Lecture

Networking Lesson Plan Week 9 Addendum


WAN’s


The connection of multiple LAN’s together forms what has been named Wide Area Network.(WAN). The WAN is also known as the Internet or World Wide Web. In reality, the Internet is a collection of smaller WAN’s. They are connected by a backbone ring of connectivity that connects 14 major portal sites. This connectivity is at 148OC with more speed planned in the future. These 14 sites use IPv6 for its addressing.

Most of us use a somewhat slower connectivity speed that the backbone. Of course, the WAN’s must accommodate multiple (many thousands if not millions) of users simultaneously.


Modems


Modem comes from the two terms -  Modulate and demodulate

A modem connects your computer to an ISP that connects to the WAN via a telephone connection.

Modems use several different command sets to establish communication. Some of the more common command sets are:


V series  Standards that cover today’s modems, with speeds up to 56 Kbps. (could be 64 but US Govt required the use of one bit – in US only sends 7 bits and stop bit instead of 8 data bits.


Hayes-Compatible Standards  The set of transmission signals, commands, used originally by Hayes modems for exchanging status information, such as readiness to send or receive.


Example command line strings are:

AT&F – loads factory default settings

ATSO – answer on first ring

ATATCHD3 – sets up DTR

ATE0 – sets up echo off

ATMO – turns off audio output


AT&FS0=1+c1+d2+k3+q9+w at = attention, FS0 means first ring, c1 means carrier detect, D2 means Data Terminal Ready, K3 means use hardware flow control, and Q9 refers to the type of compression, and W means write it to memory.


Other types of modems available include Cable modems, ISDN modems, and DSL modems.


Modems of all types communicate to the WAN through the phone company. Nowadays they call the phone company by another name, common carrier. It used to be called POTS which stands for Plain Old Telephone Service.

Uses RJ 11 Connectors and 2 pair cable – color code of cable is red, green black, yellow

First phone uses red, green

Second phone uses black, yellow

Old system used black, yellow to carry ring tone (48 volts)




POTS uses the following protocols among many others


Basic Rate Interface (BRI)  A form of ISDN that is typical in home use. There are two B (bearer) channels that carry data at the rate of 64 Kbps


and


Primary Rate Interface (PRI)  A form of ISDN that is generally used to connect a company’s telephone network. The line is divided into many channels.


Common Carriers allow connectivity using one of two methods. They are dial-up networking (DUN)  A client service using regular telephone lines to connect to a network.


Virtual Private Network (VPN)  An alternative to using a dial-up network connection. Is a network connection between two computers. With a VPN, a remote user can securely access the internal network from a remote location. – This is a point to point connection.


The common carrier uses either a


circuit-switched network A network that creates a direct physical connection between the sender and receiver such as a T1, Fractional T1 (1.544 MBS), DSL, T2 (6.312 MBS), T3 (44.736 MBS), or T4 (274.76 MBS)


or a


packet switching network. A technology used to route an entire message from one system to another. That message is routed through intermediate (go-between) station and does not involve a direct physical connection between the sender and receiver.



Examples of packet switching include


X.25 derived from the original 1822, one wont see this very much anymore. 64 kbs but had error correction – uses a dial up PAD Packet Assembler/disassembler





Frame Relay – also old technology that one won’t see too often but terms used are still around a lot. Had no error checking and was not too reliable as a result.



ATM – Asynchronous Transfer Mode – packet size 53 bytes – uses cell switching runs at from 25 MBS to 155 MBS – uses multiplexes as shown





SONet – Synchronous Optical Network – uses the same format as token ring (uses a software packet called a token to pass permission to speak on the network). Uses speeds called OC1 54 MBS, OC2 155.5 MBS, OC3 622 MBS, and OC4 2.5GBS





Broadband ISDN – high speed dial up modem – eh


CATV – modem across the cable TV channel – pretty good – uses filters to separate data from TV signal on the cable.


SMDS – forget about – too expensive parts and wont find anywhere. But packet length is 7168 bytes – Switched Multimega bit Fata Service




Wireless WAN – runs on 2.4GBS – same as cell phone but uses radio frequencies.


Encapsulation – a method of keeping data safe and secure as it travels through the carriers facilities. Never has to be decoded and reassembled. This encapsulation treats the entire packet as if it were one package instead of individual bits.

Dedicated lines use PPP (HDLC and SLIP are the old kinds)

Most common is PPP – point to point protocol. – uses Network Control Protocol to encapsulate – derived from HDLC – uses authentication, compression, and multiple links

Circuit Switches channels use PPP and SLIP

Packet Switching Circuits use x.25, frame relay, or ATM – uses error control and correction – high overhead and not used much today.


NOTE: WAN costs are 80% of an IT budget nowadays.


Print this page – place your name on it and turn in to the instructor by Friday of this week Same day as the chapter test.