Network Infrastructure Concepts Flashcards
Definition of a Network
Network: In its most simple form, a network consists of two or more computers connected to each other by an appropriate transmission medium that allows them to share data.
Give all types of networks
Types: LANs, WANs, MANs
What is the purpose of a network?
Purpose: Provide services and resources to users
What are the modern forms of networks?
Modern: web applications, social networking, VoIP, multimedia conferencing
What historically would share data over a network?
Historically: files, folders, printers, email, databases
What are LANs based upon
Ethernet (networking product)
Who developed Ethernet
DIX consortium( Digital Equipment Corporatio[DEC],Intel and Xerox)
Who maintains Ethernet standards
Maintained by IEEE [Institute of Electrical and Electronics Engineers] (802.3 standards)
Give all types of Ethernet
Types:
10 Mbps (10BASE)
Fast Ethernet (100BASE)
Gigabit Ethernet (1000BASE)
10G Ethernet (10GBASE)
True or False
Ethernet is not flexible, self-contained, scalable
False
Ethernet is flexible, self-contained, scalable
What is complementary to IEEE 802.11 standards (Wi-Fi)
WLANs
What are the two classes of LANs
SOHO and Enterprise Network
Definition of SOHO
SOHO: business network with server and clients, using single Internet appliance as an access point, Ethernet switch, Internet modem, Internet router.
Definition of Enterprise Network
Enterprise network: usually dedicated single-function connectivity appliances.
Definition of SME
Small and Medium-Sized Enterprise (SME): network supporting tens of users; multiple switches, access points, routers.
Definition of Enterprise LAN
Enterprise LAN: hundreds or thousands of servers and clients; multiple enterprise-class switches, access points, and routers.
Definition of CAN
Campus Area Network (CAN) = LAN spanning multiple nearby buildings.
Definition of UTP
UTP: Unshielded Twisted Pair
Features of UTP
Most widely used
Four copper conductor pairs
Insulating sheath
Twisted to reduce crosstalk and EMI
Paired wires carry equal/opposite signals
PVC jacket
Works well in low interference; has limited range, may exhibit attenuation
What are the standards for CAT 5
Frequency: 100 MHz
Capacity: 100 Mbps
Max Distance : 100m (328 ft)
Network Applications: 100BASE-TX
What are the standards for CAT 5e
Frequency: 100 MHz
Capacity: 1 Gbps
Max Distance : 100m (328 ft)
Network Applications: 1000BASE-T
What are the standards for CAT 6
Frequency: 250 Mhz
Capacity: 1 Gbps or 10 Gbps
Max Distance : 100m(328 ft) or 55m(180 ft)
Network Applications: 1000BASE-T or 10G BASE-T
What are the standards for CAT 6A
Frequency: 500 Mhz
Capacity: 10 Gbps
Max Distance : 100m(328 ft)
Network Applications: 10GBASE-T
Definition of STP
STP: Shielded Twisted Pair
Features of STP
Shielded Twisted Pair (STP)
Originally used the braided shield to reduce interference and crosstalk; can be bulky, difficult to install.
Modern STP uses screened cables; shield positioned around all pairs.
Shielded Cat 53/6/6A:
F/UTP (also ScTP)
U/FTP
Modern STP solutions incorporate grounding in each element.
Definition of Plenum
Plenum: An air handling space, including ducts and other parts of the HVAC system in a building.
Features of Plenum Space
Typically a false ceiling, maybe raised floor.
May be used for communications wiring.
Can be the conduit for fire.
What does general-purpose(non-plenum) use
General-purpose non-plenum cable uses PVC; marked CMG/MMG or CM/MP
True or False
Plenum cable must not emit smoke, must self-extinguish, meet other fire safety standards.
True
Features of Plenum
Uses treated PVC or FEP; can be less flexible, does not affect bandwidth.
Marked CMP/MMP.
For what modular does twisted pair cabling for Ethernet terminated
RJ-45 connectors
Features of Ethernet twisted pair terminated with RJ-45 connectors
8P8C (8-position/8-contact)
Color-coded (Blue, Orange, Green, Brown)
1st conductor in pair has white/stripes
2nd conductor in pair is a solid color
Features of ANSI/TIA/EIA 568 termination
T568A is shown
T568B:
Pin 1=Orange/White; Pin 2=Orange; Pin 3=Green/White; Pin 4=Green
What cable has the same termination at both ends?
Normal (straight-through) cable
Wiring Standards for Twisted Pair:
Features of crossover cable that has T568A at one end, T568B at the other.
Previously used for direct connections.
Now Gigabit Ethernet interfaces can automatically cross over with standard cable.
Wiring Standards for Twisted Pair:
Why should you avoid mixing standards
Both are common.
