Network Fundamentals + Lans|Week 1 lecture + readings (chapter 1 all and chapter 7.1, 7.2, 7.3) Flashcards
What does the OSI Model stand for? Eg, the O___ ___ ___ ___ model is shortened to ‘the OSI’ model.
Open Systems Interconnection Reference
The OSI model was developed in what year?
1984
Who (the ____ _____ ____) created the OSI model?
The International Organization for Standardization
The ISO made the OSI. True or false?
True
How many layers does the internet model have?
5
how many layers does the OSI model have?
7
What layer defines the rules governing the transmission of data bits, such as voltages of electricity, number of bits per second, and the physical format of cables and connectors used?
Layer 1: The Physical Layer
What layer marks where a message starts and where it ends?
Layer 2: The Data Link Layer
Layer 2, the data-link layer, performs error detection and correction. True or false?
True
The network layer, layer 3, performs routing. True or False?
True
The transport layer, layer 4, determines the next computer to which the message should be sent, so the message can follow the best route through the network, and finds the full address for that computer if needed. True or False?
False, the transport layer is involved with end-to-end.
The transport layer, layer 4, deals with end-to-end issues, such as entering and departing the network. True or false?
True
Which two layers perform error checking? Type: Layer __ and layer ___
Layer 2 and layer 4
Which layer fragments packets if needed?
Layer 4, transport layer
What are the 7 layers of the OSI model?
Physical, Data Link, Network, Transport, Session, Presentation, Application
What is layer 5 in the OSI model?
Session Layer
What is layer 6 in the OSI model
The presentation layer
what is layer 7 in the OSI model
The application layer
Which layers of the OSI model does the internet model collapse/condense together?
the top three layers
cables and satellites are examples of what?
media
computers, modems and switches are examples of what
hardware devices
The application layer in the internet model is perfectly the same as the application layer in the OSI model. True or false?
false, the application layer in the internet model includes layer 5 (session), 6 (presentation) and 7 (application) of the OSI model.
The application layer in the internet model includes the application, presentation and session layers of the OSI model. True or false?
True
What do people call the group containing the data-link layer and the physical layer?
Hardware layers
When people group the transport and network layers, what do they call that?
internetwork layers
what are the three groups of layers
hardware, internetwork, and application
what protocol is used for Web applications?
HTTP
what does HTTP stand for
Hypertext Transfer Protocol
Some expects use the word ‘packet’ to mean what?
Protocol Data Unit
All layers except the physical layer create a new PDU as the message passes through them. What does PDU stand for?
Protocol Data Unit
what does TCP stand for?
Transmission Control Protocol
what does UDP stand for?
User Datagram Protocol
What is the term which describes how the PDU at a higher level is placed inside the PDU at the lower level so that the lower level PDU wraps around the higher ones?
encapsulation
An advantage of layers is that using different software and protcols is that PDUs add to the total amount of data that must be sent and that the different software packages increases the computing power needed in computers. True or false?
false, its a disadvantage
The set of software used to understand the different protocols is called a protocol what?
stack
An advantage of using layers is that it makes it easier to develop web applications as the software does not need to perform error checking or routing as those are performed by the data link and network layers. True or false?
true
For communication to be successful, each layer in one computer must be able to communicate with its matching layer in the other computer. What ensures that the software used at the different layers is the same?
Standards
Standards define what which explain how hardware and software that conform to the standard are required to operate?
protocols
What is a de facto standard?
A de facto standard is one that emerges in the marketplace and are supported by several vendors, but have no official standing.
An example of a de facto standard is _____.
Microsoft Windows, or any other program or hardware used commonly in the industry but doesn’t have an official standard saying that it must be used.
A __ ____ standard is developed by an official industry or government body.
de jure
A de jure standard is also known as a ____ standard. These are developed by governments or official bodies.
formal
the International Organisation for Standardization makes technical recommendations about data communication interfaces. They are known as the ISO. True or false.
True
The Physical Layer (layer 1) uses the following standards: HTTP, HTML, MPEG, H.323, SMTP, IMAP, and POP. True or false?
False, those are all application layer protocols. (Layer 7 OSI, layer 5 internet)
The Transport layer uses ____ and ____
TCP and UDP
The network layer uses ____
IP
The data-link layer uses cables and modems, true or false
false, these are physical layer devices. Data link layer is concerned with the delivery of frames in a local area network. So it uses ethernet, wifi, but is responsible for the flow control over those cables and modems so the media doesn’t get overloaded.
Ethernet (LAN), frame relay(WAN), and T1 (MAN and WAN) are found at layer 2, the data link layer. True or false?
true
cables, modems and routers are found at what layer?
1, Physical layer
A ___ ____ ____ is a group of computers located in the same general area.
