • Error reporting (e.g, unreachable hosts, networks, or ports), and other (control) communication.
    • ICMP messages use IP datagram protocol.
    • Include messages for echo request/response (ping).

    Traceroute and ICMP

    • Traceroute uses ICMP to determine the paths to a destination.
    • ICMP messages are used to report the source and intermediate routing processes.

    Network Layer: "Control Plane" Roadmap

    What is Network Management?

    • Managing autonomous systems (networks) of thousands of interacting hardware and software components
    • Similar to jet airplane, or nuclear power plant management.

    Components of Network Management

    • Managing server (entity) and devices (equipment) that have configuration and operational data stored in a MIB database (management information base)

    Network Operator Approaches to Management

    • CLI (command-line interface), SNMP, MIB, NETCONF, and YANG techniques
    • Protocols for managing networks

    SNMP protocol

    • Two ways to communicate data and operational commands; request/response, and trap mode.

    SNMP Protocol (Message Types)

    • Detailed table of SNMPv3 PDU types.

    SNMP: Management Information Base (MIB)

    • MIB (management information base): defines managed devices' operational and some configuration data.

    Note: Exercises

    • Multiple exercises on calculating network costs in different scenarios and network designs using Bellman Ford algorithm.

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    Computer Networking: A Top-Down Approach (2021) Chapter 5 PDF

    Description

    Test your knowledge of Software-Defined Networking (SDN) concepts, including centralized control, the role of controllers, and the Distance Vector Algorithm. This quiz covers both the theoretical principles and practical components of SDN architecture and algorithms. Whether you are a student or a professional, this quiz will help reinforce your understanding of these critical networking technologies.

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