Computer Networks

Describe the Bus Topology (Wired Network)

- All devices are connected to a single coaxial network cable - Terminators are required at both ends of the cable to prevent signal bounce - Antiquated technology - Only on end device can be active on the network at a time Data signals travel in both directions and are received by all devices on the network - Single break in the cable can take down entire network

What is a Client-Server Network Architecture (3 Characteristics)

- Network is composed of clients and servers. Servers provide resources, Clients consume resources -Servers provide centralized control over network resources -Centralizes user accounts, security, and access controls to simplify network adminstration

Describe the Ring Topology

-All devices are connected in a circular fashion -Each computer is connected to two other computers -Data travels from node-to-node with each computer handling data, either unidirectional or bidirectional -Each device(node) in the ring regenerates the signal, acting as a repeater -Failure of a single node can take down the entire network -Fiber Distributed Data Interface (FDDI) uses two counter-rotating ring topologies for redundancy

What is a Peer-to-Peer Network Architecture? (3 Characteristics)

-Its where all computers on a network are peers and there is no centralized control over shared resources. -Any device can share resources with others as it pleases. - All computers can act as either clients or servers

What is the Ad hoc topology

-Peer-to-Peer (P2P) wireless network where no wireless access point (WAP) infrastructure exits -The devices communicate directly with each other Personal Area Networks (PANs) are common example of Ad hoc wireless networks

What is the Infrastructure Topology

-Wireless network uses a Wireless Access Point (WAP) as its central connecting device -Infrastructure wireless networks (WLANs) are commonly used in homes and small offices

What does Application Layer in TCP/IP translate to in OSI?

1) Application Layer 2) Presentation Layer 3) Session Layer

List the 7 layers of OSI from top to bottom.

1) Application Layer 2) Presentation Layer 3) Session Layer 4) Transport Layer ----------------- 5) Network Layer 6) Data Link Layer 7) Physical Layer

List the 4 layers of TCP/IP Model

1) Application Layer 2) Transport Layer 3) Internet Layer 4) Network Interface Layer

What does Network Interface Layer in TCP/IP translate to in OSI?

1) Data Link Layer 2) Physical Layer

3 types of firewall generations?

1) Filtering Rules.(Whitelist vs Blacklist) 2) Circuit level Firewalls (Monitors TCP Sessions) 3) Next-Gen Firewall (more advanced)

Explain how SSL/TLS work. 5 Steps

1. The user initiates the connection by typing the website address. The browser initiates the SSL/TLS communication by sending a message to the website's server. 2.The website's server sends back the public key or certificate to the user's browser. 3.User's browser checks for public key or certificate. If it is ok, it creates a symmetric key and sends it back to the website's server. If the certificate is not ok, the communication fails. 4.On receiving the symmetric key, the website's server sent the key and encrypted the requested data. 5.The user's browser decrypts the content using a symmetric key, which completes the SSL/TLS handshake. The user can see content as now connection is established.

What is the address range of a class A network?

1.0.0.0 -126.255.255.255

How large is a TCP header in terms of bytes?

20 bytes

What OSI Layer are Routers part of?

3

What is the 3-Way handshake in TCP?

3-Way Handshake creates a virtual connection between the source and destination before data is sent

How many octets is an IPv4 Address?

4 octets, 32 bits

You can only borrow up to how many of the host bits?

6

How large is a UDP header?

8 bytes

What is the backbone network?

A backbone network is a centralized infrastructure that is designed to distribute different routes and data to various networks. It also handles management of bandwidth and various channels.

What is a Network Interface Card (NIC)?

A computer hardware (network adapter) component that connects a computer to a computer network.

Describe the Mesh Topology

A decentralised network in which every node is connected to every other node.

What are Switches?

A device for connecting computers and other network capable devices together to form a network. They also act as bridges, which connect more than one network, allowing them to function as one network. They work by memorizing the MAC Address of each device connected to it via a MAC address table (CAM table) It's a Layer 2 OSI Device

What is the importance of implementing a Fault Tolerance System?

A fault tolerance system ensures continuous data availability. This is done by eliminating a single point of failure.

What are the functions of a network administrator?

A network administrator has many responsibilities that can be summarized into 3 key functions: installation of a network, a configuration of network settings, and maintenance/troubleshooting of networks.

