Consider a network with five nodes, N1 to N5, as shown below.

The network uses a Distance Vector Routing protocol. Once the routes have stabilized, the distance vectors at different nodes are as following

N1 : ( 0, 1, 7, 8, 4 )
N2 : ( 1, 0, 6, 7, 3 )
N3 : ( 7, 6, 0, 2, 6 )
N4 : ( 8, 7, 2, 0, 4 )
N5 : ( 4, 3, 6, 4, 0 )

Each distance vector is the distance of the best known path at that instance to nodes, N1 to N5, where the distance to itself is 0. Also, all links are symmetric and the cost is identical in both directions. In each round, all nodes exchange their distance vectors with their respective neighbors. Then all nodes update their distance vectors. In between two rounds, any change in cost of a link will cause the two incident nodes to change only that entry in their distance vectors

After the update in the previous question, the link N1-N2 goes down. N2 will reflect this change immediately in its distance vector as cost, $$\infty $$. After the NEXT ROUND of update, what will be the cost to N1 in the distance vector of N3?

Consider a network with five nodes, N1 to N5, as shown below.

The network uses a Distance Vector Routing protocol. Once the routes have stabilized, the distance vectors at different nodes are as following

N1 : ( 0, 1, 7, 8, 4 )
N2 : ( 1, 0, 6, 7, 3 )
N3 : ( 7, 6, 0, 2, 6 )
N4 : ( 8, 7, 2, 0, 4 )
N5 : ( 4, 3, 6, 4, 0 )

Each distance vector is the distance of the best known path at that instance to nodes, N1 to N5, where the distance to itself is 0. Also, all links are symmetric and the cost is identical in both directions. In each round, all nodes exchange their distance vectors with their respective neighbors. Then all nodes update their distance vectors. In between two rounds, any change in cost of a link will cause the two incident nodes to change only that entry in their distance vectors

The cost of link N2 - N3 reduces to 2 in (both directions). After the next round of updates, what will be the new distance vector at node, N3?

Consider different activities related to email:

m1: Send an email from a mail client to a mail server
m2: Download an email from mailbox server to a mail client
m3: Checking email in a web browser

Which is the application level protocol used in each activity?

A layer-4 firewall (a device that can look at all protocol headers up to the transport layer) CANNOT