next »

[Hijpo]

Right, so iv been onto an etutor for the course im doing.  I want to know how A gets B's IP address in order to ARP it.

So she tried to explain it to me by way of a postman pat story.
Posty has a letter, he goes into an estate of old and new houses. He knows the address of the old ones so he goes to each of the new ones until he reaches the right one. To which i replied but how does he know what house to go to. She said the address is on the envelope, or in network terms encoded in the packet. I said, right thats what i do understand, what my question is "where did the address on the envelope come from in the first place?"

i then gave her my example. Say there are 7 random people sitting in a room. I walk in and say "i want to talk to barry". so barry stands up and says "im barry". Now myquestion is how do i know there is someone in the room called barry?


She said that i was going very deep into the TCP/IP protocols and that i wasnt expected to have that level of understanding for the exam.

[Stevie]

You want to know how a pc knows the ip address in the first place right?

Simple, you provide it or a dns server provides it.

You open up ping to ping a pc by ip, you provide the ip address.
You ping the pc by name and a dns server resolves that name to an ip and gives it to you.
You map a drive to a remote system you need to know the name of the system right?

Arp is about resolving an ip you already know to a mac address you don't.

Your Barry analogy doesn't really work here. Any device on a network that wants to talk to another device needs an ip address to work with and almost always learned from dns or hard coded into the application you're working with.

[Wooster]

Think about it this way: How did you know you wanted to talk to someone called Barry in that room?
You'd have asked someone or consulted a directory, and you wouldn't have been there at all unless you had a reason for it.

Say you set up you laptop in a new office and need to print something on a network printer. Your laptop will have no idea if there even is an available printer until it starts asking around (Search For Printers) and the Network Printers start sticking their hands in the air.

IRL Say you have an accident while on holiday. You don't know where the local hospital is or any of the doctors names until you call the emergency services, or someone with local knowledge takes you there, but accessing that resource is easier and faster once the relationship is established.

Same goes with the internet.
You don't know a particular page even exists to begin with until you ask a search engine to have a look at the pages it has prior knowledge of, it sorts out whether they are relevant or not, and gives you a list of URL's (more correctly URI's)  to choose from. Once you open the URL, the page is cached locally (a relationship is established on your computer and in your mind if you remember the URL (which is why we use URL's)) and you don't have to go to so much trouble the next time.

[Hijpo]

Exactly lads, i knew there was something providing you with the address's i just didnt know what it was thats why i cooked up the barry story 

thank you thank you thank you