Exam 3 MIS 4363
how to find the number of bits that we need to borrow to create the needed number of subnets
# of bits needed to create the # subnets required
how to calculate the IP addresses of the subnet, hosts, and direct broadcast
-subnet address = subnet mask in decimal (usually ends in a zero) + incremental value -Range of Host addresses = (subnet address + 1) to (direct broadcast address - 1) -Broadcast Address = Next subnet address using the increment - 1
WAN Topology
1. Ring-based design: "n - 1" circuits needed to lease -Con - More HOPS 2. Star-based design: Pick 1 Hub and connect all computers to it -Pro - At most 2 HOPS, 1 for talking to hub 3. Full-mesh design: all computers connected -Pro - 1 HOP anywhere -Con - High cost, *only do if have a bunch of money 4. Partial-mesh design: most, but not all computers are connected -"partial star with a ring" = Ring + partial star -Very common -Make star based on NW traffic between computers *Ex: DB servers need to have a dedicated circuit so need to use star to connect them
Which of the following is the expected data rate on a 100Base-T network? 10 Mbps 100 Mbps 500 Mpbs 1000 Mbps
100 Mbps
In a 100Base-T network, the distance of cable from a switch to a client computer should not exceed: 25 meters. 50 meters. 100 meters. 200 meters.
100 meters.
The most commonly installed wired Ethernet these day is: 100Base-T or 1000Base-T over Cat 5e. 10Base-t over Cat5. 1000Base-FX over single mode fiber optic cable. 1000Base-t/F over Cat6.
100Base-T or 1000Base-T over Cat 5e.
Types of WAN
3 WAN technologies: Lease a circuit from a common carrier (AT&T, Sprint, Cox, etc.) 1. Dedicated-Circuit service 2. Packet-Switched service More reliable🡪 run over a line in the cloud with only your private traffic 3. Use Internet with virtual private network (VPN) Cheaper, less reliable 🡪 runs over the internet(INTERNET IS NOT WAN) -Anyone can get access to your VPN because public NW traffic
Current WLAN frequencies
802.11ac 2.4 GHz and 5 GHz / 8 Channels 100 Meters / 433 Mbps
What are the two basic components of a backbone network?
A network cable and the hardware devices that connect other networks to the backbone network
directional antenna
A type of antenna that issues wireless signals along a single direction, or path.
Power over Ethernet (PoE)
A wired networking standard that allows electrical power to be sent along with data over standard Ethernet cables
WLAN components
AP connect to clients with radio frequency waves clients each with own NIC
You have been assigned to manage the 802.11ac wireless network shown in figure below. How should the wireless channels be configured on Access Points A, B, and C? All access points should use the same channel. Access points should use different wireless standards. All access points should use different SSIDs. All access points should use different channels.
All access points should use different channels.
Some countries, like China, don't allow users to connect to certain Internet services, such as Facebook. However, if you use a VPN connection to your university/company, you are able to connect to Facebook. Why does this happen? Because the whole packet will be encrypted and they can't read the IP address. Because using VPN, the IP destination address will be your university's IP address rather than Facebook's IP address. Because they don't know what VPN means. Because VPN will not use China's routers and will bypass their infrastructure completely.
Because using VPN, the IP destination address will be your university's IP address rather than Facebook's IP address.
Advantages and disadvantages of having ONLY a core router
Broadcast traffic (ARPs) would be increased but costs would be lower as well as maintenance and management
Your company decided to use dedicated-circuit services for its WAN. What device will be installed at all premises that will be connected in the WAN? CSU/DSU PVC PAD SVC
CSU/DSU
There are two common options when purchasing Internet connection for your home - DSL or Cable. What is the main difference between these two services? Only DSL uses a line splitter. Only Cable requires a modem. Cable is a shared multipoint circuit, while DSL is a point-to-point circuit. You can have more devices on your home network if you use DSL.
Cable is a shared multipoint circuit, while DSL is a point-to-point circuit.
how to know if IP address can be assigned or not.
