dns, ssh, ssl, ppt

1. DNS, SSH

2. DNS
• The Internet's system for converting alphabetic names into numeric IP
addresses.
• For example,
• When a Web address (URL) is typed into a browser, DNS servers
return the IP address of the Web server associated with that name.
• DNS converts the URL www.company.com into the IP address
204.0.8.51.

4. Why is DNS important?
• DNS is like a phone book for the Internet.
• If you know a person’s name but don’t know their telephone number,
you can simply look it up in a phone book.
• DNS provides this same service to the Internet.
• When you visit http://yahoo.com in a browser,
• Your computer uses DNS to retrieve the website’s IP address of
204.13.248.115

5. DNS Records
• A record - The record that holds the IP address of a domain. Learn
more about the A record.
• AAAA record - The record that contains the IPv6 address for a domain
(as opposed to A records, which list the IPv4 address). Learn more
about the AAAA record.
• CNAME record - Forwards one domain or subdomain to another
domain, does NOT provide an IP address. Learn more about the
CNAME record.
• MX record - Directs mail to an email server. Learn more about the MX
record.

6. DNS Records(contd:)
• TXT record - Lets an admin store text notes in the record. These
records are often used for email security. Learn more about the TXT
record.
• NS record - Stores the name server for a DNS entry. Learn more about
the NS record.
• SOA record - Stores admin information about a domain. Learn more
about the SOA record.
• SRV record - Specifies a port for specific services. Learn more about
the SRV record.
• PTR record - Provides a domain name in reverse-lookups. Learn more
about the PTR record.

7. TYPES OF DOMAIN
• Genetric Domain
• Country Domain

8. GENERIC DOMAIN
• A domain name is the sequence of labels from a node to the root, separated by dots (“.”s),
read left to right
• Domain names are limited to 255 characters in length

9. Country Domain
• There are also country code top-level domain names for every nation,
like:
• .pk, Pakistan
• .ae, Arab Emirates
• .us, United States
• .mx, Mexico
• .uk, United Kingdom etc.
These are called “country code” top-level domains (ccTLDs).

10. Top Level Domains
• A Top Level Domain refers to the part of a domain name that comes
after the period.
• there's a comparatively static number of Top Level Domains;
• .com,
• .edu,
• .gov,
• .info
• .org
• are just a few key examples.