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82 Cards in this Set

  • Front
  • Back
[001] What does TCP stand for?
[001] Transmission Control Protocol
[002] What does IP stand for?
[002] Internet Protocol
[003] What does OSI stand for?
[003] Open Systems Interconnection
[004] What is the 5-step encapsulation process?
[004] 1. Create application data and headers 2. Package data for transport 3. Add destination and source network address 4. Add destination and source data link address 5. Transmit the bits
[005] What are the 7 layers of the OSI reference model?
[005] 7. Application 6. Presentation 5. Session 4. Transport 3. Network 2. Data Link 1. Physical
[006] What are the 4 layers of the TCP/IP reference model?
[006] 4. Application 3. Transport 2. Internetwork 1. Network Interface
[007] What is a L3PDU?
[007] L3PDU stands for layer 3 protocol data unit, which would be the layer 3 headers, trailers, and all data encapsulated inside
[008] What terms describe the contents of data encapsulated by the data link, network, and transport layers, respectively?
[008] Frame, packet, and segment
[009] What are the benefits of layering?
[009] 1. Easier to learn 2. Easier to develop 3. Multivendor Interoperability 4. Modular Engineering
[010] What header or trailer does a router discard as a side-effect of routing?
[010] The data-link header and trailer
[011] Which pins are used by an Ethernet NIC to send? Which to receive?
[011] Pins 1 and 2 are used to send, 3 and 6 to receive.
[012] What are the typical functions defined by physical layer protocols?
[012] 1. Cabling (defines the number of wires and type of shielding)
2. Connectors (Defines shape of connector and number of pins)
3. Pins (Defines the purpose of pins)
4. Voltage and Current (Defines electrical characteristics of the endpoint devices)
5. Encoding (Defines how a device signals a binary 1 or 0 onto the transmit pin)
[013] Why are the wires twisted into pairs in electrical cables?
[013] Twisting pairs of wires reduces electromagnetic interference cause by the electrical current.
[014] What is attenuation?
[014] Attenuation is the tendency of electical current to grow weaker the farther it has to travel.
[015] What are the typical functions defined by data link layer protocols?
[015] 1. Arbitration (Determines when it is appropriate to use the physical medium) 2. Addressing (Ensures that the correct recipient receives and processes the data) 3. Error Detection (Determines whether the data made the trip across the physical medium successfully) 4. Identification of the encapsulated data (Determines the type of header that follows the data link header)
[016] What does CSMA/CD stand for?
[016] Carrier Sense Multiple Access with Collision Detection. It is the algorithm that helps devices in half duplex mode avoid collisions.
[017] Which layer is responsible for detecting corrupt data, and how is this accomplished?
[017] Layer 2 is responsible for error detection. Each data link header includes either an FCS or CRC field which contains the result of a mathematical formula applied to the data in the frame. If the computer receiving the frame runs the same formula and obtains a different result, the data was corrupted in transit.
[018] Which layer is responsible for error correction?
[018] Layer 3 is responsible for error correction
[019] What do the acronyms FCS and CRC stand for?
[019] FCS stands for Frame Check Sequence, and CRC stands for Cyclical Redundancy Check
[020] What was the maximum distance 10BASE2 ethernet could travel?
[020] 185 meters
[021] What was the maximum distance 10BASE5 ethernet could travel?
[021] 500 meters
[022] Which three companies originally developed ethernet?
[022] Xerox, Intel, and DEC (Digital Equipment Corp)
[023] What does MAC stand for?
[023] Media Access Control
[024] What are the steps in the CSMA/CD algorithm?
[024] 1. A device with a frame to send listens until the Ethernet is not busy. 2. When the Ethernet is not busy, the sender begins sending the frame. 3. The sender listens to make sure that no collision occurred. 4. Once the senders hear the collision, they each send a jamming signal, to ensure that all stations recognize the collision. 5. After the jamming is complete, each sender randomizes a timer and waits that long. 6. When each timer expires, the process starts over again at step 1.
[025] What is a repeater and how does it work?
