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

What happens when a timer expires for a host group?

  • Responses are suppressed for all hosts.
  • The timer resets for the host group.
  • A Report is generated for the corresponding host group. (correct)
  • All hosts report simultaneously.
  • What does Report Suppression achieve?

  • Ensures all hosts report immediately.
  • Prevents duplicate Reports from being sent. (correct)
  • Forces a timer reset across all hosts.
  • Allows hosts to combine Reports into one.
  • What is the significance of a TTL value of 1 for IGMP messages?

  • IGMP messages are forwarded between networks.
  • It increases the response time for hosts.
  • IGMP messages are restricted to the local network. (correct)
  • It allows multicast packets to propagate beyond the local network.
  • What occurs when TTL is greater than 1 in multicast routing?

    <p>Multicast routers can forward IP Multicast datagrams.</p> Signup and view all the answers

    What is the maximum response time (D) related to?

    <p>The time a host can wait before responding to a query.</p> Signup and view all the answers

    What is the range of multicast addresses classified as Class D?

    <p>224.0.0.0 to 239.255.255.255</p> Signup and view all the answers

    What multicast address is used to reach all hosts and all routers on a network?

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

    Which multicast address range is reserved for routing protocols?

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

    What will happen to a multicast address when an application using it is terminated?

    <p>It is dynamically unassigned.</p> Signup and view all the answers

    Which of the following addresses is reserved for IGMPv3?

    <p>224.0.0.22</p> Signup and view all the answers

    What is the hexadecimal format of a MAC address?

    <p>12 hex digits (48 bits)</p> Signup and view all the answers

    Which multicast address is specifically designated for all DVMRP routers on a network?

    <p>224.0.0.4</p> Signup and view all the answers

    Which of the following statements is true regarding multicast datagrams directed to reserved address ranges?

    <p>They are dropped by multicast routers.</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 hexadecimal representation of a broadcast Ethernet frame's address?

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

    Which range of addresses are reserved for IP multicast?

    <p>01:00:5e:80:00:00 to 01:00:5e:7f:ff:ff</p> Signup and view all the answers

    What does the -r option do when using netstat?

    <p>Shows the kernel IP routing table.</p> Signup and view all the answers

    Which option will netstat use to show both multicast and unicast addresses?

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

    What component of the MAC address is assigned by the manufacturer?

    <p>The second six digits.</p> Signup and view all the answers

    What address does a multicast frame contain?

    <p>A unique multicast MAC address for a protocol.</p> Signup and view all the answers

    Which statement about the address range 224.0.0.0 to 239.255.255.255 is true?

    <p>It is reserved for multicast addresses.</p> Signup and view all the answers

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

    <p>To facilitate IP multicast support</p> Signup and view all the answers

    Which version of IGMP introduced a leave processing mechanism?

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

    What does a multicast router do when there are no hosts joined to a multicast group?

    <p>Stops forwarding packets to that group</p> Signup and view all the answers

    In IGMP, what is the purpose of a General Query?

    <p>To check the status of all multicast group memberships on a network</p> Signup and view all the answers

    What additional capability does IGMPv3 provide compared to earlier versions?

    <p>Support for source-filtering</p> Signup and view all the answers

    What happens in IGMPv1 when a host wants to leave a multicast group?

    <p>The router infers the host has left after a timeout</p> Signup and view all the answers

    How does a host respond when it receives an IGMP query for a multicast group it belongs to?

    <p>It sends a membership report to confirm participation</p> Signup and view all the answers

    Which of the following statements regarding IGMP is true?

    <p>Hosts can join multiple multicast groups simultaneously.</p> Signup and view all the answers

    What is the main purpose of an IGMP leave message?

    <p>To notify the router that a host wants to leave a multicast group.</p> Signup and view all the answers

    Which address is used as the destination IP address when sending an IGMP group-specific query?

    <p>224.0.0.2</p> Signup and view all the answers

    What is the maximum length of IGMP messages?

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

    Which of the following IGMP types correspond to a report message in IGMPv1?

    <p>0x12</p> Signup and view all the answers

    In IGMPv1, which of the following statements is true regarding leaving a group?

