Podcast
Questions and Answers
What does RREP stand for in the context of AODV protocol?
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?
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?
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?
During the forward path setup in AODV, what is the goal of minimizing RREPs?
What occurs if the source node S learns of a better route after starting data transmission?
What occurs if the source node S learns of a better route after starting data transmission?
What does a Route Error Packet (RERR) indicate in the context of DSR?
What does a Route Error Packet (RERR) indicate in the context of DSR?
What responsibility does the DSR-specific software take if no link-level ACK exists?
What responsibility does the DSR-specific software take if no link-level ACK exists?
What action does the source node take after receiving a Route Error Packet?
What action does the source node take after receiving a Route Error Packet?
How does DSR perform routing in multi-hop wireless ad hoc networks under stationary conditions?
How does DSR perform routing in multi-hop wireless ad hoc networks under stationary conditions?
Which feature characterizes the operation of DSR in a wireless ad hoc network?
Which feature characterizes the operation of DSR in a wireless ad hoc network?
What must a node do when it broadcasts a Route Request Packet (RREQ)?
What must a node do when it broadcasts a Route Request Packet (RREQ)?
What happens when a destination node receives a RREQ and does not have a route back to the source?
What happens when a destination node receives a RREQ and does not have a route back to the source?
What is included in the header of the packet during Basic Route Discovery?
What is included in the header of the packet during Basic Route Discovery?
Which of the following is NOT part of the responsibilities of a node transmitting a packet?
Which of the following is NOT part of the responsibilities of a node transmitting a packet?
What is the first action a source node (S) takes when it wants to communicate with node D and finds no existing route?
What is the first action a source node (S) takes when it wants to communicate with node D and finds no existing route?
During the route maintenance phase, what does a node rely on to confirm packet delivery to the next hop?
During the route maintenance phase, what does a node rely on to confirm packet delivery to the next hop?
In dynamic source routing, what was the purpose of including the route to the sender in the RREQ's route table?
In dynamic source routing, what was the purpose of including the route to the sender in the RREQ's route table?
Which statement about ad-hoc networks is true?
Which statement about ad-hoc networks is true?
What distinguishes AODV from DSR in ad-hoc routing protocols?
What distinguishes AODV from DSR in ad-hoc routing protocols?
What is a necessary condition for a node to send a Route Reply Packet (RREP)?
What is a necessary condition for a node to send a Route Reply Packet (RREP)?
What information does each node maintain concerning the RREQ?
What information does each node maintain concerning the RREQ?
What happens to nodes that are not included in the path determined by the RREP?
What happens to nodes that are not included in the path determined by the RREP?
What occurs when the RREQ reaches the destination in the AODV protocol?
What occurs when the RREQ reaches the destination in the AODV protocol?
How is the first RREP propagated from the destination to the source?
How is the first RREP propagated from the destination to the source?
Which of the following statements about neighbor nodes is correct in the context of the AODV protocol?
Which of the following statements about neighbor nodes is correct in the context of the AODV protocol?
What is the function of a node upon receiving an RREQ that it cannot satisfy?
What is the function of a node upon receiving an RREQ that it cannot satisfy?
How long do nodes wait before deleting their reverse pointers if they are not in the RREP path?
How long do nodes wait before deleting their reverse pointers if they are not in the RREP path?
What does the reverse path setup allow in AODV protocol?
What does the reverse path setup allow in AODV protocol?
What does a node that receives RREQ for D from S represent?
What does a node that receives RREQ for D from S represent?
Which of the following best describes what happens when node C receives RREQ from G and H?
Which of the following best describes what happens when node C receives RREQ from G and H?
Why does node D not forward the RREQ?
Why does node D not forward the RREQ?
What does the reverse path setup in AODV signify?
What does the reverse path setup in AODV signify?
What role do forward 'next-hops' play in AODV?
What role do forward 'next-hops' play in AODV?
What does the representation of links on the reverse path indicate?
What does the representation of links on the reverse path indicate?
How are routing table entries relevant during data delivery in AODV?
How are routing table entries relevant during data delivery in AODV?
Which of the following correctly identifies a characteristic of the data delivery phase in AODV?
Which of the following correctly identifies a characteristic of the data delivery phase in AODV?
In a typical AODV operation, what happens after a node successfully receives an RREQ?
In a typical AODV operation, what happens after a node successfully receives an RREQ?
Which action does NOT take place during the route request phase in AODV?
Which action does NOT take place during the route request phase in AODV?
What depicts the broadcast transmission in AODV?
What depicts the broadcast transmission in AODV?
What is the main purpose of the links on the path taken by RREP?
What is the main purpose of the links on the path taken by RREP?
What situation would cause a node to prevent further RREQ forwarding?
What situation would cause a node to prevent further RREQ forwarding?
Which part of AODV describes the forwarding of data packets using established paths?
Which part of AODV describes the forwarding of data packets using established paths?
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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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