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109 Cards in this Set
- Front
- Back
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What layer determines if sufficient resources exist for communication to occur between two computers?
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Application
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What layer does SMTP function at?
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Application
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What layer does FTP function at?
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Application
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What layer does SNMP function at?
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Application
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What layer does Telnet function at?
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Application
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What layer performs protocol conversion?
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Presentation
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What layer performs encryption?
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Presentation
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What layer performs compression?
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Presentation
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What layer synchronizes computers involved in a communication?
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Session
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What layer handles connection establishment, data transfer, and connection release?
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Session
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What layer does NetBIOS function at?
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Session
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What layer repackages messages into smaller formats?
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Transport
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What layer provides error-free delivery and error handling functions?
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Transport
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What layers does NetBEUI function at?
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Transport and Network
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What layer does TCP function at?
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Transport
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What layer does SPX function at?
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Transport
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What layers does NWLink function at?
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Transport and Network
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What layer handles logical addressing?
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Network
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What layer handles routing?
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Network
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What layer handles traffic management?
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Network
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What layer does IP function at?
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Network
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What layer does IPX function at?
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Network
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Where does the routers and brouters function at
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Network
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What layer packages raw bits into frames?
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Data Link
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What is the purpose of packaging raw bits into frames?
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they are transmittable across a network
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What layer includes a Cyclical Redundancy Check (CRC)?
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Data Link
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What are the two sublayers of the Data Link layer?
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LLC and MAC
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What does the LLC sublayer use to create links for the MAC sublayer?
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Destination Service Access Points and Source Service Access Points A80
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Which layer does switches, bridges, and brouters function
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Data Link
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Which layer does multiplexers and repeaters (Hubs) resides
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Physical
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How many bits/bytes are in MAC address
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48 bits / 6 bytes
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What protocol is used to map MAC addresses to IP addresses?
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ARP
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What is the 5-step encapsulation process?
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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
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What are the 7 layers of the OSI reference model?
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7. Application 6. Presentation 5. Session 4. Transport 3. Network 2. Data Link 1. Physical
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What are the 4 layers of the TCP/IP reference model?
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4. Application 3. Transport 2. Internetwork 1. Network Interface
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What is a L3PDU?
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L3PDU stands for layer 3 protocol data unit, which would be the layer 3 headers, trailers, and all data encapsulated inside
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What terms describe the contents of data encapsulated by the data link layer
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Frame
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What terms describe the contents of data encapsulated by the network layer
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Packet
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What terms describe the contents of data encapsulated by the transport layer
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Segment
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What are the benefits of layering?
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1. Easier to learn 2. Easier to develop 3. Multivendor Interoperability 4. Modular Engineering
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What header or trailer does a router discard as a side-effect of routing?
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The data-link header and trailer
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Which pins are used by an Ethernet NIC to send? Which to receive?
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Pins 1 and 2 are used to send, 3 and 6 to receive.
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What are the typical functions defined by physical layer protocols?
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"1. Cabling (defines the number of wires and type of shielding)
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Why are the wires twisted into pairs in electrical cables?
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Twisting pairs of wires reduces electromagnetic interference cause by the electrical current.
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What is attenuation?
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Attenuation is the tendency of electical current to grow weaker the farther it has to travel.
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What are the typical functions defined by data link layer protocols?
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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)
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Accronym CSMA/CD
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Carrier Sense Multiple Access with Collision Detection. It is the algorithm that helps devices in half duplex mode avoid collisions
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Which layer is responsible for detecting corrupt data, and how is this accomplished?
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Layer 2 (Data Link) 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.
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Which layer is responsible for error correction?
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Layer 3 (Network) is responsible for error correction
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Accronym FCS
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Frame Check Sequence
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Accronym CRC
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Cyclical Redundancy Check
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What was the maximum distance 10BASE2 ethernet could travel?
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185 Meter
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What was the maximum distance 10BASE5 ethernet could travel?
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500 Meter
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Which three companies originally developed ethernet?
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Xerox, Intel, and DEC (Digital Equipment Corp)
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Accronym MAC
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Media Access Control
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What type of cable is used to connect two hubs or two switches?
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Crossover cable
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Which pins do hubs and switches use for sending? Which for receiving?
