Chapter 1 - Internetworking Flashcards
(100 cards)
0
Q
What does OSI stand for?
A
Open Systems Interconnections Model
1
Q
What is an internetwork?
A
When you connect two or more networks via a router and configure a logical addressing scheme such as IP or IPv6
2
Q
What is network segmentation?
A
Breaking up a massive network into a number of smaller ones
3
Q
What is a hub?
A
- They connect network segments together.
- They don’t segment networks
4
Q
What type of network device would you use to break up a collision domain?
A
A switch
5
Q
What is a broadcast?
A
A broadcast means that a network delivers one copy of a packet to each destination
6
Q
What 6 things commonly cause LAN traffic congestion?
A
- too many hosts in a collision or broadcast domain
- broadcast storms
- too much multicast traffic
- low bandwidth
- adding hubs for connectivity to the network
- a bunch of ARP broadcasts
14
Q
What type of network device would you use to break up a broadcast domain?
A
A router
15
Q
What are the 2 advantages to using a router in your network?
A
- They don’t forward broadcasts by default
- They can filter the network based on layer 3 information such as the IP address
16
Q
What are the 4 ways a router functions in your network?
A
- Packet switching
- Packet filtering
- Internetwork communications
- Path selection
17
Q
What is a routing table?
A
A routing table is a map of your internetwork, used to make best path selections to get data to its proper destination and forward packets to remote networks
18
Q
What are the functions of a switch?
A
- Employed to add functionality to a network LAN
- Optimise performance by providing more bandwidth
- They switch frames from one port to another within the switched network
19
Q
What is a collision domain?
A
- A scenario where one device sends a packet out on a network segment and every device on that network segment is forced to listen to it.
- If each device tries to transmit a collision will occur.
- Each and every port on a switch represents a collision domain allowing data to flow more smoothly
20
Q
What is a switch?
A
They create separate collision domains within a broadcast domain
21
Q
What do the top 3 layers of the OSI model do?
A
They define how applications within the end stations will communicate with each other as well as users.
22
Q
What do the bottom four layers of the OSI model do?
A
They define how data is transmitted end to end
23
Q
What is the application layer?
A
- It provides a user interface.
- Identifying and confirming the communication partners availability.
- Verified required resources
- Applications like Word don’t reside at the application layer, but rather interface with the application layer protocols
- Some applications that do reside at application layer include Telnet, FTP, TFTP
24
Q
What is the presentation layer?
A
- It presents data and handles processing such as encryption and compression
- Responsible for data translation and code formatting
- Ensures that data transferred from the application layer of one system can be read at the application layer of another
25
Q
What is the session layer?
A
- Responsible for setting up, managing and dismantling sessions between presentation layer entities.
- Keeps different applications data separate.
- Communication co-ordinated via 3 different modes:
- Simplex
- Half Duplex
- Full Duplex
26
Q
What is simplex communication?
A
One way communication
27
Q
What is half duplex communication?
A
Two way communication with only one way taking place at a time preventing interruption
28
Q
What is full duplex communication?
A
Devices can transmit and receive at the same time
29
Q
What is the transport layer?
A
- segments and reassembles data into a single data stream
- services at this layer take data from upper layer applications and combine into one concise data stream
- provides end to end data transport services and can establish logical connection between source and destinations hosts
- uses TCP and UDP
- can also hide details of network dependent information from higher layers and provide transparent data transfer
- can be connection oriented or connection less
30
Q
What does reliable networking mean?
A
- means acknowledgements, sequencing and flow control will be used
- used at transport layer
31
What is connection oriented communication?
- must establish connection before sending of data
| - three way handshake
32
What are the steps in a three way handshake?
- SYN (synchronisation) - connection agreement
- SYN ACK (acknowledgement) - acknowledges request, establishes connection parameters, receivers sequencing synchronised so bi-directional connection can be established
- ACK - notifies destination host that connection has been accepted and established. Data transfer can begin
33
What is flow control? (2)
- ensures data integrity at the transport layer by allowing applications to request reliable data transport between systems
- prevents host on one side from overflowing buffers on the other
34
What 4 things will reliable data transport achieve?
