COMPUTER NETWORKING EXAM QUESTIONS
AND ANSWERS VERIFIED 100% CORRECT
R17. Suppose Host A sends Host B a TCP segment encapsulated in
an IP datagram. When Host B receives the datagram, how does the
network layer in Host B know it should pass the segment (that is, the
payload of the datagram) to TCP rather than a UDP or to something
else? ANSWER -Typically the wireless router includes a DHCP server.
DHCP is used to assign IP addresses to the 5 PCs and to the router
interface. Yes, the wireless router also uses
NAT as it obtains only one IP address from the ISP.
R18. Suppose you purchase a wireless router and connect it to your
cable modem. Also suppose that your ISP dynamically assign your
connected device (that is, your wireless router) one IP address. Also
suppose that you have five PCs at home that use 802.11 to wireless
connect to your wireless router. How are IP addresses assigned the
five PCs?
Does the wireless router use NAT? Why or why not? -
ANSWER -See Section 4.4.4
,R19. Compare and contrast the IPv4 and the IPv6 header fields. Do
they have any fields in common? -ANSWER -Yes, because the entire
IPv6 datagram (including header fields) is encapsulated in an an IPv4
datagram
R20. It has been said that when IPv6 tunnels through IPv4 router, IPv6
treats the IPv4 tunnels as link layer protocols. Do you agree with this
statement? Why or why not? -ANSWER Link state algorithms:
Computes the least-cost path between source and destination using
complete, global knowledge about the network. Distance-vector
routing: The calculation of the least-cost path is carried out in an
iterative, distributed manner. A node only knows the neighbor to
which it should forward a packet in order to reach given destination
along the least-cost path, and the cost of that path from itself to the
destination
R21. Compare and contrast link state and distance-vector routing
algorithms. -ANSWER -Key:
,1.Link-state algorithms is a global routing algorithm, and it requires
each node to know the cost of each link in the network. Also,
whenever a link cost changes, new link cost must be sent to all
nodes.
Distance-vector algorithm is a decentralized routing algorithm, and it
requires message exchanges between directly connected Neighbors
at each iteration. When link costs change ,the DV algorithm will
propagate the results of the changed link only if the new link cost
result in a changed least-cost path for one of the nodes attached to
the link.
2.LS is an O(n^2)algorithm requiring O(nE)messages ,and that it
potentially suffers from oscillations. The DV algorithm can converge
slowly and have routing loops .DV also suffer from the count-to-
infinity problem.
3. When a router fails, under LS, a router could broadcast an incorrect
cost for one of its attached links; under DV, a node can advertise
incorrect least-cost paths to any/all destinations.
R22. Discuss how a hierarchical organization of the Internet has made
it possible to scale to millions of users. -ANSWER -
, Routers are aggregated into autonomous systems (ASs). Within an
AS, all routers run the same intra-AS routing protocol. Special
gateway routers in the various ASs run the inter-autonomous system
routing protocol that determines the routing paths among the ASs.
The problem of scale is solved since an intra-AS router need only
know about routers within its AS and the gateway router(s) in its AS.
R23. Is it necessary that every autonomous system use the same
intra-AS routing algorithm? Why or why not? ANSWER -No. Each AS
has administrative autonomy for routing within an AS.
R24. Consider Figure 4.37. Starting with the original table in D,
suppose that D receives from A the following advertisement:
Destination Subnet Next Router Number of Hops to
Destination z c 10 w __ 1 x __ 1
.........
Will the table in A change? If so how? -ANSWER -No. The
advertisement tells D that it can get to z in 11 hops by way of A.
However, D can already get to z by way of B in 7 hops. Therefore,
AND ANSWERS VERIFIED 100% CORRECT
R17. Suppose Host A sends Host B a TCP segment encapsulated in
an IP datagram. When Host B receives the datagram, how does the
network layer in Host B know it should pass the segment (that is, the
payload of the datagram) to TCP rather than a UDP or to something
else? ANSWER -Typically the wireless router includes a DHCP server.
DHCP is used to assign IP addresses to the 5 PCs and to the router
interface. Yes, the wireless router also uses
NAT as it obtains only one IP address from the ISP.
R18. Suppose you purchase a wireless router and connect it to your
cable modem. Also suppose that your ISP dynamically assign your
connected device (that is, your wireless router) one IP address. Also
suppose that you have five PCs at home that use 802.11 to wireless
connect to your wireless router. How are IP addresses assigned the
five PCs?
Does the wireless router use NAT? Why or why not? -
ANSWER -See Section 4.4.4
,R19. Compare and contrast the IPv4 and the IPv6 header fields. Do
they have any fields in common? -ANSWER -Yes, because the entire
IPv6 datagram (including header fields) is encapsulated in an an IPv4
datagram
R20. It has been said that when IPv6 tunnels through IPv4 router, IPv6
treats the IPv4 tunnels as link layer protocols. Do you agree with this
statement? Why or why not? -ANSWER Link state algorithms:
Computes the least-cost path between source and destination using
complete, global knowledge about the network. Distance-vector
routing: The calculation of the least-cost path is carried out in an
iterative, distributed manner. A node only knows the neighbor to
which it should forward a packet in order to reach given destination
along the least-cost path, and the cost of that path from itself to the
destination
R21. Compare and contrast link state and distance-vector routing
algorithms. -ANSWER -Key:
,1.Link-state algorithms is a global routing algorithm, and it requires
each node to know the cost of each link in the network. Also,
whenever a link cost changes, new link cost must be sent to all
nodes.
Distance-vector algorithm is a decentralized routing algorithm, and it
requires message exchanges between directly connected Neighbors
at each iteration. When link costs change ,the DV algorithm will
propagate the results of the changed link only if the new link cost
result in a changed least-cost path for one of the nodes attached to
the link.
2.LS is an O(n^2)algorithm requiring O(nE)messages ,and that it
potentially suffers from oscillations. The DV algorithm can converge
slowly and have routing loops .DV also suffer from the count-to-
infinity problem.
3. When a router fails, under LS, a router could broadcast an incorrect
cost for one of its attached links; under DV, a node can advertise
incorrect least-cost paths to any/all destinations.
R22. Discuss how a hierarchical organization of the Internet has made
it possible to scale to millions of users. -ANSWER -
, Routers are aggregated into autonomous systems (ASs). Within an
AS, all routers run the same intra-AS routing protocol. Special
gateway routers in the various ASs run the inter-autonomous system
routing protocol that determines the routing paths among the ASs.
The problem of scale is solved since an intra-AS router need only
know about routers within its AS and the gateway router(s) in its AS.
R23. Is it necessary that every autonomous system use the same
intra-AS routing algorithm? Why or why not? ANSWER -No. Each AS
has administrative autonomy for routing within an AS.
R24. Consider Figure 4.37. Starting with the original table in D,
suppose that D receives from A the following advertisement:
Destination Subnet Next Router Number of Hops to
Destination z c 10 w __ 1 x __ 1
.........
Will the table in A change? If so how? -ANSWER -No. The
advertisement tells D that it can get to z in 11 hops by way of A.
However, D can already get to z by way of B in 7 hops. Therefore,
