300+ [REAL TIME] Multicast Interview Questions

1. What Is Multicast?

Multicast is a method of sending the data from one source to so many receivers.

2. What Are The Protocols Used In Multicast?

IGMP –
Provides the communication between host and Router

PIM(IPV4), MLD(IPV6)-
Provides the communication between Router and Router

IGMP Snooping & CGMP –
Provides the communication between Router & Switch

3. What Is Igmp?

IGMP is a protocol which enables the host to join particular group by signalling the router.

4. What Is The Difference Between Igmpv1 And Igmpv2?

• In IGMPV1 there are only 2 messages are used ( Membership Query and Membership Report) whereas in IGMPV2 there is one more message extra( Query, Report and Leave).
• In IGMPV1 there is no Group Membership Query message.
• There is no Querier Election mechanism in IGMPV1.

5. What Is The Use Of Multicast Distribution Tree?

Multicast Distribution Tree specifies the path between source and Receiver in which multicast traffic should be forwarded.

There are mainly two types of Multicast Distribution Trees

1. Source Tree
2. Shared Tree

6. What Is The Source Tree ?

Source Tree:

• Used in both PIM Sparse Mode and Dense Mode.
• Uses Source as the Root of the Multicast Tree and Receivers are acting like branches.
• It is also known as Shortest Path Tree because it uses the shortest path between source and receiver.
• Every Router in Source Tree will add (S,G) Entries in multicast routing table.

      Where S = Source or Sender IP address ( Unicast) (192.1.1.1)

        G = Destination IP address ( Multicast IP address) (224.5.5.5)

7. What Is The Shared Tree?

• Used in both PIM Sparse Mode only.
• Uses Rendezvous Point as the Root of the Multicast Tree and shortest path tree will be created between i) Source & RP ii) Receiver & RP
• It is also known as Root Path Tree or Core Based Tree.
• Every Router in Source Tree will add (*,G) Entries in multicast routing table.

    Where  * = All Sources

               G = Destination IP address ( Multicast IP address)(224.5.5.5)

8. What Is Pim?

PIM is a protocol used between the routers to forward multicast traffic. PIM works in two modes

1. PIM Dense Mode
2. PIM Sparse Mode

9. What Is Packet Filter?

Packet filter is a standard router equipped with some extra functionality. The extra functionality allows every incoming or outgoing packet to be inspected. Packets meeting some criterion are forwarded normally. Those that fail the test are dropped.

10. What Is Traffic Shaping?

One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.

11. What Is Multicast Routing?

Sending a message to a group is called multicasting, and its routing algorithm is called multicast routing.

12. What Is Region?

When hierarchical routing is used, the routers are divided into what we will call regions, with each router knowing all the details about how to route packets to destinations within its own region, but knowing nothing about the internal structure of other regions.

13. What Is Silly Window Syndrome?

It is a problem that can ruin TCP performance. This problem occurs when data are passed to the sending TCP entity in large blocks, but an interactive application on the receiving side reads 1 byte at a time.

14. Describe How The Multicast Protocol Works?

Multicast protocol or Internet protocol delivers a singles message to multiple machines. One packet from the source is replicated and sent to the destination. Every multicast message requires a multi case group. The group defines the addresses which will receive the message. The group is defined by the class D address. Different routing protocols are used to find the multicast groups and build routes for them. Distance Vector Multicast protocol is one of them. The receiver, to whom the multicast packet is sent to, needs to ‘join’ the group. Joining the group is enabled and managed by IGMP. Multicast routers are used to transmit the messages from one network to another.

15. Describe How To Control The Scope Of Multicast Transmissions.?

Controlling the scope of multicast transmission restricts the range of group members. TTL (Time To Live) is one of the mechanisms to limit the scope. If the TTL value is small, packets would only be multicast to smaller distance destinations. More the value of TTL, more would be the scope of transmission to a larger number of machines. Administrative scoping is another mechanism. In this, transmission is restricted to a specific address space of an organization or a site.

16. Explain Why Use Multicasting?

1. When the same message or packet needs to be sent to multiple destinations, multicasting is used.
2. Within campus and offices, using multicasting file distribution can be done.
3. System messages, news and videos can be sent at the same time.
4. More commonly used for audio and video streaming. 
5. Used for programming on MBone which allows the users at high-bandwidth points to receive video and sound programming.
6. It also uses a protocol which allows the signal to be encapsulated as TCP/IP packet.

17. What Is A Socket?

A socket is used to connect an application to a network protocol. A socket enables communication between a client and a server. The communication is started when the client is assigned a local port number, and binds a socket to it. The client writes on the socket and gets information from server by reading it.

18. What Are Sockets? How Do Sockets Work?

A socket is used to connect an application to a network protocol. A socket enables communication between a client and a server. The communication is started when the client is assigned a local port number, and binds a socket to it. The client writes on the socket and gets information from server by reading it. The Socket class is used to communicate. It provides rich set of methods for both asynchronous and synchronous data transfer. ConnectAsync is used to start an asynchronous connection. SendAsync and ReceiveAsync are used to send and receive data. Shutdown and close methods are used to shutdown and close the sockets.