- segments delivered are acknowledged back to sender
- segments not acknowledged are re-transmitted
- segments are sequenced back in order upon destination
- manageable data flow maintained to avoid congestion, overflowing, data loss
35
What is the purpose of an indicator with regards to flow control?
Allows receiving hosts buffer to indicate to sender to stop sending data until current data has been processed
36
What are the four characteristics of a connection oriented transfer?
- uses 3 way handshake
- uses sequencing
- acknowledges connection
- uses flow control
37
What are the 3 types of flow control?
- buffering
- windowing
- connection avoidance
38
What are windows?
It is the quantity of segments, measured in bytes that the transmitting machine is allowed to send without receiving an acknowledgement
39
What are the two window sizes that can be used?
1 and 3
40
What happens to data transfer with a window size of 1?
Sending machine will wait for an acknowledgement for each data segment in transmits before transmitting another
41
What happens to data transfer with a window size of 3?
Allows 3 segments to be transmitted before sending an acknowledgement
42
What is positive acknowledgement with re-transmission?
- requires a receiving machine to communicate with the transmitting source by sending an acknowledgement message to the sender when it receives the data
- sender documents each segment measured in bytes and then sends and waits for acknowledgement before sending next segment
- when sending a segment, transmitting machine starts a timer and re-transmits segment if no acknowledgement is received
43
What is session multi-plexing?
- transport layer working in tandem with session layer
- separates data from different applications
- happens when a client connects to a server with multiple browser sessions open
- client data from each browser session must be separate when the server application receives it
44
What is the network layer?
- manages device addressing
- tracks location of devices on the network
- determines best way to move data
45
Which layer of the OSI model is responsible for transporting traffic between devices that aren't locally attached?
Network layer
46
Which network device is used at layer 3?
Router
47
Steps to how a router works
1. Packet received on router interface
2. Destination IP address is checked
3. If packet isn't destined for that router it will lookup destination address in routing table
4. Router chooses an exit interface
5. Packet sent out the interface to be framed and out to the local network
6. If router can't find an entry for the packets destination network in the routing table then the packet is dropped
48
What 2 types of packets are used at the network layer?
Data and Route update
49
What is a data packet?
- used to transport data through the internetwork
50
What is a routed protocol?
Protocol used to support data traffic,e.g. IP, IPv6
51
What is a Route update packet?
Used to update neighbouring routers about the other routers connected on the internetwork
52
What is a routing protocol?
Protocols that send route update packets
53
4 critical routing protocols for CCNA
- RIP
- RIPv2
- EIGRP
- OSPF
54
Which type of packet is used to help build and maintain routing tables?
Route update packets
55
What is a protocol specific network address?
- A protocol ha uses a specific addressing scheme, e.g. IP, IPv6
- A router must keep a routing table for each one, e.g. Similar to a sign on a street in different languages
56
What is the interface in relation to a routing table?
The exit interface a packet will take when destined for a specific network
57
What is the metric in relation to the routing table?
Distance to the remote network
58
What does RIP stand for?
Routing Information Protocol
59
What is the hop count in relation to routing?
The number of routers data passes through to reach its remote network
60
Characteristics of a router
- router by default will not forward any broadcast or multicast packets
- routers use the logical address in the network layer header to determine the next-hop router to forward the packet to
- routers can use access lists to control security based on the type of packets allowed to enter or exit an interface
- routers can simultaneously provide layer 2 bridging functions through the same interface
- layer 3 devices provide connections between VLANs
- routers can provide QoS for specific types of network traffic
61
What are the 4 characteristics of the data link layer?
- provides for the physical transmission of data
- handles error notification
- handles network topology
- handles flow control
62
At which layer does the following occur:
- ensuring that messages are delivered to the proper device on a LAN using a hardware address
- translation of messages from the network layer into bits for the physical layer to transmit
Data Link Layer
63
How are messages processed at the data link layer?
1. Formats the message (called a data frame)
2. Adds customised header containing hardware source and destination address
3. Information stripped off at receiving end and only packet remains
64
True or False, routers care were a particular host is located?
False
65
Which type of network device is concerned with where a network is located and how to reach it?
