Ad-Hoc Networks and AODV Routing

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Questions and Answers

What does RREP stand for in the context of AODV protocol?

Routing Reply Procedure

Route Request Error Protocol

Route Reply Packet (correct)

Routing Response Error Packet

What action can the source node S take as soon as it receives the first RREP?

Immediately update all routing information

Wait for the last RREP confirmation

Establish a reverse path to destination D

Initiate transmission of data (correct)

What is indicated by the term 'forward pointer' in the context of AODV?

A method for routing data back to the source

A temporary storage for route requests

A link to the next hop towards the destination (correct)

A mechanism for sending feedback to the source node

During the forward path setup in AODV, what is the goal of minimizing RREPs?

To simplify the route discovery process Signup and view all the answers

What occurs if the source node S learns of a better route after starting data transmission?

The source updates its routing information Signup and view all the answers

What does a Route Error Packet (RERR) indicate in the context of DSR?

A broken link in the routing process. Signup and view all the answers

What responsibility does the DSR-specific software take if no link-level ACK exists?

It sends back an ACK to the source. Signup and view all the answers

What action does the source node take after receiving a Route Error Packet?

Removes the broken route from the routing table. Signup and view all the answers

How does DSR perform routing in multi-hop wireless ad hoc networks under stationary conditions?

With zero routing overhead. Signup and view all the answers

Which feature characterizes the operation of DSR in a wireless ad hoc network?

Completely on-demand routing processes. Signup and view all the answers

What must a node do when it broadcasts a Route Request Packet (RREQ)?

Append itself to the RREQ's route table if it has not been previously recorded Signup and view all the answers

What happens when a destination node receives a RREQ and does not have a route back to the source?

It initiates a new Route Discovery process to find a route back Signup and view all the answers

What is included in the header of the packet during Basic Route Discovery?

A unique Request ID and the address of the sender Signup and view all the answers

Which of the following is NOT part of the responsibilities of a node transmitting a packet?

Updating the source route based on the next hop's signal strength Signup and view all the answers

What is the first action a source node (S) takes when it wants to communicate with node D and finds no existing route?

It initiates a Route Discovery protocol Signup and view all the answers

During the route maintenance phase, what does a node rely on to confirm packet delivery to the next hop?

A standard part of the MAC layer functionality Signup and view all the answers

In dynamic source routing, what was the purpose of including the route to the sender in the RREQ's route table?

To facilitate a bi-directional communication path Signup and view all the answers

Which statement about ad-hoc networks is true?

They allow nodes to connect and communicate without a central coordinator Signup and view all the answers

What distinguishes AODV from DSR in ad-hoc routing protocols?

AODV is based on distance vectors while DSR uses source routing Signup and view all the answers

What is a necessary condition for a node to send a Route Reply Packet (RREP)?

The node must have a route in its cache to the source Signup and view all the answers

What information does each node maintain concerning the RREQ?

The address of the neighbor from which it received the first copy of the RREQ Signup and view all the answers

What happens to nodes that are not included in the path determined by the RREP?

They delete their reverse pointers after a timeout period Signup and view all the answers

What occurs when the RREQ reaches the destination in the AODV protocol?

The reverse path is fully set up for RREP to travel back Signup and view all the answers

How is the first RREP propagated from the destination to the source?

It travels using the previously established reverse path Signup and view all the answers

Which of the following statements about neighbor nodes is correct in the context of the AODV protocol?

Certain neighbor nodes may not be able to satisfy the RREQ Signup and view all the answers

What is the function of a node upon receiving an RREQ that it cannot satisfy?

It rebroadcasts the RREQ to its neighbors Signup and view all the answers

How long do nodes wait before deleting their reverse pointers if they are not in the RREP path?

3000 ms Signup and view all the answers

What does the reverse path setup allow in AODV protocol?

RREP to travel back to the source once RREQ is fulfilled Signup and view all the answers

What does a node that receives RREQ for D from S represent?

A node that has received a route request Signup and view all the answers

Which of the following best describes what happens when node C receives RREQ from G and H?

Node C does not forward RREQ again Signup and view all the answers

Why does node D not forward the RREQ?

