Section 2: Introduction to networking concepts Flashcards
What does OSI stand for?
Open systems interconnection model
Aside from the number of layers, how are OSI and TCP/IP different models from each other?
OSI is more granular in how it accomplishes data transfer
What does MAC stand for and what is a MAC address?
MAC stands for Media Access Control and a mac address is a 12-digit hexadecimal number assigned to each device connected to a network
Does TCP/IP ‘frame’ information?
Yes, they are generated at layer 2
What does TCP/IP stand for?
Transmission control protocol / internet protocol
What are the layers of TCP/IP?
- From the bottom up:
1. Network Interface
2. Network
3. Transport
4. Application
What are the layers of OSI?
- From the bottom up:
1. Physical
2. Data link
3. Network
4. Transport
5. Session
6. Presentation
7. Application
What is the relationship(s) between layers in OSI and TCP/IP?
- Layers 1 and 2 of OSI correspond to layer 1 of TCP/IP
- Layer 3 of OSI corresponds to layer 2 of TCP/IP
- Layer 4 of OSI corresponds to layer 3 of TCP/IP
- Layers 5/6/7 of OSI correspond to layer 4 of TCP/IP
In TCP/IP, what is the application layer responsible for? What protocols are commonly used in this layer? What number is it?
Communication between nodes. Common protocols include HTTP/HTTPS, secure shell (SSH), and network time protocol (NTP). It is the fourth layer.
In TCP/IP, what is the transport layer responsible for? What protocols are commonly used in this layer? What number is it?
End to end transport of data. Common protocols here are user datagram protocol (UDP), and Transmission control protocol (TCP). It is the third layer.
In TCP/IP, what is the network layer responsible for? What protocols are commonly used in this layer? What number is it?
Defines logical transmissions for the whole network. Common protocols include Internet Protocol (IP), Internet Control Message Protocol (ICMP), and Address Resolution Protocol (ARP). It is layer 3
In TCP/IP, what is the network interface layer responsible for? What number is it?
Establishes how data should be physically sent through the network. It is the first layer.
In OSI, what is the application layer responsible for? What number is it?
Responsible for network applications (like HTTP or FTP) and their production of data to be transferred over the network. It is the seventh layer.
In OSI, what is the presentation layer responsible for? What number is it?
Responsible for translating data over the network as well as encrypting data for security (if encryption is used). It is the sixth layer.
In OSI, what is the sessions layer responsible for? What number is it?
Responsible for connection establishment, session maintenance, and authentication. It is the fifth layer.
In OSI, what is the transport layer responsible for? What number is it?
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The heart of OSI
- Provides services to the application layer and receives services from the network layer
- Responsible for the reliable delivery of data
- It segments and reassembles data in the correct order for it to be sent to the receiving device
- May also handle the reliable delivery of data and any entries of data that are lost or corrupted
- It is the fourth layer.
In OSI, what is the network layer responsible for? What number is it?
Responsible for transmission of data between hosts in different networks as well as routing of data packets and Implemented through the use of devices like routers and some switches. It is the third layer.
In OSI, what is the data link layer responsible for? What number is it?
Responsible for error free delivery of data to the receiving node or device. A physical way of ensuring data continuity. Implemented through devices such as switches and bridge devices, as well as anything with a network interface (like wireless cards or wired network cards). It is the second layer.
In OSI, what is the physical layer responsible for? What number is it?
Responsible for the physical connections of the devices in a network. Hubs, repeaters, modem devices, physical cabling. It is the first layer.
Describe opening a web page in the OSI model:
- Layer 7: You open a web browser and type an address into the search bar
- Layer 6: Command is encrypted as it is sent (and decrypted by receiving server)
- Layer 5: Establishes the connection between your laptop and websites server and maintains it while you accomplish your tasks on the website
- Layer 4: Data is transferred, segmented, and then numbered. This allows the network to send manageable sizes of information ( about 1,500 bytes max), and then reassembled correctly.
- Layer 3: Receives the segments, and transmits them across the network as packets. Adds source and destination IP addresses to each data packet. The destination IP address will be the router on the network that will move data off the local network. The series of routers between that router and the destination server will determine how the packet is moved across the various networks between them
- Layer 2: Receives the packets and adds physical addressing by adding sender and receiver MAC addresses to each data packet. This information forms a unit called a frame.
- Layer 1: Receives the frames and data and sends them via the local media (wires etc.) to the switches, routers, etc. along the network path.
Name 6 network media devices
Modem, router, bridge, switch, hub, and repeater
What does a modem do?
Sends and receives information. Allows computers to send digital information over analog lines.
What does a router do?
A point of connection between two or more networks. Connects networks to each other.
What does a switch do?
A more complex version of a hub which is used to connect devices in a specific network.
What does a bridge do?
Connects two or more networks.