A router
66
Which layer is responsible for the unique location of a device on a local network
Data link layer
67
Which layer of the OSI uses hardware addressing?
Data Link
68
Way are the two sub-layers of a Data Link layer?
Media Access Control
| Logical Link Control
69
What is Media Access Control?
Defines how packets are placed on the media using physical addressing
70
What is contention media access?
first come first served (everyone shares the same bandwidth)
71
What is a logical topology?
Signal path through a physical topology
72
What is logical link control?
Responsible for identifying network layer protocols and then encapsulating them
Tells the data link layer what to do with a packet once a frame is received
73
How does logical link control work?
Host receives a frame and looks in the LLC header to find out whe a packet is destined at the network layer, e.g. IP protocol
74
What is a router?
They provide a separate broadcast domain for each interface
75
What is the difference between a switch and a bridge? (2)
A switch has more ports and enhanced management ability and features
76
What is a vLAN?
Used to logically break up broadcast domains in a layer 2 switched network
77
Who was OSI created by?
International Organisation for Standardisation (ISO)
78
What is OSI?
Describes how data and network information are communicated from an application on one computer through network media to an application on another computer
79
What does binding mean in relation to OSI?
Software that maps to another layers protocols
80
What are the advantages of the OSI model? (5)
- divides the network communication process into smaller and simpler components facilitating component development, design and troubleshooting
- allows multi vendor development through standardisation of networking components
- encourages industry standardisation by clearly defining the functions performed at each layer
- allows various types of network hardware and software to communicate
- prevents changes in one layer to affect another layer
81
What is a protocol data unit (PDU)?
Data that is encoded with control information at each layer of the OSI model
82
What is a PDU called at the transport layer?
A Segment
83
What is a PDU called at the network layer
Packets
84
What is a PDU called at the data layer?
Frames
85
What is a PDU called at the physical layer?
Bits
86
What is another name for hardware based bridging?
Layer 2 switching
87
What does ASIC stand for and at which layer is it used?
- Application Specific Integrated Circuit
| - Layer 2
88
How is latency measured?
It's measured from the time a frame enters a port until it exits a port
89
Process of determining location of specific sending device (3 steps)
1. Switch reads each frame as it passes through the network
2. Switch puts source hardware address in a filter table and keeps track on which port the frame was received on
3. Information then used to determine specific location of sending device
90
What is transparent bridging?
When the destination device is on a different segment the frame can only be transmitted to that segment
91
What does a switch do if it receives a frame with a destination hardware address not found in its filter table?
Forwards the frame to all connected segments
92
Layer 2 devices propagate layer 2 broadcast storms which can affect performance.which device would you use to stop. A broadcast storm?
A router
93
What are the two biggest benefits of a hub over a switch?
- Each switch port is its own collision domain
- Each device on every segment plugged into a switch can transmit simultaenously (in a hub only one device can transmit at a time)
94
What are the two functions of the physical layer?
Sends bits and receives bits
95
What are the two ways that media represents bit values at. The physical layer?
- Audio tones
| - State transitions (changes in voltage from high to low and vice versa)
96
Why are specific protocols needed for different types of media at the physical layer? (3)
- to describe the proper bit patterns to be used
- to describe how data is encoded into media signals
- to describe the various qualities of the the attachment media's physical interface
97
At which layer would you identify the interface between the Data Terminal Equipment (DTE) and Data Communication Equipment (DCE)?
The physical layer
98
Is the DCE located at the service provider or device?
Service provider
99
Is the DTE located at the service provider or device?
Device
100
How are the services available to the DTE normally accessed? (3)
- modem
- cHannel service unit (CSU)
- data service unit (DTU)
101
What is a hub?
A hub is a multi port repeater meaning that all devices plugged into a hub are on the same collision and broadcast domain
102
When using a hub what happens when one host transmits?
All other hosts must stop and listen until that host has transmitted before being able to transmit themselves
103
True or false, does a hub examine traffic when being transmitted?
False
104
What kind of network does a hub create?
A physical star
105
Ethernet networks run a logical bus topology? What is it?
The signal has to run through the network from end to end
106
What is the purpose of a hub?
To enlarge the area covered by a single LAN segment
