General Questions Part 1 Flashcards
FCS
Frame Check Sequence (FCS) is an error-detecting code added to a frame in a communications protocol to determine if the frame arrived intact.
Preamble
The preamble functions like the outriders in a presidential motorcade. They tell everyone ahead to wake up and pay attention: something important is coming. Apart from being a “get ready” notification, the preamble also serves as a clock synchronization device.
Full Duplex
Send and receive data simultaneously
Half Duplex
Cannot send and receive data simultaneously
CSMA/CD
Short for carrier sense multiple access/collision detection. Before a node transmits data, it checks or listens to the network. When the network is not busy, the node sends its data. If it detects traffic, it will wait a random amount of time and try again. Collision Detection (CD) will happen if two or more nodes send data down the wire and they collide, the nodes will be notified and wait a random amount of time and try again. No longer an issue on modern networks, happened on older Ethernet networks with hubs.
Carrier Sense
Can detect what is going on over the transmission medium.
Multiple Access
Every node on the network has equal rights to access and use the shared medium, but they must take turns.
Collision Detection
If two or more nodes send data down the wire and they collide, the nodes will be notified and wait a random amount of time and try again.
Broadcast Domain
A broadcast domain is a logical division of a computer network in which all nodes can reach each other by broadcast at the data link layer. A broadcast domain can be within the same LAN segment or it can be bridged to other LAN segments. Separated by routers.
Collision Domain
A collision domain is a network segment connected by a shared medium or through repeaters where simultaneous data transmissions collide with one another. Separated by switch/bridge.
Unicast
One-to-one relationship, one station sending information to another single station.
Broadcast
One-to-many relationship, send from one station to all stations on a broadcast domain.
Multicast
One-to-many relationship, send from one station to all interested stations.
LAN
Local Area Network - A group of devices in the same broadcast domain
VLAN
Virtual Local Area Network - A group of devices in the same broadcast domain, separated logically rather than physically.
VLAN ID
Virtual Local Area Network Identification - 12 bits long, 4,094 VLANS.
Trunking
Trunking is a technique used in data communications transmission systems to provide many users with access to a network by sharing multiple lines or frequencies. As the name implies, the system is like a tree with one trunk and many branches. Trunking is commonly used in very-high-frequency (VHF) radio and telecommunication systems.
Trunking can also be defined as a network that handles multiple signals simultaneously. The data transmitted through trunking can be audio, video, controlling signals or images.
Loop Protection
IEEE standard 802.1D to prevent loops in bridged (switched) networks. Without loop protection, two switches connected to each other will send traffic back and forth forever.
IEEE standard 802.1D
Prevents loops in switched networks, used practically everywhere.
What are the STP port states?
Blocking - Not forwarding to prevent a loop
Listening - Not forwarding and cleaning the MAC table
Learning - Not forwarding and adding to the MAC table
Forwarding - Data passes through and is fully operational
Disabled - Administrator has turned off the port
RSTP
Rapid Spanning Tree Protocol (IEEE 802.1w). Latest upgrade to STP, convergence from 30 to 50 seconds to 6 seconds. Backwards compatible with 802.1D STP.
Routing Table
Data table stored in a router that lists the routes to a particular network destination.
Static Routing
Add routes to a router manually, done by an admin.
Dynamic Routing
Routes in a router are added automatically.
Default Route
When no route is listed in the routing table, use the route that’s defined as default.
Ephemeral Ports
Ports that temporary and not permanent, ports range from 1,024 - 65,535.
Ports
Permanent ports that are well-known, ports range from 0 - 1,023.
How many bits are IPv4 and IPv6 addresses?
IPv4 - 32 bits, 4 octets in decimal
IPv6 - 128 bits, addresses in hexadecimal
Dual-stack routing
Routing that allows both IPv4 and IPv6 to be used interchangeably, most modern networks have support for this. Each protocol has it’s own configuration.
Teredo/Miredo
End-to-End tunneling which allows IPv6 through IPv4 networks that do not have dual-stack routing.
Packet/Traffic Shaping
Used on computer networks to delay some or all datagrams to bring them into compliance with a desired traffic profile. Used to optimize or guarantee performance, improve latency, or increase usable bandwidth for some kinds of packets by delaying other kinds.
QoS
Quality of Service - Description or measurement of the overall performance of a service, such as a telephony or computer network or a cloud computing service, particularly the performance seen by the users of the network. To quantitatively measure quality of service, several related aspects of the network service are often considered, such as packet loss, bit rate, throughput, transmission delay, availability, jitter, etc.
NAT
Network Address Translation - Translates private network IP address into public IP addresses that can routed over the internet.
Port Forwarding
Also called Destination NAT or Static NAT. Translates public port/IP addresses to private port/IP addresses to access internal services.
