2.2 Compare & contrast common networking hardware Flashcards
What is the Internet?
Global network of networks
What does the core of the internet consist of?
Fiber optic links connecting IXPs
IXPs (Internet eXchange Points) are locations where ISPs and network operators interconnect their networks
Why do ISPs use transit & peering arrangements?
Transit is a paid arrangement where an ISP buys access to the broader internet from another ISP. Peering is a mutual agreement between 2 ISPs to exchange traffic directly without charging each other, usually at IXPs. This ensures the ISP’s customers can access external websites, services, and networks.
To control traffic beyond their network boundaries
Meaning to & from parts of the Internet they don’t directly control
ISPs are tiered based on their reliance on transit arrangements.
What is a transit arrangement in internet connectivity?
When an ISP pays another ISP to route traffic to destinations it doesn’t serve
What is a peering arrangement in internet connectivity?
When ISPs exchange traffic between their networks without payment
How do users connect to the ISP’s network?
via the ISP network’s nearest Point of Presense (PoP)
i.e. a local telephone exchange
What is an Internet connection type?
Media, hardware, & protocols for connecting to ISP’s PoP
PoP = Point of Presense
i.e. Satellite, Fiber, Cable, DSL, Cellular, & WISP
What does it mean that a WAN interface is typically point-to-point?
There are only 2 devices connected to the media
Unlike Ethernet where multiple devices can be connected through switches
What do modems do?
Establishes the physical connection to the WAN interface
A WAN interface is a network interface on a network device to connect to a WAN
What do routers do?
Use IP to route and forward data between networks
IP = Internet Protocol
Meaning of ISP?
Internet Service Provider
What global telecom network do many internet connections use?
PSTN
PSTN = Public Switched Telephone Network
What cabling is used at the core of the PSTN?
PSTN = Public Switched Telephone Network
Fiber optic
What cabling is used at the edge of the PSTN?
PSTN = Public Switched Telephone Network
Copper
What is the edge of the PSTN referred to as?
POTS, “local loop”, or “last mile”
POTS = Plain Old Telephone System
How does DSL work?
Using the PSTN’s POTS as the communication channel
Meaning the PSTN’s copper cabling is used (the edge)
PSTN = Public Switched Telephone Network | POTS = Plain Old Telephone System
Meaning of DSL?
Digital Subscriber Line
2 types of DSL?
- ADSL
- SDSL
How does ADSL differ from SDSL?
Providing a fast downlink but a slow uplink
How does SDSL differ from ADSL?
Offering the same uplink & downlink speeds
These connections are ideal for businesses and branch offices, with higher upstream data transfer.
How are LANs connected to the telephone cabling in DSL?
Via DSL modem
DSL modems can be a standalone device or be embeded as a function of a SOHO router
What does the DSL modem’s RJ11 WAN port connect to?
Phone point
what does the DSL modem’s RJ45 port connect to?
Router
Why does DSL require splitters at each phone socket?
To separate voice & data signals
splitters can be self-installed on each phone point or it may be integrated into sockets
How is cable internet provided?
CATV services
CATV services are aka HFC, Broadband Cable, & Cable
Meaning of CATV?
Cable Access TV
Why are CATV networks described as HFC?
Hybrid Fiber Coax
Integrates fiber optic core with copper coaxial cables for customer connectivity
Downlink bandwidth of Cable internet based on DOCSIS?
DOCSIS (Data Over Cable Service Interface Specification) defines the standards for transmitting data over cable TV systems.
- 38 Mbps (North America)
- 50 Mbps (Europe)
Uplink bandwidth of Cable Internet based on DOCSIS?
DOCSIS (Data Over Cable Service Interface Specification) defines the standards for transmitting data over cable TV systems.
27Mbps
Cable used to connect cable modems to routers?
RJ45 cable
How do cable modems connect to the access provider’s network?
Via coaxial cable with F-type connectors
Coaxial cable links premises to a CMTS in a street, which sends data traffic to the ISP’s PoP and then to the Internet via fiber backbone.
Meaning of FTTx?
Fiber To The X
Purpose of FTTx?
Upgrade last-mile connectivity using fiber optic cables
This is done for higher internet bandwidth
FTTx is an initiative to to deploy fiber optic technology closer to end-users
2 types of FTTx projects?
- FTTC
- FTTP
Meaning of FTTC?
FTT Curb
Meaning of FTTP?
FTT Premises
How does FTTC work?
Extends fiber link to a cabinet for multiple subscribers
Copper wiring is still used to connect to customers
How do DSL service providers support FTTC?
via VDSL
Meaning of VDSL?
Very high-speed DSL
How does VDSL differ from other DSL types?
Achieves higher bit rates at the expense of range
VDSL allows for symmetric & asymmetric modes
asymmetric downlink bandwidth of VDSL?
52 Mbps
asymmetric uplink bandwidth of VDSL?
6 Mbps
Symmetric bandwidth of VDSL?
bandwidth is the same on up & downlink
26Mbps
What does VDSL2 specify?
