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89 Cards in this Set
- Front
- Back
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What does PPP stand for?
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Point-to-point Protocol
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What layer protocol is PPP, and what is that layers name?
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Layer 2
Data-link Layer |
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What is a Wan PPP connecion also called? There are two.
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Serial Connection or Leased-line Connection.
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What does PPP provide.
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Multiprotocol LAN-to-WAN connecion. *including TCP/IP, IPX and Apple Talk simultaneously,
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What technologies can PPP provide Transprot over?
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ATM, Frame Relay, ISDN and Optical links
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Name 2 Security protocols for PPP.
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PAP (Password Authentication Protocol)
CHAP (Handshake Auththentication Protocol) |
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Serial Communication is the process of transmitting...?
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A single bit ata time over a communicaionts circuit channel
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Why are Parallel cables not used for WAN comunication, why are they slower.
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Clock Skew (all bits sent at same time but not received at same time, then must be Synchronized)
Length of cable increases Clock Skew CrossTalk |
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What is Clock Skew?
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All bits sent at same time but not received at same time, then must be Synchronized
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What device would the serial standard RS-232 use on or be found on?
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Common PC's and/or Laptops.
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What device would the serial standard RS-232, and RS-423 use on or be found on?
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Common PC's and/or Laptops
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What device would the serial standard V.35 be use on or be found on?
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Modem-to-Multiplexer,Used by most Routers and DSU (Data service unit) to T1 carriers.
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What is the serial standard v.35 designed for?
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Higher data rates and connectivity between DTEs(Data Terminal Equipment) and DCEs (Data Communicaitons Equipment) over digital lines.
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What does HSSI stand for?
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High-Speed Serial Interface
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What device would the serial standard V.35 be use on or be found on?
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Routers that connect LANs to WANs
and LANs to Token Ring networks |
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What is the bit rate of HSSI?
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Rate of up to 52Mbps
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What does DCD stand for and define it?
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Data Carrier Detect
Indicates that the carrier for the Transmit is ON. |
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What does DTR stand for and define it?
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Data Terminal Ready
Tell teh modem that the comptuer is ready to transmit. |
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What does DSR stand for and define it?
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Data Set Ready
Simular to DTR Indicates that the data set is ON. |
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What does CTS stand for and define it?
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Clear to Send
Acknowledge the computer's RTS signal. |
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What does RTS stand for and define it?
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Request to Send
Request clearance to send data to modem |
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What does TDM stand for and define it?
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Time-division Multiplexing
Signal method that divides the bandwith of a single link into separate channels or time slots |
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Give a brief description of what TDM does.
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Transmits two or more channels of the same link link by allocating a different time interval (time slot) for the transmission of each channel; In effect the channels take turns using the link
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What does MUX stand for?
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Multiplxer
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How is the first time slot represented in TDM transmission?
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TS0 (Zero)
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What dose a MUX do?
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Accepts input from attached devices in a round-robin fashion and transmits the data in a never-ending orginized pattern, if devises are not sending data the MUX will send empty slots.
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What does STDM stand for?
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Statistical time-division multiplexing.
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Why was STDM created?
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Created to over come the inefficiency of TDM sending empty time-slots when devices connected are idel and not sending data
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How dose STDM improve TDM?
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STDM uses variable time slot length, allowind channels to compete for any free (empty) time-slot. If a device is not trasmitting STDM does not send an empty slot but will allow anothers devices data to be inserted into this empty slot and not wast banwidth/time on the tramsmmision link
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Name 2 examples of STDM.
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ISDN
SONET |
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What is SONET a standard for?
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Optical Transport
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When dealing with STDM when you have traffic ariving from 4 places each with a bit rate of 2.5 Gbps; Give the formula to determin the Out link rate. Also give the numbers used in the formula and what the out link rate would be.
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(Incoming bit rate) * n
n = number of incomming streams 2.5Gbps * 4 incoming streams = 10Gbps |
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What does DS0 (zero) stand for?