T568A mandated for US government and by TIA 570 residential cabling standard
True or False
Gigabit Ethernet has no more than 100 m of cable between switch and computer
True
Features of solid cabling
Single thick wire for permanent links, aka “drop cables”
Links RJ-45 port on a wall plate with patch panel
Terminates in IDC
Features of patch cord connects RJ-45 port on the panel to port on the switch
Stranded cable; flexible, less efficient
5 m maximum length
Definition of wire stripper/cutter
Wire stripper/cutter: for cutting wire and stripping insulation and cable jackets.
Definition of punch-down tool
Punch-down tool: fixes conductors into an IDC.
Definition of crimper
Crimpers: fix a jack into a cable.
What should you do when you cable test.
Cable testing:
Verify wiring installation and termination just after making connections, with access to cable runs.
Simpler than during user device setup.
Consider:
Patch cord between PC and wall.
Wall port and wall cabling.
The port on the patch panel and a patch cord to the switch port.
Test with a known good cable.
Various troubleshooting devices.
Definition of Multumeter
Multimeter: basic cable testing tool; tests for copper wire continuity, the existence of short, the integrity of terminator.
Definition of Wire Map Tester
Wire map tester: identifies transpositions and reverse pairs.
Definition of Advance Testers
Advanced testers: show cable’s physical/electrical properties.
Definition of Certifiers
Certifiers: test and certify installation to a category.
Definition of Loopback plug
Tests a port
Connects pin 1 to pin 3 and pin 2 to pin 6
What are electrical signals on copper wire subjects too?
To interference/attenuation.
What does light signals on fiber optic cable resist
Interference, eavesdropping, attenuation.
What does fiber optic cables support
Supports higher bandwidth, longer cable runs.
What is SMF
Single-Mode Fiber
What is MMF
Multi-Mode Fiber
Features of SMF
Small core, long-wavelength, near-infrared signal generated by the laser.
Data rates up to 10 Gbps or more; cable runs of many kilometers (suitable for WANs).
Features of MMF
Larger core, shorter wavelength.
Less expensive optics, less expensive deployment.
Lower signaling speeds, shorter distances (suitable for LANs).
What are the types of connectors for fiber optic cabling
Straight Tip (ST), Subscriber Connector (SC), Lucent/Local Connector (LC).
True or False
Patch cords can have the same or mixed connectors.
True
True or False
Connectors damage easily; plug/unplug only when needed.
True
Features of Coaxial Cabling
Two conductors share the same axis.
Signal conductor insulated; second wire mesh conductor acts as EMI shield and as ground.
What is coaxial cabling available as
Coax is also available with tri- or quad-shielding.
What is RG(Radio Graded) standard categorize by
categorizes cable by thickness and impedance.
Types of Coaxial Cabling by the RG standard
RG-6: thicker core, better quality, often used as drop/patch cable in modern CATV and broadband.
RG-59: thinner core; drop cable for older CATV/cable modems; used in CCTV.
What is coaxial cabling shielding is also available?
Coax is also available with tri- or quad-shielding.
What connectors are at the ends of coaxial cabling?
BNC connectors at cable end in most cases.
Also screw-down F-connectors.
What connects coaxial cables
BNC couplers can connect cables.
What cable types must the impedance of the coaxial cable match.
50 or 75 ohm
What do 10BASE-5/Thicknet and 10BASE-2/Thinnet support
Supported 10 Mbps, up to 500 m and 185 m, respectively.
Coax is now obsolete for LANs but what is it used for.
In use for CCTV and drop cables for CATV and Internet.
What does a Hybrid Fiber Coax (HFC) do?
Coax links fiber trunk in street to a customer cable modem.
Less attenuation than TP but bulkier, harder to install.
Definition of NIC
Network Interface Card (NIC) port provides a connection to network media.
Features of NIC
Data signals must come in regular units with a consistent format.
Each node must be able to address other nodes.
Ethernet data link protocol provides addressing, framing functions.
Various encoding mechanisms; NIC transceiver transmits and sends in agreed frame format.
Where is the NIC in a PC
Usually onboard the motherboard.
Features of NIC
Maybe PCIe expansion board.
All onboard cards support copper-based Ethernet with RJ-45 ports.
Expansion cards may support:
Fiber optic.
Multiple port types.
Multiple ports of the same type (can be bonded for higher-speed links).
Defintion of a MAC adresss
MAC address: unique address for each Ethernet adapter port.
What does a MAC address provide
Provides value for frame source and destination fields.
How many bytes does a MAC address contain
48 bits/6 bytes.
How is a MAC address shown
Shown as 12 hex digits:
May have colon, hyphen, or no separator.
Examples: 00:60:8c:12:3a:bc or 00608c123abc.
What does a LED status show?
Show connection status
Features of a LED that’s part of an Ethernet NIC
Link light shows if the network signal is present.
Activity light flickers when packets are received/sent.
Speed light possible on multi-speed adapters.
Dual-color LEDs combine functions.