A very short range rate of 100Mbps (bi-directional)
short range is 100m/300 feet.
What does it mean that DSL modems are not interchangeable?
A DSL modem of 1 type may not support a different type of DSL
An ADSL modme is unlikely to support VDSL, though most VDSL modems support ADSL
How does FTTP work?
Connecting ISP’s fiber optic cable directly to customer’s building
How is FTTP implemented as?
PON
(PON = Passive Optical Network)
In an PON, where does the fiber cable connect to?
(This is about FTTP) (PON = Passive Optical Network)
an OLT (Optical Line Terminal)
The OLT is located in a street cabinet
In a PON, what happens after the fiber cable connects to an OLT?
(This is about FTTP) (PON = Passive Optical Network) (OLT = Optical Line Terminal)
Splitters direct subscriber traffic to ONTs at their premises
Meaning of ONT?
Optical Network Terminal
What do ONTs in a PON do?
(This is about FTTP) (PON = Passive Optical Network)
Converts the optical signal to an electrical one
The optical signals carried by fiber optic cables are converted into electrical signals by the ONT to be used by the customer’s devices
How is an ONT in a PON connected to the customer’s router?
(This is about FTTP) (PON = Passive Optical Network)
RJ45 copper wire patch cord
What identity do IP addresses contain?
Identity of network & a host within that network
MAC addresses only identify a hardware port
What do firewalls do?
Filters allowed & denied hosts & protocols
Meaning of ACL?
Access Control List
What is an ACL?
The firewall’s configured rules
What do ACLs list?
Network addresses, protocol types, & traffic permissions
What do networking hardware do?
Forwards data & connects devices
i.e. routers, switches, patch panels, NICs, SDN, etc.
Meaning of NIC?
Network Interface Card
Purpose of NICs?
Allow devices to connect to Ethernet networks
What standard do most PC MOBO NICs support?
1000BASE-T Ethernet
NICs may also support other types of Ethernet, like fiber optic
Why may NICs have multiple ports of the same type?
To bond for a higher-speed link
i.e. 4 gigabit Ethernet ports could be bonded to give a nominal lnk speed of 4Gbps
What kind of addresses do NICs have?
MAC addresses
Meaning of MAC?
Media Access Control
Where is the destination & source MAC address placed in Ethernet frames?
Header
What does a MAC address consist of?
48-bit hexadecimal number
MAC addresses can be writen with color or hyphen separators or no separators at all (i.e. 00 : 60 : 8c : 12 : 3a : bc or 00608c123abc)
How many values does the hexadecimal numbering system have?
16
What are the hexadecimal values?
0-9 & A-F
What does each Hexadecimal digit represent?
4 bits
So hex number “60” = 01100000 (96)
What are computers in a office setup typically connected to?
Wall ports linked to a patch panel
What is the rear of a patch panel used for?
Terminate wall cables to IDC punchdown blocks
IDC = Insulation Displacement Connector
What does the front of a patch panel have?
Pre-wired RJ45 ports to connect to a switch
What cable is used to connect a port on a patch panel to a switch?
Patch cord
What were hubs used for?
Implementing the 10BASE-T & 100BASE-T Ethernet cabling designs
aka “Star topology”
What is the 10BASE-T & 100BASE-T Ethernet cabling design referred to as?
Star topology
This is because each end system is cabled to a concentrator (the hub)
How does a hub work?
Repeats incoming data from one port to all the other ports
Each connected device receives & processes it, even if it’s not for them
What is a collision domain?
Network segment where devices contend for a shared communication channel
This can lead to collisions which can slow down network performance
When do devices connected to a hub ignore received frames?
When frames don’t match its MAC address
What happens when a collision occurs in a hub?
The more computers there are, the more collisions
All devices must wait a random period of time before trying again
This random backoff period help reduce the likelihood of collisions happ
The random backoff reduces collision recurrence.
What does it mean that communication in hubs are half-duplex?
A computer can send or receive, but not at the same time
Why are hubs practically obselete?
Thye aren’t compatible with Gigabit Ethernet
Hubs are typically only used in niche cases, often to support older equipment that needs to remain operational.
How do Switches differ from hubs?
Forwarding frames to the destination MAC address
Rather than broadcasting frames to all devices
How are switches able to route frames?
By decoding frames to identify the source & destination MAC addresses
Each switch port is a separate collision domain, eliminating contention
What does it mean for devices on a switch to have full-duplex?
Devices can send & receive simultaneously at the full speed
The full speed is dependent on the network cabling & NIC
What happens when a switch encounters a new source MAC address?
It records it in its MAC address table
What happens if a switch needs to forward a frame to an unknown destination MAC address?
It broacasts the frame to all ports except the one it arrived on
This process is known as flooding
How do unmanaged switches differ from managed switches?
Functioning without requiring any configuration
Plug it in, connect hosts, and it sets up Ethernet connections automatically
What type of switch is embedded in most SOHO router/modems?
