Semster 2 Chapters 2-3
What is and example of a DCE and DTE?
DCE- (Date Communication Equipment)- provide physcal
connections to the network, forwards traffic, and provides
clocking a clocking signal used to synchronize data transmission between DCE and DTE devices.
ex. Modem, Interface Cards
DTE (Data Treminal Equipment)- Devices at the user
end of a user-network interface that serves as a data source,
destination, or both. DTE connects to a data network through a DCE.
ex. Computer, Protocol Translator, Multiplexers
Be able to describe:
Frame Relay -- uses high-quality digital facilities; uses simplified framing with no error correction mechanisms, which means it can send Layer 2 information much more rapidly than other WAN protocols
Point-to-Point Protocol (PPP) -- described by RFC 1661; two standards developed by the IETF; contains a protocol field to identify the network layer protocol
Simple Data Link Control Protocol (SDLC) -- an IBM-designed WAN data link protocol for System Network Architecture (SNA) environments; largely being replaced by the more versatile HDLC
Serial Line Interface Protocol (SLIP) -- an extremely popular WAN data link protocol for carrying IP packets; being replaced in many applications by the more versatile PPP
Link Access Procedure Balanced (LAPB) -- a data link protocol used by X.25; has extensive error checking capabilities
Link Access Procedure D-channel (LAPD) -- the WAN data link protocol used for signaling and call setup on an ISDN
D-channel. Data transmissions take place on the ISDN B channels
Link Access Procedure Frame (LAPF) -- for Frame-Mode Bearer Services;
a WAN data link protocol, similar to LAPD, used with frame relay technologies
Cicuit switched services
Describe the different kinds of memory used in a router; know what software each type of memory normally contains:
RAM/DRAM -- Stores routing tables, ARP cache, fast-switching cache, packet buffering (shared RAM), and packet hold queues. RAM also provides temporary and/or running memory for the routerís configuration file while the router is powered on. RAM content is lost when you power down or restart.
NVRAM -- nonvolatile RAM; stores a routerís backup/startup configuration file; content remains when you power down or restart.
ROM -- contains power-on diagnostics, a bootstrap program, and operating system software; software upgrades in ROM require replacing pluggable chips on the CPU
Flash -- erasable, reprogrammable ROM; holds the operating system image and microcode; allows you to update software without removing and replacing chips on the processor; content remains when you power down or restart; multiple versions of IOS software can be stored in Flash memory
What protocol does a WAN use to make path determination decisions?
What layer does a router operate at and what kind of addresses does it use to make decisions?
Layer three, IP adresses
What is the difference between Frame relay service and X.25?
Frame relay is becoming more popular because X.25 is older and less efficent
enable-lets you do things
logout/exit-lets you leave the router
?-tells you available commands
User EXEC mode
Interface configuration (intS0)
Interface- where packets exit and enter the router
Router will hold 22 lines
Space bar to see the more screen.
WANs provide for the exchange of data packets/frames betweeen routers/bridges and the LANs they support.
WAN interconnects LANs that usually have a large geographic area between
offer serices including:
WAN serial interfaces
Routers can operate as:
Area border routers
Autonomous system boundary routers
WAN bandwidth switches
Service provider equipment that connects to WAN bandwidth for voice, data,
and video communications.
Also called CSU/DSUs (channel service units/digital service units)
Interface with voice-grade connection in order to convert analog signal to digital.
Represents the DCE side of the DTE/DCE connection.
Concentrates dial-in and dial-out services.
Equipment is usually at the service provider's site.
What layers of the OSI layer do the WAN standards describe?
Physical and Data Link Layers
WAN Physical Layer
Protocols that descrbe how to provide electrical, mechanical, operational, and functional connections for WAN . services
These services ar most often obatained from WAN service providers such
as ROBCs, alternate carriers,
post-telephone, and telegraph (PTT) agencies.
Describes the interface between the data terminal equipment (DTE) and the
data circuit-terminating equipment
Typically, the DCE in the service provider and the DTE is the attached device.
Several physical layer standards specefying this interface between the
DTE and DCE are...
Data Link Layer
Wan data link protocols describe how frames are carried between systems on a single data link
They include protocols designed to operate over dedicated point to point,
multiport, and multiaccess switched
WAN standards are defined and managed by a number of recognized authorities
including ITU-T, ISO, IETF, &
WAN Data Link Encapsulation
High-Level Data Link Control (HDLC)
Cisco default encapsulation; typically used between running Cisco IOS; replacing SDLC.
Streamlined, no windowing or flow control.
May not be compatible with each vendor depending on the way each vendor has chosen to implement it
HDLC supports both point to point and multipoint configurations with minimal overhead.
Uses high-quality digital facilities
Uses simplified framing with no error correction mechanism (connectionless)
It can send layer 2 information much more rapidly than other WAN products
PPP (point to point protocol)
Developed by IETF, replaced SLIP
Contains a field to identify the network protocol
PPP can check for link qualiy during connection establihment
Supports PAP and CHAP
WAN Technologies Overview
Dedicated: xDSL, T1, E1, T3, E3, SONET
Analog: Dial-up Modem, Cable Modems, Wireless
Cicuit Switched: POTS, ISDN
Packet Switched: X25, Frame, Relay
Switched: ATM, SMDS
Basic Cisco Router Commands:
User EXEC mode
global configuration-router donfiguration file
copy, run, start
router configration-chnges the routing protocol
interface configuration (intS0)