OSI Model Flashcards
The main device used to break up collision domains, this is also done by default.
Switch
The main device used to break up broadcast domains, by default. They also break up collision domains.
Router
Two advantages to using routers in your network:
1) They don’t forward broadcasts by default
2) They can filter the network based on layer 3 information such as an IP address.
4 ways a router functions in your network:
Packet switching
Packet filtering
Internet-work communication
Path selection
Main purpose of (layer 2) Switches
Forward or filter FRAMES
Optimize a LAN’s performance
Provide more bandwidth for the LAN’s users
Layer 7 of OSI:
Application (All)
Layer 6 of OSI:
Presentation (People)
Layer 5 of OSI:
Session (Seem)
Layer 4 of OSI:
Transport (To)
Layer 3 of OSI:
Network (Need)
Layer 2 of OSI:
Data Link (Data)
Layer 1 of OSI:
Physical (Processing)
Application layer functions:
File, print, message, database, and application services. File transfers Email Enabling remote access Network management activites Client/server processes Information location
Presentation layer functions:
Translation services to ensure successful data transfer
Session layer functions:
Dialog control.
Setup, management, and dismantling sessions between Presentation layer entities and keeping user data separate.
Uses three different modes: simplex, half-duplex, and full-duplex.
One-way communication.
Simplex
Two-way communication in only one direction at a time.
Half-duplex
Two-way communication involving transmitting and receiving at the same exact time.
Full-duplex
Transport layer functions:
Segments and reassembles data into a single data stream. Takes all the various data received from upper-layer applications, then combine it into the same, concise data stream. (TCP and UDP)
TRANSPORT:
For reliable transport to occur, a device that wants to transmit must first establish a connection-oriented communication session with a remote device-its peer system-known as a call setup or a three-way handshake. Once this process is complete, the data transfer occurs, and when it’s finished, a call termination takes place to tear down the virtual circuit.
Connection-Oriented Communication
often referred to as OVERHEAD
TRANSPORT:
Its job is to ensure data integrity at the TRANSPORT LAYER by allowing applications to request reliable data transport between systems.
Flow control
TRANSPORT:
A service is considered connection-oriented if it has the following characteristics:
A virtual circuit, or “three-way handshake,” is set up.
It uses sequencing. (Segments placed in order)
It uses acknowledgments.
It uses flow control.
TRANSPORT:
The quantity of data segments, measured in bytes, that a transmitting machine is allowed to send without receiving an acknowledgement is called?
A window
TRANSPORT:
A technique that requires a receiving machine to communicate with the transmitting source by sending an acknowledgement message back to the sender when it receives data.
Positive ACKNOWLEDGEMENT with retransmission
TRANSPORT:
Transport layer, working in tandem with the Session layer, also separates the data from different applications, an activity known as:
Session multiplexing
Network layer functions:
Manage device addressing, tracks the location of devices on the network, and determines the best way to move data.
By default, will not forward any broadcast or multicast packets.
Use the logical address in a Network layer header to determine the next-hop router to forward the packet to.
Use access lists, created by an admin, to control security based on the types of packets allowed to enter or exit an interface.
Provide layer 2 bridging functions if needed and can simultaneously route through the same interface.
Provide connections through VLANS
Provide QoS for specific types of network traffic
Routers
Data link layer functions:
Provides the physical transmission of data and handles error notification, network topology, and flow control.
Data link layer formats the messages, each called a ____________, and adds a customized header containing the hardware destination and source address.
Data frame
Responsible for the actual unique identification of each device that resides on a local network.
Data link layer
The IEEE Ethernet Data Link Layer has two sub-layers:
Media Access Control (MAC)
Logical Link Control (LLC)
Defines how packets are placed on the media. Contention for media access is “first come/first served” access where everyone shares the same bandwidth-hence the name.
Physical addressing is defined here as well as logical topologies.
Media Access Control (MAC)
Responsible for identifying Network layer protocols and then encapsulating them. Header tells the Data Link layer what to do with a packet one a frame is received.
Logical Link Control (LLC)
Layer 2 switching is considered hardware-based bridging because it uses specialized hardware called:
Application-specific integrated circuit (ASIC)
High gigabit speeds with very low latency rates.
The time measured from when a frame enters a port to when it exits a port.
Latency
Physical layer functions:
Send bits and receives bits.
Changes in voltage from high to low and low to high.
State transitions
Bit length and expression form of a MAC address
48 bits, hexadecimal
HTTP, POP3, SMTP: protocols.
Application (Layer 7)
TCP, UDP: protocols.
Transport (Layer 4)
IP: protocol.
Network (Layer 3)
Ethernet, Point-to-Point Protocol (PPP), T1: protocols.
Data Link (Layer 2)
Two computers use a protocol to communicate with the same layer on another computer. Header information added by a layer of the sending computer is processed by the same layer of the receiving computer.
Same-layer interaction
On a single computer, one layer provides a service to a higher layer. The software or hardware that implements the higher layer requests that the next lower layer perform the needed function.
Adjacent-layer interaction
