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.