18 Questions
What is the primary purpose of the BGP protocol in Internet inter-AS routing?
To obtain subnet reachability information from neighboring ASs
What is the maximum number of hops allowed in RIP distance metric?
15 hops
What is the algorithm used by OSPF to compute routes?
Dijkstra's algorithm
What type of routing protocol is RIP?
Distance Vector protocol
What is the purpose of the gateway router in hierarchical routing?
To connect to routers in other ASes
What is the primary difference between intra-AS and inter-AS routing protocols?
Intra-AS protocols run within an AS, while inter-AS protocols run between ASes
What is the primary reason for using tunneling in the transition from IPv4 to IPv6?
To enable communication between mixed IPv4 and IPv6 routers
What is the purpose of the 'flow label' field in the IPv6 header?
To facilitate Quality of Service (QoS) processing
What is the result of a router's forwarding table determining the local forwarding at a particular router?
The output link address is determined
In the context of graph abstraction, what does the cost of a link (x,x') represent?
The inverse of the bandwidth of the link
What is the key question in the context of graph abstraction?
What is the least-cost path between two nodes?
What is the size of the fixed-length header in an IPv6 datagram?
40 bytes
What is the primary function of ICMP in a network?
To report errors and communicate network-level information
What type of ICMP message is sent when a packet's TTL expires?
Type 11, Code 0
What is the motivation behind the development of IPv6?
To address the 32-bit address space shortage
What is the purpose of the source quench ICMP message?
To control congestion in a network
What is the stopping criteria for a Traceroute operation?
When the destination host returns an ICMP 'port unreachable' message
What is the purpose of the router discovery ICMP message?
To discover the IP address of a neighboring router
Study Notes
Network Layer
- The network layer is responsible for routing data between devices on different networks.
Distance Vector Algorithm
- The distance vector algorithm is used in RIP (Routing Information Protocol) and requires O(nE) messages.
- Each node advertises its link costs to its neighbors, and convergence time varies.
Hierarchical Routing
- Hierarchical routing is used to aggregate routers into regions called autonomous systems (AS).
- Each AS runs its own intra-AS routing protocol, and gateway routers connect ASes.
- Intra-AS routing algorithms are used within an AS, and inter-AS routing algorithms are used between ASes.
Intra-AS Routing Algorithms
- RIP (Routing Information Protocol) is a distance vector algorithm that uses hop count as its distance metric.
- OSPF (Open Shortest Path First) is a link state algorithm that uses a topology map to compute routes.
Inter-AS Routing Algorithm
- BGP (Border Gateway Protocol) is used for inter-AS routing and is the de facto interdomain routing protocol.
- BGP allows ASes to exchange reachability information and propagate it to all routers in the AS.
IPv6 Datagram Format
- IPv6 datagrams have a fixed-length 40-byte header and do not allow fragmentation.
- The header format includes priority, flow label, payload length, next header, and source and destination addresses.
Transition from IPv4 to IPv6
- The transition from IPv4 to IPv6 is challenging because not all routers can be upgraded simultaneously.
- Tunneling is used to carry IPv6 datagrams as payloads in IPv4 datagrams.
Interplay between Routing, Forwarding, and Graph Abstraction
- Routing algorithms determine the end-to-end path through the network.
- Forwarding tables are used to determine local forwarding at each router.
- Graph abstraction is used to model the network, where nodes represent routers and edges represent links.
Graph Abstraction: Costs
- Costs are assigned to each link in the graph, which can be based on factors such as bandwidth, congestion, or latency.
- The cost of a path is the sum of the costs of its individual links.
ICMP (Internet Control Message Protocol)
- ICMP is used by hosts and routers to communicate network-level information.
- ICMP messages are used for error reporting, echo request/reply, and route advertisement.
Traceroute and ICMP
- Traceroute uses ICMP messages to trace the path of packets through the network.
- ICMP messages are used to report errors and provide diagnostic information.
Test your knowledge of ICMP, its role in error reporting, and its functions in network communication. This quiz covers ICMP message types, codes, and their uses in diagnosing network issues.
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