Day 4 Flashcards
multiplexing
the process of combining and transmitting multiple analog or digital signals via a single transmission medium
Time Division Multiplexing (TDM)
the process of combining analog or digital signals with each signal having its own timeslot to transmit or receive data via a single carrier.
Frequency Division Multiplexing (FDM)
the process of combining analog or digital signals with each signal having its own frequency to operate within
Wave Division Multiplexing (WDM)
a method of multplexing data from two or more inputs and transmitting them over the same fiber-optic cable where each input is propagated on its own wavelength (color)
Time division multiple access (TDMA
a satelite and cellular technology that interweaves multiple digital signals by dividing each channel into sub-channels, providing service to multiple users simultaneously.
each user is given a timeslot to transmit and receive data
Code Division Multiple Access (CDMA)
data is spread out over the entire available bandwidth of the carrier.
the data is sent in small pieces over a number of discrete frequencies .
bandwidth on the carrier is spread by means of a coder
Types of circuits used in WAN’s
point to point, packet switched, and circuit switched
point to point (pt2pt)
a communications path that is a direct connection between two endpoints.
can be expensive.
the line is reserved 24/7
circuit switching
a networking method that establishes a fixed path between the transmitting and receiving stations.
multiple circuits connect together to establish a path for the communication.
(similar to old school telephone networks)
packet switching
a technology based on transmitting packets via multiple paths at the same time
WAN protocols
Key protocols include HDLC, PPP, X.25, and Frame relay
High-level data link control (HDLC)
an encapsulation method for data on serial links that will not encapsulate multiple protocols on the same link, so you cannot identify the type of protocol being carried.
each vendor develops their own proprietary HDLC for their own equipment
Frame Check Sequence
provides a method for the receiving device to determine if the frame experienced transmission errors
Point-to-point protocol (PPP)
allows users to connect to IP networks using modems or dedicated leased lines.
PPP encapsulates the network layer protocol.
PPP is relatively slow.
PPP is non proprietary and is used to connect WAN links when equipment is purchased from different vendors.
frame relay
a packet switching technology.
frame relay provides for dynamic-bandwidth and congestion control features with the use of forward explicit congestion notificaiton (FECN) and backward explicit congestion notification (BECN)
Forward Explicit congestion notification (FECN)
transmitted source terminal requesting the destination terminal slow down its requests for data
Backward explicit congestion notification (BECN)
transmitted by destination terminal requesting the source terminal send data more slowly
Committed information rate (CIR)
congestion control with frame relay works by providing a guaranteed minimum bandwidth for each user
x.25
one of the oldest packet-switched services available and developed before OSI model.
Used by ATM’s in the 1980’s.
Required a PAD to operate.
Packet assembler/disassembler (PAD)
used to perform buffering of data, packet assembly, and packet disassembly when network devices are too simple to implement full x.25 functionality
Multi-Protocol Label Switching (MPLS)
considered a layer 2.5 technology.
allows routers to label data and use specific connection paths.
The entry and exit point of an MPLS domain are Label Edge Routers (LER’s), which add and remove labels.
Label Switch Routers (LSR’s) are routers that simply forwards traffic based on label information.
Internet Control Message Protocol (ICMP)
an error reporting mechanism for the IP protocol.
sends error reports back to the originator of the datagram.
PING
a utility that uses ICMP the messages Echo and Echo reply to request a response from a remote host to verify if it is available for communication.
- t: continue pinging until interrupted with a CTRL+C
- l: set the size of the ping packet
Traceroute
uses ICMP to send messages then uses the returning ICMP Time Exceeded error messages to identify routers from source to destination.
the Windows command to use Traceroute is tracert
Internet Group Management Protocol (IGMP)
a protocol used with IP multicast. multicast addresses are assigned based on traffic type, not individual hosts.
If a specific multicast service is desired, a host notifies the upstream router or switch that they want to receive it. .
This notification gives the requesting device group membership.
Transport Layer Protocols
handle data delivery between computers.
rely on ports for proper communication, which reference application layer protocols
Transmission Control Protocol (TCP)
reliable, connection oriented transport layer protocol
TCP Three-way handshake
used to establish a logical connection prior to the transmission of data.
Step 1: the initiating computer sends a SYN message
Step 2: the destination computer acknowledges with a SYN/ACK message
Step 3: the initiating computer sends its own acknowledgement ACK message.
User Datagram Protocol (UDP)
an unreliable, connectionless protocol that does not guarantee data transmission.
