Why is IP addrssed used if MAC is there to make an endoint unique ?
sidd
Why is IP addrssed used if MAC is there to make an endoint unique ?
Thanks,
Siddharth
Walter Roberson
sidd <siddhar...@gmail.com> wrote:
>Why is IP addrssed used if MAC is there to make an endoint unique ?
MAC is only required to be unique per LAN.
MACs are organized by manufacturer, not by some kind of
logical connectivity. What mechanism do you propose to allow your
equipment where-ever to find an efficient path to my equipment
over here, when your equipment could turn out to have a MAC that is
just one digit different than mine, or your equipment could turn
out to have a MAC that is completely different from mine?
Barry Margolin
> Hi,
>
> Why is IP addrssed used if MAC is there to make an endoint unique ?
MAC addresses don't contain network location information that helps you
figure out how to get packets to the LAN that the endpoint is on.
It's like the reason we put addresses rather than social security
numbers on envelopes.
--
Barry Margolin, bar...@alum.mit.edu
Arlington, MA
*** PLEASE don't copy me on replies, I'll read them in the group ***
pk
> Hi,
>
> Why is IP addrssed used if MAC is there to make an endoint unique ?
Beyond the other very good reasons already given, there is also the fact
that MAC addresses are used only in certain kind of networks (eg ethernet).
There are data-lik technologies that do not use MAC addresses for physical
addressing.
David Schwartz
> Hi,
>
> Why is IP addrssed used if MAC is there to make an endoint unique ?
Knowing something unique about someone does not always help you find
them. Knowing their *location* in a way that makes sense for the
network you're using, on the other hand, is very useful.
MAC is a local address, like 'in my kitchen on the leftmost chair'.
It's great if you're in my house and need to find someone. It's not
helpful if you're in another city. IP address is more like a postal
address. It will get you to the right house from any city.
DS
Jim Logajan
> Why is IP addrssed used if MAC is there to make an endoint unique ?
Because historically not all network endpoints used Ethernet. A modem link
is a classic and common example where you can have an IP address endpoint
without having a MAXC address. In fact many point-to-point links did not
(and do not) have MAC addresses. Plus, there were other competing link
layer protocols that had their own address schemes back when the Internet
Protocol was designed.
Lastly, using MAC addresses requires dispensing with address subnets, which
help reduce the size of routing tables to manageable sizes and minimize
table update requirements.
Barry Margolin
<272c7971-b232-47e4...@k36g2000pri.googlegroups.com>,
David Schwartz <dav...@webmaster.com> wrote:
> MAC is a local address, like 'in my kitchen on the leftmost chair'.
> It's great if you're in my house and need to find someone. It's not
> helpful if you're in another city. IP address is more like a postal
> address. It will get you to the right house from any city.
Sorry, I already used that analogy a couple of days ago, you're going to
have to find your own.
Jim Logajan
> In article
> <272c7971-b232-47e4...@k36g2000pri.googlegroups.com>,
> David Schwartz <dav...@webmaster.com> wrote:
>
>> MAC is a local address, like 'in my kitchen on the leftmost chair'.
>> It's great if you're in my house and need to find someone. It's not
>> helpful if you're in another city. IP address is more like a postal
>> address. It will get you to the right house from any city.
>
> Sorry, I already used that analogy a couple of days ago, you're going to
> have to find your own.
Boy, it's a lucky thing that I decided not send the followup I was
composing earlier today that criticized that analogy. I would have been
insulting more than one person! ;-)
Um, wait a tick... !
Barry Margolin
Jim Logajan <Jam...@Lugoj.com> wrote:
I got an email reply the other day praising my analogy, and asking
permission to incorporate it into their site. I guess you can't please
everyone.