What is DHCP?

A protocol used to automate the assignment of IP Address. It stands for Dynamic Host Control Protocol and is the successor to BOOTP.

What is a Firewall?

A security barrier that prevents unauthorized access to or from private networks

What is an anonymous FTP site?

A site that allows guests to download files without having an account on that site

What is a subnet mask?

A subnet mask is a mechanism that allows a network device to divide an IP address into a network and host number

What are DHCP Relay Agents

A system used to forward DHCP requests and replies between a DHCP server and clients when the DHCP server is on a different network This allows you to not have a DHCP server on each network

What is a VPN?

A virtual private network (VPN) is a communication tunnel that provides point-to-point transmission of both authentication and data traffic over an intermediary network.

What is a WAP

A wireless access point, a device that uses a radio transceiver to allow wireless connections to a network, in effect creating its own network.

What are the 3 specific topologies for wireless networks?

Ad hoc, Infrastructure, and Mesh

What are SSL/TLS Certificates?

An SSL certificate is a digital certificate that authenticates a website's identity and enables an encrypted connection. SSL/TLS is a standard security protocol that ensures the confidentiality and integrity of data while in transit. It encrypts the data flow between the web browser and web server. The webserver and browser exchange keys to decrypt the data

Where is the best place to install an Anti-virus program?

An anti-virus program must be installed on all servers and workstations to ensure protection. That's because individual users can access any workstation and introduce a computer virus. You can plug in their removable hard drives or flash drives.

What is a node?

Any entity or addressable device on a network that can be managed

Explain the importance of authentication

Authentication is the process of verifying a user's credentials before he can log into the network. It is normally performed using a username and password. This provides a secure means of limiting access from unwanted intruders on the network.

What are the authentication levels of SSL/TLS certificates?

Authentication levels refer to the trustworthiness of a hosted URL. Certifying Authority (CA) issue certificates to an organization on validating their identities. It mainly categorizes Domain Validation (DV), Organization Validation (OV) and Extended Validation (EV).

What is a APIPA

Automatic Private Internet Protocol Addressing - when auto IP but cannot find DHCP server

Why are Switches more secure than Hubs?

Because data doesn't have to travel through each port in a switch (unlike hubs), just the intended destination

What is a "broadcast" network transmission type?

Broadcast message to all nodes

What is Brouter?

Brouter is also known as Bridge Router. It is a device that acts as both a bridge and a router. As a bridge can forwards data between the networks. It also routes the data to specified systems within a network.

How do Switches help prevent collisions?

By allowing traffic that goes in one port to only repeat out to the destination port only

What is the advantage of address sharing?

By using address translation instead of routing, address sharing provides an inherent security benefit. That's because host PCs on the Internet can only see the public IP address of the external interface on the computer that provides address translation and not the private IP addresses on the internal network.

What is the difference between CSMA/CD and CSMA/CA?

CSMA/CD, or Collision Detect, retransmits data frames whenever a collision occurred. CSMA/CA, or Collision Avoidance, will first broadcast intent to send prior to data transmission.

What does a CSR look like?

CSR is base 64 encoded text to start with "—-BEGIN CERTIFICATE REQUEST—-" and end with"—-END CERTIFICATE REQUEST—-" lines.

What is the Physical aspect of Ethernet?

Cabling, Connectors, Equipment

What is a CAN

Campus Area Network

What is a Certificate Signing Request (CSR)?

Certificate Signing Request or CSR is encoded information that contains the applicant's information such as a common name, a name of an organization, email address, city, state, and country. This encoded information is used by certifying authority (CA) to issue an SSL certificate to the applicant.

What is CIDR Notation?

Classless Inter-Domain Routing. A shortcut way of telling us what the subnet mask is. For example /24 is Class C

Which is harder to setup P2P or Client Server?

Client Server

What is the DHCP DORA process?

Client requests an IP address by broadcasting a "DHCP Discover" message on its local subnet When the DHCP server receives the request, it'll respond with a "DHCP Offer" message containing an IP address and lease information If no DHCP server is available, the client will use Automatic Private IP addressing (APIPA) alternate configuration if its configured The client then accepts the "DHCP Offer" by replying with a "DHCP Request" message to the DHCP server The DHCP server assigns the client the address and sends a "DHCP Acknowledgement"

Explain clustering support

Clustering support refers to the ability of a network operating system to connect multiple servers in a fault-tolerant group. The main purpose of this is the in the event that one server fails, all processing will continue on with the next server in the cluster.

