Semester 2 - Review
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Routers
4 Basic Components
CPU
Memory
DRAM/RAM - Stores ARP tables, running config, packet buffering, lost when powered off
NVRAM - Stores start-config, is not lost when powered off
Flash - erasable, reprogrammable, contains IOS
ROM - POST, bootstrap, limited IOS copy
Interfaces
Console port - initial configuration setup
Auxiliary Port - for modem connection into the router
Network ports - Ethernet - AUI, FDDI, Token Ring: Lan connections
Serial ports - V.35, RS-232, ISDN: WAN connections
Bus
This is what connects all the devices to each other. Just like in a PC
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Functions
Best path selections
Dynamic Routing
Address representation of topologies
Broadcast filtering
Segment large LAN's
Connect LAN's to LAN's, LAN's to WAN's
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WAN Protocols
Defined by the following
Physical Layer Standards
EIA/TIA-232, EIA/TIA-449, V.24, V.35, X.21, G.703, EIA-530
DTE (Data Terminal Equipment) - attached device(router), DCE (Data Circuit Equipment) - service provider equipment (CSU/DSU)
HDLC - High-Level Data Link Control
Supports point to point AND mulitpoint, minimal overhead
Frame Relay
High quality digital facilities, no error correction
Packet Switched
Can send Layer 2 information faster than any other WAN protocol
PPP - Point to Point
Defined in RFC 1661 by IETF
SDLC - Simple Data Link Control Protocol
Used by SNA, replaced by HDLC
SLIP - Serial Line Interface Protocol
Popular Layer 2 protocol, used with IP, being replaced by PPP
LAPB - Link Access Procedure Balanced
Layer 2 protocol, uses X.25, extensive error correction
LAPD - Link Access Procedure D-channel
ISDN D-channel, Layer 2 protocol for signaling and call setup, circuit switched
LAPF - Link Access Procedure Frame
Similar to LAPD, frame mode bearer service used with Frame Relay
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