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Pins 3 and 6 for sending, 1 and 2 for receiving.
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What is a repeater and how does it work?
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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.
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What is a hub and how does it work?
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[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.
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[027] What is a switch and how does it work?
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[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.
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[028] How do switches eliminate collisions?
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[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.
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[029] How do switches improve performance of ethernet segments?
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"029] 1.) eliminate collisions and need for CSMA/CD
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[030] What is the difference between half duplex and full duplex?
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[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.
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[031] What is a collision domain?
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[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.
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[032] What is the cable connecting two hubs or two switches called?
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[032] A trunk
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[035] Why must a NIC operating in Half Duplex mode use its loopback circuitry?
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[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.
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[039] What type of LAN is defined by the ANSI X3T9.5 standard?
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[039] ANSI FDDI
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Accronym OUI
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Organizationally Unique Identifier. It is the 3 byte code assigned to each NIC manufacturer by the IEEE.
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Accronym BIA
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[042] Burned-In Address. It is the MAC address burned into the ROM chip on a NIC.
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Accronym UAA
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[043] Universally Administered Address. It is another name for the BIA.
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What is Unicast?
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A unicast address identifies a single device on a LAN
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What is broadcast?
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A broadcast address identifies every device on a LAN
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What is multicast?
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A multicast address identifies a subset of devices on a LAN.
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What is the broadcast address in both hex and decimal form?
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[045] Hex = FFFF.FFFF.FFFF Decimal = 255.255.255.255
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Accronym DSAP
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[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. 1 Byte
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Accronym SNAP
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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. TheSNAP header is 2 bytes long, follows immediately after the normal data link header, and is specified with an "AA" in the DSAP field.
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Accronym MTU
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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.
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adjacent layer interaction
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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
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same-layer interaction
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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
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decapsulation
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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
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encapsulation
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placement of data from higher layer protocol behind header (and trailer) of next lower protocol
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frame
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refers to data-link header, trailer plus data
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networking model
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any set of protocols and standards collected in a comprehensive grouping that, when followed by devices allow all devices to communicate
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packet
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grouping of info includes network layer header and encapsulated data - does not include headers/trailers below network layer
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protocol data unit (PDU)
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OSI term referring to a grouping of info by a particular OSI layer (data and headers of Layer X)
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segment (TCP)
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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
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segment (ethernet)
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a single Ethernet cable or a single collision domain
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Name the layers in the OSI Reference Model
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Application, Presentation, Session, Transport, Network, Data Link, Physical
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7th layer, Interfaces between network and application software, includes authentication services
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Application layer (OSI)
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6th layer, Defines the format and organization of data, includes encryption
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Presentation layer (OSI)
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5th layer, establishes and maintains end-to-en bidirectional flows between endpoints. includes managing transaction flows
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Session layer (OSI)
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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
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Transport layer (OSI)
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3rd layer, logical addressing, routing, and path determination
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Network layer (OSI)
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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.
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Data link layer (OSI)
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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
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Physical layer (OSI)
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What is 1000BASE-T
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name for gigabit ethernet standard, uses four-pair copper cabling, speed of 1000Mbps, max cable length 100m
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What is 100BASE-TX
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name for IEEE Fast Ethernet, uses two-pair copper cabling, speed of 100Mbps, max cable length 100m
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What is 10BASE-T
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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
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crossover cable
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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
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full duplex
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communicating in whtich two devices can concurrently send and receive data - allowed when CSMA/CD logic is disabled on ethernet LANs
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half duplex
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communication in which only one device at a time can send - enforced in Ethernet lan by CSMA/CD algorithm
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hub
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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
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pinout
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documentation/implementation of which wires inside cable connect to each pin position in any connector
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protocol type field
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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
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shared Ethernet
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Ethernet that uses hub, or original coaxial cabling - devices take turns and share bandwidth
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straight-through cable
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connects wire on pin 1 to pin 1 on other end of cable, pin 2 to pin 2 etc
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switch
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network device that filters, forwards, and floods ethernet frames base on destination address of each frame
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switched Ethernet
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Ethernet that uses a switch, devices connected on one port do not share bandwidth with devices on other ports
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twisted pair
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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
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