IP over MPLS vs Ethernet over MPLS?

FrankGuthrie

I was watching the following video:
ATM, Frame Relay, and MPLS - CompTIA Network+ N10-006 - 1.4 - YouTube

And at 3:25 I see the following on the slide:
IP Packets, ATM cells, Ethernet Frames


Doesn't a IP packet have a Layer 2 Ethernet header. So what is he trying to say. What does he try to make clear by separating IP and Ethernet? Doesn't the fact that he applies IP tell you that is carried by Ethernet at Layer 2?

OctalDump

That's the lovely thing about multi-layered networking: you can mix and match different layers. So IP can run over ethernet or ATM or half a dozen different wireless standards or tunnelled inside something else, including itself. And ethernet can run on a bunch of different copper cables or a bunch of different optical cables. And on top of ethernet, you still have other options besides IP, like Fibre Channel IPX/SPX or the ancient DECnet and AppleTalk.

And yeah, MPLS can carry a bunch of different things, hence the name. The idea is to give an abstraction so that poor network engineers aren't spending all their time and effort adapting between different layer 2 protocols as data moves across complex, heterogenous networks.

FrankGuthrie

So my thinking of IP and Ethernet being inseparable is wrong. ATM as layer 2 can be used while IP is running at Layer 3, correct?

networker050184

Yes, IP packets can be carried in ATM cells.

james43026

OctalDump wrote: »

That's the lovely thing about multi-layered networking: you can mix and match different layers. So IP can run over ethernet or ATM or half a dozen different wireless standards or tunnelled inside something else, including itself. And ethernet can run on a bunch of different copper cables or a bunch of different optical cables. And on top of ethernet, you still have other options besides IP, like Fibre Channel IPX/SPX or the ancient DECnet and AppleTalk.

And yeah, MPLS can carry a bunch of different things, hence the name. The idea is to give an abstraction so that poor network engineers aren't spending all their time and effort adapting between different layer 2 protocols as data moves across complex, heterogenous networks.

Octaldump hit the nail on the head with this post.

FrankGuthrie

Looking at the uploaded picture, We see Ether/IP is being used and i think this has been used in that combo (ethernet/IP) combination for 30-40 years now, but what happens when traffic needs to traverse the WAN. You used to not have ethernet capabilities on the WAN, right??? So whenever the packer went over the WAN, was the Ethernet header removed and replaced by ant ATM header??? Or was the Ethernet header encapsulated into the ATM header together with the IP header:


How does this work. Can anyone describe this to me, maybe with an illustration??

If we have to 2 pc's in two different locations, how will the packet format look like when it moves from left to right:

reload@

You have to think about where the layer 2 information is relevant. Even if it's all Ethernet, do you think that the layer 2 information would stay the same along the way?

If you pinged google.com, do you think your PC would know the mac address for Google's web server?

FrankGuthrie

reload@ wrote: »

You have to think about where the layer 2 information is relevant. Even if it's all Ethernet, do you think that the layer 2 information would stay the same along the way?

If you pinged google.com, do you think your PC would know the mac address for Google's web server?

Wel that's where my doubt is. No it does not know the MAC address of the google webserver, but it wil use the MAC address of the gateway/Router, but when it leaves the LAN, i think it' s a different story, as IP wil take over and Ethernet/MAC addressing is less important. But I might be wrong.

networker050184

Correct. L2 is local link significant. Just because one side uses Ethernet it doesn't mean the other can't use frame relay or something else. The IP packet is delivered regardless. These days it will likely be Ethernet end to end though.

FrankGuthrie

Ok, so nowadays it is going to Ethernet through the whole path, but it did not used to be. so when ever the packet left the network, the packet was either changed or encapsulated in another technology correct?

networker050184

Packets aren't changed. The L2 headers put on for each link do. Even if it's all Ethernet the L2 header changes.

FrankGuthrie

But if I would send the packet lets say over ISDN, then we would be talking about Layer 1, so the packet would not be changed, but it would only be the Layer 1 media which would be different, correct?

networker050184

ISDN has it's own L2 headers as well.

FrankGuthrie

Ah ok,

Looking at the frame below


The data portion would house the following:
IP | TCP | Data

Correct?

FrankGuthrie

Anyone who can verify me above comment.

networker050184

The data portion is whatever you are transporting in the L2 frame. Most likely an IP packet yes.

FrankGuthrie

Thank you for the confirmation, I think I'm getting the grasp of looking at the difference at L1/L2 when speaking about difderen technologies like ISDN. SONET, MPLS etc...