RFC (Request for Comments)
The Request For Comments (RFC) are a collection of documents about various topics of the Internet, containing protocol specifications and alike.
It is important to understand that not all RFC documents are protocol specifications; the main categories are: Informational, Proposed Standard, Draft Standard, Standard, Experimental, Best Current Practice and For Your Information. RFC documents may also extend or update a given other RFC document, or make it obsolete. There are even April 1st jokes, which can easily be recognized by the date of publication and the often odd title and abstract.
You will find all RFC documents at the Internet Engineering Task Force (IETF) RFC repository. An useful address is The RFC Editor where you can search for specific keywords in order to find relevant RFC documents (and even Internet Drafts, which are drafted potential RFC documents).
RFC's are typically referenced by their number, so you might see something like "the TCP RFC 793" or only "RFC 793" in a document.
Various official assignments of protocol numbers and other properties can be found at the Internet Assigned Numbers Authority (IANA)'s Protocol Numbers and Assignment Services page. This information used to be maintained in the Assigned Numbers RFC. but the last of those was RFC 1700, which is now outdated.
RFC 1166 has an out-of-date list of IP address ranges. To find out to whom an IP address belongs, you can use various "WHOIS" services:
Latin America and Caribbean: Latin American and Caribbean Internet Addresses Registry (LACNIC) WHOIS site.
Famous RFC examples
The following will list some famous RFC's related to the common InternetProtocolFamily:
ARP RFC 826 "An Ethernet Address Resolution Protocol"
BOOTP RFC 951 "BOOTSTRAP PROTOCOL (BOOTP)"
DHCP RFC 2131 "Dynamic Host Configuration Protocol"
DNS RFC 1034,1035 "DOMAIN NAMES"
FTP RFC 959 "FILE TRANSFER PROTOCOL (FTP)"
HTTP RFC 2068 "Hypertext Transfer Protocol -- HTTP/1.1"
ICMP RFC 792 "INTERNET CONTROL MESSAGE PROTOCOL"
IPv4 RFC 791 "INTERNET PROTOCOL"
NetBIOS RFC 1001,1002 "NetBIOS SERVICE ON A TCP/UDP TRANSPORT"
NFS RFC 1014,1057,1094,1813 "XDR/SUN-RPC/NFS/NFSv3"
NNTP RFC 977 "Network News Transfer Protocol"
PPP RFC 1661 "The Point-to-Point Protocol (PPP)"
SMTP RFC 821,822 "SIMPLE MAIL TRANSFER PROTOCOL"
UDP RFC 768 "User Datagram Protocol"
TCP RFC 793 "TRANSMISSION CONTROL PROTOCOL"
You will find more RFC references at the specific protocol pages.