SDN and Networking Concepts Quiz

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Questions and Answers

What is the primary focus of routing within a single Autonomous System (AS)?

Quality of the routes used

Policy orientation of routing

Routing complexity

Performance realized on the route (correct)

What is required to assign an IP address to a web server?

Using an existing DNS server

Obtaining a range from a local ISP (correct)

Connecting to a global ISP

Contracting with a domain name registrar

Which protocol does a local ISP use to advertise a /24 prefix to other ISPs?

OSPF

BGP (correct)

RIP

EIGRP

Which characteristic of an SDN architecture involves separating decisions about network control from the data forwarding?

Decoupling of data and control plane Signup and view all the answers

What does OpenFlow allow in the context of SDN?

Flow-based forwarding based on header field values Signup and view all the answers

What does the term 'unbundling' in SDN refer to?

Separation of data plane switches, SDN controllers, and applications Signup and view all the answers

Which component of an SDN architecture is responsible for monitoring and controlling network devices?

SDN controller Signup and view all the answers

For what purpose do network-control applications in an SDN serve?

Programming and controlling the network Signup and view all the answers

What is the primary factor used to select routes when multiple options share the highest local preference value?

Shortest AS-PATH Signup and view all the answers

In the route selection algorithm, after local preference and AS-PATH, what criteria does BGP use next?

Hot potato routing Signup and view all the answers

Why might CDNs choose not to use IP-anycast?

BGP routing changes can disrupt TCP connections. Signup and view all the answers

What happens when a BGP router receives multiple advertisements for the same IP address?

It treats them as different paths to one location. Signup and view all the answers

What is the role of the local-preference attribute in route selection?

It defines the policy of the local AS for route preference. Signup and view all the answers

Which statement is true regarding BGP’s route-selection process?

BGP prioritizes routes with the highest local preference first. Signup and view all the answers

What is a consequence of using IP-anycast for DNS queries?

Different packets may reach different server instances. Signup and view all the answers

What is the first step in BGP's route selection algorithm?

Assigning a local preference value to routes. Signup and view all the answers

What happens if a router detects its own AS in the AS-PATH?

It rejects the route advertisement. Signup and view all the answers

Which IP address is considered the NEXT-HOP for the route 'AS2 AS3 x' from AS1?

The IP address of the left interface on router 2a. Signup and view all the answers

What is the primary goal of hot-potato routing?

Quickly forward packets out of the AS. Signup and view all the answers

How is cost defined for selecting the route to a NEXT-HOP router?

By the number of links traversed. Signup and view all the answers

When adding an outside-AS prefix to a forwarding table, which protocols are utilized?

BGP and OSPF. Signup and view all the answers

What determines the decision for a router like 1b when selecting the least-cost path to the NEXT-HOP?

The number of links traversed. Signup and view all the answers

If multiple routes to the same prefix exist, what is the first action BGP takes?

Selects the route with the lowest cost. Signup and view all the answers

What might cause two routers within the same AS to choose different AS paths to the same prefix?

Different costs to each NEXT-HOP. Signup and view all the answers

What is the primary purpose of the Border Gateway Protocol (BGP)?

To route packets across multiple Autonomous Systems (ASs). Signup and view all the answers

How does BGP determine the 'best' route?

Based on reachability information and policy decisions. Signup and view all the answers

What type of routing protocol is BGP classified as?

Distance-vector protocol. Signup and view all the answers

What does a router’s forwarding table contain in BGP?

Records in the form (prefix, interface number). Signup and view all the answers

Which type of router connects to external ASs in BGP?

Gateway router. Signup and view all the answers

What is meant by CIDRized prefixes in BGP?

A representation of subnets or collections of subnets. Signup and view all the answers

Which statement about BGP routing tables is true?

They often contain over half a million routes. Signup and view all the answers

How does BGP facilitate packet routing between ASs?

It advertises subnet existence to neighboring ASs. Signup and view all the answers

What describes the path that AS2 relays to AS1 regarding the subnet with prefix x?

AS2 AS3 x Signup and view all the answers

What type of BGP connection is established between routers in different ASs?

External BGP (eBGP) Signup and view all the answers

Which port is used for BGP connections?

179 Signup and view all the answers

Which statement correctly describes the role of iBGP in route propagation?

iBGP connects routers in the same AS and propagates information. Signup and view all the answers

What are the two important attributes included in a router's advertisement of a prefix?

NEXT-HOP and AS-PATH Signup and view all the answers

How does a router choose between multiple paths to a destination?

By evaluating BGP attributes. Signup and view all the answers

How does gateway router 2c utilize the information received from eBGP?

