Networking & Devices

Hubs & Bridges

You probably won’t encounter either of these in modern networking.

Switches and routers have effectively replaced hubs and bridges.

Hub

Operates at layer 1 of the OSI model.
Devices used to connect several computers together.
Any signal that is received on a hub is copied to all other ports. (See: noisy.)

There are two types of hubs; Active and Passive.

Active vs. Passive

Active:

• Includes the ability to regenerate and boost the signal (repeating) before sending to other ports
• Can be used to extend the length of a network

Passive:

• Simply a physical connection point for computers
• Not responsibly for amplifying or regenerating signals
• Cannot be used to extend the length of a network

Bridges

Operate at layer 2 of the OSI model.
Key functions:

• Join similar topologies (e.g One ethernet network to another ethernet network)
• Divide network segments into multiple collision domains
• Isolate network traffic

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Considerations:
Bridges forward broadcast packets.
(Broadcasts are addressed to all computers.)

Cannot perform intelligent path selection.
(Path between sender and destination will always be the same.)

Switches

Operates at layer 2. (Data link layer)
Uses MAC addresses to determine where to transmit data.
Provides centralized connectivity, similar to a hub but much smarter.

Switches examine Layer 2 header info. from incoming packets.
Based on this information, they forward the packets to a specific port.
This improves performance and reduces overhead.

Advantages:
Increases available network bandwidth
Increases network performance;
Helps regulate flow of traffic
Reduces collisions
Increases security

Disadvantages:
Cost
(WAS) More Expensive
Can be difficult to troubleshoot
Devices can be spoofed
Proper design and configuration is needed

Managed v Unmanaged Switches

Managed:
Often referred to as an ‘intelligent switch’
Has it’s own IP and config interface
Typically connected using special software or dedicated management port

Unmanaged:
Device that performs switching without any user intervention
Cannot control the functions of this type of switch
Can often be more cost effective for smaller deployments

Routers

Intelligent devices used to determine the best path for transmitting data between networks.
Routing tables are used to store network addresses.
Routers can transmit data across multiple networks, e.g IP subnets.

Routers operate at layer 3 of the OSI model. (Network layer)
More concerned with networks than individual pc’s.
They support various network types:

• LAN
• WAN
• Copper
• Fiber

As long as it’s TCP/IP, routers can route traffic appropriately.

Key Functions of Routers

• Connect multiple networks together, unlike switch/hub
• Routers do not forward broadcasts
  • Broadcast domains are broken up
• Determine the best route to the destination based on
  • Distance (how many routers will be crossed) (distance vector routing)
  • Congestion (how much traffic is on a given route)

Access Points, Repeaters & Extenders

Access Points

Any point that enables users access to a network.
Commonly used when referencing a wireless AP.
e.g an AP that enables users to connect over wireless.

Repeaters + Extenders

Operate at Physical layer (L1) of the OSI model.
Designed to improve signal range and strength by amplifying any signal they receive.

Once you hit the max distance of your AP, you could put a repeater or extender down, and then increase the range.

Network Controllers

Network Interface Card (NIC)

PCs connect to a switch via a NIC
NICs can be wired or wireless

Network devices require at least one interface (A NIC is an interface)
Can be hardwired or modular.
Modular means a card like the one you insert into mobo

NIC Properties

• Speed and duplex
  • Full duplex
  • Half duplex
  • Auto negotiate
• Wake on LAN
  • Enables PC to be turned on or woken up by a network message

Duplex refers to direction of traffic.
Duplex itself means traffic can go both ways.
Simplex being a single way, like listening to radio in car.
Full/Half characteristics mean can communication occur at the same time between two systems
Half Duplex means taking turns - I can send, but while I’m sending you have to listen.

Cable & DSL Modems

Modems

• Hardware devices used to connect to a remote network, or the Internet
• The term is a contraction of “modulate” and “demodulate”
  • Sends and receives data.