Give all legacy networking appliances and definitions
Legacy appliances include:
Hub: center of Ethernet star topology, works as a multiport repeater.
Repeater: retransmits the signal to overcome distance limitations.
Bridge: divides the network into segments (collision domains) to reduce contention and collision.
True or False
A switch is not an appliance at the core of modern networks.
False
A switch is an appliance at the core of modern networks.
In a modern network what does act like.
Ethernet switch in the modern network acts like a hub, repeater, and bridge.
Features of micro-segmentation
Switches have up to 48 ports.
Multiple switches can connect to the switched fabric with thousands of ports.
Each port is a separate collision domain.
Establishes point-to-point link (virtual circuit) between any two nodes.
Collisions only occur if the port is half-duplex (attached to a legacy card or node).
Collisions only affect that segment, not the whole network.
Features of an unmanaged switch
Unmanaged switch:
Performs micro-segmentation without configuration.
May be found in small networks (4 or 8 port switches).
Embedded in most ISP’s Internet routers/modems.
Features of a managed switch
Managed switch:
For larger workgroups and corporate networks.
Unmanaged out of the box, but can be configured administratively.
Can provide thousands of access ports by linking switches.
Can divide into virtual LANs (VLANs).
Definition of Power over Internet
Supplies power from a switch port over Cat 5 or better to a powered device.
Features of PoE
PoE-enabled switches are called end-span/end-point PSE.
A power injector can be used if the switch does not support PoE.
The switch detects if the connected device is PoE-enabled.
More efficient than powering each device through a wall socket.
Network-management software can control devices, apply power schemes.
Give all the two standards for PoE
Two IEEE standards (both now in 802.3-2012):
802.3af
802.3at (PoE+)
Features of Ethernet of Power
SOHO networks are unstructured, use a single router, incorporate smart appliances.
Wireless is an obvious solution; WLAN bandwidth may be adequate.
There may be interference issues or appliances may not support Wi-Fi.
Ethernet over Powerline uses building power circuits; overlays carrier signal to transfer Ethernet frames.
The adapter plugs into an electrical outlet; provides RJ-45 ports.
No configuration is needed, but security can be configured.
Standards defined by IEEE 1901, managed by HomePlug Powerline Alliance.
What is Wireless Networking?
A range of connectivity products and devices.
Personal area networking to Internet connectivity.
Usually uses radio waves for transmission, tuned to a specific frequency.
What is the range of RF
RF ranges from 3 KHz to 300 GHz
Give all features of wireless frequencies and channels
Subdivided into bands (FM radio and TV are VHF band)
Radio spectrum use regulated by governments
Standardized by ITU
Frequency use requires a license
Some unregulated frequencies
What standard does Wifi equal?
IEEE 802.11 standards = Wi-Fi
(Transfer rates for optimal installation; frequencies lack penetration; may be interference; data rate may drop with distance.)
What is the max transfer rate and band for 802.11a (1999)
Maximum Transfer Rate
54 Mbps
Band
5 GHz
What is the max transfer rate and band for 802.11b (1999)
Maximum Transfer Rate
11 Mbps
Band
2.4 GHz
What is the max transfer rate and band for 802.11g (2003)
Maximum Transfer Rate
54 Mbps
Band
2.4 GHz
What is the max transfer rate and band for 802.11n (2009)
Maximum Transfer Rate
288.8 Mbps/stream (Single Channel)
600 Mbps/stream (Bonded Channels)
Band
2.4/5 GHz
What is the max transfer rate and band for 802.11ac (2013)
Maximum Transfer Rate
1.7 Gbps (at time of writing)
Band
5 GHz
What is the features of 2.4 GHz frequency bands in 802.11
2.4 GHz:
Longer wavelength, longer range, propagates better through solids
Does not support many individual channels; is often congested
Increased risk of interference
Achievable data rates less than 5 GHz
What is the features of 5 GHz frequency bands in 802.11
5 GHz:
Less effective at solid surface penetration
Lower range than 2.4 GHz
More individual channels; less congestion
Higher data rates
Give a descrpition of the range of wireless frequencies
Range:
2.4 GHz: maximum indoor range ~30-45 m (100–150 ft).
5 GHz: maximum indoor range up to ~30 m.
Absolute range less important than number of clients to support and wall/ceiling construction.
Give the channels and description of wireless frequiencies
Channels:
2.4 GHz: up to 14 channels, considerable overlap, co-channel interference.
Special codes distinguish pattern of each node.
Channel can become saturated.
5 GHz: 23 non-overlapping channels:
More WANs in same area or access points closer together, higher client device density.
True or False
802.11a/b/g considered legacy standards, limited to old equipment
True
Give a full description of 802.11n
More bandwidth than legacy standards.
Multiplexes 2-4 antennas using MIMO.
AxB:C notation (transmit antennas, receive antennas, simultaneous streams).
Can use 2.4 GHz or 5 GHz band (preferred).
