Networking Flashcards
TCP
-Transmission Control Protocol
-Connection-Oriented
–a formal connection setup and close
-‘Reliable’ delivery
–Recovery from errors
–Can manage out-of-order messages or retransmissions
-Flow control
–The receiver can manage how much data is sent
UDP
-User Datagram Protocol
-Connectionless (no formal open or close to the connection)
-“Unreliable” delivery
–No error recovery
–No reordering of data or retransmissions
-No flow control
–Sender determines the amount of data transmitted
Why would you ever use UDP?
-Real-time communication
-There’s no way to stop and resend the data
-Time doesn’t stop for your network
-DHCP (Dynamic Host Configuration Protocol)
-TFTP (Trivial File Transfer Protocol)
Communications that use TCP and why
-Connection-oriented protocols prefer a ‘return receipt’
-HTTPS (Hypertext Transfer Protocol Secure)
-SSH (Secure Shell)
-The application doesn’t worry about out-of-order frames or missing data
-TCP handles all of the communication overhead
Non-ephemeral ports
-Permanent port numbers
-Ports 0-1023
-Usually on a server or service
Ephemeral ports
-Temporary port numbers
-Ports 1024 through 65,535
-Determined in real time by the client
Port Numbers
-TCP and UDP ports can be any number between 0-65,535
-Most servers use non-ephemeral port number
-Port numbers are for communication not security
-Service port numbers need to be well-known
-Important for firewall rules (port-based security)
FTP
-File Transfer Protocol
-tcp/20 = active mode data
-tcp/21 = control
-Transfers files between systems
-Authenticates with a username and password
-Some systems use a generic/anonymous login
SSH
-Secure Shell
-Encrypted communication link
-tcp/22
-Looks and acts the same as Telnet
Telnet
-Telecommunication Network
-tcp/23
-Login to devices remotely (console access)
SMTP
-Simple Mail Transfer Protocol
-Server t server email transfer
-tcp/25
-Also used to send mail from a device to a mail server
Other protocols are used for clients to receive emails (IMAP, POP3)
DNS
-Domain Name System
-Converts names to IP addresses
-upd/53
DHCP
-Dynamic Host Configuration Protocol
-Automated configuration of IP address, subment mask, and other options
-udp/167, udp/168
-Requires a DHCP server
DHCP Dynamic/Pooled
-IP addresses are assigned in real-time from a pool
-Each system is given a lease and must renew at a set interval
DHCP Reservation
-Addresses are assigned by MAC address in the DHCP server
-Manage addresses from one location
HTTP
-Hypertext Transfer Protocol
-Communication in the browser and by other applications
-tcp/80
HTTPS
-Hypertext Transfer Protocol Secure
-Secure communication in the browser
-Encrypted
-tcp/443
POP3
-Post Office Protocol version 3
-Receive emails from an email server
-Authenticate and transfer
-tcp/110
-Basic mail transfer functionality
IMAP
-Internet Message Access Protocol v4
-tcp/143
-Receive emails from an email server
-includes management of email inbox from multiple clients
SMB
-Server Message Block
-Protocol used by Microsoft Windows
-File sharing, printer sharing
-“CIFS” - Common Internet File System
-using NetBIOS over TCP/IP (Network Basic Input/Output System)
–udp/137 = NetBIOS name services (nbname)
–tcp/139 = NetBIOS session service (nbsession)
-Direct over tcp/445 (NetBIOS-less) (Direct SMB connection over TCP w/o the NetBIOS transport
SNMP
-Simple Network Management Protocol
-Gather statistics from network devices
-udp/161 = queries
-udp/162 = traps
LDAP
-Lightweight Directory Access Protocol
-tcp/389
-Store and retrieve information in a network directory
-Commonly used in Microsoft Active Directory
RDP
-Remote Desktop Access Protocol
-Share a desktop from a remote location
-tcp/3389
-Can connect to an entire desktop or just an application
-Clients for Windows, macOS, Linux, UNIX, iPhone, Android, and others
Routers
-Routes traffic between IP subnets
–Makes forwarding decisions based on IP address
-Often connects diverse network types (LAN, WAN, copper, fiber)
Switches
-Bridging done in hardware
–Application-Specific Integrated Circuit (ASIC)
–Forwards traffic based on data link address
-The core of an enterprise network
