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.
Cloud computing vs Data Center?
Data Center are typically data storage facility run by IT department or leased site. It provided un un interrupted service.
Cloud: are off premises service and provided ON Demand basics and resources are available fast and with minimal management error.
Core Layer
Core layer:Provides optimal transport between sites and high-performance routing. Due the criticality of the core layer, the design principles of the core should provide an appropriate level of resilience that offers the ability to recover quickly and smoothly after any network failure event with the core block.
Multilayer Switches between buildings
Distribution layer
Provides policy-based connectivity and boundary control between the access and core layers.
Like Multilayer switch which can do routing etc
Access layer
Provides workgroup/user access to the network.
Like Switches to Host/PC
Three-Tier Model
This design model is typically used in large enterprise campus networks, which are constructed of multiple functional distribution layer blocks.
Two-Tier Model or Collapsed core
Two-Tier Model or Collapsed core ( Combination of Core and Distribution layer )
is more suitable for small to medium-size campus networks (ideally not more than three functional disruption blocks to be interconnected), where the core and distribution functions can be combined into one layer, also known ascollapsed core-distribution architecture.
Leaf layer and Spain layer
The Leaf layer consists of access switches that connect to devices like servers, firewalls, load balancers, and edge routers.
The Spine layer (made up of switches that perform routing) is the backbone of the network, where every Leaf switch is interconnected with each and every Spine switch.
Crossover cable
- Use when connecting like devices together
- Switch to Switch (auto detect on most switches will work with straight-through cables, but crossover is the correct choice)
- Switch to Hub ( hub is similar to a switch )
- Hub to Hub
- Router to Router
- Router to PC
- PC to PC
- Switch to Switch
Straight-through cable
- Use when connecting unlike devices together
- Also known as a patch cable
- For a straight-through, use 568B on both ends
- Switch to pc
- Switch to Router
