I need help with these two questions for the figure. It can confuse me. Problem
ID: 3814379 • Letter: I
Question
I need help with these two questions for the figure. It can confuse me. Problem 5: Consider the example internet shown in the figure on the next page. Suppose the source S1 send a packet to Group B. a. Show how the routers flood the network in DVMRP b. Show, if any, how the routers get pruned Problem 6: Consider the example internet shown in the figure on the next page. Suppose we are using PIM-SM for multicast. a. Show how the host Hijoins the multicast (you need to show what does each router need to transmit and to where) b. Show how the host H2 joins the multicast (you need to show what does each router need to transmit and to where) c. Show how the host H3joins the multicast (you need to show what does each router need to transmit and to where) d. Suppose now that si need to transmit to Group B, what will happen?Explanation / Answer
Hi,
Please find the answers to the question below:-
Problem 5
a):-
USING DVMRP
The S1 will send its packet to the routers on its interfaces since S1 has R1 and R2 on its interfaces it send packets to both. Then the receiving routers will again flood those packets to all routers in their routing table except the one from which the packet came till it reaches the destination.
Sending routers
Receiving routers
S1
R1,R2
R1
RP
R2
R4
RP
R7
R4
R5
R7
R6
R5
R6
When the packet reaches to the routers, the router shares the packet with all the hosts attached to it.So in this case when packet reaches to the router R5, R4 and R1 the packet send by S1 reaches to it destined address i.e. group B having host H1,H2,H3.
b) Many parts of the network receive traffic although there are no receivers there. These routers know they have no receivers and they can then send prune messages back towards the source to stop unnecessary traffic flowing. This the way how routers get pruned .In this figure no router gets pruned as all have the receivers to receive packets.
Problem 6:-
USING PIM-SM
For a, b, c, d
In order to join a multicast group, G, a host conveys its membership information through the Internet Group Management Protocol (IGMP).
Then following activities happens:-
HOST
Interface Router
Rendezvous point Router
Explanation
H1
R4
RP
The router R4 will send a join message to the router RP which is rendezvous point for all the routers. Each router along the path toward the RP builds a wild card (any-source) state for the group and sends Join/Prune messages on toward the RP. For this routers R4,R2,R1 are the routers which will send message to RP
H2
R5
RP
The router R5 will send a join message to the router RP which is rendezvous point for all the routers. Each router along the path toward the RP builds a wild card (any-source) state for the group and sends Join/Prune messages on toward the RP. For this routers R5,R6,R7 are the routers which will send message to RP
H3
R1
RP
The router R1 will send a join message to the router RP which is rendezvous point for all the routers. Each router along the path toward the RP builds a wild card (any-source) state for the group and sends Join/Prune messages on toward the RP. For this routers R1 is the only router which will send message to RP
This state creates a shared, RP-centerd, distribution tree that reaches all group members.
d) S1 transmitting to Group B
Below steps are performed when data is end to group in PIM-SM
STEP1:-When a data source S1 first sends to a group, its Designated Router (DR) unicasts Register messages to the Rendezvous Point (RP) with the source's data packets encapsulated within.
STEP2:- If the data rate is high, the RP can send source-specific Join/Prune messages back towards the source 1 and the source's data packets will follow the resulting forwarding state and travel un-encapsulated to the RP.
STEP 3:- Whether they arrive encapsulated or natively, the RP forwards the source's de-capsulated data packets down the RP-centered distribution tree toward group members H1, H2, H3.
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Please let me know in case any information is required.
Sending routers
Receiving routers
S1
R1,R2
R1
RP
R2
R4
RP
R7
R4
R5
R7
R6
R5
R6