Wireless Mobile & Multimedia Networking Lecture 2: IGMP
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Questions and Answers

What is the purpose of Report Suppression in a host group?

  • To ensure all Reports are sent immediately after a timer expires.
  • To generate multiple Reports for better accuracy.
  • To delay sending Reports until the timer has fully expired.
  • To prevent duplicate Reports when a timer is running. (correct)

    • How is Maximum Response Time (D) defined?

  • The average time a host takes to respond to queries.
  • The fixed time in which all hosts must respond.
  • The minimum amount of time a host can wait before responding.
  • The maximum time a host can wait before responding to a query. (correct)

    • What does a TTL value of 1 indicate for IGMP messages?

  • Messages are forwarded through multiple routers.
  • Messages are only sent to the local network. (correct)
  • Messages can reach distant hosts across different networks.
  • Messages are blocked by local firewalls.

    • What is the role of TTL in relation to IP Multicast packets?

    <p>It specifies the maximum distance a packet can travel.</p> Signup and view all the answers

    When a Report is generated after a timer expires, what is the intended effect?

    <p>To spread Reports over a fixed time interval for better network management.</p> Signup and view all the answers

    What is the primary function of the Internet Group Management Protocol (IGMP)?

    <p>To manage membership in multicast groups</p> Signup and view all the answers

    Which version of IGMP introduced a mechanism for hosts to explicitly leave a multicast group?

    <p>IGMPv2</p> Signup and view all the answers

    What type of IGMP query is used by routers to determine if specific multicast groups have active members?

    <p>Group-specific query</p> Signup and view all the answers

    What happens when a multicast router does not have any active hosts for a multicast group?

    <p>It removes the group from its table after a timeout</p> Signup and view all the answers

    Which version of IGMP allows for source-filtering capabilities?

    <p>IGMPv3</p> Signup and view all the answers

    How do hosts indicate their membership in a multicast group in response to an IGMP query?

    <p>By sending a membership report</p> Signup and view all the answers

    Which IGMP version does not support group-specific queries?

    <p>IGMPv1</p> Signup and view all the answers

    What kind of query is characterized by a group address set to zero?

    <p>General query</p> Signup and view all the answers

    Which range of addresses is reserved for the use of routing protocols?

    <p>224.0.0.0 to 224.0.0.255</p> Signup and view all the answers

    What is the purpose of the IGMP protocol?

    <p>To manage multicast group memberships</p> Signup and view all the answers

    Which of the following multicast addresses is reserved for all hosts and all routers on a network?

    <p>224.0.0.1</p> Signup and view all the answers

    What will happen when an application utilizing a multicast address is terminated?

    <p>The multicast address is implicitly released</p> Signup and view all the answers

    Which of the following addresses is used for all RIP2 routers in a network?

    <p>224.0.0.9</p> Signup and view all the answers

    What is the correct address range owned by an Autonomous System with the number 0x8080?

    <p>233.128.128.0 to 233.128.128.255</p> Signup and view all the answers

    How many hex digits are there in a MAC address?

    <p>48</p> Signup and view all the answers

    What type of multicast addresses should routers not forward if they fall within a specific range?

    <p>224.0.0.0 to 224.0.0.255</p> Signup and view all the answers

    What does a unicast Ethernet frame contain?

    <p>The unique MAC address of the destination receiver</p> Signup and view all the answers

    What is the destination address for a broadcast Ethernet frame?

    <p>FF:FF:FF:FF:FF:FF</p> Signup and view all the answers

    Which range of MAC addresses is reserved for IP multicast?

    <p>01:00:5e:00:00:00 to 01:00:5e:7f:ff:ff</p> Signup and view all the answers

    Which option for the netstat command provides the routing table?

    <p>-r</p> Signup and view all the answers

    What are the valid classes of multicast addresses mentioned in the content?

    <p>Class D addresses</p> Signup and view all the answers

    What binary pattern represents all 1's in a broadcast frame?

    <p>11111111:11111111:11111111:11111111</p> Signup and view all the answers

    What command can be used to display both unicast and multicast addresses?

    <p>netstat -a</p> Signup and view all the answers

    What type of address is 224.0.0.0 considered in the context of multicast?

    <p>Multicast address</p> Signup and view all the answers

    What action is taken when a host wants to leave a group in IGMPv1?

    <p>No report is sent.</p> Signup and view all the answers

    Which of the following IP addresses is used for IGMP general queries?

    <p>224.0.0.1</p> Signup and view all the answers

    What is the typical length of an IGMP message?

    <p>8 bytes</p> Signup and view all the answers

    Which octet represents the leave message in the IGMP message format?

    <p>0x17</p> Signup and view all the answers

    What is the purpose of the report delay timer in IGMP?

    <p>To avoid multiple reports being sent at once.</p> Signup and view all the answers

    What does the first octet of an IGMP message indicate when it is set to 0x11?

    <p>It indicates a query message.</p> Signup and view all the answers

    What is the significance of the value assigned to the report delay timer?

    <p>It is randomly chosen.</p> Signup and view all the answers

    Which of the following statements about IGMP group addresses is incorrect?

