Networking Flashcards
TCP
Transmission control Protocol (TCP)
- Establishes a connection between the sender and recipient using a handshake sequence of SYN, SYN/ACK, and ACK packets.
- Assigns each packet a sequence number so that it can be tracked.
- Allows the receiver to acknowledge (ACK) that a packet has been received.
- Allows the receiver to send a negative acknowledgement (NACK) to force retransmission of a missing or damaged packet.
- Allows the graceful termination of a session using a FIN handshake.
The main drawback is that this connection information requires multiple header fields. Using TCP can add 20 bytes or more to the size of each packet.
TCP is used when the application protocol cannot tolerate missing or damaged information
UDP
User Datagram Protocol (UDP)
connectionless, non-guaranteed method of communication with no sequencing or acknowledgements. There is no guarantee regarding the delivery of messages or the sequence in which packets are received.
UDP is suitable for applications that do not require acknowledgement of receipt and can tolerate missing or out-of-order packets.
Routers
- A SOHO router often simply routes between its local network interface and its WAN/Internet interface.
- A LAN router divides a single physical network into multiple logical subnetworks. Each logical network becomes a separate broadcast domain.
This type of router generally has only Ethernet interfaces.
A WAN or border router forwards traffic to and from the Internet or over a private WAN link. This type of router has an Ethernet interface for the local network and a digital modem interface for the WAN
Switch
- provisions one port for each device that needs to connect to the network.
- Unlike a hub, an Ethernet switch can decode each frame and identify the source and destination MAC addresses.
- It can track which MAC source addresses are associated with each port.
unmanaged switch
- function without requiring any sort of configuration
- You just power it on and connect some hosts to it, and it establishes Ethernet connectivity between the network interfaces without any more intervention
- unmanaged switches with four or eight ports used in small networks.
- There is an unmanaged four-port switch embedded in most of the SOHO router/modems supplied by Internet Service Providers (ISPs) to connect to their networks.
managed switches
- Switches designed for larger LANs (VLAN support)
- A typical workgroup switch will come with 24 or 48 access ports for client PCs, servers, and printers. These switches have uplink ports allowing them to be connected to other switches.
- An enterprise might also use modular switches. These provide a power supply and fast communications
- Configuring a managed switch can be performed over either a web or command line interface.
Patch Panels
- In most types of office cabling, the computer is connected to a wall port and—via cabling running through the walls—to a patch panel. The cables running through the walls are terminated to insulation displacement connector (IDC) punchdown blocks at the back of the panel.
- The other side of the patch panel has prewired RJ45 ports. A patch cord is used to connect a port on the patch panel to a port on an Ethernet switch.
Hubs
- is a legacy network hardware device that was used to implement the 10BASE-T and 100BASE-T Ethernet cabling designs. This design is referred to as a star topology” because each end system is cabled to a concentrator (the hub).
- A hub has a number of ports—typically between four and 48—and each computer is cabled to one port.
- The circuitry in the hub repeats an incoming transmission from a computer attached to one port across all the other ports.
- You are only likely to encounter a hub being used in very specific circumstances, such as where legacy equipment must be kept in service.
PoE
Power over Ethernet (PoE)
is a means of supplying electrical power from a switch port over ordinary data cabling to a powered device (PD), such as a voice over IP (VoIP) handset, camera, or wireless access point. PoE is defined in several IEEE standards:
- 802.3af allows powered devices to draw up to about 13 W.
- 802.3at (PoE+) allows powered devices to draw up to about 25 W
- 802.3bt (PoE++ or 4PPoE) supplies up to about 51 W (Type 3) or 73 W (Type 4) usable power.
PoE-enabled switch
is referred to as endspan power sourcing equipment (PSE)
- Powering these devices through a switch is more efficient than using a wall-socket AC adapter for each appliance
- If the switch does not support PoE, a device called a “power injector” (or “midspan”) can be used. One port on the injector is connected to the switch port. The other port is connected to the device. The overall cable length cannot exceed 100 m.
access point (AP)
Not a wireless router
- A wireless router is a router and an access point is a single device
- extends the wired network onto the wireless network
- The MAC address of the AP’s radio is used as the Basic Service Set Identifier (BSSID).
Firewall
Software or hardware device that protect a network segment or individual host by filtering packets to an acces control list.
