add HTTP->PHY draft

http_to_phy.md

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+# So You Want to Make Internet Lasagna?
+
+## The Recipe
+
+| Communication | Discovery |
+| ------------- | --------- |
+| HTTP          |           |
+| TCP           | DNS       |
+| IP            | DHCP      |
+| Ethernet      | ARP       |
+
+<br>
+
+## Starting from HTTP
+
+HTTP (Hypertext Transfer Protocol), is what browsers use talk to web servers to send and receive web pages,
+do basic transactions, like sending a form from your browser to the server, requesting some database 
+information for display, or updating your account settings.
+
+Good learning resources for HTTP:
+- https://developer.mozilla.org/en-US/docs/Web/HTTP/Overview
+- https://developer.mozilla.org/en-US/docs/Web/HTTP/Messages#http_requests
+
+<-- Link to expanded, less curated library of topical info -->  
+<-- Branch into REST/GraphQL here -->
+
+## Diving into the meat and potatoes with TCP and IP
+
+HTTP responses and requests are a sequence of bytes, chunked up and sent in packets, 
+often through a protocol called TCP (Transmission Control Protocol). TCP provides a few
+nice guarantees which make writing reliable network code a little easier. 
+When a message gets sent via TCP, it ensures that chunks get passed to the application
+in order. If packets get dropped along the way, or arrive out of order, TCP handles resending
+ missed packets and buffering before the application gets the packet, until order can be restored.
+
+Good learning resources for TCP:
+- https://www.youtube.com/watch?v=4IMc3CaMhyY
+- https://www.youtube.com/watch?v=F27PLin3TV0
+- https://www.youtube.com/watch?v=IP-rGJKSZ3s
+
+<-- Link to expanded, less curated library of topical info -->  
+<-- Branch into UDP, QUIC, TLS, etc. via link here -->
+
+IP (Internet Protocol) sits directly below TCP, but often gets bundled together. IP is a
+small header attached right above the protocol header, and contains important information,
+like where the packet is coming from, and where the packet needs to go, so network hardware
+along the way can route it from A->B to reach it's destination
+
+Good learning resources for IP:
+- https://www.youtube.com/watch?v=rPoalUa4m8E
+- https://www.youtube.com/watch?v=VWJ8GmYnjTs
+
+<-- Link to expanded, less curated library of topical info -->  
+<-- Branch into TUN via link here -->
+
+<br>
+
+## Making it Tractable
+
+So, how do you take all that theory and make it stick? How do you send a real packet yourself?
+Some good outlets for exercises:
+- https://beej.us/guide/bgnet/html/
+- https://github.com/shuveb/zerohttpd
+
+## Taking the Real Plunge
+
+Ok, so you've got some of the basics down, and you're ready for some serious spelunking?
+Let's talk Ethernet and PHY.
+- https://www.youtube.com/watch?v=XaGXPObx2Gs&list=PLowKtXNTBypH19whXTVoG3oKSuOcw_XeW
+
+<br>
+
+## Buttoning up with Discovery Protocols
+
+So, how does the computer get an IP address? How do we know what the router's IP is?
+How do find the IP address of "https://handmade.network/" so we can send it a request?
+Discovery protocols to the rescue!
+
+## Putting on the ARP Goggles
+
+At the bottom of the protocol stack, ARP (Address Resolution Protocol) is how your computer
+reaches out and understands the local network it lives on. When an ethernet cable gets plugged into
+your computer, it broadcasts an ARP packet, gathering responses to know how to address
+messages directly to specific local machines. The initial ARP packet contains the MAC
+address of the computer sending, and responses from all machines that want to be discovered
+get fired back with their MAC addresses in tow.
+
+Good learning resources for ARP:
+- https://www.saminiir.com/lets-code-tcp-ip-stack-1-ethernet-arp/
+
+<-- Link to expanded, less curated library of topical info -->  
+<-- Branch into TAP via link here -->
+
+## Finding the Mailman with DHCP
+
+DHCP sits near the middle, but is incredibly important. When you want to send a packet to a network
+beyond your own, somebody has to deliver that packet. To find the packet post office, your computer
+broadcasts a DHCP discover packet, and collects IP offers from all DHCP servers on the network.
+At that point, typically it will fire off a request for the first IP it recieves, and get a
+confirmation or denial for that request. DHCP acks typically also contain the IP address of the router,
+the local DNS server, and more
+
+Good learning resources for DHCP:
+- https://docs.microsoft.com/en-us/windows-server/networking/technologies/dhcp/dhcp-top
+
+<-- Link to expanded, less curated library of topical info -->  
+<-- Branch into PXE Booting via link here -->
+
+## Using the DNS Phonebook
+
+DNS sits at the top acting as a final, important, icing on the cake. The job of DNS is primarily to
+provide lookup services for domain names. To resolve "https://handmade.network/" into an IP address
+so we can send it an HTTP request, we send a lookup request to the DNS server, and it will do the requisite
+forwarding until it either has an IP address to send back, or fails.
+
+Good learning resources for DNS:
+- https://www.cloudflare.com/learning/dns/what-is-dns/
+
+<-- Link to expanded, less curated library of topical info -->  
+<-- Branch into DNS over HTTPS / DNS Lookup Security via link here -->
+
+## Fun Tangents
+
+- Network Bridging
+- DHCP Robin Hood
+- PXE Booting
+- SMTP
+- Routing and Switching
+- BGP
+- TLS/SSL
+- Inspection and Testing Tools: tcpdump, wireshark, netcat and more