CCENT - ICND1
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What are the 7 layers of the OSI model?
- Data Link
What is same-layer interaction on different computers?
The two computers use a protocol to communicate with the same layer on another computer. The protocol defined by each layer uses a header that is transmitted between the computers, to communicate what each computer wants to do.
What is adjacent-layer interaction on the same computer?
On a single computer, one layer provides a service to a higher layer. The software/hardware that implements the higher layer requests that the next lower layer perform the needed function.
What is a segment, packet and frame
- Segement: TCP header and data
- Packet: IP header and data (may include TCP header in data)
- Frame: Link Header - data - Link Trailer (data may include packet and segment headers)
OSI model vs. TCP/IP model
OSI: physical, data link, network, transport, session, presentation, application
TCP/IP: application, transport, internet, network access
What are the benefits of a layered network model?
Less complex, standard interfaces (routers/switches), easier to learn, easier to develop (program changes and product development), multivendor interoperability, modular engineering (web browser or Microsoft TCP/IP)
on a computer that receives data over a network, the process in which the device interprets the lower-layer headers and, when finished with each header, removes the header, revealing the next-higher-layer PDU (protocol data unit; grouping of info by OSI layer)
the placement of stat from a higher-layer protocol behind the header (sometimes header and trailer_ of the next-lower-layer protocol. IE. an IP packet being encapsulated in and ethernet header and trailer to be sent over ethernet.
refers to data link header and trailer, plus the data encapsulated between the header and trailer
Define networking model
term referring to any set of protocols and standards collected into a comprehensive grouping that, when followed by the devices in a network, allow all devices to communicate. IE. TCP/IP or OSI models.
logical grouping of informantion that includes the network layer header and encapsulated data, but does not include any headers or trailer below the network layer.
Protocol Data Unit: OSI term to refer to generically grouping of information by a layer of the OSI model.
In TCP, used to describe a RCP header and its encapsulated data (L4PDU). Also in TCP, the process of accepting a large chunk of data from the application yaer and breaking it into smaller pieces that fit into TCP segments. Segment in Ethernet is either single cable or a collision domain.
What are the functions of the OSI layers?
- Physical: defines cabling and connectors, procedure details for transmitting bits
- Data Link: formats data into frames appropriate for transmission on layer 1. Defines rules for when layer 1 medium can be used and means by which to recognize transmission errors
- Network: logical addressing, routing and path determenation
- Transport: provides services between host computers. Connection establishment and termination, flow control, error recovery, segmentation of data for transmission
- Session: establishes and maintains end to end bidirectional flows between end points
- Presentation: defines the format and organization of data, includes encryption
- Application: interfaces between network and application software, includes authentication services
What is ethernets speed, name, IEEE standard and cable type/length?
10 mbps, 10base-t, IEEE 802.3, copper 100m
What is fast ethernets speed, name, IEEE standard and cable type/length?
100 mbps, 100base-t, IEEE 802.3u, copper 100m
What is Fiber Gigabit ethernet's speed, name, IEEE standard and cable type length?
1000 mbps, 1000base-lx or 1000base-sx, IEEE 802.3z, fiber 550sx/5km lx
What is Copper ethernet's speed, name, IEEE standard and cable type/length?
1000 mbps, 1000base-t, 802.3ab, 100m
What does CSMA/CD stand for?
Collision sense multiple access with collision detection
- -device that wants to send a frame waits until the LAN is silent before attempting to send.
- -If a collision does occur, the device that cause the collision waiats a random amount of time and then trys again.
How does a crossover cable work?
Send and recieve pins are swapped on one end, pins 1 & 2 are 3 & 6, pins 3 & 6 are 1 & 2.
Devices that transmit on 1 &2 and receive on 3 & 6?
PC NIC's, routers, WAP ethernet interface, printer ethernet interfaces
Devices that transmit on 3 & 6 and receive on 1 & 2?
Hubs and switches
Explain the Steps of CSMA/CD
- 1. device with a frame to send listens until the ethernet is not busy
- 2. when ethernet is not busy, the sender begins sending the frame
- 3. the sender listens to make sure that no collision occurred.
- 4. if collision occurs, the devices that were sending frames each send a jamming signal to ensure all stations recognize collision.
- 5. after jamming is complete, each sender randomizes a timer and waits that long before resending the collided frame
- 6. when timer expires the process starts over
any communication in which the communicating devices can send and recieve data.
any communication in which only one device at a time can send data
LAN device that allows for centralized cabling, repeats any received data out all ports (logical bus). Layer 1 device
Documentation and implementation of which wires inside cable connect to each pin position in a connector
Define protocol type
Field in a LAN header that identifies the type of header that follows the LAN header. Includes DIX (ethernet field, IEEE 802.2 DSAP field and SNAP protocol field
Define shared ethernet
Ethernet that uses a hub or coaxial cable, results in devices taking turns sending data and sharing bandwidth.
Network device that filters, forwards, and floods ethernet frames based on destination address of each frame.
Define switched ethernet
Ethernet that uses a switch, not a hub. Each device connected to one port and do not have to contend for bandwidth on another port
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