Can use channel bonding in 5 GHz band to deliver more bandwidth.
Nominal data rates 288.8 Mbps (single channel) and 600 Mbps (bonded channels).
Give a full description of 802.11ac
Continues development of 802.11n.
Works in 5 GHz range.
Can use 2.4GHz range for legacy standards in mixed mode.
Aims for throughput comparable to Gigabit Ethernet.
Supports channel bonding to 80 or 160 MHz channels; 8 special streams vs. 4; denser modulation.
Needs high-end equipment for sufficient antennas for 8 streams.
Theoretical data rate with 8 streams and 160 MHz channel bonding ~6.93 Gbps.
True or False
Most Wi-Fi networks are Infrastructure mode
True
How does a client connect to a network
Each client connects with an Access Point (AP)
What is BSS
Basic Service Set
What is the MAC address of a AP called
BSSID
What is an AP
AP is bridge between wired/wireless network (Distribution System)
AP connects to network like a host computer
What is a WDS
Wireless Distribution System (WDS)
What tasks does a AP complete
Extends network without a cabled backbone.
Bridge mode and repeater mode.
Can be complex; can be compatibility issues with different vendors’ devices.
True or False
Range extender is simpler residential solution; can work with powerline adapter.
True
What is the description of a configuration called Ad-hoc and Wi-Fi Direct
Stations configured to make direct peer-to-peer connections.
Older standards: ad-hoc mode.
Modern approach: Wi-Fi Direct.
What is the description of a configuration called
Wireless Mesh Network (MSN)
Part of 802.11s standard.
Nodes (Mesh Stations) can discover each other and make peer connections to form Mesh Basic Service Set.
Mesh stations perform path discovery and forwarding.
Routing protocol such as Hybrid Wireless Mesh Protocol (HWMP).
What is the description of a configuration called
Personal Area Network (PAN)
Using wireless connectivity to connect to devices with a few meters.
Printers, smartphones, headsets, etc.
Features of wireless network card
Each Wi-Fi network station needs network adapter compatible with 802.11 standard in use on network.
Onboard adapters; expansion boards; USB-connected adapters.
Link-layer MAC address like Ethernet cards.
Defintion of Internet Backbone
Internet backbone: high-bandwidth backbones connecting Internet eXchange Points (IXPs).
Who created internet connections
Created by telecommunications companies and academic institutions .
Organized nationally and internationally.
What do business and home networks use to connect to the internet
ISP( Internet Service Provider)
What does an ISP allocate
ISP allocates IP addresses, registers domain names, hosts email and websites.
What do Enterprise ISP offer
Enterprise ISPs offer high bandwidth through fiber optic cable.
Features of a ISP
Network connects to ISP’s Point of Presence (PoP).
Dial-up, broadband (DSL, FTTx, cable), wireless connections.
Most use PSTN (aka POTS, “local loop,” “last mile”).
Give a description of a broadband internet access
A range of technologies
“Always on”
Data transfer rates much higher than dial-up
Give a description of DSL
DSL uses high frequencies in digital phone line for communications.
Filter separates DSL signals from voice traffic.
Advanced modulation and echo cancelling enable high-bandwidth, full-duplex.
DSL “modem” connects to phone system (usually router/modem/AP appliance).
Phone line connects to DSL modem bank (DSLAM).
PPP over ATM (PPPoA) or PPP over Ethernet (PPPoE).
Give a full description of DSL type Asymmetrical DSL (ADSL)
Consumer version; fast downlink, slow uplink
Various iterations
ADSL2+: downlink rates up to ~24 Mbps; uplink rates up to ~1.4 Mbps
Providers may restrict data download
Cable quality, number of users may affect speed
Max range ~2 miles/3 km
Give a full description of DSL type Symmetric DSL
Same uplink and downlink speeds
Useful for businesses, branch offices
Give a full description of DSL type Very High Bitrate DSL (VDSL)
High bit rate at expense of range
Symmetric and asymmetric modes
Asymmetric: 52 Mpbs downstream/6 Mpbs upstream over 300 m/1000 ft
Symmetric: 26 Mbps in both directions
VDSL2: 100 Mpbs bi-directional rates for very short range
Give all features of Fiber Optic Internet Access
Higher bandwidth, a longer distance than copper cable
Has replaced copper as core of telecommunications networks
Being extended to individual homes and businesses
Two principal types of fiber optic network services:
Cable TV providers
Telecom providers
What is HFC
Hybrid Fiber Coax (HFC)/Cable (“broadband cable” “cable”): Connection through CATV service, combines fiber core with coax to customer.
How does a Cable modem connect to a local network
The cable modem connects to the local network through an Ethernet adapter.
What does DOCSIS v3 allow
DOCSIS v3 allows multiplexed channels for higher bandwidth.
What can a coax do when it’s on a premises
Coax links all premises in a street with CMTS to ISP PoP via fiber backbone.
