Newbie networking question here...

Do ISPs generally use the same link layer protocols (Ethernet, ARP to relate to network layer 3, etc.) that are used on LANs? In school I learned in some detail about Ethernet, how hosts ARP for the MAC address of another host, wrap the IP packets in Ethernet frames that travel through switches to the correct host, and so on. But once the IP packets leave a LAN I'm not too sure what happens.

I googled around, and came across things like PPP and PPPoE, but am not too sure I understand their significance. Are these like "Ethernet" (layer 2 protocol) for networks beyond LANs. On ISPs' networks, do they have a bunch of routers connected to a switch that all use ARP-like protocols do find each others MAC and send the packets?

I guess I'm looking for a clearer picture of what happens to my packets as they become encapsulated at the link layer, from the time it leaves my router to the time they end up at the destination network. I'm not asking about routing protocols/algorithms and stuff like that, but rather the link layer stuff. Any resources for further reading would be much appreciated also.

  • Not sure whether or not this would be on topic here. Roughly, no, not the same, but you can find some logical similarities like using MACs for frame ID. It would depend on the ISP, but if you want an intro to the topic, try looking up DOCSIS tech specs and guides, which would be what many cable companies use to provide internet.
    – Radhil
    Dec 11, 2015 at 19:41

2 Answers 2


Some layer-2 protocols use MAC addresses, and some don't. For example, PPP uses something different. Your router will encapsulate in the layer-2 protocol which is used on the link to the ISP, and that link may or may not use MAC addresses.

Unless you work for the ISP you can't know what a particular ISP does internally because there are many different ways that ISPs do things.

Resource recommendations are off-topic, so we can't help with reading resources.


Routers are comes on layer 3 which is the network layer that layer having some specialized protocol to connect each other(rip, ospf, and bgp.. Etc) , isp network has own hierarchy model, all isp are connected together with some policies though your packet gets encapsulate network layer header it I'll deliver on the correct layer 3.again it's de capsules sends packet to data link layer and finally its delivers to the destination host using Mac address.. enter image description here

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