Personal fav….pin 22, think about a computer using a modem to contact another modem, how does a computer working with a modem know how to make a phone call, essentially this I what you do make a phone call to send data, …reminisce BNS got this new tech, mainframe comp and they had a telephone and fit into a device attached to a computer, u pick up the phone and heard this noise and put it to the ……acoustic coupler, a company called haze who made acoustic couplers, though themselves why not put a computer chip that can recognize basic basic commands… and they did, they invented the modern modem, 70% of people today, they will discover two things they are using RS-232 they are using Haze Compatible instructions<-- all the rage, haze instructions all start with AT what happens OS software in ur computer understands haze commands if you try to call someone it will send a attention command to ur modem, you want to modem to dial
AT [D]pulse1231321
Something called tone dialling and pulse dialling, lets say u wants pulse the os in the software in the old days you had to install the isp number the modem will recognize the above and the modem will send out a ringing sound to the DCE and the dce hears the ring ring sounds the modem has to ask the computer if its ok to answer the sound, the modem actually asked if it was ok to answer an incoming call, it will do so through
PIN22 ring control
It will signal down DTR, and it will know to answer the phone, if you were an isp then you would be great cause you want to answer incoming calls as fast as possible cause the isp always wanted auto answer, some modem automatically answer ATA
How many functions do we got,
that the half duplex, for the 70% people of the world still using modems its no longer half duplex, no phone company offers half duplex any more everything is full-duplex, what is full-duplex, send and receive at the same time.
Theirs is flow control one of the great instincts of control data is getting to the destination with out loosing data and getting their error free
Any activity that prevents the loss of data ----FLOW CONTROL
Look at this your ISP is sending stuff to you stuff is going to the modem, the way file transer programs work, data set through the serial port and they are stored in memory the os knows that the computer memory is getting used up sooner or later, pretend you want to download a file and write to ur floppy disk…floppies are slow…sooner or later the memory is getting used up and needs to write to disk, what happens to incoming data, it could get lost Rs-232….Request to send and Control send to flow control the data, if the computer knows not to send data it will stop sending pulses request send, the modem now goes it will not send data and will send signals the other modems to stop sending data, now that the floppy writing has finished it will then tell its okay to send, if the modem detects the line is busy it can send signals using clear to send, ……request send clear to send is used to flow control purpose/--this is what we have to tell him
Look on the internet RS-232 despite the fact is has their RS-232 Tutorial, no more physical layer stuff …Analog and Digital physical layer considerations Multiplex Interfaces physical layer…..start talking about protocols….cause we love protocols
First protocol we are going to talk about IP we will talk about IP next Friday, what we are talking about now is our first opportunity to get some marks, which will be next week, at least three marks, three percent of the course marks can be gained next week if you can go to back it has two configurations
R1 has a config
R2 has a config
You simplay type in the config for both routers hook the routers up rogether using serial cables S1 S0 hand also hook up a work station to the Ethernet port of the routers if he can ping form one to the other your up three percent.
What you do when your doing a config, you provide an ip addresss to that serial interfaces you provide the ip address to both Ethernet ports, what is an IP address,
Where do they com from, IP 4 bits long , they have to be unique, there are different classes, and the ip address is two address one the network and the other part identifies the computer on that network. Theirs millions of networks in the world, Seneca college has dozens of networks. Each network has a network identifier and a component that identifies the computer in the network
What are the class? Why were the classes developed, it was an accident, back in the beginning of the internet when their was a few organizations using this, if you examine the fundamental protocols the internet uses, its actually tremendously inefficient, the guys who invented ip were computer programmers they decided arbitrarily to have a 4 byte address, they decided to use the 1st byte to be a network identifier because about a dozen people on the network, they reserved these bits, the other were all host bits, on individual networks, Network one would be 0000001, 00000010, 4 the internet grew, 256 networks, they sat down and said lets change this lets make the old way class way, but have a new scheme have a range of addresses, and make B
0-127 A
B 1000000 - 128
1011111 – 191
Host 64 k
IEEE class C
1100000 - 192
1101111 – 223\
255-32
Static ip in the work station
Subnetting, why do we have subnets?
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