2- How does a mobile node secure registration messages using the FA Challenge mechanism?
3- To verify the integrity of a message that has an authentication extension appended, what does the recipient do?
4- What are the main differences between IPv6 and IPv4?
5- Consider a Mobile Node with a single interface whose Home Address is 192.168.10.30 and Home Agent is 192.168.10.1. Let us assume that the MN roams away from home to FA 192.168.100.6, and then to another FA, 192.168.200.6. It then finds itself still roaming, but not within the domain of a FA. At this point, it obtains a Collocated CoA and continues to roam. After some times, it returns home. Explain step by step of the sequences of the above problem.
6- Describe macro mobility and micro mobility in mobile IP.
7- Explain the differences between WiFi and WiMax.
8- True or False: Before a 802.11 station transmits a data frame, it must first send an RTS frame and receive a corresponding CTS frame.
9- Consider a 802.11 mobility environment in which a wireless station moves from one BSS to another within the same subnet. When the APs are interconnected with a switch, an AP may need to send a frame with a spoofed MAC address to get the switch to forward frames properly. Why?
10- Suppose there are two ISPs providing Wi-Fi access in a particular café, with each ISP operating its own AP and having its own IP address block.
A. Further suppose that by accident, each ISP has configured its AP to operate over channel 11. Will the 802.11 protocol completely break down in this situation? Discuss what happens when two stations, each associated with a different ISP, attempt to transmit at the same time.
B. Now suppose that one AP operates over channel 1 and the other channel 11.
11- Consider two mobile nodes in a foreign network having a foreign agent. Is it possible for the two mobile nodes to use the same care-of address in mobile IP? Explain your answer.
12. Consider the following scenario. Node A is registered with a Home Agent (HA) in Austria under the IP address 126.96.36.199. Node B is registered with a HA 188.8.131.52 in Belgium under the IP address 184.108.40.206. Both nodes are initially in their home networks.
• Node B moves to a subnet in Switzerland controlled by a Foreign Agent (FA) 220.127.116.11.
• Node A initiates a TCP connection with node B (node A knows B’s domain name).
• Node A moves to the same Swiss subnet, and then continues using the same TCP connection.
13. Describe all relevant packets exchanged between all entities in this scenario, assuming that
nodes A and B use
a. Basic Mobile IP with a FA COA.
b. Basic Mobile IP with co-located COA.
c. Mobile IP with the reverse tunneling extension (FA COA or co-located COA). (Hint: You might want to look at RFC 3024 to get some details right.)
d. Mobile IP with the route optimization extension. Can both FA COAs and co-located COAs be used with this extension?
14. Describe the type of exchanged packets, and the IP addresses they contain.
15. Mobile IP
a) List the entities of mobile IP and describe data transfer from a mobile node to a fixed node and vice versa. Why and where is encapsulation needed?
b) Show the steps required for a handover from one foreign agent to another foreign agent.
c) Name the inefficiencies of mobile IP regarding data forwarding from a corresponding node to a mobile node. What optimizations are possible and what additional problems do they cause?
d) Explain packet flow if two mobile nodes communicate and both are in foreign networks. What additional routes do packets take if reverse tunneling is required?
e) Show the structure of the packets of each step (slides 9-10) between the original mobile user and the (now mobile) correspondent.
16. What are the problems with TCP over wireless network?
f) We described the snoop protocol when the MH is the TCP-receiver. What is the problem with snoop when the MH is the TCP-sender?
g) Describe a possible solution to this problem
18. According to RFC 2581 on TCP congestion control, a TCP receiver should use the delayed ACK algorithm. This algorithm gives the receiver the option to delay an ACK, if it is for an in-order segment, but must acknowledge every second full-sized segment. What are the main drawbacks of this algorithm in wireless networks?
19. Consider two mobile nodes in a foreign network having a foreign agent. Is it possible for the
two mobile nodes to use the same care-of-address? Explain your answer.
20. Consider a mobile node MN from network X. The user of MN wishes to communicate with a corresponding node CN in network Y. The node MN moves from X to a foreign network A.
• Describe the sequence of messages that are required in Mobile IPv4 so that MN and CN can continue
to communicate. Give the purpose of each message, where it is from, where it is to, and the path that it takes. Include both the user data messages and the Mobile IP control messages.
• Now, consider the case where CN moves to foreign network B while MN is still in the foreign network A. Can CN and MN still communicate? (Does Mobile IP support both endpoints moving?) Show the message flow to indicate how it will succeed or fail in this case.
A foreign Agent may broadcast constantly advertisements by agents who have different challenges included. Therefore a mobile node may be using unused challenges for the authentication. For authentication to a foreign agent FA the mobile nodes have to include a new defined extension known as MN-FA challenge extension to tell which challenge is used in its authentication extension. Then some rules are defined to judge if an authentication extension is valid in regard to FA change. The FA challenge is in the registration of request message with AAA authentication extension and mobile foreign authentication extension. When an authenticator is generated it includes the extension then the challenge is authenticated through the foreign authentication extension.
To verify the integrity of a message that has an authentication extension appended, the recipient will compare the value of the authenticator in the extension that is appended to that in storage.
IPv4 is the old version of protocol used for internet. It numeric address is written in 32-bit decimal of four numbers kept apart by a period .This numbers are within the range of zero to 255.For example 0. 0 .0 .0 to 255 .255. 255. 255.While IPv6 is newer version of internet protocol with a 128-bit numeric addresses which are written in hexadecimal.