What are Static Ip Addresses commonly used in?

Commonly Used in: DNS Servers Web Servers Network Printers Default Gateway (Routers)

What is data encapsulation?

Data encapsulation is the process of breaking down information into smaller manageable chunks before it is transmitted across the network. It is also in this process that the source and destination addresses are attached into the headers, along with parity checks.

Logical Connections?

Data transporting across the physical media

Describe Layer 2 OSI

DataLink Layer The "Switching" Layer Ensures that messages are delivered to the proper device on a LAN using hardware addresses MAC (Media Access Control) address Only concerned with the local delivery of frames on the same network Responsible for packaging the data into frames for the physical layer Translates messages from network layer into bits for the physical layer

What is Layer 1 in OSI?

Defines the physical and electrical medium for network communication Sends bits and receives bits (1 or 0) Responsible for network hardware and physical topology

What is DoS?

Denial of Service: Hackers overwhelm a website with too many requests that makes it crash

How to create subnets

Each bit we borrow is equal to 2^1 subets Borrow 1 Host bit = 2^1 = 2 new subnets Borrow 2 Host Bits = 2^2 = 4 subnets

What is the importance of Encryption on a network?

Encryption is the process of translating information into a code that is unreadable by the user. It is then translated back or decrypted back to its normal readable format using a secret key or password. Encryption help ensure that information that is intercepted halfway would remain unreadable because the user has to have the correct password or key for it.

True or False, OSI model is implemented in real world

False

What are the maximum networks and hosts in class A, B, and C network?

For Class A, there are 126 possible networks and 16,777,214 hosts. For Class B, there are 16,384 possible networks and 65,534 hosts. For Class C, there are 2,097,152 possible networks and 254 hosts

What layer does IP address translate to for both TCP/IP and OSI?

For OSI, its in the Network Layer. For TCP/IP its in the Internet Layer

What are gateways?

Gateways provide connectivity between two or more network segments. It is usually a computer that runs the gateway software and provides translation services. This translation is a key in allowing different systems to communicate on the network.

What is the DNS hierarchy for www.mail.yahoo.com?

Goes searches com then yahoo then the mail server.

Give example of LAN

Home Network, Office network

How to determine number of network hosts?

Hosts Per Network : 2^h - 2, where h is the number of host bits available We subtract the two because each network includes a network address and broadcast address that are not available for use by network end devices

What are Hubs?

Hubs are hardware devices that connect a number of devices together to form a single network segment. Hubs are fine for small networks e.g. a home office but not for larger LANs. When a hub receives data from the rest of the network it sends it to all the devices connected to it. Although the only device that will process the data will be the device with the correct MAC address the fact that data is sent to all devices means there are data collisions & data transfer is slowed down. It's a Layer 1 OSI Device

IP vs MAC: Which Address is a Logical Address?

IP

IP vs MAC: Which allows network communication via routers?

IP

IP vs MAC: Which do you typically find in a WAN?

IP

What is a IP Address?

IP Address is a logical address used in order to uniquely identify a device on a IP network

Each device on a network is assigned what 3 addresses?

IP, subnet mask, and default gateway

Where is P2P common?

In homes and small businesses

What is a Hamming code?

In telecommunication, Hamming codes are a family of linear error-correcting codes that generalize the Hamming(7,4)-code, and were invented by Richard Hamming in 1950. Hamming codes can detect up to two-bit errors or correct one-bit errors without detection of uncorrected errors.

How does dynamic host configuration protocol aid in network administration?

Instead of having to visit each client computer to configure a static IP address, the network administrator can apply dynamic host configuration protocol to create a pool of IP addresses known as scopes that can be dynamically assigned to clients.

What is ICMP?

Internet control message protocol - used for testing basic connectivity, diagnostics, control, and error messaging

What is a point to point link?

It refers to a direct connection between two computers on a network. A point to point connection does not need any other network devices other than connecting a cable to the NIC cards of both computers.

