SECFND 6: Network Applications Flashcards
DNS Resource Record
RR defines the DNS data types that are stored in the DNS database. SOA, MX, A, AAAA, NS, PTR, CNAME
stub DNS resolver
Client device OS
DNS recursive resolver
DNS server that processes requests. Queries the authoritative DNS server for RR information
Open DNS recursive resolver
Allow queries from all addres (8.8.8.8, etc.)
Authoritative DNS Server
Responsible for all domain RR’s. Provide auth responses to DNS recursive resolvers
DNS Zones
In addition to being divided into domains, the DNS name space is partitioned into zones to simplify DNS database management..
Zone file is a text file.
A record
Maps names to IPv4 addresses
AAAA
Map hostnames to IPv6 addresses
MX record
Maps DN to mail servers for that domain
PTR record
PTR points to a canonical name. The most common use is for implementing reverse DNS lookups, mapping an IP address to the hostname.
NS Record
identifies the DNS servers that are responsible (authoritative) for a zone.
CNAME record
specify that a domain name is an alias for another domain name, which is the “canonical” domain name.
TXT Record
used to associate any arbitrary text with a hostname. Used for DKIM
SOA Record
Start of authority. Each zone contains an SOA record. Identifies the name server that is the best source of information for the data within the zone. The SOA record also contains various other parameters that define the behavior of the DNS server.
DNS Recursive query steps
- DNS resolver queries DNS recursor.
- DNS recursor sends query to root name server.
- Root name servers send a DNS referral to DNS recursor informing it to ask the gTLD name servers for the .com/.net/,org domain space.
- DNS recursor sends query to gTLD servers looking for domain name (cisco.com)
- GTLD servers send DNS referral to DNS recursor informing it to ask the cisco.com name servers about domain name space.
- DNS recursor sends a query to ns1.cisco.com or ns2.cisco.com
- Cisco servers send auth DNS response to DNS recursor with A RR info
- DNS recursor sends a response to the DNS resolver
Dynamic DNS
Connects to DDNS provider with unique login name. Service links discovered public IP address with a hostname in the DNS system.
URI
All URL’s are URI’s, but not vice versa
URL part: Protocol
http, https, ftp, etc.
URL part: path
/video. Path typically refers to a file or location on the web server. Like a directory structure.
URL part: parameters
aka Query string. ?docid=96673&hl=en. The docid=96673 parameter in this example reference a specific video file in the path. The hl=en parameter specify the language,
URL part: named anchor
00h01m15s. Typically the fragment is used to refer to an internal section within a web document. In this case, the fragment means skip to 1 minute and 15 seconds into the video.
HTTP referer
Address of previous web page from where a link was followed
Cooking info is sent in:
Request header, response header, stored in Client browser
Two client scripting languages
JavaScript, VBscript
