Timeline for One Missed Point in Data Link Layer Concept?
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 20, 2021 at 14:46 | comment | added | Ron Trunk | Let us continue this discussion in chat. | |
| Oct 20, 2021 at 14:44 | comment | added | Effie | @RonTrunk this is the problem! DL layer is supposed to be link-local, and network layer is supposed to interconnect links. | |
| Oct 20, 2021 at 14:02 | comment | added | Ron Trunk | @Effie The DL layer is designed to operate independently of any network layer. While it's true that 99.9% of today's use is IP, that wasn't always the case. DL could be used by itself, and was designed for that case. | |
| Oct 20, 2021 at 13:58 | comment | added | Effie | @RonTrunk well, i am assuming that there is a network layer on top of layer 2. I know, there are enough protocols that communicate, let's call it "link-locally", and then they will use source addresses for what you describe. But they are in most cases kinda network control protocols in a sense that they are there to establish connectivity or to be able to send packets. This statement does not apply to application payload in general. | |
| Oct 20, 2021 at 13:46 | comment | added | Ron Trunk | @Effie You're assuming an IP stack. DL layer can (and does) operate independently. | |
| Oct 20, 2021 at 13:20 | comment | added | Effie | Actually, how exactly do you fill ARP cache from receiver frames? you can only do it if the sender IP is on your network, so the only system that can do it is the next router of the sender's host. Then having source address for the next sender reply is just false in general... | |
| Oct 20, 2021 at 13:16 | comment | added | Effie | yes, but usually, receiver needs to know "identity" of the sender, which is not the mac address, of the last sending hop. And filling ARP cache is an optimization, it is not necessary. | |
| Oct 20, 2021 at 12:09 | comment | added | Ron Trunk | I disagree. There is an (perhaps unstated) assumption that 2-way communication is taking place, so the receiver needs to know who to reply to. Also, the receiver needs to know who sent the message so it can distinguish between several received messages. | |
| Oct 20, 2021 at 11:50 | comment | added | JFL | Thanks , bad habit to think mainly about wired Ethernet. I slightly edited my answer but feel free to provide an additional answer (or edit mine if you wish) | |
| Oct 20, 2021 at 11:49 | history | edited | JFL | CC BY-SA 4.0 |
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| Oct 20, 2021 at 11:49 | comment | added | Zac67♦ | Exactly - the source MAC address is used for MAC bridge learning and little else. "Avoiding an unnecessary ARP lookup" might create security problems, so I don't think this is widely used. | |
| Oct 20, 2021 at 10:55 | comment | added | Effie | layer 2 can have notion of connection or layer message, it depends on layer 2. Most wireless layer 2 have notions of ACKs. | |
| Oct 20, 2021 at 10:52 | history | answered | JFL | CC BY-SA 4.0 |