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Gateway : this device is placed at a network node and interfaces with another network that uses different protocols. It works on  OSI layers 4 to 7 . Router : a specialized network device that determines the next network point to which it can forward a data packet towards the ultimate destination of the packet. Unlike a gateway, it cannot interface different protocols. It works on  OSI layer 3 . Switch : a device that allocates traffic from one network segment to certain lines (intended destination(s)) which connect the segment to another network segment. Unlike a  hub , a switch splits the network traffic and sends it to different destinations rather than to all systems on the network. It works on  OSI layer 2 . Bridge : a device that connects multiple  network segments  along the  data link layer . It works on  OSI layer 2 . Hub : a device that connects multiple Ethernet segments, making them act as a single segment. When using a hub, ev...

Differentiate between types Frame Relay High performance Physical & Data link levels Designed for ISDN Error correction is for higher levels Connection oriented  PVC's Frame Relay VCis 2x DTE with packet switched network inbetween, eah VC is identified by a Data Link Connection Identifier (DCLI) ISDN - Integrated Services Digital Network Physical, Data Link, Network, Transport Layers set of comms protocols HDLC - ISO standard Data Link Layer, bit based for sync. serial links High Level Data Link control Cisco HDLC Won't communicate with any other vendor's PPP Async or Sync Uses Link Control Protocol to build data link connections Compression CHAP / PAP authentication Uses NCP to support IPX, IP, Appletalk, Decnet etc. Frame Relay Terms CO - Central Office CPE - Customer Premise Equipment DCE DTE - typically routers DLCI demarc - Termination point of service provider's cable PSE - packet switch exchange PVC ...

OSI 7 layer model Application File, Print, database, apps,web Presentation Encryption, compression, translations, ebdic etc. Session Dialog control - nfs, sql, rpc , Connection establishment, data transfer, connection release Transport End to end connection, Flow control, Data integrity, Retransmissions Segments re-ordered before delivery, Make / tear down virtual circuits Network Routing , Map of network (logical) Data Link Framing Ensures messages delivered to correct device MAC - Media Access Control Framing with header & trailer.  contains MAC address of source & destination Media Access - method of communicating with Physical medium Logical Topology - eg Star shaped "ring" in TR error detection LLC - Logical Link Control Optional Flow control with stop/start codes error correction Destination Service Access Point (DSAP) and Source SAP allow upper-layers to work over different LANs by providing comms between Netw...

Cisco Certified Network Associate (CCNA) Exam Code No: 640 – 802 Chapters Routing Protocol             Static Routing             Default Routing             Dynamic Routing                         RIP                         RIPv2                         IGRP                         EIGRP          ...