Give the upload and download speed of DOCSIS
DOCSIS: Downlink up to 38 Mbps (North America) or 50 Mbps (Europe); and uplink up to 27 Mbps.
Give a description of Fiber to the X (FTTx)
Solutions where fiber replaces copper in the “last mile”
Give a description of Fiber to the Premises (FTTP)/
Fiber to the Home (FTTH)
Most expensive, not widespread
Fiber link terminated at customer premises equipment
Give a description of Fiber to the Node (FTTN)
Fiber to the Curb/Cabinet (FTTC)
Fiber to communications cabinet at street
Similar to HFC, but consumer link uses VDSL over phone wiring (not coax)
Give a full description of Dial-Up Internet Access
Telephone connection between computers.
Uses entire frequency range; not efficient, low bandwidth.
Phone charges apply; lines cannot be used for voice at the same time.
Modems at each end convert digital-analog (MOdulation/DEModulation).
What are the disadvantages of Dial-Up Internet Access
Disadvantages: low data transfer, time to establish connection, errors
What is the fastest modem of Dial-Up Internet Access
Fastest modems ~33.6 Kbps; speed limit of the phone line
Theoretical maximum downlink ~56 Kbps
What are Dial-up Internet Access still used for
Has been superseded; still in use as a backup or for areas without other support
How can Dial-up Internet Access speed be increased
Compression may improve data transfer
Give a full description of ISDN Internet Access
Digital circuit-switched technology for voice, video, data.
Uses copper telephone wiring if of sufficient quality.
Uses digital signatures for both voice and data; no analog conversions.
Dial-up service billed by line rental and usage; establishes a connection in ~1 second.
Used to connect LANs and for remote workers.
Remains in use for telecom core; superseded by DSL/cable for subscribers.
Terminal Adapter connects to PC or router; to a network via NT1 device.
What are the two classes of ISDN Internet Access and give a full description of each?
Two classes:
BRI: two 64 Kbps “B” data channels for data and one 16 Kbps “D“ control channel.
PRI: 23 or 30 “B” channels, one 24 Kpbx “D” channel.
Where is fixed wireless internet access used?
Wired broadband may not be available:
In rural areas
In older buildings where not possible to run new cable
What are the options for the fixed wireless internet access used?
Two options:
Satellite
Line of Sight (LoS) Wireless Internet Provider (WISP)
Give a description of the satellite which gives fixed-wireless internet access
Large coverage area with VSAT microwave antenna aligned to the orbital satellite.
Super High-Frequency range (3-30 GHz).
Satellite television receivers for domestic use; use growing for businesses, especially rural.
Transfer rates vary: 6 Mbps / 15-20 Mbps down typical.
Can be severe latency problems.
Dish at customer aligned with satellite; connects via coax to DVB-S modem.
Give a description of the LoS WISP
Ground-based microwave antennas aligned with each other; transmit if no physical obstruction (usually atop tall buildings).
Spans great distances; no cabling infrastructure; lower latency than satellite.
Hard to maintain a line of sight; expensive.
WISP may use Wi-Fi or proprietary equipment.
The range of frequencies; may be affected by 5G cellular phone service deployment.
Give a full description of Cellular Radio Networks
Wi-Fi bands have a restricted range; fixed wireless requires a large antenna.
Cellular radio wireless networking allows long-distance communications over smartphone devices.
Also used by IoT devices.
Connects to nearest transmitter; base station range of up to 5 miles.
The transmitter connects the phone to mobile/landline networks.
850 / 1900 MHz bands (Americas); 900 / 1800 MHz bands (rest of world).
Give a full description of 2G
GSM phones using a SIM card; international, and AT&T in the US
TIA/EIA IS-95 (cdmaOne) handsets managed by a provider with CDMA; Sprint and Verizon
Data access built on top of existing voice network using CSD
Must establish a data connection to the base station, incurring charges; maximum ~14.4 Kbps
Give a full description of 3G
Deployed packet-switched technology to mobiles
GPRS/EDGE; HSPA+; CDMA2000/Evolution Data Optimized (EV-DO)
Give a full description of 4G
LTE: converged 4G standard supported by all network providers, requires a SIM. Maximum 150 Mbps down; 20 Mpbs real-world
LTE-A: Intended to provide 300 Mbps down; 40 Mbps current real-world
Give a full description of 5G
Target is for 1 Gbps if stationary or slow-moving; 100 Mbps if fast-moving
Available in trial areas; commercially in ~2020
70 Gpbs in test conditions
True or False
Routers use the logical network and host IDs.
True
Give two different types of routers and definitions of both routers
LAN router: divides a physical network into logical networks.
WAN (edge/border) router: joins separate networks (i.e.; LAN to the Internet).
True or False
Route/path to the destination is selected either dynamically or statically; the packet moves by hops along the path to the target.
At target, the hardware address determines the destination node.