Describe OSI Layer 7

Its the Application Layer Where users interact with the computer Acts as an interface between an application and end-user protocols Provides an interface to communicate with the network Applications doesn't reside in the application layer, but instead interfaces with application-layer protocols Example Application Layer Protocols: E-Mail: IMAP4, POP3, SMTP Web Browser: HTTP, HTTPS Remote Access: SSH, Telnet

What is a Mesh Topology for Wireless Networks

Just like a wired mesh design, wireless mesh networks utilizes several wireless access points (nodes) to create a robust wireless network that is Scalable Self-Healing Reliable (redundancy)

What is LAN

Local Area Network

What are the 2 Sublayers of the DataLink Layer

Logical Link Control (LLC) Layer Error Control and Flow control Detect and correct corrupted data frames Limits amount of data sent so devices aren't overwhelmed Media Access Control (MAC) Layer Physical Addressing (MAC Address) 48-Bit MAC Address burned on NIC

IP vs MAC: Which Address is a Physical Address?

MAC

IP vs MAC: Which address is burned on a NIC?

MAC

IP vs MAC: Which allows intercommunication via hubs, switches, and routers?

MAC

IP vs MAC: Which do you typically find in a Local LAN ?

MAC

What does MAC Address stand for?

Media Access Control

What is a MAN

Metropolitan Area Network that interconnects users with computer resources in a city

What is a Network Address Translation (NAT)?

NAT is a mechanism where private, nonroutable IP addresses are translated to public routable IP addresses and vice versa.

What is NS record?

Name Server records are used by top level DNS to direct traffic to the Content DNS server that contains the authoritative DNS records.

What is the Logical aspect of Ethernet?

Network Access Method (CSMA Carrier Sense Multiple Access)

Describe Layer 3 OSI

Network Layer The "Routing" Layer Provides local addressing (IP addressing) and routing services

How many network bits is in a Class B network? host bits? What is its address range?

Network bits: 16 Host bits: 16 Address range : 128.0.0.0 - 191.255.255.255

How many network bits is in a Class C network? host bits? What is its address range?

Network bits: 24 Host bits: 8 Address range : 192.0.0.0 - 223.255.255.255

How many network bits is in a Class A network? host bits?

Network bits: 8 Host bits: 24

What does Internet Layer in TCP/IP translate to in OSI?

Network layer

How does a network topology affect your decision to set a network?

Network topology dictates what media you must use to interconnect devices. It also serves as a basis on what materials, connectors, and terminations that is applicable for the setup.

What is the main purpose of OSPF?

OSPF, or Open Shortest Path First, is a link-state routing protocol that uses routing tables to determine the best possible path for data exchange.

What is a "Multi-cast" network transmission type?

One-to-Many

What is a "Unicast" network transmission type?

One-to-one transmission

What is the OSI Model?

Open Systems Interconnection reference model. It's a conceptual framework showing us how data moves throughout a network

What is a PAN?

Personal Area Network

What is a MAC Address?

Physical Address of a network card. Represents the OSI Data Link layer

What are the two main aspects of a network

Physical Connection and Logical Connection

What is Ping?

Ping is a utility program that allows you to check connectivity between network devices on the network. You can ping a device by using its IP address or device name, such as a computer name.

Explain the term Pipelining

Pipelining describes the sequencing of processes. When any new task begins before an ongoing task is finished, it is called sequencing.

What are pre-shared key encryption algorithms?

Pre-shared key encryption algorithms refer to the symmetric key used to encrypt data between browser and web server. The most commonly used algorithms are Twofish, AES, or Blowfish as pre-shared key encryption algorithms.

Describe Layer 6 OSI

Presentation Layer Ensures that data transferred from one system's application layer can be read by the Application Layer on another one Provides character code conversion, data compression, and data encryption/decryption Example: Google Chrome HTLM Converted to ASCII Format Example Layer 6 File formats Web Browser: HTML, XML, JS Graphics File: JPEG Audio: MP3 Encryption: SSL

What is a private IP address?

Private IP addresses are assigned for use on intranets. These addresses are used for internal networks and are not routable on external public networks. These ensures that no conflicts are present among internal networks while at the same time the same range of private IP addresses are reusable for multiple intranets since they do not "see" each other.

Explain profile in terms of networking concepts

Profiles are the configuration settings made for each user. A profile may be created that puts a user in a group, for example.

What are proxy servers, and how do they protect computer networks?