    <p>No report is sent when a process leaves a group.</p> Signup and view all the answers

    What happens when a host receives a query in IGMP?

    <p>It starts a report delay timer.</p> Signup and view all the answers

    Which version of IGMP first introduced the group leave functionality?

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

    If a host needs to leave a specific multicast group in IGMPv3, which address is used for the leave message?

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

    What does the second octet of an IGMP message represent?

    <p>The type of IGMP message being sent.</p> Signup and view all the answers

    Which destination IP address is used for an IGMP general query?

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

    Study Notes

    Wireless Mobile & Multimedia Networking Lecture 2: IGMP

    • IGMP is a protocol for IP multicast
    • IGMP operates on a single Ethernet segment
    • Multicast routers track membership in multicast groups
    • Routers maintain a table of multicast groups that hosts have joined
    • Routers forward packets only when a host is still in the group
    • IGMP supports joining, leaving, membership queries, and membership reports

    Multicast Addresses

    • Class D addresses are multicast addresses
    • The range of multicast addresses is from 224.0.0.0 to 239.255.255.255
    • Multicast addresses are dynamically assigned
    • Multicast addresses are released (implicitly) when an application terminates
    • Specific ranges of multicast addresses are reserved for routing protocols and topology discovery

    Reserved IP Multicast Addresses

    • The range 224.0.0.0 to 224.0.0.255 is reserved
    • Multicast routers do not 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 protocols may reserve specific multicast groups

    IP Multicast Addresses for Autonomous Systems (AS)

    • Each AS (autonomous system) owns a range of multicast addresses
    • Example: AS 0x8080 owns the range 233.128.128.0 to 233.128.128.255

    MAC Addresses

    • MAC addresses consist of 12 hexadecimal digits (48 bits)
    • Ethernet addresses have three types:
      • Unicast: Unique destination MAC address
      • Broadcast: All binary 1s (FF:FF:FF:FF:FF:FF)
      • Multicast: Unique multicast MAC address for applications, protocols, or data streams

    Mapping Multicast Address: IP -> MAC

    • Class D IP addresses (with 01:00:5e in the first 3 bytes) are reserved for IP multicast

    netstat command

    • netstat -nra displays numeric IP addresses, routing table, and all addresses

    IGMP Messages

    • IGMP query: used by routers to learn about groups on an attached network (general or group-specific)
    • IGMP membership report: a host responds to an IGMP query indicating membership in certain groups
    • IGMP join report: a process joining a multicast group
    • IGMP leave: a process leaving a group (with some versions)

    IGMP Protocol

    • IGMP operates at the network layer
    • It is specifically used for tracking multicast memberships
    • The Destination IP address is a group address
    • The Source IP address is the initiating host's address

    IGMPv1 Packet Format

    • IGMPv1 messages are 8 bytes long
    • Includes version, type, checksum, and 32-bit class D address

    IGMPv2 and IGMPv3 Packet Format

    • These versions have a specific format which differ from IGMPv1
    • The first octet defines the type; Query (0x11), vl Report (0x12), v2 Report (0x16), v3 Report (0x22), Leave (0x17)

    Timing Issues

    • Query interval: Hosts respond to queries with a delay (random value) to spread out reports
    • Maximum response time: Maximum time a host waits before responding to a query
    • Report suppression: Prevents duplicate reports

    Time-To-Live (TTL)

    • TTL is a scope-limiting parameter for IP multicast datagrams
    • It controls the number of hops a multicast packet can travel
    • IGMP messages always have TTL=1 to restrict them to the local network
    • Multicast routers can have TTL > 1 to forward packets further

    IGMP Versions Comparison

    • A table comparing features of IGMPv1, IGMPv2, and IGMPv3 (e.g., message formats, join/leave functionality, query types) is also presented.

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    Description

    Explore the intricacies of IGMP, a protocol vital for IP multicast within Ethernet networks. This quiz covers multicast address ranges, membership management, and reserved IP multicast addresses critical for networking professionals. Test your understanding of these concepts essential for effective network design and operation.

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