    <p>Group addresses for IGMPv1 are always fixed.</p> Signup and view all the answers

    In IGMP messages, what is indicated by a type value of 2?

    <p>Sent by a host.</p> Signup and view all the answers

    What is the destination IP address for the IGMP membership report?

    <p>The group's specific address.</p> Signup and view all the answers

    Study Notes

    Wireless Mobile & Multimedia Networking Lecture 2: IGMP

    • IGMP is a simple protocol for supporting IP multicast
    • IGMP operates on a physical network (e.g., a single Ethernet segment)
    • Multicast routers use IGMP to track memberships in multicast groups.
    • A multicast router maintains a table of multicast groups and hosts joined.
    • The router only forwards packets if a host in the group is still connected.
    • The router doesn't track which specific host is connected to the group.

    Topics

    • Multicast addresses
    • IGMP protocol

    IP Multicast Addressing

    • All Class D addresses are multicast addresses
    • The format is 1110 followed by the 28-bit multicast group ID.
    • Class D addresses range from 224.0.0.0 to 239.255.255.255
    • Multicast addresses are dynamically assigned
    • The address is released when an application ends.

    Reserved IP Multicast Addresses

    • The range of addresses from 224.0.0.0 to 224.0.0.255 is reserved for routing protocols and low-level topology discovery.
    • Multicast routers shouldn't forward multicast datagrams with destination addresses in this range.
    • Important permanent multicast groups include:
      • 224.0.0.1: All hosts and routers on a network
      • 224.0.0.2: All routers on a network
      • 224.0.0.22: IGMPv3
      • Other permanent groups are reserved for specific protocols (e.g., RIP2, DVMRP, PIM).

    IP Multicast Addresses for AS

    • Autonomous Systems (AS) have their own multicast address ranges.
    • Example: AS 0x8080 owns the range 233.128.128.0 to 233.128.128.255.

    A Quick Revision of MAC Address

    • MAC addresses consist of 12 hexadecimal digits (48 bits).
    • Ethernet addresses have three types:
      • Unicast: Contains the MAC address of the destination receiver.
        • The first six digits are assigned by IEEE to identify the manufacturer.
        • The last six digits are unique hardware IDs assigned by the manufacturer.
      • Broadcast: Contains all binary 1s (FF:FF:FF:FF:FF:FF).
      • Multicast: Contains a unique multicast MAC address for an application, protocol, or data stream.

    Mapping Multicast Address: IP → MAC

    • Ethernet addresses with the initial 3 bytes 01:00:5e are reserved for IP multicast.
    • The range is 01:00:5e:80:00:00 to 01:00:5e:7f:ff:ff.

    netstat

    • The netstat command is used to display network connections and routing tables.
    • Options include:
      • -n: Displays IP addresses numerically.
      • -r: Displays the routing table.
      • -a: Displays all available addresses (unicast and multicast).

    netstat -g

    • netstat -g displays all multicast group memberships for all interfaces on the current host.

    IGMP

    • The Internet Group Management Protocol (IGMP) is used for IP multicast on a network.
    • Supports: joining, leaving, querying membership and sending membership reports.
    • IGMP operates on a single network segment.

    Versions of IGMP

    • IGMPv1: No explicit leave mechanism; uses timeout for group membership.
    • IGMPv2: Includes a "leave processing" mechanism and group-specific queries; is now a default in many systems.
    • IGMPv3: Supports source filtering, enabling receivers to signal a router about a traffic source.

    IGMP Messages

    • IGMP query: Used by routers to identify groups on attached networks.
    • Group-specific queries: Identify if a specific group has members.
    • Membership report: A host responds with yes to a query if it's still in the group.
    • Join report: sent when a process joins a group.
    • Leave message: sent when a process leaves a group (IGMPv2/v3 only).

    IGMP Protocol

    • Diagram shows the flow of IGMP messages between hosts and routers.

    IGMPv1 Packet Format

    • IGMP messages are typically 8 bytes long.
    • The first octet specifies the message type (query or report).

    IGMPv2 and IGMPv3 Packet Format

    • Shows the data fields, including Type, Maximum Response Time, Checksum, Group Address.

    Timing Issues

    • Query interval: Host receives a query and starts a report delay timer using a randomly chosen value.
    • Maximum response time: The max time a host can wait before responding to a query.
    • Report suppression: Host stops the timer and suppresses duplicate reports.

    Time To Live (TTL)

    • TTL is a scope limiting parameter.
    • Controls the number of hops an IP multicast packet is allowed to propagate.
    • TTL = 1 for local network multicast (e.g., IGMP messages) which don't get forwarded by routers.

    Summary of Comparison

    • Table comparing IGMPv1, IGMPv2, and IGMPv3 features and details.

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    Related Documents

    Wireless Mobile & Multimedia Networking Lecture 2 PDF

    Description

    This quiz focuses on IGMP, a protocol for IP multicast. It covers its operation on physical networks, how multicast routers manage group memberships, and details on multicast addressing, including Class D addresses. Test your understanding of these critical networking concepts.

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