Networking Concepts: ARP and Wireless Networks

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Questions and Answers

Which approach allows routers to handle mobility by advertising the address of a visiting mobile node?

Router advertisement (correct)

End-system handling

Direct routing

Indirect routing

What is the primary function of routing tables in the context of mobility?

To indicate emergency contacts

To update mobile user preferences

To show the location of mobile nodes via longest prefix match (correct)

To manage call forwarding services

In the indirect routing method, where does communication from the correspondent go before reaching the mobile?

Through the mobile's home network (correct)

To the mobile's international network

Directly to the correspondent's network

To a local office of the service provider

Which of the following is NOT mentioned as a way to find a mobile friend frequently changing locations?

Contact their workplace Signup and view all the answers

What feature of the mobile network enables scalability to billions of devices?

Routing table exchanges Signup and view all the answers

What does A use to find B's MAC address when it is not in A's ARP table?

ARP Signup and view all the answers

In the context of ARP, what does TTL stand for?

Time to Live Signup and view all the answers

What action does B take in response to A's ARP request?

Replies with its MAC address Signup and view all the answers

What is the primary role of the ARP protocol in a network?

To resolve IP addresses to MAC addresses Signup and view all the answers

If A has an ARP table that is empty initially with respect to B, what must A do to successfully send data to B?

Broadcast an ARP request Signup and view all the answers

Which information is typically stored in an ARP table?

IP addresses and their corresponding MAC addresses Signup and view all the answers

What will happen if A does not receive a response from B after sending an ARP request?

The request will timeout and A will reissue the ARP request Signup and view all the answers

When does A use the ARP protocol in its operation?

When it needs to resolve a MAC address for a known IP address Signup and view all the answers

What does CSMA/CA stand for in the context of 802.11 networks?

Carrier Sense Multiple Access with Collision Avoidance Signup and view all the answers

In 802.11 LAN architecture, what does the Basic Service Set (BSS) refer to?

A group of wireless hosts connected only to a single AP Signup and view all the answers

What is the primary responsibility of an access point (AP) in a wireless LAN?

To facilitate communication between wireless hosts and the internet Signup and view all the answers

What happens when an arriving host attempts to associate with an AP?

It scans channels and listens for beacon frames to find available APs. Signup and view all the answers

What is a limitation of the 802.11 CSMA protocol?

It does not provide collision detection for ongoing transmissions. Signup and view all the answers

Why is interference a concern when multiple APs operate on the same frequency channel, such as 2.4 GHz?

Because overlapping channels can lead to degraded network performance. Signup and view all the answers

What process typically follows the association of a wireless host with an AP?

The host usually runs DHCP to obtain an IP address within the AP's subnet. Signup and view all the answers

What is the significance of beacon frames in wireless networks?

They provide information about an AP's SSID and MAC address for host association. Signup and view all the answers

What is the primary focus of the mobility spectrum from the network perspective?

Devices maintaining ongoing connections while moving Signup and view all the answers

What challenge arises when a device moves from one network to another?

The network must be informed of the device's new location Signup and view all the answers

How can routers help in managing the mobility of devices?

By advertising the IP address or cell number of mobile nodes Signup and view all the answers

What does the longest prefix match in routing tables indicate?

The location of the mobile node Signup and view all the answers

In what scenario is the spectrum of mobility particularly interested?

Devices moving among multiple provider networks Signup and view all the answers

What is a limitation if a device only moves within the same provider network?

It doesn't introduce mobility challenges for the network Signup and view all the answers

What happens to the packets when a device moves to a new network?

They need to be forwarded based on the device's new location Signup and view all the answers

What is indicated by a device that moves among access points (APs) within one provider’s network?

The device maintains ongoing connections while moving Signup and view all the answers

What is the primary challenge of mobility in wireless networks?

Handling the mobile user who changes point of network attachment Signup and view all the answers

Which of the following elements is NOT part of a wireless network?

Cabling infrastructure Signup and view all the answers

What does multipath propagation in wireless communication refer to?

Multiple signals arriving at different times from various paths Signup and view all the answers

How does increasing distance affect free space path loss in wireless communication?

It decreases the signal strength Signup and view all the answers

Which standard indicates the highest maximum data rate among the given options?

802.11ax Signup and view all the answers

What does the hidden terminal problem in wireless networks indicate?

Some devices are unaware of each other's signals and interference Signup and view all the answers

In Code Division Multiple Access (CDMA), what is used to differentiate users sharing the same frequency?

Chipping sequences Signup and view all the answers

What suffers due to fading in wireless signals?

Signal strength as it propagates Signup and view all the answers

What is the typical maximum data rate for the 802.11ac standard?

3.47 Gbps Signup and view all the answers

Which characteristic affects the maximum possible transmission rate in a wireless channel?

Coherence time Signup and view all the answers

What is the main frequency band commonly used by most IEEE 802.11 standards?

2.4 GHz Signup and view all the answers

Which of the following statements about 4G and 5G networks is TRUE?

5G networks primarily use SDN technology. Signup and view all the answers

Which of the following best describes a base station in a wireless network?

A relay connected to the wired network responsible for sending packets Signup and view all the answers

What is the role of multiple access protocols in wireless links?

To coordinate access to the wireless link Signup and view all the answers

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.