18-01-2013, 03:49 PM
ROUTER
[attachment=47573]
Introduction
WAN introduction and devices
MODEM technologies
Router Functions
Router Hardware
Internal components of a router
Router Function
Linking WANs and LANs
Interconnecting communication lines
Path determination and packet switching
Application of security rules
Protocol conversion (encapsulation)
E.g. HDLC, PPP etc.
Introduction to WANs
A wide area network (WAN) is a data communications network spanning a large geographic area such as a region, country or the entire planet
A WAN may interconnect LANs
May use microwave, satellite, fibre-optic, phone lines etc. to cover distances
WAN Devices
Switch connects PCs, servers etc. to a router
Ethernet cannot travel large distances so MODEM is used
MODEM terminates a data circuit – data circuit-terminating equipment (DCE)
Communication server allows many users access to a MODEM link
Use of MODEM in WANs
MODEM = Modulator and Demodulator
Translates between Ethernet and WAN technology and back again
Permits long distance communications
Router Operation
Layer 3 device
Accepts PDUs on incoming network
Examines PDU data
Makes decision(s) for next stage of PDU journey
May modify PDU contents (not payload)
Passes PDU on to outgoing network
Network Path Determination
Router accepts packet and views inside Network Layer header
IP address of destination carried in Network Layer header and other information
Destination IP address looked up in routing table
Packet passed to appropriate exit interface
Inside a Router
Router is a dedicated computer
Contains hardware found in most PCs
Does not have hard disk – Flash memory is used instead to hold IOS
NVRAM used to hold configuration files
DRAM used to hold routing tables, buffering, ARP cache etc
CPU, ROM and interfaces too
[attachment=47573]
Introduction
WAN introduction and devices
MODEM technologies
Router Functions
Router Hardware
Internal components of a router
Router Function
Linking WANs and LANs
Interconnecting communication lines
Path determination and packet switching
Application of security rules
Protocol conversion (encapsulation)
E.g. HDLC, PPP etc.
Introduction to WANs
A wide area network (WAN) is a data communications network spanning a large geographic area such as a region, country or the entire planet
A WAN may interconnect LANs
May use microwave, satellite, fibre-optic, phone lines etc. to cover distances
WAN Devices
Switch connects PCs, servers etc. to a router
Ethernet cannot travel large distances so MODEM is used
MODEM terminates a data circuit – data circuit-terminating equipment (DCE)
Communication server allows many users access to a MODEM link
Use of MODEM in WANs
MODEM = Modulator and Demodulator
Translates between Ethernet and WAN technology and back again
Permits long distance communications
Router Operation
Layer 3 device
Accepts PDUs on incoming network
Examines PDU data
Makes decision(s) for next stage of PDU journey
May modify PDU contents (not payload)
Passes PDU on to outgoing network
Network Path Determination
Router accepts packet and views inside Network Layer header
IP address of destination carried in Network Layer header and other information
Destination IP address looked up in routing table
Packet passed to appropriate exit interface
Inside a Router
Router is a dedicated computer
Contains hardware found in most PCs
Does not have hard disk – Flash memory is used instead to hold IOS
NVRAM used to hold configuration files
DRAM used to hold routing tables, buffering, ARP cache etc
CPU, ROM and interfaces too