Proxy servers primarily prevent external users who are identifying the IP addresses of an internal network. Without knowledge of the correct IP address, even the physical location of the network cannot be identified. Proxy servers can make a network virtually invisible to external users.

Discuss some public-key encryption algorithms used in SSL.

Public key encryption is used to exchange the symmetric key between browser and web server. Some of the algorithms used Elliptic curve cryptography (ECC), RSA etc.

What is a RIP?

RIP, short for Routing Information Protocol is used by routers to send data from one network to another. It efficiently manages routing data by broadcasting its routing table to all other routers within the network. It determines the network distance in units of hops.

What is the RSA algorithm?

RSA is short for Rivest-Shamir-Adleman algorithm. It is the most commonly used public key encryption algorithm in use today.

Explain Redirector

Redirector is a kind of software which intercepts file or prints I/O requests and translates them into network requests. This component comes under the presentation layer.

What does Ethernet refer to?

Refers to a family of standards that define the Physical and logical aspects of the world's most popular type of LAN.

What is a Link?

Refers to the connectivity between two devices.

What is a PTR record type in DNS?

Resolves an IP address to a domain name

What is a AAAA DNS record type?

Resolves domain name to Ipv6 address

Common DNS Record Types: What is A?

Resolves domain name to an IPv4 Address

What is a CNAME DNS record?

Resolves on domain name to another domain name, allowing multiple domain names to be resolved to the same IP address

When it comes to networking, what are rights?

Rights refer to the authorized permission to perform specific actions on the network. Each user on the network can be assigned individual rights, depending on what must be allowed for that user.

How can you manage a network using a router?

Routers have a built-in console that lets you configure different settings, like security and data logging. You can assign restrictions to computers, such as what resources it is allowed access or what particular time of the day, they can browse the Internet. You can even put restrictions on what websites are not viewable across the entire network.

How SSL/TLS uses both asymmetric and symmetric encryption?

SSL used symmetric encryption to encrypt data between browser and web server. In contrast, asymmetric encryption is used to exchange generated symmetric keys, which validates the client and server's identity.

Describe Layer 5 OSI

Session Layer Responsible for setting up, managing and then tearing down sessions between network devices Ensures data from different application sessions are kept separate. Coordinates communication between systems Start, Stop, Restart

Describe the TCP/IP Model

Similar to OSI but is based on 4-layer model.

Give an example of a PAN

Smart Phone to Laptop connection

What is sneakernet?

Sneakernet is believed to be the earliest form of networking wherein data is physically transported using removable media, such as disk, tapes.

Describe the Star Topology

Star topology consists of a central hub that connects to nodes. This is one of the easiest to setup and maintain. Central Device is single point of failure

What does 10Base-T mean?

The 10 refers to the data transfer rate, in this case is 10Mbps. The word Base refers to base band, as oppose to broad band. T means twisted pair, which is the cable used for that network.

What is the 5-4-3 rule, and in which architecture is it used?

The 5-4-3 rule is used in 10Base2 and 10Base5 Ethernet architectures. In this rule, there can be a maximum of five segments in a network connected with four repeaters. Out of these five segments, only three segments can be populated with nodes.

What is a DNS?

The Domain Name System (DNS) converts domain names or host names into IP addresses. Instead of having to remember a host's IP address, DNS allows you to use a friendly name to access the host. For example, it is easier to remember http://www.cisco.com than 198.133.219.25.

What is a default gateway?

The IP address of the router that can send data from your network.

What protocols fall under the Application layer of the TCP/IP stack?

The following are the protocols under the TCP/IP Application layer: FTP, TFTP, Telnet, and SMTP.

Explain EGP

The full form of EGP is Exterior Gateway Protocol. It is the protocol of the routers. It is the neighboring autonomous systems that help you to identify the set of networks that you will able to reach within or via each independent system.

What is the Loopback Address?

The loopback address refers to the local system or localhost.

What is Modem?

The main aim of the Modem is to produce a signal that can be transmitted easily and decoded to reproduce the digital data in its original form. Modems are also used for transmitting analog signals, from Light Emitting Diodes (LED) to radio.

What is the main job of the ARP?

The main task of the ARP or Address Resolution Protocol is to map a known IP address to a MAC layer address.

What is asymmetric and symmetric encryption?