[025] A repeater allows ethernet segments to extend beyond the maximum length the signal can travel along the cable. This is accomplished by listening to a signal and interpreting the bits as 0's and 1's, then generating a clean new signal on the other segment. A repeater does NOT simply amplify the signal since that would amplify any noise picked up along the way.
[026] What is a hub and how does it work?
[026] A hub is a device that has multiple ethernet ports. It repeats signals received on one port to all the other ports. Hubs operate at layer 1 - they do not know which device is connected to which port.
[027] What is a switch and how does it work?
[027] A switch is a device that has multiple ethernet ports. It operates at level 2 - it knows which devices are connected to which ports and repeats frames received on one port to the port to which the destination device is connected (and only that port). Switches also have memory buffers to hold multiple frames transmitted simultaneously.
[028] How do switches eliminate collisions?
[028] First, by only repeating frames on the port to which they are addressed. Second, by using memory buffers to hold multiple frames transmitted simultaneously.
[029] How do switches improve performance of ethernet segments?
[029] 1.) eliminate collisions and need for CSMA/CD
2.) creates separate bus for each port, no shared bandwidth among ports
3.)NICS can operate at Full Duplex and send and receive data simultaneously - effectively doubling their bandwidth.
[030] What is the difference between half duplex and full duplex?
[030] Half duplex allows a NIC to send OR receive at any given time - not both at the same time. Full duplex allows sending and receiving simultaneously.
[031] What is a collision domain?
[031] A collision domain defines a set of devices for which their frames could collide. All devices on a 10BASE2, 10BASE5, or 10BASET network using a hub risk collision so all devices on these types of network are in the same collision domain. Each port on a LAN switch is in its own collision domain.
[032] What is the cable connecting two hubs or two switches called?
[032] A trunk
[033] What type of cable is used to connect two hubs or two switches?
[033] Crossover cable
[034] Which pins do hubs and switches use for sending? Which for receiving?
[034] Pins 3 and 6 for sending, 1 and 2 for receiving.
[035] Why must a NIC operating in Half Duplex mode use its loopback circuitry?
[035] Since hubs don't repeat signals on the originaing port, only its other ports, when a NIC sends out an ethernet frame it repeats the signal on its own receiving twisted pair via the loopback. This is to enable NIC's to notice collisions. This is not necessary when operating in Full Duplex because the presence of a switch eliminates collisions.
[036] What is the 802.2 standard?
[036] Logical Link Control sublayer (LLC)
[037] What is the 802.3 standard?
[037] Media Access Control sublayer (MAC) - specifically, Ethernet
[038] What type of LAN is defined by the 802.5 standard?
[038] Token Ring
[039] What type of LAN is defined by the ANSI X3T9.5 standard?
[039] ANSI FDDI
[040] How many bytes are there in a unicast ethernet address? How are they broken up?
[040] 6 bytes total. The first three are the OUI, the second three are unique to that card.
[041] What does OUI stand for?
[041] Organizationally Unique Identifier. It is the 3 byte code assigned to each NIC manufacturer by the IEEE.
[042] What does BIA stand for?
[042] Burned-In Address. It is the MAC address burned into the ROM chip on a NIC.
[043] What does UAA stand for?
[043] Universally Administered Address. It is another name for the BIA.
[044] What is the difference between unicast, broadcast, and multicast?
[044] A unicast address identifies a single device on a LAN. A broadcast address identifies every device on a LAN. A multicast address identifies a subset of devices on a LAN.
[045] What is the broadcast address in both hex and decimal form?
[045] Hex = FFFF.FFFF.FFFF Decimal = 255.255.255.255
[046] What does the term "framing" refer to?
[046] Framing defines how a string of binary numbers is interpreted - it defines the fields that make up a header or trailer and what values they can hold.
[047] What does DSAP stand for, and what is it?
[047] Destination Service Access Point. It is a field in the data link header that defines the type of header to follow - in other words what type of protocol data in encapsulated in the frame.
[048] How large is the DSAP field?
[048] 1 byte
[049] What does SNAP stand for, and what is it?