It forwards the message to all routers in AS2 using iBGP. Signup and view all the answers

Which of these statements accurately describes how routers learn about subnet x?

ASs learn about subnet x through advertised paths. Signup and view all the answers

What is the primary function of access ISPs like W and Y?

To manage traffic entering and leaving their networks Signup and view all the answers

What prevents X from forwarding traffic between B and C?

Selective route advertisement policy Signup and view all the answers

Why might B hesitate to advertise the path BAW to C?

To prevent C from gaining access to W without compensation Signup and view all the answers

What main principle governs traffic flow among ISPs according to the backbone/provider ISP policy?

Traffic must originate from a source in the ISP's network Signup and view all the answers

Why are different routing protocols used for inter-AS and intra-AS?

Intra-AS routing requires less scaling and focuses on policies Signup and view all the answers

Which feature of OSPF enhances its scalability?

Hierarchical area division within an AS Signup and view all the answers

What characteristic defines a multi-homed access ISP like X?

It has connections to two different backbone providers Signup and view all the answers

What could be a potential issue with the current lack of official standards among backbone ISPs?

Difficulty in managing peering agreements Signup and view all the answers

Study Notes

Introduction to Computer Networks

This presentation covers various aspects of computer networks
Topics include routing algorithms, protocols, and control planes
Various protocols are discussed, including OSPF, BGP, ICMP, SNMP, NETCONF/YANG

Routing Algorithms

These algorithms determine the best path for data packets to travel through networks
Different algorithms exist for routing within and between autonomous systems (ASs)

Intra-AS Routing in the Internet: OSPF

OSPF (Open Shortest Path First) is an intra-AS routing protocol
It uses a link-state routing approach.
Data about network links is shared among routers

Routing Among the ISPs: BGP

BGP (Border Gateway Protocol) is an inter-AS routing protocol
It is a decentralized and asynchronous
It uses a path vector routing approach
Routers exchange information about prefixes

The SDN Control Plane

SDN (Software-Defined Networking) separates the data plane and control plane
This offers greater flexibility and programmability
SDN controllers manage network devices.
Data plane devices run the network

ICMP: The Internet Control Message Protocol

ICMP (Internet Control Message Protocol) is a network-layer protocol
It's primarily used for error reporting and communication between network devices
It carries messages inside IP datagrams.
These datagrams contain a type, code field, and data related to the message

Network Management and SNMP, NETCONF/YANG

Network management involves the control & monitoring of network components
SNMP(Simple Network Management Protocol) is a network protocol
NETCONF/YANG provide configuration & management for network devices
These protocols are commonly used to manage complex systems

IP-Anycast

IP anycast is a technique used to distribute content across multiple locations
This is widely used by content delivery networks (CDNs)
Provides services from the closest location
BGP is used to support this method

Routing Policy

Routing policy governs how paths are selected.
It takes into account factors like local preference
Backbone providers and access ISP networks have policies to prevent issues like traffic issues

Access ISP Policy

All traffic entering and exiting an access network must be destined for that network.
Selective route advertisement is used for policies in networking
This can maintain the desired network relationships

Backbone/Provider ISP Policy

There are no specific standards for backbone ISPs' routing
Rules of thumb involve traffic destined for customers of the ISP.
Individual peering agreements guide routing

Why are different inter-AS and intra-AS routing protocols used?

Routing decisions are often driven by policy issues within an autonomous system (AS) or between them
These preferences impact routing choices
Routing protocols for different scales must also be considered

Obtaining Internet Presence

Obtaining Internet connectivity involves contracting with an ISP
ISPs assign IP addresses to various components in the network
This allows network communication

SDN Controller

SDN controllers manage and control the data plane devices
A critical aspect in managing this architecture is its protocols
Communication layers and northbound/southbound interfaces are essential elements that maintain operations

OpenFlow Protocol

The OpenFlow protocol is used to communicate between the SDN controller and data plane
It uses TCP port 6653
This method establishes communication

Data and Control Plane Interaction

The data plane performs specific operations on packets
The control plane handles higher-level management like routing decisions
These communicate via protocols like OpenFlow

SDN: Past and Future

SDN aims to replace traditional network equipment with software-defined components
This enhances flexibility and scalability
Generalization of the SDN architecture, known as Network Functions Virtualization (NFV), aims for similar disruptive changes in networking

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Description

Test your knowledge on Software Defined Networking (SDN) and routing within Autonomous Systems. This quiz covers essential topics such as IP address assignment, ISP protocols, and the architecture of SDN. Perfect for those looking to deepen their understanding of modern networking principles.