The micro mobility is a term that means the mobile node’s movements are inside a network. While in contrast, the macro mobility means that there is movement between different sub networks.
WiMAX produces products that are used by wireless metropolitan networks (WMANs). while products made of Wi-Fi are built to be used in wireless Local Area network ( WLANs).
As MN leaves the address number 1it has to notify MN other network of the roaming and tells it to take care of its address.
It is false that before 802.11 stations transmits a data frame it first must send an Rts frame and a corresponding CTS frame.
The switch contains an entry in the switch forwarding table it connects the wireless station with the earlier AP. Then the new AP creates wireless frame station’s MAC and broadcasts the frames this frame will be received by another switch then the switch updates the forwarding table then the frame is forwarded to the wireless station through the new AP.
The Aps will have varying SSIDs and MAC addresses. A wireless station arriving to the café will associate with one of the SSIDs in one of the APs. After the connection their important link connecting the station. Taking the two Aps to be 1AP and 2AP the new station connects with 1AP then sends a frame when 2AP receives the frame it will not be able to processes the reason being that it is not addressed to it therefore the internet service providers can transmit at the same time in parallel otherwise their the two ISPs have the ability to work in parallel on the same channel. Moreover the two ISPs will be using the same wireless bandwidth. If wireless stations in different ISPs transmit at the same time, there will be a collision. For 802.11b, the maximum total transmission rate when it comes to both ISPs 11MBPs.
Dynamics is a program that is developed in TKK then it is implemented in the hierarchical IP. From that we can deduce that their can exist a hierarchy of FA in the midst of HA and MN. This hierarchy is in a treelike structure. The FA in the lowest level communicates with the MN. The main aim of the hierarchy is to allow Mobile IP scale well quickly to give better HO. MN doesn’t always have to register to a HA, but while moving within the FA hierarchy the tunneling can be changed internally without concerning the HA which can be located on the other side of the world and the connections can be much faster in across the FA.
The exchange protocol is internetwork Packet Exchange (IPX) operates at as a network layer protocol it is found inside the IPX/SPX protocol suite. IPX is an easy configuration of the client computers
Mobile IP entities
Mobile Node (MN)–this is a program that moves the point of attachment to different networks.
Home Agent (HA)–keeps the current location information for the mobile node. This is a router on a mobile node’s home network that dissects data destined through the mobile node; they are later delivered through the care-of address.
Foreign Agent (FA)–Router on a mobile node’s sojourned network, it gives routing services to the mobile node while the mobile node is registered.
Steps in handing over from one agent to another is
- Scanning the medium decide
- the base station
- decide on one of them
- reroute data inside the infrastructure network
- release resources with the old base station. .
In TCP packets are prone to loss while it is implemented on a wireless network due to congestion and in mobile networks when TCP packets are lost due to disconnection, handoffs and high bit error rates.
Snoop has a duty of reducing the retransmission rate regardless of transmission error.rors, and a delivery that is out-of-order on the wireless link. The problem snoop is when the MH is the sending TCP is that it will not retransmit for safe delivery. One of the solutions is to ensure that MH is the receiving TCP.
ACK has the ability to be to bring up greater delay as it associates with other application and arrangement. If algorithm in use is Nagle’s algorithm you send a third party, the data will be arranged by the sender up to when an ACK is received. In case the sender will not send enough packets to fill a segment size the transfer will be at a stand still until when the ACK delay timeout.
It can happen that Two mobile have the same care-of –address in the same Foreign agent. This is because when it happens that the care-of-address is the address of the visited network, then the addresses will happen to be equal. Once the visited network opens the received datagram and decides the address of the mobile and then separates addresses that will have to be in use when sending the packets differently and separately across mobiles in a Foreign Agent.
When a Mobile user is received by a Foreign Network and links to the network, the Mobile Node gets an IP addresses. Then the Mobile Node is started to run a Registration Protocol. Registration Protocol is used hierarchically and the tunnel is brought forth through the Foreign Agent hierarchy following specific procedure. Each Foreign Agent on the way can check for a tunnel for the specified Mobile node , This will enable them to produce local tunnel updates to give new registration, the protocol goes up to the Home Node which then confirms the tunnel creation. Tunnels are created in a descending order after the MN has been accepted properly by the HA. The lifetime of the tunnel is decided upon during registration by the Mobility Agents .To keep the tunnel open keep Alive protocol is used. The messages includes A foreign Agent may broadcast constantly advertisements by agents who have different challenges included. Therefore a mobile node may be using unused challenges for the authentication. For authentication to a foreign agent FA the MN have to include a new defined extension known as MN-FA challenge extension to tell which challenge is used in its authentication extension. Then some rules are defined to judge if an authentication extension is valid in regard to FA change. The FA challenge is in the registration of request message with AAA authentication extension and mobile foreign authentication extension. When an authenticator is generated it includes the extension then the challenge is authenticated through the foreign authentication extension. Then CN send a confirmation message.
Even when the CN moves to another network they will still communicate since it will be registered on the foreign network with the same Care Address but the messages will be routed to the new network following the same sequence.
Oracle, (2015).Retrieved 21 June 2015, from http://docs.oracle.com/cd/E19455-01/806-7600/6jgfbep0v/index.htm
Tml, (2015) Retrieved 21 June 2015, from http://www.tml.tkk.fi/Studies/Tik-110.350/2000/Homework’s/assignment_10_model.html
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