Dial-Up

• Internet connection established using a modem and standard telephone line
• Models dial into the Internet Service Provider (ISP) to establish an internet connection
• Slow speeds
  • Maximum of 56Kbps

Then came DSL:

Digital Subsriber Line

• Popular method for transferring digital signals over standard telephone lines
• DSL modems are used to connect to a DSL Internet Service Provider
  • Has superseded dial-up modems
• Certain models have built-in Wi-Fi capabilities (didn’t come along until quite a bit later)

Cable Modems

Hardware devices that use coax cable TV lines to provide high-speed Internet access.
Had an always-on connection + fast data transfer rates.

Patch Panels

Structured Cabling

Official term, but it’s a fancy term for being organized.

Patch Panels

• Mounted hardware assembly containing multiple ports.
• Used in a LAN to house multiple cable connections.
• Ports are used to connect/manage LAN cables
  • Incoming and outgoing

Types of patch panels

• Based on the number of ports
  • 12-port
  • 24-port
  • 48-port
• Cable Specs
  • Cat5E
  • Cat6
  • Cat6A
  • Cat7

Network Racks

• Metal frame chassis that stacks + categorizes diff. networking components
  • Patch panels
  • Switches
  • Routers
• Patch cords can be used to connect a patch panel to a network switch

Power over Ethernet (PoE)

Technology used for wired Ethernet LANs.
Enables electrical current to be carried over data cables as an alternative to power cords.

Commonly used when implementing wireless APs in remote locations that don’t have power outlets, e.g ceilings.

Device has to be capable of accepting PoE, specifically designed for it. If it is you just need to run data cable to it.

Next Gen PoE

• IEEE 802.3bt, also referred to as “Next Generation PoE”
• Powerful enough to support:
  • Kiosks
  • Terminals
  • LED lighting
  • Security card readers
  • Security cameras

Ethernet over Power

Technology used to transmit data using common electrical wiring.
In order to function properly, an electrical outlet and an Ethernet over power adapter are required.
Both devices must be on the same electrical circuit.

Ideal when it is not possible to run cables for a network connection.
Considered an alternative to Wi-Fi.

Example:
Plug router into an EoP box, plug box into plug socket

Then plug PC into other EoP box, and plug box into plug socket
boom, get network’d son

Firewalls

• Can be hardware and software based.
• Used to allow or deny a connection based on a set of rules.
• Can use packet filters which use rules based on IPs and ports.
• Stateful filters maintain session state info (keeps track of everything happening between 2 endpoints during entire communication, like recording a phone call)

Hardware Firewalls

• Specialized network appliance
• Placed between network and untrusted network
• Port and IP address rules
• Can act in various roles
  • Content filter (e.g block youtube)
  • VPN concentrator (single point all outside users access your network through)
  • Honeypot

Software Firewall

• Usually run on host (PC)
• Small office or home computer
• usually only port based
• Control internet access per application
• If operating system becomes compromised, so does the firewall

Content Filters

• Can be part of the firewall or a seperate device.
• They analyze packets and examine the content then allow or deny the request based on the rules you set up.
• Common filters include executables, emails, or known dodgy sites.

Cloud-Based Network Controllers

• On-premise controllers use a process called wireless backhaul
  • Communication is tunneled back to the controller
    • Control-plane
    • Data-plane
• Cloud-managed wireless LAN
  • APs connect to a virtual controller
    • Controller is typically located in a public cloud

Imagine an environment like a university campus - they might need to blanket the entire campus with wireless so you can always connect. This might involve hundreds or even thousands
of access points. This is fine, but from a management perspective this is very demanding. everyone of those APs needs to be configured and needs some kind of management.

Then you need to either configure and manage all of them manually, or used a cloud-based network controller.

It gathers info from all of those APs in a process known as backhaul (communication tunneled back to controller). This includes info known as control-plane and data-plane.

Control-plane essentially contains instructions, like traffic lights or lanes on the road. Means to manage the traffic.
Data-plane is the traffic itself.