Networking¶

DNS¶

DNS Zone is an administrative boundary that allows managing one or more domain and sub-domains.
- Each zone must have one primary name server and at least one secondary name server
Server Types
- Recursive Resolver: first server contacted by client for resolution, unless cached, asks root name server
- Root name server: directs to appropriate TLD name server
- TLD Name server: directs to the authoritative name server
- Authoritative name server: final step, returns IP if it's A record, or alias name if it's CNAME record

SOA: Start of Authority, information about server that supplies other records
NS: Name Server Used by top level DNS to redirect traffic to content DNS server
A, AAAA: Address, IP6
MX: Mail Exchange, defines mail server for the domain
TTL: Time To Live (typically 2 days, but can be lowered to 5 minutes)
CNAME: Canonical Name points to an A record, can’t point to Zone Apex Record
Zone Apex Record: naked domain name (without subdomain)
Alias: AWS/Route53 specific, like CNAME but can point to Zone Apex Record
PTR: reverse DNS, IP to domain
NS: Name server

OSI Layers

Num	Unit	Layer	Type	Function
1	bits	physical	Media	Media signal, binary transmission
2	frame	data link	Media	physical addressing (MAC & LLC)
3	packet	network	Media	path determination and logical addressing
4	segment	transport	Host	end-to-end connection and reliability
5	data	session	Host	inter-host communication
6	data	presentation	Host	data representation and encryption
7	data	application	Host	network process and application

Components: Forests, Domains, Resources (includes Users,Groups)
Forest is the top level component
Forest contains one or more domains and name is derived from the root domain
domains within a forest trust each other, i.e. user authenticated by one domain, can access resources belonging to another domain
separate forests don't trust each other unless connected by cross-forest trusts
v/s Google Cloud
- AD considers users as resources and thus are managed within a domain. GCP, except for service accounts, users are managed by Cloud Identity or Google Workspace