Week 4 - IP Addressing, DNS, Subnets Flashcards
Domain Name System
Name server
A central database that translates
domain names and host names to IP addresses (or IP addresses to names)
Simplified network management
dramatically
This method worked for local networks, but not for resources on the Internet
- Resource record
– A file containing resource information or characteristics about a zone or domain
DNS on the Internet
Internet’s Domain Name System (DNS)
Associates an IP address (such as 204.21.112.110) with an actual name (such as server1)
Network resources can be accessed by easy to remember names
Goal of DNS
Goal of DNS is to decentralize administration
- DNS is a distributed and hierarchical database
– Allows controlling DNS management locally
Local DNS server
– Can handle cached hostname requests
– Doesn’t contain information on every hostname on the Internet
– Forwards requests for unknown hostnames to a forwarder
Forwarder
A type of DNS server
–Forwarder’s job is to handle off
site requests generated at the system known as “localhost”
DNS Forwarder is a server on a network used to forward DNS queries for external DNS names to
DNS servers outside of that network
- Can have up to three forwarders in DNS configuration
– These servers enable you to: - Forward unresolved queries to an off site DNS server
- Cache results on your local DNS server
DNS on the internet
Caching
A feature that stores DNS queries on the local site for fast hostname to IP address resolution
Local administrators can manage local DNS servers
Root DNS servers
Centrally controlled public DNS servers
– Control the Internet’s top
level domains (TLDs)
How is a DNS Database structured?
DNS database is structured as an inverted tree
– Also known as domain namespace
– Root at top of the tree
– Top Level Domain’s beneath it
– Nodes (leaves) of the tree are called domains and have labels
* Such as .gov for U.S. government domain
–Domain names are derived from node labels
–Each level of hierarchy is separated by dots in domain name
Root DNS Servers
13 Independent Root Servers Worldwide
* Run by organisations such as:
– Internet System Consortium
– Versign Inc
– NASA
– US Dept of Defence
– US Army
– University of California
- Each Root Server is actually a cluster of servers
distributed around the world (increased reliability)
DNS Zone
Zone
A portion of the DNS namespace that has been delegated to other servers/administrators
Zone file
- DNS zone file is a text file that stores resource records and other data for a zone
Zone file MX RR
Identifies mail servers (mail exchangers) for a zone
Zone file A RR
A (address) RR
– Most common resource record
– Used to resolve a hostname to an IPv4 address for locating a resource
Zone file PTR RR
PTR (pointer) RR
– Used to resolve an IPv4 address to its hostname
– Performs the reverse of what an A RR does
Zone file CNAME RR
CNAME (canonical name) RR
– Enables you to create an alias for a host
Day in life of a web request
journey down protocol stack application, transport, network, link
putting it all together:
goal: identify, review, understand protocols (at all layers) involved in seemingly simple
scenario:
requesting www page
student attaches laptop to campus
network, requests/receives www.google.com
What is AWS?
AWS is a secure cloud platform that offers a broad set of global cloud based products
- AWS provides you with
on demand access to:
– Compute resources
– Storage resources
– Network resources
– Database resources
– other IT resources
– and management tools