Node D is the intended target of the RREQ Signup and view all the answers

What does the reverse path setup in AODV signify?

The establishment of a return path for RREP Signup and view all the answers

What role do forward 'next-hops' play in AODV?

They are set up when RREP travels along the reverse path Signup and view all the answers

What does the representation of links on the reverse path indicate?

The path taken for route replies Signup and view all the answers

How are routing table entries relevant during data delivery in AODV?

They are used for forwarding data packets Signup and view all the answers

Which of the following correctly identifies a characteristic of the data delivery phase in AODV?

No actual path is stored during RREP traversal Signup and view all the answers

In a typical AODV operation, what happens after a node successfully receives an RREQ?

It acknowledges the RREQ by sending a route reply Signup and view all the answers

Which action does NOT take place during the route request phase in AODV?

Path setup is initiated for data delivery Signup and view all the answers

What depicts the broadcast transmission in AODV?

The initial route request sent by source Signup and view all the answers

What is the main purpose of the links on the path taken by RREP?

To assist in establishing reverse paths Signup and view all the answers

What situation would cause a node to prevent further RREQ forwarding?

Already having forwarded RREQ once Signup and view all the answers

Which part of AODV describes the forwarding of data packets using established paths?

Data Delivery Phase Signup and view all the answers

Study Notes

Ad-Hoc Networks

Ad-hoc networks are a type of wireless network that can be set up without a centralized infrastructure.
They operate on a peer-to-peer basis where each device is responsible for its own data transmission and routing.

Ad-hoc Routing Algorithms

Routing algorithms are essential for data transmission and communication across ad-hoc networks.
The goal is to find the best path for data to reach its destination.
Popular algorithms include Ad-Hoc On-Demand Distance Vector Routing (AODV) and Dynamic Source Routing (DSR).

Ad-Hoc On-Demand Distance Vector Routing (AODV)

AODV is a reactive routing protocol for ad-hoc networks.
It establishes routes on demand, when a node needs to communicate with another node.
AODV uses a combination of Route Request (RREQ) and Route Reply (RREP) packets to discover and maintain routes.

Reverse Path Setup in AODV

Each node stores the address of the neighbor from which it received the first copy of the RREQ.
These entries are kept for a sufficient time to allow the RREQ to traverse the network and produce a reply.
When a RREQ reaches the destination, the path is set up in reverse to facilitate RREP transmission back to the source.

Forward Path Setup in AODV

A node receiving a RREP propagates the first RREP towards the source using the established reverse path.
Nodes outside the determined path time out after 3000 ms and delete their reverse pointers.
Multiple RREPs towards the source are unnecessary, the first one is sufficient for data transmission.
The source can start data transmission as soon as it receives the first RREP.

Dynamic Source Routing (DSR)

DSR is another reactive routing protocol that focuses on dynamically discovering routes and maintaining them.
It utilizes source routes, which are sequences of hops a packet should follow to reach its destination.

Basic Route Discovery in DSR

A sender node broadcasts a Route Request Packet (RREQ) when a route is needed.
The RREQ contains a unique Request ID and the sender's address.
If a receiver node is the destination or has a route to the destination, it sends a Route Reply Packet (RREP).
Intermediate nodes append their address to the RREQ, and broadcast the updated RREQ if they don't already have a route to the destination or are not the source.

Basic Route Maintenance in DSR

Each node transmitting a packet is responsible for confirming its receipt by the next hop.
This confirmation is handled by the MAC layer (e.g., Link-level ACKs in 802.11).
If no MAC confirmation exists, software handles sending back an ACK.
When a node reaches the maximum retransmissions of a packet, a Route Error Packet (RERR) is sent back to the source, indicating a broken link.

Comparison of AODV and DSR:

AODV uses a hop-by-hop approach, while DSR uses source routing.
AODV offers lower overhead for route discovery, DSR generally has lower overhead for route maintenance.
DSR is more suited to dynamic environments with frequent changes in network topology.
AODV might be preferred in less dynamic scenarios.

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Description

Test your knowledge on ad-hoc networks and the AODV routing algorithm. This quiz covers how ad-hoc networks function, their key routing protocols, and the specifics of AODV. Explore the concepts of routing paths and data transmission in decentralized networks.