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
Choosing an AWS service
The service you select depends on:
* business goals
* technology requirements
Amazon compute services
Amazon EC2
AWS Elastic Beanstalk
Amazon ECS
AWS Storage services
Amazon S3
Amazon S3 Glacier
Amazon EBS
AWS Database Servcies
Amazon RDS
Amazon DynamoDB
Amazon Redshift
AWS Networking and content delivery services
Amazon VPC
Amazon Cloudfront
Elastic Load Balancing
AWS Security, identity and compliance services
AWS IAM
AWS Shield
AWS KMS
AWS Management and Governance services
AWS Config
AWS CloudTrail
AWS Cloudwatch
AWS Cost Management Services
AWS Cost & Usage Report
AWS Budgets
AWS Cost Explorer
Public and Private IP
IPv4: 54.63.10.198
Over 4 Billion possible IP address available
Originally the designers of IPv4 thought that was enough….but its not!!!
In order to prevent a shortage of Ipv4 addresses:
Public and Private IP address are used
Public IP
Publicly registered on the Internet
* Managed by Internet Service Providers
* Public IP address is needed to access Internet
Private IP
NOT Publicly registered
* Used and managed internally within a local network
* Local router assigns Private IP addresses
* Cannot be used to access the Internet
Network Address Translation (NAT)
Used to convert:
– Private IP into Public IP
– Public IP back to Private IP
Internal addresses are
disguised behind one
publicly accessible
address
- Impossible for external
hosts to initiate connection unless
firewall is specifically configured to forward specific traffic to specific
internal addresses
Port Forwarding
Redirection of a network packet from one address/port combination to another
Subnetting
The practice of dividing a network into 2 or more networks is called subnetting
- Subnet: Logical Division of an IP network
