0xor1day

Introductory Networking

3 min read

OSI Model (open systems interconnection)

Application: provide networking options to programs to transmit data || → Data Presentation: translates data into a standardised format || → Data Session: sets up a session with network || → Data Transport: TCP (transmission control protocol - sustained ) and UDP (user datagram protocol - speed) || → Data segments/ Datagrams Network: destination of request - figures out the best route IPV4 || → Data packets Data Link: Add MAC address from Network Interface Card unique. physical address used to identify destination || → Data frames Physical: Hardware → Data Bits

Encapsulation Information containing details specific to the layer in question is added on the start of the transmission - increase security and integrity.

De-encapsulation reverse of Encapsulation. stripping off the added information as it goes

TCP/IP model (Transmission Control Protocol / Internet Protocol) - control the flow of data and how data packets are addressed and sent -four layers version of OSI

  1. Application (Application, Presentation, Session)
  2. Transport (Transport)
  3. Internet (Network)
  4. Network Interface (Data Link, Physical)

-Three-way handshake- I. SYN - synchronise - computer sends request to remote server to initialzie a connection II. SYN/ACK - synchronise/acknowledgement - Remote server responds with acknowledgment and syn bit III. ACK - computer returns acknowledegment

Networking Tools - Ping ping - used to test whether a connection to a remote resource is possible ICMP protocol - network layer of OSI model, Internet layer of TCP/IP used to determine the IP address of a server hosting a website

Networking Tools - Traceroute traceroute - used to map the path your request takes a it heads to the target machine requests go through various servers, traceroute allows to see each of the connections (intermediate steps) Windows(tracert) - ICMP network OSI, Internet TCP/IP - UDP

Networking Tools - whois whois - get a list of available info about domain registration get information such as data validation, registrar, registration date, exp date, last update date, status, servers etc

Networking Tools - Dig dig @ - allows for manual query recursive DNS servers - used to troubleshoot network Answer section - returns answer with IP address for the domain queried TTL - time to live of queried DNA record - when to stop considering the record as valid - request data again past the date (seconds)

  1. Request made by computer
  2. computer checks local cache for IP
  3. send request to recursive DNS server (stored in router)
  4. send request to root name server - get the closest server to request
  5. Top-level domain - split into extensions .com vs .co.uk (keep track of level down)
  6. Authoritative name servers - store DNS records
  7. Request sent back to computer

CISCO SELF STUDY GUIDE BY STEVE MCQUERRY***

Graph View