Week 8 Flashcards
What are Domain Names?
Devices are labeled with numeric IP addresses
Domain names are names for the numeric IP addresses
What is a DNS?
DNS translates human-readable domain names into machine readable IP addresses
What is Shared Hosting?
An IP address mapped to multiple host names
What are the 4 DNS requirements?
Scalability
Efficiency
Reliability
Maintainability
What does the scalability part of the DNS mean?
Hierarchial Design:
Root
Top Level Domain
Second Level Domain
Third Level Domain
What does the Redundancy part of the DNS mean?
Each logical root server refers to multiple physical ones
What does the Reliability part of the DNS mean?
No single point of failure
What are Root DNS servers?
Top Level, represented by (.)
First point of contact if a DNS resolver can’t resolve a name
What are Top-Level Domain Servers?
Organizational
(com, org, edu, gov, net)
or
Geographical
(uk,us,eg,sp,de)
Managed by ICANN (Internet Corporation for Assigned Names and Numbers)
What are Authoritative Servers?
Hold the complete data for a domain’s DNS records
Source of DNS responses
To ensure maintainability authoritative servers must be updated automatically
What are Sub-domains?
Web addresses may utilise multiple subdomains separated by periods (pronounced “dot) in a hierarchical fashion
Each domain manages its subdomains
What is DNSSEC?
Attackers exploit vulnerabilities in the DNS - it doesn’t check for credentials before accepting an answer
DNSSEC adds a layer of trust on top of DNS
What does DNSSEC use?
Asymmetric Encryption
Hash Functions
What is Asymmetric Encryption?
Uses pair of keys (private and public)
Using encryption key as the public key (private communication)
Using decryption key as public key
What are Hash Functions?
Hash function takes data of arbitrary size, M, and returns a fixed-size number, H(M)
How is a Digital Signature created?
DNS Data is put through hash function which gets hash value
Then encrypted with private key to make digital signature which is then attached to DNS data
Which makes Signed DNS Data (DNS data + digital signature)
How is a DNS Response verified?
DNS is put through hash function to get Hash Value
Encrypted Hash decrypted with public key to get Hash Value
If Hash Values are equal then DNS Response is Verified
What is the Hourglass Model?
Internet Protocols have an hourglass shape
What are the 2 protocols the transport layer provides?
Transmission Control Protocol (TCP)
The User Datagram Protocol (UDP)
How is information sent in networking?
Information is sent by combining headers (supplemental data) and payloads (the actual contents that you wish to send)
How is application level data used? (hint: chopped)
Application level data is chopped up into smaller pieces. TCP pairs up each such piece of data with a TCP header to form segments
What are Networking Ports?
Ports are used to map data to the correct process
Some port numbers are reserved for use by specific application layer protocols, eg. port 80 for HTTP
What are all the features of TCP services?
Connection-oriented communication
End-to-end communication
Complete reliability
Full duplex communication
A stream interface
Reliable connection startup
Graceful connection shutdown
What is Connection-Oriented Communication?
TCP provides connection oriented communication - an application sets up a connection, uses it, and tears it down
What is End-to-end communication?
TCP provides end-to-end communication - a connection has exactly two endpoints
What is Complete Reliability?
Data will be received exactly as sent even if that means resending
What is Full-Duplex Communication?
Data may be sent and received simultaneously
What is a Stream Interface?
A continuous stream of data is sent and received
What is Reliable Connection Startup?
TCP provides reliable connection start-up through a three-way handshake - communication always starts properly
Why are Sequence Numbers important?
If all connections start numbering segments from the same number, the receiver might confuse segments from different sequential connections
What is Graceful Connection Shutdown?
TCP provides Graceful Connection shutdown through a four-way handshake - communication always finishes properly
What are the 4 fields of the UDP Header?
Source Port
Destination Port
Length
Checksum
What are the 4 Services of the UDP?
Connectionless communication
End-to-end communication
Best-effort reliability
A message interface
What is Connectionless Communication?
Application does not set up or tear down a connection
What is End-to-end communication?
Connection has exactly 2 endpoints
What is Best Effort Reliability?
Data may be lost, duplicated or delayed
What is a Message Interface?
Individual data items are sent and recieved
What are the benefits of TCP vs UDP?
TCP provides full reliability, with high latency
UDP provides best effort reliability with minimal latency