True
Give all the ways that routers and modems connect to the internet and also what happens when they are connected to the internet
Routers and modems both connect to the Internet:
Modem makes a physical link (like a switch).
The router makes logical forwarding decisions.
Often bundled in one device.
Give a solution to the following problem:
Switched enterprise networks can have thousands of ports; inefficient to treat as one logical network.
Use VLANs on managed switches to group ports into logical subnets.
VLANs communicate through routers.
Also provides filtering and monitoring to improve security.
Definition of a Protocol
Protocol: Rules and formats enabling systems to exchange data.
Definition of a Protocol Suite
Protocol Suite: A collection of several protocols used for networking are designed to work together.
Give all the characteristics of a TCP/IP Protocol
Networks have converged on the use of TCP/IP protocol suite
Originally developed by US DoD; now an open standard
IETF working groups implement development
RFCs are published standards
Packet-based protocols
Routers select the path for packets
Main protocols handle addressing and transport
Divided into a four-layer model
Give a full description of Link/Network Interface Layer
Puts frames on the physical network
Not TCP/IP protocols as such; networking products and media (Ethernet, Wi-Fi)
Communications on the local network
Data packaged in frames
Nodes identified by MAC address
Give a full description of the Network Layer(IP Protocol)
IP provides packet addressing and routing
Best-effort delivery; unreliable, connectionless
Give a full description of the Transport Layer (TCP/UDP protocol)
TCP guarantees orderly packet transmission
UDP provides non-guaranteed packet transfer but is faster
Give a full description of Application Layer
Numerous protocols for network configuration, management, services; use TCP/UDP ports
ARP: Finds MAC address associated with IP address
ICMP: delivers status and error messages (used by ping and tracert)
Give a description of the Source IP address
Identifies the sender of the datagram by IP address.
Give a description of the Destination IP address
Identifies the destination of the datagram by IP address.
Give a description of Protocol
Indicates whether data should be passed to TCP or UDP at the destination.
Give a description of Checksum
Verifies the packet’s integrity at the destination.
Give a description of Time to Live
The number of hops the datagram can stay on the network before it is discarded; avoids endless looping of undeliverable packets.
Each router decreases the TTL value by at least one.
What digits can only be used in binary?
In binary, a digit can only be 0 or 1
What power is the value of the digits?
Values of the digits are powers of 2
Give a full description of subnet masks
IP address encodes both network ID and host ID.
A subnet mask separates them by “masking” the host.
Binary 1 in the mask = address digit is part of the network ID.
The size of the network portion of the subnet mask determines how many networks and hosts are allowed in a given addressing scheme.
Expressed in dotted-decimal or as network prefix (contiguous number of 1s in the mask).
Hosts communicate directly if on the same network
IP protocol uses subnet mask to compare source/destination network ID
If on the same network, delivers locally
If on a different network, sends to the router
What should a host always have?
The host must have an IP address and subnet mask; should have other parameters for proper network/Internet communication.
Give a description of the parameter IPv4 address subnet mask.
Both are required for every interface; can be set manually.
Address: dotted-decimal notation; identifies host and network.
The subnet mask determines if other hosts are local or remote.
Give a description of the parameter default gateway
The IP address of a router to send packets outside of the local network.
If no gateway, the host can only communicate on a local network.
Give a description of the parameter client DNS
The IP address of the DNS server to provide host/domain name resolution and locate Internet resources.
DNS is also used on most local networks.
Often the gateway address; often a second server address provided for redundancy.
Give a description of static addressing
Static addressing:
The administrator manually configures each host.
Must update manually if host changes subnet.
Must track address allocations to avoid duplication.
Can be time-consuming and error-prone.
Only used for systems with dedicated functionality.
Give a description of dynamic addressing
The DHCP server allocates addresses.
Give a full description of DHCP
DHCP client contacts server on boot and requests address.
Also provides other parameters (subnet mask, default gateway).
Limited time leases.
Information configured on a server; client updated when lease renewed.
Give a full description of Link-local
APIPA
The fallback mechanism for DHCP client if DHCP server is unavailable.
Host self-configures with an address on 169.254.x.x network.
“Link-local” is a generic term; “APIPA” is a Microsoft term.
Communication with other APIPA hosts on the same network only.
Give a full description of the DHCP reservation
For hosts that need the same address each time.
Configure DHCP server with reserved host address per MAC address.
Centralized, easier to implement than static addressing.
What must each host address be and who allocates a host address.
On the Internet, each host address must be unique; usually allocated by ISP.
(Few organizations have enough individual addresses; various methods to overcome this issue.)
What addresses do internal hosts use?
Internal hosts can use addresses in a Class A, B, or C private range defined by RFC 1918 (10.0.0.0 to 10.255.255.255; 172.16.0.0 to 172.31.255.255; 192.168.0.0 to 192.168.255.255).
What gives internet access to a private address host.