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digital signal level zero
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Give the bit rate and Voice slots for DS0(zero).
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Rate = 64Kbps
Voice slots = 1 DS0(zero)s |
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Give the bit rate and Voice slots for DS1(zero).
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Rate = 1.544 Mbps
Voice slots = 24 DS0(zero)s |
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Give the bit rate and Voice slots for DS2(zero).
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Rate = 6.312 Mbps
Voice slots = 96 DS0(zero)s |
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Give the bit rate and Voice slots for DS3(zero).
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Rate = 44.736 Mbps
Voice slots = 672 DS0(zero)s or 28 DS1s |
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What is another name for the Demarcation Point?
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Demarc
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What does Demarc represent?
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The point where the telephone company's responsibilities and the Owner/customer responsibilities begin.
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What does DTE stand for?
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Data Termination Equipment.
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What does DCT stand for?
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Data Communications Equipment.
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What does CPE stand for?
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Customer premises equipment.
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What is the DTE; what does it do?
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The device (router, computer, printer, ect. that would connect directly to the service provider) at the users end of the user-network interface. The DTE connects to a data network through the DCE. (Data Communications Equipment
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What is the DCE; what does it provide?
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Provides physical connection (commonly a modem or CSU/DSU [Channel Serivce Unit/Data Service Unit]) to the network, it provides clocking signal which is used to synchronize data transmission between DCE (Data Communications Equipment.) and DTE (Data Termination Equipment) and forward trafic.
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What CSU/DSU stand for?
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Channel Serivce Unit/Data Service Unit
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What does EIA stand for?
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Electronics Indusry Association.
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What does ITU-T stand for?
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International Telecommunication Union Telecommunications Standardizations Sector
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What does the ITU-T (International Telecommunication Union Telecommunications Standardizations Sector) call the DCE?
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Data Circuit-Terminating Equipment
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What type of cable is used to connect a DTE ((Data Termination Equipment)) to a DTE (Data Termination?Equipment)
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null modem serial cable
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Name 2 main wires crossed on a null modem serial cable?
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Tx (transmit) and Rx (receive)
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Name a standard serail connector that would connect to a Cisco router?
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DB-60
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What is the serial cable called that Cisco introduced that is more compact than the DB-60 and has a 26-pin connector?
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Smart Serail Cable
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When using a null modem cable to connect a DTE to a DTE what MUST be configured and why?
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One of the serial must be comfigured as the DCE end.
To provied the clock signal for the connection. |
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What does RS stand for?
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Recommended Standard
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What does UART Stand for, where is it located and what does it do?
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Universal Asynchronous Receiver/Trasmitter.
Located on the motherboard on a PC. Converts the group bits of parallel to a serial stream bits. NOTE: It is the DTE in the PC for serial connections in accordance with RS-232C Standards: |
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What is done to data before crossing a WAN and at what layer is this done?
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It is Encapsulated into frames using a Encapsulaion Protocol before crossing the WAN link.
Layer 2 the Data link Layer. |
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What type of Encapsulaion Protocol would you use for a Leased Line?
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HDLC (High-Level Data-link Control), PPP (Point-to-Point Protocol), SLIP (Serial Line Internet Protocol)
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What type of Encapsulaion Protocol would you use for Circuit-Switched?
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HDLC (High-Level Data-link Control), PPP (Point-to-Point Protocol), SLIP (Serial Line Internet Protocol)
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What type of Encapsulaion Protocol would you use for Packet-Switched?
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X.25, ATM (Asynchronous Transfer Mode), Frame Relay
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What does HDLC stand for and define and describe it?
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High-Level Data link Control
A bit Oriented Synchronous data link protocol that specifies a data encapsulation method on a synchronous serial link using frame characters and checksums. Default encapsulation type on point-to-point connections, dedicated links and circuit-switched connections, is now the basis for synchronous PPP used by many servers to connect to a WAN, most commonly the internet. Provides both connectionless and connection-oriented service |
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What does PPP stand for and define and describe it?
