Why Do We Need IP Addresses? - Computerphile

A Computerphile viewer asked the question: Why do we need IP addresses when every network interface has its own Mac address? - I put it to Dr Richard Mortier; University Lecturer in the Computer Laboratory at the University of Cambridge

This video was filmed and edited by Sean Riley.

[devluz]

The concept is actually simpler than it sounds. It is just quite hard to find a really good explanation. Here is my try (work in progress):

MAC address is a unique name for each network card. You can use it to address one device in a crowd of devices so everyone knows who you are talking to. It is like standing in a group of 20 people and shout a name like JIMMY FUCK YOU. Everyone hears the message but only jimmy will be pissed off because it is clear you mean him ...

This system doesn't work in big networks like the internet though as you can not simply shout something every computer in the whole internet receives ... thus they need an address system there.

IP addresses are used for that address system. Instead just a name it uses a hierarchy like a post system (e.g. like Country, City, Street name, Number just more suitable for computers to understand). So instead of shouting around you write a neat post card add jimmys address and the content "FUCK YOU" and then you send it.

[pjvenda]

This is very cool and it's a joy to listen to Dr.Mortier who definitely knows very well what he's talking about.

However I believe an important point has been missed - which is that MAC is a local addressing scheme of certain technologies, such as ethernet and wireless 802.11. IP on the other hand is meant to be agnostic of the technology used to transfer data across networks that could be interconnected using multiple different technologies. Both addressing models exist at different layers or abstraction levels.

For example a 3G radio could be used by a device to implement a TCP/IP stack which means it understands and can be addressed by an IP but locally it may not have a MAC address because it uses a different addressing scheme. Even if I'm wrong about 3G specifically there are cases in which MAC addresses do not apply, such as direct dial up connections, ppp over atm, etc.

[TaurusWD]

I liked the analogy. My favorite one that I use when teaching people is to relate it to cars. MAC = VIN, and IP = Parking Space Assignment. IP subnets are then related to parking lots and how using your parking space number from Lot A may not work for Lot B, and ideally the entire time wherever you drive your car it still has the same MAC/VIN. :)

[Douglas_Gillette]

A 32 bit IPv4 address has structure. It is hierarchical. This is super important in understanding how packet switched networks function and how routing functions.

[criskity]

If PCs have Mac addresses, why don't Macs have PC addresses?

[vyli]

great video, I enjoy Dr. Mortier's explanations on networking, because I'm lacking in background knowledge on networking a lot and these videos are helping me to learn more.

[kirby]

To really explain, you'd need to talk about Layer 2 vs Layer 3 networking... but I guess this gets at least a little bit of the information across.

[UltimatePerfection]

Do an episode on decentralized web solutions such as ipfs and zeronet.

[jndominica]

I like how they sometimes trace a criminal from a police station on TV, and he appears to be operating on their own local network.

Here it used to be that phone numbers had the same structure to them, where a phone had a fixed known prefix of a city and an area in it of about 2-5 km in it (8000 or so phone number space). Only in the recent couple years a new regulation was put into place where customer was given a "right" to keep is phone number as he moves to another location. That seemed quite impractical to me.

[stonent]

MAC addresses are organized by the vendor that made the card and then a unique card within that vendor's grouping. So there is no logical organization to a group of them across a huge network that would be useful. IP addresses are organized by an addressing scheme that gets progressively more specific. Much more like an envelope address. You would first put all of the mail going to the same country in a pile and send it to that country. Then you'd sort that by the and then send them on their way. Then City, neighborhood, street, and finally house. It's the router's job to look at an IP and determine the fastest or most reliable path to its destination.

[tipomartins]

Studying Computer Science at University of MInho in Portugal. I can only hope to have my masters at University of Nottingham.

[shadowworks]

I have on queation is it posible to have a working phone of pc whithout a mac adres and stil acces the internet ?

[Fearlsz]

Why Do We Need IP Addresses? So we can get ddossed

[salerio]

that was a terrible description of IP against MAC addresses. Please do it again. Sequential MAC addresses could be on different continents never mind next door streets. This is important and needs explaining, if you could also do Layer 3 vs Layer 4 switching/routing it would also help. Ta.

[nandkudasai]

nice explanation.
so it goes to "addressing"

[bakjamgaiass]

Haha. Good to see Dr. Mortier recycling that old school printer paper

[GeoNeilUK]

Considering Mr Robot (great users of the astu command) used an IP address containing a number over 255, I'd guess the malformed IP addreses in TV programmes and films are deliberate.

[Lion_McLionhead]

MAC addresses could have been structured the same as IP addresses to allow fast lookup tables on a global network. They're a legacy part of IPV4 no-one ever bothered to remove. Newer protocols like IPV6 & Bluetooth only use 1 address layer, consolidating the manufacturer data with the routing information into 1 big address.

[bootblacking]

Where the hell do you find that old-ass printer paper in 2015?

[again]

Well i didn't understand what is the difference between ip and mac