Topic 1 - Network Fundamentals Flashcards
OSI Model Layers
Application (Layer 7) Presentation (Layer 6) Session (Layer 5) Transport (Layer 4) Network (Layer 3) Data Link (Layer 2 Physical (Layer 1)
TCP/IP model
Application Layer / Process
Transport Layer / Host-to-Host
Internet Layer
Link Layer/ Network Access Layer
OSI model in terms of a reference model.
Layer 7 - HTTP, FTP Layer 6 - Telnet, X.25 Layer 5 - L2TP, PPTP Layer 4 - TCP, UDP Layer 3 - RIP, OSPF Layer 2 - ARP Layer 1 - Ethernet
Explain TCP
- TCP is a full-duplex, connection-oriented, reliable and accurate protocol.
- If a TCP packet is not received, the hosts will communicate this and the sending host can send the packet again. Before transmitting, a sending host establishes a connection with the TCP host.
- This is done via a few handshake messages.
- 3 way hand shacks:
SYN (Host to Server) —–> SYN/ACK ( Server to Host ) ——> ACK ( Host to Server ) —> Connection Established
example: Videos
Explain UDP
UDP requires less bandwidth than TCP because it doesn’t care about reliability. It doesn’t need to be connection-oriented and know whether a packet is received or not. The best example of this is Voice over IP. VoIP packets are real-time. They are played as they’re received. If one is not received, it doesn’t make sense to retransmit it because it would be out of order anyways when it is received. So it makes sense for VoIP application developers to use UDP for their transport layer protocol.
Features of UDP: Voip
TCP Port numbers
FTP - 20,21 Telnet - 23 SMTP - 25 DNS - 53 Http - 80 POP - 110 NNTP -119 HTTPS - 443
UDP Port numbers
DNS - 53
DHCP - 67, 68
SNMP - 161
NTP - 123
Firewalls?
Firewalls - designed to prevent unauthorized access to your network. Layer 4 device.
Adaptive Security Appliances - ( ASA )
Asecurity device that combines firewall, antivirus, intrusion prevention, and virtual private network (VPN) capabilities. It provides proactive threat defence that stops attacks before they spread through the network.
Autonomous AP
Configured individually, fully functional like Switch. AP can be overloaded if the neighbour goes down.
Controller based AP
Controlled by controller, fully controlled by WLC.
All the configurations are done on controller.
Controller tells if the neighbour goes down
Load balances user connection to each AP
Public cloud
Available for public. Either free or Pay per use model
Private Clouds
Application and services are offered in private for a specific organisation such as government. It has better security
Hybrid
Hybrid is generally made of two or more clouds.
Custom clouds
these are built to meet needs of specific industry like Health care or media. It an be private or Public.