- A basic firewall is configured with rules, referred to as a network access control list (ACL)
PoE
PoE: IEEE 802.3af-2003
– The original PoE specification
– Now part of the 802.3 standard
– 15.4 watts DC power, 350 mA max current
PoE+
PoE+ : IEEE 802.3at-2009
– Now also part of the 802.3 standard
– 25.5 watts DC power, 600 mA max current
PoE++
PoE++: IEEE 802.3bt-2018
– 51 W (Type 3), 600 mA max current
– 71.3 W (Type 4), 960 mA max current
– PoE with 10GBASE-T
Cable modem
Broadband
– Transmission across multiple frequencies
– Different traffic types
* Data on the “cable” network
– DOCSIS (Data Over Cable Service Interface Specification)
* High-speed networking
– Speeds up to 1 Gigabit/s are available
* Multiple services
– Data, voice, video
DSL modem
- ADSL (Asymmetric Digital Subscriber Line)
– Uses telephone lines - Download speed is faster than the upload
speed (asymmetric)
– ~10,000 foot limitation from the central office (CO)
– 52 Mbit/s downstream / 16 Mbit/s upstream are
common
– Faster speeds may be possible if closer to the CO
ONT
- Optical network terminal
– Fiber to the premises - Connect the ISP fiber network to the copper network
– Demarcation point (demarc) in the data center
– Terminal box on the side of the building - Line of responsibility
– One side of the box is the ISP
– Other side of the box is your network
Network Interface Card (NIC)
- The fundamental network device
– Every device on the network has a NIC
– Computers, servers, printers, routers, switches,
phones, tablets, cameras, etc. - Specific to the network type
– Ethernet, WAN, wireless, etc. - Often built-in to the motherboard
– Or added as an expansion card - Many options - Single port, multi-port, copper, fiber
MAC
Each Ethernet NIC port has a unique hardware/physical address, called the “media access control” (MAC) address.
SDN
SDN (Software Defined Networking)
network functions are divided into three layers :
Infrastructure layer / Data plane
– Process the network frames and packets
– Forwarding, trunking, encrypting, NAT
Control layer / Control plane
– Manages the actions of the data plane
– Routing tables, session tables, NAT tables
– Dynamic routing protocol updates
Application layer / Management plane
– Configure and manage the device
– SSH, browser, API
802.11
Wireless networking (802.11)
– Managed by the IEEE LAN/MAN
Standards Committee (IEEE 802)
* Many updates over time
– Check with IEEE for the latest
* The Wi-Fi trademark
– Wi-Fi Alliance handles interoperability testing
802.11a
- One of the original 802.11 wireless standards
– October 1999 - Operates in the 5 GHz range
– Or other frequencies with special licensing - 54 megabits per second (Mbit/s)
- Smaller range than 802.11b
– Higher frequency is absorbed by objects in the way - Not commonly seen today
802.11b
- Also an original 802.11 standard - October 1999
- Operates in the 2.4 GHz range
- 11 megabits per second (Mbit/s)
- Better range than 802.11a, less absorption problems
- More frequency conflict
– Baby monitors, cordless phones,
microwave ovens, Bluetooth - Not commonly seen today
802.11g
- An “upgrade” to 802.11b - June 2003
- Operates in the 2.4 GHz range
- 54 megabits per second (Mbit/s) - Similar to 802.11a
- Backwards-compatible with 802.11b
- Same 2.4 GHz frequency conflict problems as 802.11b
802.11n (Wi-Fi 4)
- The update to 802.11g, 802.11b, and 802.11a
– October 2009 - Operates at 5 GHz and/or 2.4 GHz
– 40 MHz channel widths - 600 megabits per second (Mbit/s)
– 40 MHz mode and 4 antennas - 802.11n uses MIMO
– Multiple-input multiple-output
– Multiple transmit and receive antennas
802.11ac (Wi-Fi 5)
- Approved in January 2014
– Significant improvements over 802.11n - Operates in the 5 GHz band
– Less crowded, more frequencies (up to 160 MHz
channel bandwidth) - Increased channel bonding - Larger bandwidth usage
- Denser signaling modulation
– Faster data transfers - Eight MU-MIMO downlink streams
– Twice as many streams as 802.11n
– Nearly 7 gigabits per second
802.11ax (Wi-Fi 6)
- Approved in February 2021
– The successor to 802.11ac/Wi-Fi 5 - Operates at 5 GHz and/or 2.4 GHz
– 20, 40, 80, and 160 MHz channel widths - 1,201 megabits per second per channel
– A relatively small increase in throughput
– Eight bi-directional MU-MIMO streams - Orthogonal frequency-division multiple access (OFDMA)
– Works similar to cellular communication
– Improves high-density installations
RFID
RFID (Radio-frequency identification)
* It’s everywhere
– Access badges
– Inventory/Assembly line tracking
– Pet/Animal identification
– Anything that needs to be tracked
* Radar technology
– Radio energy transmitted to the tag
– RF powers the tag, ID is transmitted back
– Bidirectional communication
– Some tag formats can be active/powered
NFC
NFC (Near field communication)
* Two-way wireless communication
– Builds on RFID, which is mostly one-way
* Payment systems
– Major credit cards, online wallets
* Bootstrap for other wireless
– NFC helps with Bluetooth pairing
* Access token, identity “card”
– Short range with encryption support
RFID
Radio Frequency ID (RFID)
passive device that only responds when scanned at close range (up to about 25 m) or a powered, active device with a range of 100 m.
long-range fixed wireless.
- Wireless access point in a house with the stock antennas
– You might get a range of 40 to 50 meters - Try connecting two buildings located miles from each other
– Fixed directional antennas and increased signal strength - Outdoors
– Minimal signal absorption or bounce - Directional antennas
– Focused, point-to-point connection - Wireless regulations are complex
– Refer to your country’s regulatory agency - Frequency use
– Unlicensed 2.4 GHz or 5 GHz frequencies
– Additional frequencies may be available
– Additional licensing may be required - Signal strength
– Indoor and outdoor power is usually regulated - Outdoor antenna installation is not trivial
– Get an expert, be safe