The major difference between symmetric and asymmetric cryptography is the use of the single key for encryption and decryption in the case of symmetric cryptography, while the use of the public and private key for encryption and decryption in the case of asymmetric cryptography

What is the source route?

The source route is a sequence of IP addresses that helps you to identify the route a datagram. You can include the source route in the IP datagram header.

What are the different ways of securing a computer network?

There are several ways to do this. Install a reliable and updated anti-virus program on all computers. Make sure firewalls are setup and configured correctly. User authentication will also help a lot. All these combined would make a highly secured network.

What are computer network protocols used for?

They provide rules on how to govern the exchange of data and enable effective communication between machines.

What is the "tracert" command?

This can be used to find the route that data travels to reach a specific computer.

What is netstat?

This command line command provides access to information about all TCP/IP connections.

What is meaning by tunnel mode?

This is a mode of data exchange wherein two communicating computers do not use IPsec themselves. Instead, the gateway that is connecting their LANs to the transit network creates a virtual tunnel. So, it uses the IPsec protocol to secure all communication that passes through it.

Explain Extended Validation (EV) authentication in SSL

This is the highest level of validation done by the Certifying Authority (CA) to issue a certificate to an organization. Here, CA validates ownership, physical location, state, and country of organization. This process can be done by physically verifying the organization's location and checks the legal existence.

Explain Domain Validation (DV) authentication in SSL.

This is the lowest level of validation done by the Certifying Authority (CA) to issue a certificate to an organization. Here, CA only verifies whether an organization controls the domain or not. This process can be done via email.

Explain Organization Validation (OV) authentication in SSL.

This is the medium level of validation done by the Certifying Authority (CA) to issue a certificate to an organization. Here, CA validates the name, state, and country of an organization. This process can be done by physically verifying the organization's location.

How do wireless networks communicate at its most basic level?

Through Radio Frequencies

What does Transport Layer in TCP/IP translate to in OSI?

Transport Layer

Describe layer 4 OSI

Transport Layer Ensure data is delivered error-free and in sequence Segments data and reassembles correctly Can be connection-oriented (3-way handshake) or connectionless Considered the "Post Office" Layer TCP (Transmission Control Protocol) UDP (User datagram protocol) Responsible for two data flow control measures Buffering Store data in memory buffers until destination device is available Windowing Allows device in session to determine the "window" size of data segment sent.

What is a Computer Network?

Two or more connected computers sharing resources with one another

What protocol can be applied when you want to transfer files between different platforms, such as UNIX systems and Windows servers?

Use FTP (File Transfer Protocol) for file transfers between such different servers. This is possible because FTP is platform-independent.

What is a MX record?

Used for mail exchange servers (email servers)

Why use subnets?

Using default Class A, B , and C subnets (called Classful IP Addressing) is inefficient Wastes unused IP Addresses (Public IP addresses) Allows you to create multiple logical networks that exists within a single Class A, B, or C network Breaks up larger networks into multiple smaller sub-networks, which are called subnets Allows for more efficient routing via router summarization

Explain the term Passive Topology

When a computer in the network listen and receive the signal, they are called passive topology.

What is a WAN

Wide Area Network that extends over a large geographical distance, typically multiple cities and countries

Physical Connections?

Wires, cables, wireless media

When you move the NIC cards from one PC to another PC, does the MAC address gets transferred as well?

Yes, that's because MAC addresses are hard-wired into the NIC circuitry, not the PC. This also means that a PC can have a different MAC address when another one replaced the NIC card.

You need to connect two computers for file sharing. Is it possible to do this without using a hub or a router?

Yes, you can connect two computers, using only one cable. A crossover type cable can be used in this scenario. In this setup, the data transmit pin of one cable is connected to the data receive pin of the other cable, and vice versa.

What is an IP Address?

a unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network.

What is a Router?

an intelligent connecting device that examines each packet of data it receives and then decides which way to send it onward toward its destination

Describe UDP

connectionless, unsequenced best effort delivery. Sends data but does not check to see if it is received

What do logical topologies describe?

how data flows throughout a network

IP Address is broken down into what two parts?

network and host address

What is a SOHO?

small office/home office. "All in one" that has router, WAP, and firewall built in

What do physical topologies describe?

the placement of network devices and how they are physically connected