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Point-to-Point Protocol
Successor to SLIP. Provides Router-to-Router and Host-to-Network Connections over Synchronous and Asynchronous circuits PPP works with several network protocols like IP (Internet Protocol) and IPX (internetwork Packet Exchange) It Also Has built-in security mechanisms PAP (Password Authentication Protocol) and CHAP (Challenge Handshake Authentication Protocol) |
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What does SLIP stand for and what is it?
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Serial Line Internet Protocol.
A standard protocol for point-to-point serail connections using TCP/IP, largely displaced by PPP. |
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What does LAPB stand for and define and describe x.25/LAPB?
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Link Access Procedure, Balance
Is and ITU-T (International Telecommunication Union Telecommunications Standardizations sector) standard that defines how connections between DTC and DTE are maintained for remote terminal access and computer communications in public data networks. X.25 specifies LAPB, a data link layer Protocol (Layer 2), X.25 is a predecessor of Frame Relay. |
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Describe Bit-oriented Protocol.
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Bit-oriented Protocol is data link layer Protocol that can transmit frames regardless of frame content, provide full-duplex operation and are more efficient and reliable data is transmitted as a steady stream of bits.
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What is the current standard for HDLC?
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ISO 13239
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What is a bit-oriented Synchronous data link layer protocol developed by ISO(International Organization for Standards) that uses synchronous serial transmission to provide error free communication between two points and allows flow control and error control through the use of acknowledgments, each frame has the same format whether it is a data frame or a control frame.
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HDLC (High-Level Data link Control)
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What does HDLC (High-Level Data Link Control) use to mark the begining and end of each frame?
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Delimiter or Flag
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What is cHDLC
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Cisco High-Level Data Link Contorl)
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What is the difference between cHDLC (Cisco High-Level Data Link Contorl) and HDLC (High-Level Data Link Contorl)
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cHDLC (Cisco High-Level Data Link Contorl) Uses a Protocol field to support multiprotocol environments.
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In HDLC (High-Level Data Link Contorl) and cHDLC (Cisco High-Level Data Link Contorl) what are the name of the 3 formats used?
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Information - (I) Frame
Supervisory - (S) Frame Unnumbered - (U) Frame |
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Describe a Information frame/
I-Frame |
Sends and receives Sequence numbers and the P/F (poll final) performs flow and error contorl.
NOTE to KNOW: The send sequence number refers to the number of the frame to be sent next. The receive sequence number provides the number of the frame to be received next Both sender and receiver maintain sequence numbers |
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Describe a Supervisory frame/S-Frame.
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Provides control information. Can request and suspend transmission, report on status, and acknowledgel recipt of I-Frames.
NOTE: S-Frames do not have an information field. |
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Describe a Unnumbered frame/U-frame.
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Used to support control purposes and are not sequenced.
NOTE: Some U-Frames have Information field. |
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Name MAIN Features that PPP (Point-to-Point Protocol) includes that HDLC (High-Level Data Link Control) does not.
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Link Quality Management - If too many errors detected link taken down.
Supports PAP (Password Authentication Protocol and CHAP (Challenge Handshake Authentication Protocol) Authentication Uses HDLC (High-Level Data Link Control) Protocol as a basis for encopsulating datagtams over point-to-point links. Uses Extended version of LCP (Link Control Protocol) to establish, configure and test the data link connection. It has a family of NPC (Network Control Protocols) to establish and configure different network layer protocols. Operates across any DTE/DCE interface but requires Duplex Circuit. |
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What is LPC and what does it do?
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Link Control Protocol
Provides automatic configuration of the interfaces at each end. Handling varying limits on packet size Detecting common misconfiguration errors Terminating the link * Detemining when a link is functioning properly or when it is failing SHORT ANSWER: Is the rel working layer part of PPP, sits on top the physical layer and has a role in establishing, configuring and testing the data-link connections between devices. |
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PPP can operate across ant DTE/DCE interfaces what is the only absolute requirement imposed by PPP?
