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Questions and Answers
Which approach allows routers to handle mobility by advertising the address of a visiting mobile node?
What is the primary function of routing tables in the context of mobility?
In the indirect routing method, where does communication from the correspondent go before reaching the mobile?
Which of the following is NOT mentioned as a way to find a mobile friend frequently changing locations?
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What feature of the mobile network enables scalability to billions of devices?
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What does A use to find B's MAC address when it is not in A's ARP table?
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In the context of ARP, what does TTL stand for?
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What action does B take in response to A's ARP request?
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What is the primary role of the ARP protocol in a network?
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If A has an ARP table that is empty initially with respect to B, what must A do to successfully send data to B?
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Which information is typically stored in an ARP table?
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What will happen if A does not receive a response from B after sending an ARP request?
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When does A use the ARP protocol in its operation?
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What does CSMA/CA stand for in the context of 802.11 networks?
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In 802.11 LAN architecture, what does the Basic Service Set (BSS) refer to?
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What is the primary responsibility of an access point (AP) in a wireless LAN?
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What happens when an arriving host attempts to associate with an AP?
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What is a limitation of the 802.11 CSMA protocol?
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Why is interference a concern when multiple APs operate on the same frequency channel, such as 2.4 GHz?
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What process typically follows the association of a wireless host with an AP?
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What is the significance of beacon frames in wireless networks?
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What is the primary focus of the mobility spectrum from the network perspective?
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What challenge arises when a device moves from one network to another?
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How can routers help in managing the mobility of devices?
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What does the longest prefix match in routing tables indicate?
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In what scenario is the spectrum of mobility particularly interested?
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What is a limitation if a device only moves within the same provider network?
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What happens to the packets when a device moves to a new network?
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What is indicated by a device that moves among access points (APs) within one provider’s network?
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What is the primary challenge of mobility in wireless networks?
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Which of the following elements is NOT part of a wireless network?
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What does multipath propagation in wireless communication refer to?
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How does increasing distance affect free space path loss in wireless communication?
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Which standard indicates the highest maximum data rate among the given options?
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What does the hidden terminal problem in wireless networks indicate?
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In Code Division Multiple Access (CDMA), what is used to differentiate users sharing the same frequency?
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What suffers due to fading in wireless signals?
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What is the typical maximum data rate for the 802.11ac standard?
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Which characteristic affects the maximum possible transmission rate in a wireless channel?
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What is the main frequency band commonly used by most IEEE 802.11 standards?
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Which of the following statements about 4G and 5G networks is TRUE?
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Which of the following best describes a base station in a wireless network?
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What is the role of multiple access protocols in wireless links?
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Study Notes
Recap: ARP protocol in action
- A requests the MAC address of B using an ARP request if B's MAC address is not in A's ARP table.
- B responds with an ARP response, providing its MAC address.
4G/5G cellular networks
- They are now embracing the Internet protocol stack, including SDN.
- Two key challenges are wireless communication over wireless links and handling mobile users who change their network attachment points.
Elements of a wireless network
- Wireless hosts include laptops, smartphones, and IoT devices.
- Wireless hosts can run applications.
- They can be stationary or mobile.
- Base stations are typically connected to wired networks.
- They relay packets between the wired network and wireless hosts in their area.
- Examples include cell towers and 802.11 access points.
- Wireless links connect mobile devices to base stations.
- They are also used in backbone links.
- Wireless links utilize multiple access protocols for coordinating access.
- They offer various transmission rates and distances, including different frequency bands.
Wired Network Infrastructure
- Acts as the backbone for wireless networks.
Characteristics of Selected Wireless Links
- 802.11 has various standards with different maximum data rates, ranges, and frequencies.
- Bluetooth offers low data rates, short ranges, and uses the 2.4 GHz band.
- 4G LTE offers mid to long-range communication, with higher data rates and uses multiple frequency bands.
- 5G offers the highest data rates, extended range, and uses various frequency bands including millimeter wave frequencies.
Wireless Link Characteristics: Fading
- Wireless radio signals lose power as the distance between the transmitter and receiver increases.
- This is due to free space path loss.
- Free space path loss is proportional to the square of the frequency and the distance.
- Higher frequencies and longer distances result in greater path loss.
Wireless Link Characteristics: Multipath
- Radio signals can reflect off objects like buildings and the ground.
- These reflected signals arrive at the receiver at slightly different times, causing multipath propagation.
Wireless Link Characteristics: Coherence time
- The amount of time a bit is present in a channel to be received.
- Influences the maximum possible transmission rate.
Wireless Link Characteristics: Hidden terminals
- Nodes that can hear each other but cannot hear a third node, leading to collisions.
- This is due to attenuation and the limited range of wireless signals.
Code Division Multiple Access (CDMA)
- Each user is assigned a unique code.
- Users share the same frequency band but use distinct "chipping sequences" for data encoding.
- This allows multiple users to transmit simultaneously with minimal interference.
- Encoding is done through multiplication of the original data with the chipping sequence.
- Decoding is done through the inner product of the encoded data and the chipping sequence.
IEEE 802.11 Wireless LANs
- Various IEEE 802.11 standards exist, offering different data rates and frequency bands.
- The most common standards include 802.11b, 802.11g, 802.11n, 802.11ac, 802.11ax, and 802.11be.
- All 802.11 standards use CSMA/CA for multiple access.
- They support both base-station and ad-hoc network versions.
802.11 LAN Architecture
- A wireless host communicates with a base station known as the access point (AP).
- A Basic Service Set (BSS) or cell is a basic architectural element of an 802.11 LAN.
- In Infrastructure mode, a BSS contains wireless hosts and an access point (AP).
- In ad hoc mode, there is no access point (AP), only wireless hosts.
802.11 Channels
- Different frequency bands are divided into channels.
- The AP administrator selects the frequency channel for the AP.
- Adjacent APs can interfere with each other if they are on the same channel.
802.11 Association
- A new wireless host must associate with an access point (AP) before it can communicate on the network.
- The host scans for beacon frames, containing information about the AP, such as SSID and MAC address.
- After selecting an AP, the host may perform authentication.
- The host usually obtains an IP address via Dynamic Host Configuration Protocol (DHCP) within the AP's subnet.
802.11 Multiple Access
- CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) is used to avoid collisions.
- Nodes do not transmit while another node's transmission is detected.
- There is no collision detection in 802.11.
Mobility Challenge
- When a device moves from one network to another, the network needs to know how to forward packets to the new location.
Mobility Approaches
- Network-based approach: routers advertise the location of mobile nodes, allowing for packet forwarding based on this information.
- End-system based approach: uses different routing techniques, either indirect or direct routing, to reach mobile devices.
Mobility and Content Providers
- A content provider relies on its own network, data centers, and public internet connectivity to deliver content to users.
- Mobility management is crucial for content delivery when users switch between different networks, such as Verizon and AT&T.
Mobility: Impact on Higher-Layer Protocols
- Higher-layer protocols like TCP and UDP need to adapt to changes in network connectivity and address information as mobile devices move between networks.
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Description
Test your knowledge on the ARP protocol and the essentials of wireless networks, including 4G/5G technologies. This quiz covers the mechanisms of ARP requests and responses, as well as the role of base stations and wireless hosts in network connectivity. Dive into the challenges faced by modern cellular networks and their integration with the Internet protocol stack.