Internet Routing III

Question 1

Why is BGP important?

Answer 1

BGP is the backbone of the global routing infrastructure, serving as the primary protocol for inter-domain routing.

BGP is the primary protocol responsible for directing data traffic between different autonomous systems (ASes) that comprise the Internet.

It ensures that data packets take the most optimal paths as they traverse various ASes, making BGP a fundamental component of the Internet’s operations.

And more…

Question 2

Why do we not use OSPF everywhere such as in inter-domain protocols and not only in intra-domain routing protocols?
What is used instead?

Answer 2

OSPF doesn’t scale to the internet since it needs to know the whole topology. And more?

BGP is used instead.

Question 3

Autonomous Systems participate in which protocol? (This question is kinda sus see answer)

Answer 3

ASes participate in the Exterior Gateway Protocol (EGP), a crucial component of inter-domain routing that enables efficient communication between different ASes.

Sus because EGP is not used any more, BGP is used instead.

Question 4

The Border Gateway Protocol (BGP) operates using a conceptual framework that involves the maintenance of three sets of state, each serving a specific purpose within the routing process:

Which are these?

Answer 4

Adj-RIBs-In
- Stands for “Adjacent Routing Information Base, Incoming”
- Has unprocessed routes learned from other BGP speakers
- Contains both reachable and unreachable routes
in case the latter later becomes reachable and can be added to Loc-RIB

Loc-RIB (Local RIB)
- Contains routes from Adj-RIBs-In selected by policy
- First hop of each route must be reachable by Interior Gateway Protocol (IGP) or static route

Adj-RIBs-Out (Adj-RIBs, Outgoing)
- Subset of Loc-RIB to be advertised to peer speakers

Question 5

What are the implications or challenges of the Border Gateway Protocol (BGP)?

Answer 5

Explicit AS Path for Loop Prevention: BGP uses AS path for loop-free routing but can face challenges with AS churn or misconfigurations.

Incomplete Path Knowledge: ASes might not have complete path information due to BGP's decentralized nature.

AS Abstraction Issues: BGP abstracts routers and links within an AS, which can lead to suboptimal routing decisions.

Non-Guaranteed Shortest AS Path: BGP decisions might not always prioritize the shortest path due to factors like policies and local preferences.

Scaling Challenges: BGP must manage a growing number of ASes and prefixes, which can be challenging.

Prefix Aggregation: This technique reduces the number of prefixes but can decrease routing granularity.

Policy and Security Concerns: BGP allows complex routing policies which can lead to intricate configurations, and it has vulnerabilities like prefix hijacking.

Question 6

Which protocol does the Border Gateway Protocol (BGP) operate on top of?

Answer 6

Transmission Control Protocol (TCP)

Question 7

The Border Gateway Protocol (BGP) defines four main types of messages. Which?

Answer 7

OPEN: Used to establish a connection with a BGP peer. It carries information such as the BGP version, the sender’s autonomous system (AS) number, and the hold time.

UPDATE: Used to advertise new routes or withdraw previously advertised routes. It provides information about a path to a particular network and the attributes of that path.

KEEPALIVE: Sent periodically between peers to ensure the connection is alive. If a router doesn't receive a Keepalive (or any other message) from its peer within the hold time, it will assume the connection is dead.

NOTIFICATION: Sent when an error is detected. It indicates to the peer that a fault has occurred and describes the nature of the error. After sending a Notification message, the BGP connection is typically closed.

Question 8

What happens if a next-hop address in BGP is not reachable?

Answer 8

The route becomes invalid for the current BGP speaker.

Question 9

In BGP route selection, what is the fundamental consideration before evaluating other attributes?

Answer 9

Whether the next-hop address of the route is reachable.

Question 10

In BGP route selection, why are routes with shorter AS paths preferred?

Answer 10

Routes with shorter AS paths are preferred as they often indicate a more direct path to the destination.

Question 11

What is the “AS Path” in the context of BGP?

Answer 11

The AS path is the sequence of ASes that the route has traversed.

Question 12

What does the “End-to-End Principle” in network design suggest?

Answer 12

Important functionality should be placed at the endpoints of the network rather than in the core. This promotes flexibility and innovation at the edges of the network.

Question 13

How does “Layering” contribute to network design?

Answer 13

Network functionality is divided into layers, with each layer responsible for specific tasks. This modular approach simplifies management, maintenance, and upgrades.

Question 14

What does the principle of “Abstraction” mean in network design?

Answer 14

The details of lower layers are hidden from higher layers, with each layer providing a well-defined interface for the layer above. It promotes separation of concerns and modularity.

Question 15

Describe the principle of “Decentralization” in the context of the Internet.

Answer 15

The Internet is a collection of interconnected networks without a central controlling authority, promoting scalability, robustness, and adaptability.

Question 16

How do “Open Standards” impact the Internet’s development?

Answer 16

Internet protocols and technologies are developed through open processes and are documented in public standards. This ensures interoperability and prevents vendor lock-in.

Question 17

Explain the principle of “Packet Switching” in network communication.

Answer 17

Data is transmitted in small packets rather than continuously, enabling efficient sharing of resources and better traffic load handling.

Question 18

What is the significance of “Stateless Communication” in networking?

Answer 18

Each packet is treated independently, without the network maintaining any state, enhancing scalability and reliability.

Question 19

What does “Best-Effort Service” mean in the context of Internet service?

Answer 19

The Internet delivers packets without guarantees of quality or delivery, offering simplicity and flexibility for a variety of applications.

Question 20

Describe the principle of “Rough Consensus and Running Code” in Internet protocol development.

Answer 20

Technical decisions are made through rough consensus among experts, and protocols are validated through running code, ensuring practical and feasible solutions.

Question 21

What is the concept of the “Public Network” in relation to the Internet?

Answer 21

The Internet is accessible to anyone with the necessary equipment and connectivity, open for global communication, collaboration, and information sharing.

Question 22

Why is “End-to-End Security” essential in network communication?

Answer 22

Security measures are best implemented at the endpoints rather than relying solely on the network. This principle enhances privacy and data protection.

Question 23

How does the principle of “Evolutionary Development” relate to the Internet’s growth?

Answer 23

The Internet is designed to evolve, accommodating new technologies and adapting to changing needs, ensuring its ongoing relevance and capability.

Question 24

What is traffic engineering in the context of networking?

Answer 24

It refers to the strategic manipulation of network traffic flows to achieve specific goals, such as optimizing performance, minimizing congestion, and improving resource utilization.

Question 25

What is a BGP Wedgie according to RFC 4264?

Answer 25

A BGP Wedgie refers to situations in BGP where multiple stable solutions exist for the routing of a specific set of prefixes (IP addresses). It occurs due to the complex interplay of BGP’s route selection criteria and the policies of different ASes.