ACL
Access Control List - Packet filter used to allow or deny traffic, can be configured for both incoming and outgoing traffic. Can filter based on criteria such as source IP, destination IP, TCP/UDP port.
Circuit Switching
A method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate.
POTS
Plain Old Telephone Service
PSTN
Public Switched Telephone Service - The world’s collection of interconnected voice-oriented public telephone networks
ISDN
Integrated Services Digital Network - A set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network.
Packet Switching
A method of grouping data that is transmitted over a digital network into packets.
SDN
Software-defined networking - an approach to network management that enables dynamic, programmatically efficient centrally managed network configuration in order to improve network performance and monitoring making it more like cloud computing than traditional network management.
Distributed Switching
Distributed switching is a virtual network distributed across all physical platforms, there is no need for physical segmentation. Distributed switching allows similar services to live on the same VLAN, segmenting the network by logical services.
Explain bit vs byte
Bit - a single digit, either a 0 or 1
Byte - Comprised of 8 bits, often call an octet
Subnet Mask
A subnet mask separates the IP address into the network and host addresses, used by the local device to determine what network the device is on.
Default Gateway
Router, allows you to communicate outside of your local subnet. The default gateway must be an IP address on the local subnet.
Loopback Address
An address to yourself, used to test TCP/IP stack on local device, ping 127.0.0.1
Ranges from 127.0.0.1 to 127.255.255.254
Reserved Address
Set aside for future use or testing.
Ranges from 240.0.0.1 to 255.255.255.254
Virtual IP Address
Not associated with a physical network adapter, rather used by a virtual machine, internal router address
Class A Address
IP address starts between 1 - 126. 8 bits for network, 24 bits for host.
Class B Address
IP address starts between 128 - 191. 16 bits for network, 16 bits for host.
Class C Address
IP address starts between 192 - 223. 24 bits for network, 8 bits for host.
Network Address
The first IP address of a subnet, all host bits are set to 0.
ex: Given 172.16.88.200 (Class B)
Network Address 172.16.0.0
First usable host address
The first IP address of a subnet that can be used by a host, all host bits are set to 0 then increase the last octet by 1.
ex: Given 172.16.88.200 (Class B)
First usable host address 172.16.0.1
Last usable host address
The last IP address of a subnet that can be used by a host, all host bits are set to 1 then decrease the last octet by 1.
ex: Given 172.16.88.200 (Class B)
Last usable host address 172.16.255.254
Network broadcast address
The last IP address of a subnet, all host bits are set to 1.
ex: Given 172.16.88.200 (Class B)
Network broadcast address 172.16.255.255
How are IPv6 addresses assigned to ISPs?
The Internet Assigned Numbers Authority (IANA) provides address blocks to Regional Internet Registries (RIR). RIR assigns smaller subnet blocks to Internet Service Providers (ISP). ISP assigns a /48 subnet to the customer.
VLSM
Variable-Length Subnet Masking (VLSM) amounts to “subnetting subnets,” which means that VLSM allows network engineers to divide an IP address space into a hierarchy of subnets of different sizes, making it possible to create subnets with very different host counts without wasting large numbers of addresses.
DHCP
Dynamic Host Configuration Protocol - a network management protocol used on Internet Protocol networks whereby a DHCP server dynamically assigns an IP address and other network configuration parameters from a pool of predefined addresses to each device on a network so they can communicate with other IP devices and networks.
APIPA
Automatic Private Internet Protocol Addressing - A link local IP address that cannot be forwarded through a router. IP range is from 169.254.1.0 to 169.254.255.254. An address between this range gets automatically assigned if DHCP is enabled on a device but unable to get a legitimate IP address. Uses ARP to confirm address isn’t in use when assigned an APIPA address.
WLAN
Wireless Local Area Network - A group of wireless devices in the same broadcast domain. Uses 80.11
MAN
Metropolitan Area Network - A network in your city, larger than a LAN.
WAN
Wide Area Network - Spans states, countries, and even globally, generally connects LAN’s across a vast distance.
CAN
Campus/Corporate Area Network - A network across a group of multiple buildings in the same area. Often buildings are connected via fiber cabling.
NAS
Network Attached Storage - a file-level (as opposed to block-level) computer data storage server connected to a computer network providing data access to a group of clients. NAS is specialized for serving files either by its hardware, software, or configuration.
SAN
Storage Area Network - a computer network which provides access to consolidated, block-level data storage. SANs are primarily used to enhance accessibility of storage devices, such as disk arrays and tape libraries, to servers so that the devices appear to the operating system as locally-attached devices.
PAN
Personal Area Network - a computer network for interconnecting electronic devices centered on an individual person’s workspace.[1] A PAN provides data transmission among devices such as computers, smartphones, tablets and personal digital assistants.