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A duplex circut, either dedicated or switched, that can operate in either an asynchronous or synchornous bit-serial mode, transparent to PPP link layer frames.
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What does NCP stand for and describe what it does in PPP (Point-to-Point Protocol)
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Manages the specific needs of its respective network layer protocols, its various components encapsulate and negotiate options for multiple network layer protocols.
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Name the 6 components of a PPP (Point-to-Point Protocol) Frame.
Give a very brief description of each. |
Flag - Indicates the beginning or end of a frame
Address - Consists if the standard broadcast address (which is the binary sequence 11111111 Control - Provides connectionless link service that does not require you to establish data links or link stations. Protocol - Consists of 2 bytes that Identify the protocol encapsulated in the frame's data field Data - 0 (zero) or more bytes that contain the datagram for the protocol specified in the Protocol field. FCS (Frame Check Sequence) - 16-bit Checksum that is used to check for bit-level errors in the PPP frame SHORT ANSWER Error detection |
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Name the 3 Phases for establishing a PPP(Point-to-Point Protocol) session.
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Phase 1 - Link establishment and configuration negotiation. -LPC must open the connection and negotiate configuration options
Phase 2 -Link Quality determination (optional) - The LPC test the link to determine whether the link quality is sufficient to bring up the network layer Protocols. Phase 3 - Network layer protocol configuration negotiation - NCP can now separately configure the network layer protocols and bring them up and take them back down at any time. |
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When establishing a Link with LCP (Link Control Protocol) in reference with PPP the LCP operation provisions for what? Also known as the three classes of LCP frames. List all three and briefly describe them.
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Provisions for:
Link-Establishment - Establish and configure a link Link-Maintenance - manage and debug a link Link-Termination - terminates a link |
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What are the 4 type’s messages that Link-Establishment Frame sends when the LCP is establishing a link.
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Configure-Request (can I)
Configure-Act (Yes you can) Configure-Nak (option recognized but not acceptable) Configure-Reject (Not acceptable and/or not recognized) |
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What are the 5 type’s messages that Link-Maintenance Frame can send after the link is established?
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Code-Reject (LCP code unknown)
Protocol-Reject (Unknown protocol ID) Echo-Request (Use me to start ping test) Echo-Reply (I see your ping I am here) Discard-Request (optionally sent to exercise the link in the outbound direction) |
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What are the 2 type’s messages that Link-Termination Frame can send after the link is established?
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Terminate-Request (You are not longer needed, Good-bye)
Terminate-Ack (I see you leaving Good-bye) |
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What are the 4 fields in a LCP (Link Control Protocol) packet?
Briefly describe each one. |
Code - identifies the type of packet.
Identifier - Used to match packet request and replies Length - Indicates total length of LCP packet Data - Information for packet |
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Name the 3 PPP (Point-to-Point Protocol) Configuration Options and what they are.
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Authentication using PAP or CHAP
Compression using either Stacker or Predictor. Multilink Combines two or more channels to increase the WAN bandwidth |
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Referring to PPP (Point-to-Point Protocol) After the LPC (Link Control Protocol) has configured and authenticated the basic link what is the next step for the NPC (Network Control Protocol) process?
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The NPC (Network Control Protocol) takes over; invoked to complete the specific configuration of the network layer protocol being used
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What does MPPP stand for?
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Multilink Point-to-Point Protocol
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What does PAP stand for and describe what it dose and it's weakness.
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Password Authentication Protocol
Two-Way hand-shake Authentication that takes place before link is established uses a username and password. Its weakness that it uses not encryption, send username and password in clear text. Only authenticates once No protection form playback or repeated trial-and-error attacks. |
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What does CHAP stand for; is it more secure that PPP, why or why not?
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Challenge Hand-shake Authentication Protocol
YES Uses 3-way hand-shake with a User-ID and password that is encoded using a hash function (Normally Message Digest 5 (MD5), and conducts periodic challenges issuing a random number and the User-ID. This allows CHAP to protect against playback attack and limits the time exposure of trial-and-error attacks. |
