OSI Layers Facts Flashcards
1
Q
Application (Layer 7)
A
- Integrates network functionality into the host operating system and enable network services
- Does not include specific applications that provide services, but rather the capability for services to operate on the network
- Most application layer protocols operate at multiple layers down to the Session and even Transport layers but are classified as application layer protocols because they start at the application layer
2
Q
Services associated with layer 7
A
- HTTP
- Telnet
- FTP
- TFTP
- SNMP
3
Q
Presentation (Layer 6)
A
- formats or presents data into a compatible form for receipt by the application layer or the destination system
4
Q
What does layer 6 ensures?
A
- Formatting and translation of data between systems
- Negotiation of data transfer syntax between systems by converting character sets to the correct format
- Encapsulation of data into message envelopes by encryption and compression
- Restoration of data by decryption and decompression
5
Q
Session (Layer 5)
A
- manages the sessions in which data are transferred
6
Q
Functions of layer 5
A
- Management of multiple session (each client connection is called a session) A server can concurrently maintain thousands of sessions
- Assignment of session ID number to each session to keep data streams separate
- The setting up, maintenance, and tearing down of communication sessions
7
Q
Transport (Layer 4)
A
- Provides a transition between the upper and lower layers of the OSI model making the upper and lower layers transparent from each other.
8
Q
Functions of layer 4
A
- End-to-end flow control
- Port and socket numbers
- Segmentation, sequencing, and combination
- Connection services, either reliable (connection-oriented) or unreliable (connectionless) delivery of data
- *** Data at the Transport layer are called segments **
9
Q
Network (Layer 3)
A
- Describes how data are routed across networks and on to destinations
10
Q
Functions of layer 3
A
- Identifying host and networks by using logical addresses
- Maintaining a list of known networks and neighboring routers
- Determining the next network point to which data should be sent. Routers use a routing protocol that takes into account various factors such as # of hops in the path, link reliability, to select the optimal path for data
- ** Data at the Network Layer are called packets ***
11
Q
Data Link (Layer 2) can is broken down to what to layers?
A
- Logical Link Control (LLC)
* Media Access Control (MAC)
12
Q
Data Link (Layer 2)
A
- defines the rules and procedures for hosts as they access the Physical Layer.
13
Q
Functions of layer 2
A
- How hosts on the network are identified (physical or MAC address)
- How and when devices can transmit on the network medium (media access control and logical topology
- How to verify that the data received from the Physical layer are error free (parity and CRC)
- How devices control the rate of data transmission between host (flow control)
- *** Data at the Data Link layer are called frames **
14
Q
Physical (Layer 1)
A
- Set standards for sending and receiving electrical signals between devices
15
Q
Functions of layer 1`
A
- How digital data (bits) are converted to electric pulses, radio waves, or pulses of light
- Specifications for cables and connectors
- The physical topology
- *** Data at the Physical layers are called bits **