Z-Wave
A wireless communications protocol used primarily for home automation. It is a mesh network using low-energy radio waves to communicate from appliance to appliance, allowing for wireless control of residential appliances and other devices, such as lighting, security systems, thermostats, windows, locks, swimming pools, and garage door openers.
Bluetooth
A wireless technology standard used for exchanging data between fixed and mobile devices over short distances using short-wavelength UHF radio waves in the industrial, scientific and medical (ISM) radio bands, from 2.402 GHz to 2.480 GHz, and building personal area networks (PANs).
NFC
Near-Field Communication - A set of communication protocols for communication between two electronic devices over a distance of 4 cm or less. Typically used for payment systems and access tokens.
ANT/ANT+
Adaptive Network Topology - A proprietary (but open access) multicast wireless sensor network technology designed and marketed by ANT Wireless (a division of Garmin Canada). It is primarily used for sports and fitness sensors.
802.11
Managed by IEEE, often updated and has different standards.
802.11a
5 GHz range, 54 Mbit/s , not common today
802.11b
2.4 GHz range, 11 Mbit/s, further range than 802.11a, lots of devices operate at the 2.4GHz frequency so subject to interference.
802.11g
2.4 GHz range, 54 Mbit/s, backwards compatible with 802.11b and is essentially an upgrade of 802.11b.
802.11n
2.4 or 5 GHz range, 40 MHz channel width, 600 Mbit/s, uses MIMO
802.11ac
5 GHz, 160 MHz channel width, 7Gbit/s, uses MIMO
MIMO
Multiple-Input and Multiple-Output - A method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation.
TDMA
Time-Division Multiple Access - is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots.[1] The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity.
CDMA
Code-Division Multiple Access - is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication channel. This allows several users to share a band of frequencies.
What is LTE when talking about 4G and LTE
Long Term Evolution - is a standard for wireless broadband communication for mobile devices and data terminals, based on the GSM/EDGE and UMTS/HSPA technologies. It increases the capacity and speed using a different radio interface together with core network improvements. Supports download rates of 150 Mbit/s.
LTE Advanced (LTE-A)
Long Term Evolution Advanced- Supports download rates of 300 Mbit/s.
Omnidirectional Antenna
Most common antenna, signal is evenly distributed on all sides
Directional Antenna
Focuses the signal in a particular direction
Wireless Survey Tools
Finds signal coverage and potential interference.
SaaS
Software-as-a-Service - is a software licensing and delivery model in which software is licensed on a subscription basis and is centrally hosted. It is sometimes referred to as “on-demand software”. Ex. DropBox
IaaS
Infrastructure-as-a-Service - Outsource your equipment but you’re still responsible for the management and security. Ex. AWS
PaaS
Platform-as-a-Service - is a category of cloud computing services that provides a platform allowing customers to develop, run, and manage applications without the complexity of building and maintaining the infrastructure typically associated with developing and launching an app. Ex. Salesforce
CASB
Cloud Access Security Broker is on-premises or cloud based software that sits between cloud service users and cloud applications, and monitors all activity and enforces security policies. A CASB can offer a variety of services such as monitoring user activity, warning administrators about potentially hazardous actions, enforcing security policy compliance, and automatically preventing malware.
DNS
Translates human-readable names into computer readable IP addresses. Hierarchical, follows a path. There are 13 root DNS server clusters with hundreds of top level domains such as .com, .net, .org, .gov, etc.
DNS Records
Resource Records - the database records of domain name services. Holds domain name and associated IP address in a text file. a DNS server has over 30 record types.
Address Records (A) and (AAAA)
Defined the IP address of a host, (A) record type is used for IPv4 and (AAAA) is used for IPv6.
Canonical Record
Is a type of resource record in the Domain Name System (DNS) which maps one domain name (an alias) to another (the canonical name).
DHCP Pool
Grouping of IP addresses, each subnet has its own scope and a scope is generally a contiguous pool of IP addresses. DHCP exceptions can be made inside the scope.
NTP
Network Time Protocol - Every devices has its own clock (every switch, router, firewall, server, workstation, etc.). These clocks automatically update with NTP servers and syncs device clock with server clock.
UTP
Unshielded Twisted Pair
STP
Shielded Twisted Pair
Plenum Space
Part of a building that can facilitate air circulation for heating and air conditioning systems usually at greater than atmospheric pressure. Space between the structural ceiling and the dropped ceiling or under a raised floor is typically considered plenum.
Plenum-rate Cable
Plenum-rated cable is not as flexible as traditional cable jackets as the jackets need to be fire-rated.
Coaxial Cables
RG-6 - Used in television/digital cable - high-speed
RG-59 - Used as a patch cables, not for long distances