Local Area Network
A ____ ____ is a large central network that connects almost everthing on a single company site.
Backbone network
A ____ ____ ____ spans city, state or natural boundaries.
Wide Area Network
A ______ ____ ____ encompasses a city or county area.
metropolitan area network
The _____ layer is the application software used by the network user.
application
The ______ layer takes the message generated by the application layer and, if necessary, breaks it into several smaller messages.
transport
The ____-____ layer formats the message to indicate where it starts and ends.
data-link
The ____ layer addresses the message and determines its route through the network.
network
The ___ layer is the physical connection between the sender and reciever.
physical
Each layer, except the physical layer, adds a ____ ____ ____ (PDU) to the message.
protocol data unit
____ ensure that the hardware and software produced by different vendors can work together.
Standards
90% of routers run what operating system?
Cisco IOS
What are the three components of a network?
A server, a client, and a circuit
Networks do not need a server. True or false?
True
Client, servers and routers are all computers. True or false?
True
an ____ is a LAN which uses the same technology as the internet, but is only accessible to those inside the organization. It is hidden from someone connecting from the wider internet.
intranet
an ____ is a LAN which uses the same technology as the internet, but is only accessible to those invited. It is accessible via password typically, but smart cards or other software can be required.
extranet
What are the components of a traditional LAN?
Client computer, server, network interface cards (NICs), network circuits, hubs/switches/access points, and network operating system.
The ______ _____ _____ (NIC) is used to connect the computer to the network cable in a wired network and is one part of the physical layer connection among the computers in the network.
network interface card
In a wireless network, the NIC is a _____ ______ that sends and receives messages on a specific _____ frequency.
In a wireless network, the NIC is a radio transmitter that sends and receives messages on a specific radio frequency.
One part of the physical layer connection among the computers in the network is a _____ ____ ____ (____). All desktop computers have a wired ____ built in, while virtually all laptops have both a wired ____ and a wireless ____.
One part of the physical layer connection among the computers in the network is a network interface card(NIC). All desktop computers have a wired NIC built in, while virtually all laptops have both a wired NIC and a wireless NIC.
Two technologies commonly used in LANs include ____ ____ (IEEE 802.3) and ____ ____ (IEE 802.11, commonly called ____)
Two technologies commonly used in LANs include wired ethernet (IEEE 802.3) and wireless ethernet (IEE 802.11, commonly called Wi-Fi)
Most LANs are built with ____ ___-____ (___) cable, ____ ___-____ (STP) cable, or ___ ____ cable.
Most LANs are built with unshielded twisted pair (UTP) cable, shielded twisted-pair (STP) cable, or fiber optic cable.
UTP (unshielded twisted pair) is lower cost than STP (shielded twisted pair). True or false?
true
What kind of cable might be appropriate for a LAN built in areas that produce electrical interference (eg hospitals near MRI scanners)?
Shielded Twisted-Pair cable
Why is fibre-optic cable perfect for backbone networks?
High capacity,good over longer distances.
What are some qualities of fiber-optic cable
High capacity, light (less than 10 pounds per 1,000 feet), thin, takes up less space than UTP, good for backbone networks (BNs)
Wireless LANs (WLANs) use ??? ???? to send data between the NIC and the access point (AP).
Wireless LANs (WLANs) use radio transmitters to send data between the NIC and the access point (AP).
Most countries permit WLANs to operate in what two frequencies?
2.4GHz and 5GHz range
What are the two purposes of network hubs and switches?
- Easy way to connect network cables: they are junction boxes. 2. Act as a repeater.
Regarding network hubs and switches, each connection point where a cable can be plugged in is called a _____?
port
Regarding hubs and switches, when no cables are plugged into a port, the signal does what?
Bypasses the unused port
Regarding hubs and switches, when a cable is plugged into a port, the signal does what?
Travels down the cable as if it were directly connected to the hub or switch.
Within LANs, the network operating system (NOS) is the software that ____ ___ ____.
Within LANs, the network operating system (NOS) is the software that controls the network.
The server version of the network operating system(NOS) provides the software that performs the functions associated with the ____-____, ____, and ____ layers and usually the computer’s operating system. (For LANs / ethernet)
The server version of the network operating system(NOS) provides the software that performs the functions associated with the data-link, network, and application layers and usually the computer’s operating system.
Regarding LANs, most ___ ____ ____(___)provide different client software versions that run on different types of computers so that Windows computers can function on the same network as Apple computers. In most cases (e.g., Windows and Linux), the client ____ software is included with the operating system.
Most NOSs provide different client software versions that run on different types of computers so that Windows computers can function on the same network as Apple computers. In most cases (e.g., Windows and Linux), the client NOS software is included with the operating system.