-May provide Power over Ethernet (PoE)
Multilayer switch
-Switch that includes routing functionality
Unmanaged switches
-Very few configuration options (plug and play)
-Fixed configuration (no VLANs)
-Very little integration with other devices (no management protocols)
-Cheaper
Managed switches
-VLAN support
(Interconnect with other switches via 802.1Q)
-Traffic prioritization (voice traffic gets a higher priority)
-Redundancy support (Spanning Tree Protocol - STP)
-Port mirroring (capture packets)
-External management (Simple Network Management Protocol - SNMP)
Access Point
-A bridge
-Extends the wired network onto the wireless network
-Makes forwarding decisions based on MAC address
-Not a wireless router
Wireless Router
- a router and an access point in a single device
Patch panels
-Combination of punch-down blocks and RJ-45 connectors
-Run from desks are made once (permanently punched down to patch panel)
-Patch panel to switch can be easily changed (no special tools - use existing cables)
Firewalls
-Filters traffic by port number
–OSI layer 4 (TCP/UDP)
–Some firewalls can filter by application
-Can encrypt traffic into/out of the network
-Can proxy traffic - a common security technique
-Most firewalls can be layer 3 devices (routers)
PoE
-Power over Ethernet
-Power provided on an Ethernet cable
-one wire for both network and electricity (ex phones, cameras, wireless APs)
-Useful in difficult-to-power areas
-Power provided at the switch
–Built-in power=endspans
–In-line power injector=midspans
PoE (2003)
-IEEE 802.3af
-The original PoE specification
-Now part of the 802.3 standard
-15.4 watts DC power, 350mA max current
PoE+ (2009)
-IEEE 802.3at
-Now part of the 802.3 standard
-25.5 watts DC power, 600 mA max current
PoE++ (2018)
-IEEE 802.3bt
-51W (type 3), 600mA max current
-71.3 W (type 4), 960mA max current
-PoE w/ 10GBASE-T
Hub
-‘Multi-port repeater’
–Traffic going in one port is repeated to every other port
-Everything is half-duplex
-Becomes less effiecent as network traffic increases
-10 megabit/100 megabit
-Difficult to find today
Cable Modem
-Broadband
–Transmission across multiple frequencies
–Different traffic type
-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 that the upload speed (asymmetric)
– ~10,000 ft limitation from the central office (CO)
– 52Mbit/s downstream / 16Mbit/s upstream are common
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 ISP
– Other side of the box is your network
NIC
-Network Interface Card
-Every device on the network has a NIC
-Specific to the network type (Ethernet, WAN, wireless, etc)
-Often built-in to the motherboard or added as an expansion card
SDN
-Software Defined Networking
-Networking devices have different functional planes of operation (data, control, and management planes)
-Split the functions into separate logical units
–extend the functionality and management of a single device
–Perfectly built for the cloud
SDN Infrastructure layer/data plane
-Process the network frames and packets
-Forwarding, trunking, encryption, NAT
SDN Control layer/control plane
-Manages the actions of the data plane
-Routing tables, session tables, NAT tables
-Dynamic routing protocol updates
SDN Application layer/management plane
-Configure and manage the device
-SSH, browser, API
Wireless Networking
-802.11
-Managed by the IEEE LAN/MAN Standards Committee (IEEE 802)
802.11a
-One of the original 802.11 wireless standards
-Operates in the 5 GHz range (or other frequencies with special licensing)
-54 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
-Operates in the 2.4 GHz range
-11 Mbit/s
-Better range than 802.11a
-More frequency conflict(baby monitors, cordless phones, microwave ovens, bluetooth)
-Not common today
802.11g
-Operated in the 2.4 GHz range
-54Mbit/s
-Backwards-compatible w/ 802.11b
-Same 2.4 GHz frequency conflict problems as 802.11b
802.11n
-WiFi 4
-The upgrade to 802.11g, b, and a
-Operates at 5 GHz &/or 2.4 Gbit/s (can be simultaneously) (40MHz channel widths)
-600Mbit/s (40 MHz mode and 4 antennas)
-Uses MIMO
–Multiple-Input Multiple-Output
–Multiple transmit and receive antennas