CISCO NETWORKING ACADEMY The WAN interface How do routers connect to the phone companies lines? to phone company
CISCO NETWORKING ACADEMY Data Terminal Equipment Routers are usually considered DTEs. DTEs are devices at the end of a user’s network that serve as a data source, destination, or both. The router is a DTE, or Data Terminal Equipment
CISCO NETWORKING ACADEMY Data Terminal Equipment Your home computer can also be a DTE. How do you connect to the phone company’s network at home?
CISCO NETWORKING ACADEMY to phone company modem DTEs and DCEs At home, you connect to the phone company’s network using a modem.
CISCO NETWORKING ACADEMY Data Circuit Equipment A modem is a type of DCE, or Data Circuit-Termination Equipment. It’s the device at the end of the service provider’s network (phone company).
CISCO NETWORKING ACADEMY Data Circuit Equipment Another type of DCE is a CSU/DSU –Channel Service Unit –Data Service Unit CSU/DSU is located at the end of the service provider’s network (phone company). connects to router Serial port.
CISCO NETWORKING ACADEMY Customer’s Network Phone Company’s Network DTEs and DCEs A DTE interfaces with a DCE to gain access to the phone company’s network. DTEDCE PC Router Modem CSU/DSU
CISCO NETWORKING ACADEMY DTEs and DCEs Router to CSU/DSU connection: –Serial port on router –V.35 port on CSU/DSU –V.35 Cable between CSU/DSU DCE DTE
CISCO NETWORKING ACADEMY phone company digital line CSU/DSU DTEs and DCEs Typical WAN configuration: CSU/DSU DCE Hayward Oakland DTE
CISCO NETWORKING ACADEMY DTEs and DCEs Our Lab’s unusual configuration: No digital phone lines, no CSU/DSUs. The WAN is simulated in our lab. Therefore, one router must play the DCE role - very unusual. Serial interface V.35 Cables Back-to-Back Hayward Oakland DTEDCE
CISCO NETWORKING ACADEMY WAN: Layer 2 WAN data-link protocols describe how frames are carried between systems on a single data path. –point-to-point –multipoint –multiaccess (Frame Relay)
CISCO NETWORKING ACADEMY WAN at Layer 2 dedicated switched
CISCO NETWORKING ACADEMY Data Link Layer: WAN Protocols
CISCO NETWORKING ACADEMY HDLC High-level Data Link Control –usually used when connecting one router directly to another (point-to-point) –also is capable of supporting multipoint connections (multiple point-to-point) (test question) –requires dedicated private digital lines –HDLC implementations are proprietary –Cisco serial interfaces default to HDLC
CISCO NETWORKING ACADEMY PPP Point-to-Point Protocol –used in point-to-point dedicated connections –used by routers over dedicated digital lines POTS users over dial-up (circuit switched) lines (Windows & Mac dial-up networking) –descendant of SLIP –open standard (RFC 1661) –allows authentication (PAP, CHAP) –allows multiple layer 3 protocols
CISCO NETWORKING ACADEMY Frame Relay –packet switched –private dedicated digital lines not required –one physical link can handle multiple logical links - (multiaccess) –descendant of X.25 –simplified frame (no error correction) relies on today’s superior data links –very fast –cheap: pay for what you use
CISCO NETWORKING ACADEMY ISDN Integrated Services Digital Network –circuit switched - (over digital voice/data line) –designed to transmit voice, data, video over existing phone lines –used primarily for remote access via modems –not very fast (especially BRI - 128 Kbps) –may disappear with the emergence of cable modems and DSL
CISCO NETWORKING ACADEMY WAN Technology Options