Almost all LANs installed today use some form of ____
Ethernet.
Ethernet was originally developed by what three companies?
DEC, Xerox and Intel.
Ethernet is a layer ____ protocol?
Ethernet is a layer 2 protocol. The data-link layer.
Every Ethernet LAN needs hardware at layer ?, the ___ layer, that matches the requirements of the Ethernet software at layer ?
Every Ethernet LAN needs hardware at layer 1, the physical layer, that matches the requirements of the Ethernet software at layer 2, the data-link layer.
What is topology?
Topology is the basic geometric layout of the network.
What is the difference between physical topology and logical topology?
Logical topology is how the network works conceptually. A physical topology is how the network is physically installed.
X X X
| | |
———————–
| | |
X X X
What topology?
A bus. All frames from any computer flow onto the central cable (or bus) and through it to all computers on the LAN.
With hubs, all computers share the same multipoint circuit and must take turns using it. This shared multipoint circuit is also called a _____ ____ because if two computers ever did accidentally transmit at the same time, there would be a _____.
With hubs, all computers share the same multipoint circuit and must take turns using it. This shared multipoint circuit is also called a collision domain because if two computers ever did accidentally transmit at the same time, there would be a collision.
What logical & physical topology does a hub have?
Logical bus, physical star
What logical & physical topology does a switch have?
Both are star topology
A ___ is an intelligent device with a small computer built in that is designed to manage a set of separate point-to-point connections. This means that each circuit connected to a ____ is not shared with any other devices.
A switch is an intelligent device with a small computer built in that is designed to manage a set of separate point-to-point connections. This means that each circuit connected to a switch is not shared with any other devices.
How many collision domains and broadcast domains do hubs have?
Hubs: 1 collision domain, 1 broadcast domain
How many collision domains and broadcast domains do switches have?
Switches: a collision domain per port, 1 broadcast domain
How many collision domains and broadcast domains do routers have?
Routers: a collision domain per port, a broadcast domain per port
What are the three modes switches can operate in?
cut-through switching, store-and-forward switching, fragment-free switching
____-____ switching involves the switch transmitting the incoming packet on the proper outgoing circuit as soon as it has read the destination address in the frame.
cut-through switching involves the switch transmitting the incoming packet on the proper outgoing circuit as soon as it has read the destination address in the frame.
An advantage of cut-through switching is _____ ____. A disadvantage is that it ____ ____ ___ ____ and cannot notice until almost all the frame has been transmitted.
An advantage of cut-through switching is low latency. A disadvantage is that it may contain an error and cannot notice until almost all the frame has been transmitted.
The method to prevent collisions is called ___ ___ ___.
media access control.
Ethernet uses ______ based media access control called Carrier Sense Multiple Access with Collision Detection.
contention
Contention-based media access control techniques involve firstly ____ until the ____ is ____ and then ____.
Contention-based media access control techniques involve firstly waiting until the circuit is free and then transmitting.
A simultaneous transmission is called a _____.
Collision.
What four things can go wrong when sending messages?
Messages can get lost, delayed (out of order), corrupted or duplicated.
Networks are comprised of three things, __1__, __2__, and __3__(or routes). Some ___1____ are end-points, others are intermediary systems. ___2____ connect ___1____ to an adjacent ___1___. ___3___ are a group of ___2____. Also ____5_____/ ____5____ing.
Networks are comprised of three things, nodes, links, and paths(routes). Some nodes are end-points, others are intermediary systems. Links connect nodes to an adjacent node. Paths are a group of links. Also time/timing.
What three ways can we classify networks?
How they operate
The geographic area they cover
The “shape” of the network (topology)
Circuit-switch networks have defined paths. Packet switched networks have no predefined path. What kind of network is a telephone network?
A circuit switched network.
What kind of topology is this:
If everyone in the room wanted to communicate, it would have to go through Carl
Star
What kind of topology is this:
- If someone up the back wanted to communicate with Carl, they would have to send it to the person in front, who would send it to the next person in front, who would send it to the next person, until it reached Carl.
Tree
What kind of topology is this:
Anyone could communicate all information via the one channel?
Bus
What kind of topology is this:
Anyone who wanted to communicate could go through Carl, but another lecturer (Damien) could also talk. But some people on the live stream couldn’t talk to the people in the class unless through someone looking at the live stream chat (or discord)
Partial Mesh
What kind of topology is this?
If someone wanted to communicate with Carl, they could communicate it to anyone else who could then communicate it to Carl or directly with Carl, in the lecture hall or online.
Full Mesh
Packets consist of a _____ which contains _____ and a _____ or ______ which contains _____.
Packets consist of a Header which contains Metadata and a Payload or Body which contains Data.
