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Update 'selected/http_to_phy.md'

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cloin 2022-05-28 04:01:42 +00:00
parent 0da41431f0
commit ae1cfcfb19
1 changed files with 6 additions and 3 deletions
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selected/http_to_phy.md
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@ -161,10 +161,11 @@ Link speed negotiation
(intel) NUC with two (usb) NICs -- VMs that would tag traffic with VLAN.
Ethernet packet tagged with VLAN 1,
```
| 1 1 1 1 1 1 1 2 | | 2i 2o |
| 2 | | NUC |
| 2 | | |
```
layer 2 ethernet -- hamachi / layer 3 ip -- openvpn
@ -177,7 +178,7 @@ Routers are layer 3
Home "router" is a router / switch combo
Network Topology -- this is mostly outside my wheelhouse; infiniband/optics?
```
"crossover cable"
A B
TX ---\/--- TX
@ -187,17 +188,19 @@ RX ---/\--- RX
A B
TX -------- TX
RX -------- RX
```
Switch maintains an ethernet routing table, uses mac addresses to determine which ports need to be routed to other ports
TTL -- preventing packets from hopping forever on layer 3 connections, ICMP is a totally separate thing
ICMP -- https://en.wikipedia.org/wiki/Internet_Control_Message_Protocol
```
SEND CHEESEBURGER TO GOOGLE
A -> HR -> ISP -> | | | | -> GOOGLE
subnet 192.168.1.X
HR -> ISP | DESTINATION UNREACHABLE {ICMP 3} | TIME EXCEEDED {ICMP 11} TTL Expires
```
Blocking ICMP is messy, be careful!
https://en.wikipedia.org/wiki/Black_hole_(networking)