[049] SubNetwork Access Protocol. Because the DSAP field is only 1 byte, it cannot define every protocol in use. The IEEE allowed the use of an extra header to define the extras. The SNAP header is 2 bytes long, follows immediately after the normal data link header, and is specified with an "AA" in the DSAP field.
[050] What does MTU stand for, and what is it?
[050] Maximum Transmission Unit. It defines the maximum size of the encapsulated data inside a data link frame. The 802.3 standard set the MTU to 1500 bytes. Thus, the maximum size of a layer 3 packet is 1500 bytes.
adjacent 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
same-layer interaction
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
decapsulation
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
encapsulation
placement of data from higher layer protocol behind header (and trailer) of next lower protocol
frame
refers to data-link header, trailer plus data
networking model
any set of protocols and standards collected in a comprehensive grouping that, when followed by devices allow all devices to communicate
packet
grouping of info includes network layer header and encapsulated data - does not include headers/trailers below network layer
protocol data unit (PDU)
OSI term referring to a grouping of info by a particular OSI layer (data and headers of Layer X)
segment (TCP)
in TCP a TCP header and data (L4PDU), also in TCP a process of accepting a large chunk of data from Application layer and breaking it into smaller pieces that fit into TCP segments
segment (ethernet)
a single Ethernet cable or a single collision domain
Name the layers in the OSI Reference Model
Application, Presentation, Session, Transport, Network, Data Link, Physical
Application layer (OSI)
7th layer, Interfaces between network and application software, includes authentication services
Presentation layer (OSI)
6th layer, Defines the format and organization of data, includes encryption
Session layer (OSI)
5th layer, establishes and maintains end-to-en bidirectional flows between endpoints. includes managing transaction flows
Transport layer (OSI)
4th layer, provides variety of services, between two host computers, including connection establishment and termination, flow control, error recovery, and segmentation of large data blocks into smaller parts for transmission
Network layer (OSI)
3rd layer, logical addressing, routing, and path determination
Data link layer (OSI)
2nd layer, formats data into frames appropriate for transmission onto some physical medium. Defines rules for when the medium can be used. Defines means by which to recognize transmission errors.
Physical layer (OSI)
1st layer, defines the electrical, optical, cabling, connectors, and procedural details required for transmitting bits, represented as some form of energy passing over a physical medium
What is 1000BASE-T
name for gigabit ethernet standard, uses four-pair copper cabling, speed of 1000Mbps, max cable length 100m
What is 100BASE-TX
name for IEEE Fast Ethernet, uses two-pair copper cabling, speed of 100Mbps, max cable length 100m
What is 10BASE-T
10-Mbps baseband Ethernet specification, using two pairs of twisted-pair calbing (categories 3, 4, 5) - 1 pair transmits, the other recieves - distance of 100m
crossover cable
swaps the pair used for transmission on one device to a pair used for receiving on the device on the opposite end of the cable - in 10BASE-T and 100BASE-TX it swaps pins 1,2 and 3,6 on the opposite end
full duplex
communicating in whtich two devices can concurrently send and receive data - allowed when CSMA/CD logic is disabled on ethernet LANs
half duplex
communication in which only one device at a time can send - enforced in Ethernet lan by CSMA/CD algorithm
hub
layer 1 device that provides a centralized connection point for LAN cabling repeating any received electrical signal out all other ports - creates a logical bus - layer 1 as it does not interpret electrical signals
pinout
documentation/implementation of which wires inside cable connect to each pin position in any connector
protocol type field
field in a LAN header identifies type of header that follows the LAN header. examples; DIX Ethernet Type, IEEE 802.2 DSAP field, and SNAP procotol Type field
shared Ethernet
Ethernet that uses hub, or original coaxial cabling - devices take turns and share bandwidth
straight-through cable
connects wire on pin 1 to pin 1 on other end of cable, pin 2 to pin 2 etc
switch
network device that filters, forwards, and floods ethernet frames base on destination address of each frame
switched Ethernet
Ethernet that uses a switch, devices connected on one port do not share bandwidth with devices on other ports
twisted pair
transmission medium consisting of two insulated wires, with wires twisted around each other in a spiral - an electrcial circuit flow over the wire pair, with curren in opposite directions, reduces the interference between the two wires