Unmanaged switch
Some older SOHO routers use LAN interfaces as hubs, limiting speed to below 1Gbps
How do managed switches differ from unmanaged switches
Having additional functonality for configuration
A managed switch will work as an unmanaged switch out of the box
How do admins manage a managed switch’s settings?
Via management port
How many ports do typical workgroup switches come with?
24 or 48 ports
What does it mean when switches have uplink ports?
They can connect to other switches
How do modular switches work?
Provide power & a backplane to link multiple switches
This enables the provisioning of hundreds of access ports via a single compact appliance
What interface is used to configure managed switches?
Web or Command-Line interface
Meaning of PoE?
Power over Ethernet
What is PoE?
A means of supplying power from a switch port to a Powered Device (PD)
A powered device lie a VoIP handset, camera, AP, etc.
3 IEEE standards PoE is defined in?
- 802.3af
- 802.3at
- 802.3bt
How much power can 802.3af deliver to devices?
up to 13W
What is the max power delivery of 802.3af?
15.4W
Why can’t 802.3af supply 15.4W rather than 13W to devices?
Due to voltage drop over the length of the cable
How much power can 802.3at deliver to devices?
Up to 25W
What is 802.3at aka?
PoE+
What is 802.3bt aka?
PoE++ or 4PPoE
How much power can 802.3bt deliver to devices?
- Up to 51W (Type 3)
- Up to 73W (Type 4)
What happens when a device connects to a PoE switch?
PoE switch detects if the device supports PoE
What happens if a PoE switch detects a PoE device?
Determines device’s power consumption & sets supply voltage level
What happens if a PoE switch detects a non-PoE device?
It doesn’t supply power over the port
Therefore, not damaging non-PoE devices
What can you use if a switch doesn’t support PoE?
Power injector
One port on the injector connects to the switch port. The other port connects to the device
What is a power injector aka?
midspan
What is the max cable length when using a power injector?
100m
This ensures optimal power delivery & network performance
What transmission media do wireless technologies use?
Radio waves
How do radio systems transfer signals?
Radio systems like AM/FM Radio broadcast, Two-way radios, Cellular networks, Wi-Fi, Satellite communication, etc.
Using transmission & reception antennas tuned to a specific frequency
What standards are most WLANs based on?
IEEE 802.11 standards
What is 802.11 aka?
Wi-Fi
What is “infrastructure mode” in wireless networking?
802.11 network framework where devices communicate with each other via one or more APs
This means the devices connect to the network via an AP
Meaning of AP?
Access Point
What does each AP create in wireless infrastructure mode?
BSS (Basic Service Set)
What is a BSS in wireless infrastructure mode?
(Basic Service Set)
Wireless network formed around an AP
What is a BSSID in wireless infrastructure mode?
MAC address of the AP’s radio
i.e. In an office with two access points, “Office_WiFi_1” has a BSSID of “00:11:22:33:44:55,” and “Office_WiFi_2” has a BSSID of “66:77:88:99:AA:BB.” These BSSIDs uniquely identify the Basic Service Sets (BSS) created by each access point.
What is the BSSID in wireless infrastructure used for?
To uniquely identiy the BSS
i.e. In an office with two access points, “Office_WiFi_1” has a BSSID of “00:11:22:33:44:55,” and “Office_WiFi_2” has a BSSID of “66:77:88:99:AA:BB.” These BSSIDs uniquely identify the Basic Service Sets (BSS) created by each access point.
What else can an AP do besides creating a wireless-only network?
Wireless-only network = infrastructure mode in Wi-Fi networking
Bridge wireless stations with wired networks
“stations” means devices connected to the wireless network
What is the “distribution system” (DS) in wireless networking?
Wired portion of the network
How is an AP joined to a network?
Via Ethernet switch
An enterprise network is likely to use PoE to power the AP over the data cabling
Meaning of SDN?
Software-Defined Networking
What is SDN?
Model that automates network provisioning & deprovisioning in the cloud
Cloud network provisioning involves configuring resources like IP addresses, virtual networks, security policies, and connectivity for deploying applications or services. network deprovisioning involves the removal or decommissioning of network resources that are no longer needed.
What layers does SDN devide network functions into?
- Application Layer
- Control Layer
- Infrastructure Layer
What are the functions of the Application Layer in SDN?
Applies business logic to prioritize, secure, & direct traffic
What are the functions of the Infrastructure Layer in SDN?
Contains devices that handle forwarding of traffic
The devices can be physical or virtual. “forwarding” here refers to switching & routing
What is the control plane of the control layer in SDN implemented by?
A virtual device referred to as the “SDN controller”
What does each layer in SDN expose?
API that can be automated by scripts that calls functions in adjacent layers
API = Application Programming Interface
By adjacent layers, it means the layers above or below it.
What is the “northbound” API (or service interface) in SDN?
API = Application Programming Interface
The interface between SDN apps & the SDN controller
What is the “southbound” API in SDN?
API = Application Programming Interface
The interface between the SDN controller & infrastructure devices
How do NICs process electrical/light signals as digital data?
Ethernet’s data link layer divides signals into frames
Frames have a consistent format defined by Ethernet standards