How is a bridge different from a router?
A bridge does not analyze data. It simply forwards data to the next network, whereas a router will.
What does a repeater do?
Extends a weak signal or general range of a connection
What does a hub do?
A device used to connect a router to a network, takes data packets from router, and sends them to devices connected in the network. A USB hub is an example of a hub.
What are the network media devices associated with the third layer of OSI and why?
Switch and router.
What are the network media devices associated with the second layer of OSI and why?
Modem, switch, and bridge
What are the network media devices associated with the first layer of OSI and why?
Modem, hub, and repeater
What is a host device?
any hardware device that has the capability of permitting access to a network via a user interface, specialized software, network address, protocol stack, or any other means
What does UTP stand for?
Unshielded twisted pair
What are the categories of UTP?
CAT1-CAT6
What is different about a coaxial cable?
Shielded with metal
What is fiber optic?
Type of cable that uses light instead of electricity to transfer data
What are the different modes of fiber optic?
Single-mode and Multi-mode
Which is better for longer distance; single- mode or multi-mode fiber?
Single-mode
What is the IEEE?
Institute of electronic and electrical engineers
What is the difference between 2.5gh and 5gh?
the higher the frequency the higher the bandwidth, but shorter the range
What does ICMP stand for?
internal control message protocol
Describe the command ping
- Sends an internal control message protocol (ICMP) echo request to a host and listens for the reply.
- If the echo is received, it will display the time it took and the time to live (TTL) left.
- Useful for troubleshooting!
Describe the command traceroute
Displays each hop (next router) in a numerical list with the hop’s IP address and the time it takes to receive the packet
- traceroute for Linux or tracert for windows
- Need admin privileges
Describe the command tracepath
Same as traceroute, but with regular privilege
Describe the command ifconfig
Similar to ipconfig. Used to configure kernel network interfaces. Used at the time of booting to configure interfaces, and used later for troubleshooting
Describe the command ARP
Address resolution protocol displays the IP to physical (MAC) address mappings for hosts that have been discovered in the ARP cache
Describe the command netstat
network statistics. displays information about active ports and their state and can be useful in troubleshooting
Describe the command nslookup
name server lookup displays information for displaying DNS info and troubleshooting DNS problems. Useful for displaying names to IP address mappings.
Describe the command dig
domain information groper is used for displaying DNS info and troubleshooting. Is a replacement for nslookup
Describe the command whois
provides information on who a domain belongs to. Primarily used in Linux. Certain pieces of information are private.
Describe the command route
Defines the paths a data packet takes through networks. Can also be used to add or remove routes. Used by local host to determine where to send traffic.
Describe the command scp
security copy protocol is used to securely copy files between servers leveraging SSH for authentication and encryption.
Describe the command ftp
File transfer protocol copies the file from one host to another host. Uses TCP.
Describe the command tftp
trivial file transfer protocol transfers a file from server to host or from host to server. It uses UDP instead of FTP so it is usually used on local networks.
Describe the command finger
displays information about a user or users on a remote system, including such things as last login and username. Primarily used on Linux.
Describe the command nmap
Network mapper scans networks to see what it can find in terms of hosts and open ports. Commonly used to find vulnerabilities on a network. Nmap is not native to either windows or Linux.
Describe the command tcpdump
Displays TCP/IP packets that are being transmitted over the network system. A form or protocol analyzer (sniffer) and is designed to show the contents of network packets in human readable form. Not native to Linux or windows.
Describe the commands telnet/ssh
allows a user to manage accounts and devices remotely. SSH is encrypted, telnet is not.
Describe a local area network
- House or office building
- Uses router or switch to manage traffic
Describe a personal area network
Connects personal devices within 20-30 meter distance. Phone → blue tooth head phones
Describe a wireless local area network
Like a LAN but data is transmitted wirelessly
Describe a campus area network
Uses a router to connect each LAN in the geographical region ‘campus sized’
Describe a metropolitan area network
city wide network. The city will run a high speed signal, usually connected to a WAN, and businesses, schools, and offices connect to it.
Describe a wide area network
No area limits to the network size. The internet is a WAN.
Describe a storage area network
Connects networks but only for storage
Describe a client-to-server network
In a client-server network model, there is a distinct server and a distinct client. The server is the system that stores data and information. The client is the machine that needs access to that data. This is the traditional model of networking since the 1990s
Describe a peer-to-peer network
In a peer-to-peer model, or P2P, there is no individually designated server or client. Each machine on the network can act as both server and client, sometimes requesting data from other nodes and sometimes answering requests from others. Bitcoin and Tor are examples of peer-to-peer networks.
Describe a Mesh network topology
Every device is connected to every other device. Difficult to manage with more than two devices. self-healing network
Describe a Star network topology
All devices are connected to one central device. Most common topology, and provides easy central control.