Internet access is provided for private-address hosts through:
A router using NAT.
A proxy server.
Give an explanation of a NAT
In NAT, the router converts the internal private IP address to a valid public address.
Give an explanation of a NAT address pool
NAT address pool itself will be limited; multiple private addresses will use a single public address.
Give an explanation of IP configuration
IP configuration is simpler and internal clients are not directly accessible from the Internet.
Explain the NAPT mapping
The mapping provided by NAPT, aka PAT, aka NAT overloading.
Each outgoing connection is assigned TCP or UDP port.
Returning traffic mapped back to address/client port.
Give a definition of a VPN and a full description of all its specifitifications
VPN: connects two private networks over a public network (the Internet).
Internet is a cost-effective way to connect users and networks but is not private.
VPN protocols create tunnels through the public network to authenticate, encrypt, and secure private communications.
Give the size of IPv4.
The IPv4 address pool is large but limited.
Give the size of IPv6.
IPv6 uses 128-bit addresses, massively increasing the address pool.
Give all improvements to IPv6
Improvements: simplified address headers, hierarchical addressing, support for time-sensitive traffic, new unicast address structure.
A large string of characters in binary or even decimal; affects clarity and accuracy.
Uses hexadecimal notation (0-9, A-F):
How is binary IPv6 address divided?
Binary IPv6 address divided into eight double-byte values using hex notation:
2001:0db8:0000:0000:0abc:0000:def0:1234
What can be ignored in an IPv6 binary address?
Leading zeros can be ignored, and a contiguous series of zeroes can be replaced by a double colon place marker:
2001:db8::abc:0:def0:1234
Give the size and the designations of different parts of the IPv6 address.
The first 64 bits are network ID, second 64 bits designate the interface
True or False
Is the IPv6 fixed in size = no subnet mask; /nn = length of routing prefix in bits.
True
Give the IPv6 global unicast address format
Global Routing Prefix: 3-bit(001) and 45( Network ID)
Subnet: 16 bit
Interface ID: 64 bit
How are IPv6 blocks assigned
IPv6 address blocks are assigned hierarchically by routers; logical address space
Give all the characteristics of IPv6
IPv6 link-local addresses used for housekeeping
Span single subnet
Nodes on the same link are called “neighbors”
Start with fe80::
Equivalent of APIPA
The IPv6 host always has a link-local address
What all the general characteristics of UDP and TCP ports
Transport-layer protocols ensure effective delivery; the content of packets is significant.
Identifies network application types by assigning a port number (0-65535).
Data from upper layers is packaged in segments, tagged with port numbers.
Passed to the network layer for delivery.
Simultaneous segment transmissions are multiplexed onto the network link; de-multiplexed at receiving host.
Can use TCP or UDP.
What is the characteristic of well-known ports?
Port: unique ID for a service using TCP or UDP for transport.
Might be persistent (for servers) or ephemeral (for clients).
IANA assigns standard (“well-known”) port numbers to services.
See course text for examples.
IANA defines ephemeral port range (49152 to 65535); some OSes use different values.
Firewalls must-have ports enabled or disabled to allow only valid traffic.
Give a description of DNS?
Hierarchical system for resolving names to IP addresses.
The database is distributed among many name servers; distributes maintenance and protects against server loss.
Root (.) at the top; then 13 TLDs (generic, sponsored, or country code); then domains.
Domain names are managed by ICANN and registered with the appropriate Domain Name Registry for the TLD.
Records are traced from root down; each server level has information about servers below in the hierarchy.
What is FQDN
FQDN shows hierarchy from most specific on left to least specific on right.
What does the domain name identify?
The domain name portion identifies the company, organization, or individual; must be unique and officially registered.
What does the hostname identify?
Host name identifies a particular server or server alias.
Describe the Authoritative name server
Holds domain records and can respond authoritatively about hosts in the domains it manages.
Required for Active Directory.
If the private domain, is not available outside the LAN; on Internet, published to name servers hosted by ISPs.
Describe the Recursive resolver
Resolves names for clients.
Client contacts resolver; resolver contacts name servers until the record is located or request times out.
DNS clients are configured with a resolver address.
Listens on UDP 53.
Definition of the web server
Web server: A server that provides client access using HTTP (defaults to port 80) or its secure version HTTPS (defaults to port 443).
Description of Web server
Organizations may lease from ISP; host directly; or use private servers (intranets)
Provides HTML pages (text files with tags), interpreted by browsers
Extended by scripts and web applications
Give the structure of a URL
1 Protocol
2 FQDN
3 File path
1 2 3
http://store.gtslearning.com/comptia/index.htm
Give the disadvantages of HTTPS
HTTP lacks security; data is sent unencrypted, with no authentication.
What is SSL/TLS used for?
SSL/TLS can be used to encrypt TCP/IP applications that use TCP connections, including HTTPS.
What do servers use to prove identity?
Servers use digital certificates from Certification Authorities to prove the identity of the server and to provide encryption.
What can emails be sent and what is used to encode emails?
Email can send text and file attachments encoded using MIME.
What is the process of mail servers?
The client sends a message to the server; the server queues messages for an SMTP session (port 25).
SMTP server uses DNS to resolve the address of the recipient’s mail server.
SMTP delivers messages; usually several “hops.”
A message is placed in store on the recipient’s server; client software connects with the mailbox using POP3 (port 110) or IMAP (port 143).
POP3 is more widely used; IMAP has more features.
What does email require
An email account requires a username, password, email address, incoming and outgoing server addresses, and protocol types.
What general occurrences could occur when using mail servers?
Mailto URL scheme: username@domainname (domain may be a company or ISP).
Different systems allow different characters; not usually treated as case-sensitive.
Mail may be rejected if incorrectly addressed if identified as spam if the mailbox is full.
Only one of many network communication types.
Give the characteristics of File and Printer Sharing
Core network functions.
May be accomplished by proprietary protocols (i.e., File and Print Services for Windows).
May use standard protocols (i.e., FTP), but may not have as much functionality.
Give a description of SMB
Underpins file and printer sharing on Windows networks; currently SMB2, but legacy clients are supported.
TCP port 445; also NetBIOS over TCP/IP (UDP and TCP port range 137-139).
Implemented as Samba on Linux.
Give a description of AFP
Performs similar function to SMB for Apple/Mac OS.
UDP or TCP port 427 (Service Location Protocol)—not required by OS X or later.
TCP port 548.
Give a description of FTP
Early TCP/IP protocol; widely used for file transfers; flexible; easy to maintain.
TCP port 21 for connection; port 20 for active transfer or server-assigned port if passive.
Client options:
Command line
Dedicated GUI
Browsers
What is an Authentication Server
Used on enterprise networks to ensure only authorized users can access accounts.
On the Windows domain, Active Directory provides authentication based on Kerberos.
AAA server consolidates authentication across multiple devices.
RADIUS is an AAA protocol.
What is a DHCP
DNS
DCHP assigns IP addresses to hosts when they connect.
DNS allows hosts to access resources by hostname and FQDN by resolving names to IP.
What is an LDAP
Network resources are recorded as objects in a directory database.
X.500 standards allow directories to interact; full standards required a complex protocol.
LDAP allows X.500-compliant queries and updates over TCP/IP.
Widely supported; TCP/UDP 389.
Uses Distinguished Names and Relative Distinguished Names as identifiers.
What is a NetBIOS/NetBT
NetBIOS first Windows network software; provided name discovery, and addressing.
NetBT runs NetBIOS over TCP and UDP ports 137-139 (name services, datagram transmission, session services).
Should be disabled unless supporting legacy Windows systems or appliances.
What is SNMP
Framework for managing/monitoring network devices.
Management system and agents.
Agent process runs on network device; maintains MIB; can initiate trap for a notable event.
System software provides oversight location, monitors agents, displays information.
Device queries=UDP 161; traps=UDP 162.
What is Endpoint Managment
Facilitates Defense in Depth security policies that require hardening to workstation level.
Can apply OS and anti-virus updates; catalog software; apply security policies; analyze logs; monitor performance and alerts.
Example: Microsoft’s SCCM.
What is a syslog
Helpful to consolidate separate device logs.
Prior to Windows 7, Windows logs were local; 3rd-party tools were used to consolidate.
Windows event subscription can forward log events to the central system.
UNIX and Linux equivalent is Syslog.
Client-server model for event collection; open format; de facto standard.
What is Embedded
Designed for a specific function.
Range from individual microcontrollers to complex industrial control systems.
May have been designed for a closed network, without connectivity.
Special design and security considerations when interacting with a data network.
Risk for maintenance and troubleshooting; require specialist knowledge.
What is Legacy
No longer supported by the vendor.
May be retained on networks to support existing services that are not practical to migrate.
Security risks.
Should be isolated from the network.
Like embedded systems, the risk for maintenance and troubleshooting; requires specialist knowledge.
What is IDS/NIDS
Software and/or hardware that monitors for and quickly detects malicious behavior.
Can also analyze and alert administrators to infrastructure problems.
Can comprise sensors, detection software, and management software; each implementation is unique.
Give the definition of IPS/NIDS
An inline security device that monitors for and blocks suspicious network and system traffic.
May drop packets, reset connections, sound alerts; at times quarantine intruders.
Examines packet contents.
UTM appliance combines firewall, A-V scanner, and IDS.
Give the definition of Proxy Server
Used on enterprise networks as an alternative to NAT.
Checks and forwards HTTP, email, or other requests from internal hosts to the Internet; returns reply to the client.
It May be transparent (no client configuration) or non-transparent (client must be configured with proxy’s IP address and port, typically 8080).