Describe a Ring network topology
Devices connect in a circular fashion. A→B→C→D→A. Each device serves as a beginning and end, so termination isn’t an issue. This topology is like a talking token at a campfire. Each person at the fire can only talk while they hold the token, and are given a limited amount of talk time
Describe a Buss network topology
One long cable, devices are plugged into cable, terminator at each end. Very simple, cheap, and easy to make but, like a walkie talkie, each computer operates in ‘half-duplex mode’ only ever sending OR receiving information. Not both.
Define SONET ring
synchronous optical network
Describe the client-to-server model
Centralized data source accessed by multiple devices. Front-end/back-end
Describe some benefits of the client-to-server model
Offloads computing power from server to client machines.
Describe some drawbacks to the client-to-server model
Scalability, version control issues, user error
Describe centralization
Centralization refers to the concentration of control, resources, and decision-making in a single, central location or entity within a computing system or network.
Describe the benefits of centralization
Allows more control over performance and availability. Higher security.
Describe a drawback to centralization
single point of failure
Describe decentralization
Puts data management and computing in the users hands
Describe some benefits of decentralization
Can operate with or without a network connection & no single point of failure
Describe some drawbacks to decentralization
Users mismanage security and data leading to loss and data falling into the wrong hands. Compatibility issues between users.
Define virtualization
the technique of converting a hardware-based resource into software
What does virtualization allow admins to do?
- Deploy new devices without needing to be onsite
- Increase the reliability of a service by removing the hardware need, a single point of failure(SPoF)
- Create snapshots or clones of virtual devices for backup purposes
- Increase or decrease the compute, storage, and network resources allocated to a virtual device on demand, as its utilization rises and falls
What does SPoF stand for?
Single point of failure
What is virtual computing?
Outsources computing to virtual machines. Mimics the old model of computer and mainframe, but this time the users computer is used to manage 1 or more virtual machines
What is a hypervisor?
Software that allows the the creation and maintenance of virtual machines
What is an OS installed on a VM called?
Guest operating system
What is a type 1 hypervisor also referred to as?
Bare metal hypervisor
What is a type 2 hypervisor also referred to as?
Hosted hypervisor
What are some benefits to type 1 hypervisors?
Doesn’t compete for resources and alleviated performance issues due to unrestricted access to hardware
What are some benefits to type 2 hypervisors?
Installed on personal computer, and therefore easier to configure than type 1.
What are some drawbacks to type 2 hypervisors?
Performance issues due to it’s restricted access to hardware.
What is cloud computing?
Computing done outside of the users physical hardware
What are some characteristics of cloud computing?
on-demand, self-service, resource pooling, elastic, accessible, and measurable. The quickness with which IT can pivot based on market demands is a huge plus to cloud computing.
What is a CSP?
cloud service provider
What are the three primary models for cloud computing?
Infrastructure, Software, and Platform ‘as a service’
What are the three cornerstones of IaaS?
server virtualization, network virtualization, and storage virtualization
Describe network virtualization
- Gives the CSP the ability to create virtual private cloud (VPC) networks for each of their customers, keeping their info private.
- Customers can create their own networks for testing and development purposes
- Virtual servers are usually the flagship service of CSPs.
- Note that CSP are not responsible for backing up data.
- A good idea is to back up data locally, and store it geographically far away.
Describe server virtualization
- CSP manages the hypervisor and underlying hardware
- Client is given access to a web portal where they can manage the VM’s
- Can customize the available resources to suit needs
- CSP will allow the customer to choose number of CPU’s, RAM, storage, number of network cards, etc.
Describe storage virtualization
CSP provides elastic storage that shrinks or expands as needed
Describe the model ‘platform as a service’
cloud provider is responsible for the virtual servers and sometimes the services that run on top of them (like a data base engine)
Describe and give some examples of the model ‘software as a service’
Could represent nearly every application you consume over the internet. Facebook, Gmail, Instagram, office 365 etc.
What are the five cloud deployment models?
Private, public, community, multi-cloud, and hybrid
Describe a private cloud deployment
- Equipment is hosted within a single companies on-site data center
- Company can maintain absolute control over the hardware, but also bare the responsibility of maintaining it
Describe a public cloud deployment
- CSP is responsible for maintaining the physical hardware
- Good analogy: Many different people live within the same apartment building (the physical computer), but each tenant (the customer) has their own apartment (a VPC) with a lock on the front door (a firewall).
Describe a community cloud deployment
- More common in universities or government
- Each tenant has a private cloud, but the maintenance of the hardware is shared amongst the community
Describe a hybrid cloud deployment
- Refers to a combination of public and private cloud
- A company may be required to maintain a private cloud, but need access to extra computing power in bursts (a public cloud)
Describe a multi-cloud deployment
a customer may use one CSP for hosting, and another for machine learning.