Can't be assigned if -All 0's in binary Host space = subnet address -All 1's in binary Host space = broadcast address
MAC in WLAN
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) -DCF and PCF
LAN components
Clients each with own Network interface cards (NICs) NW (Cat5e) cables carrying data Switch/hub -POE port for WAN to transmit electricity and data -ports for clients to transmit data
Which statement about wireless network communication is wrong? Because it uses half-duplex, it is similar to hub-based communication. Clients use CSMA/CS communication. Clients may experience more interference issues than wired Ethernet using Cat 5 cable. Because of the WPA standard, communication is considered as secure as or more secure than wired communication.
Clients use CSMA/CS communication.
Which statement about wireless network communication is wrong? Because it uses half-duplex, it is similar to hub-based communication. Clients use CSMA/CS communication. Clients may experience more interference issues than wired Ethernet using Cat 5 cable. Because of the WPA standard, communication is considered as secure as or more secure than wired communication.
Clients use CSMA/CS communication.
VLAN (Virtual LAN)
Computers are assigned to LAN segments by software rather than hardware Network managers do not need to unplug/replug physical cables to move computers from one segment to another
When would you use a VLAN backbone?
Computers that are in a different geographic locations and it makes it easier to manage broadcast traffic and can better prioritize traffic
cybersecurity implications - Securing WLAN from unauthorized users
Different SSIDs for different user groups (like OU Wi-Fi v. OU Guest Wi-Fi) MAC address filtering Encryption is a MUST
Why do many organizations use a rack for all the network equipment?
Easy maintenance and upgrade Even though can use more cable (not a big deal)
A switched backbone,that uses layer-2 switches, has less broadcast traffic than a VLAN based backbone.
False
What are the advantages of VLANs?
Faster, better at managing traffic flow Prioritize traffic Can put computers in different geographic locations on the same subnet
Physical Topology
How the network is physically installed
logical topology
How the network works conceptually
Your boss asks you to explain why you purchased switches instead of the cheaper hubs - he heard that they do the same thing. What do you tell him to justify the purchase of the switches? Hubs share network capacity with all users so they are slower than switches. You can connect more computers to a switch than to a hub. Hubs do not provide 100 Mpbs connections. Hubs have to be replaced sooner than switches because they fail more frequently.
Hubs share network capacity with all users so they are slower than switches.
Standard Ethernet version
IEEE 802.3 version
Which of the following is not a benefit of a VLAN? Enabling networks to be managed by functional workgroups. Better control over broadcast messages. Improvement of physical layout. Enhanced security.
Improvement of physical layout.
Routed Backbones
In the Core Layer Subnetted Backbones: ***every port on the core router creates its own subnet Distribution Layer Routers - older way of designing Distribution Layer Switches - newer way of designing Good Segmentation of NW's in HW
Layer-2 switches vs Routers
Layer-2 switches operates at the data link layer(MAC addresses) Routers operate at the network layer (TCP/IP)
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA),
MAC in WiFi :stop and wait still but needs an association with a specific AP so the AP will accept transmission
Which of the following services is not a dedicated-circuit service? T1 MPLS SONET T3
MPLS
MAC address filtering
Method of limiting wireless network access based on the physical, hard-wired address of the wireless NIC of a computing device.
Why are VLANs often not used?
More complex, so only used for large networks
who picks the channel for a WLAN
NIC
WLAN transmission order
NIC > AP AP > WLAN/LAN (sender to AP, receiver to AP)
passive scanning
NIC listens on all channels for a special frame called a beacon frame that is sent out by an AP.
cybersecurity implications - Securing LAN from unauthorized users
Port security / MAC address filtering Physical security: no unauthorized to wiring closets/areas of tech equipment
directory service
Provide information about resources on the LAN that are available to users
Types of Switched BN's
Rack Mounted Switched BN NW architecture-each LAN has own switch connected to a single distribution layer switch Chassis-based Switched BN NW architecture-modules (NW devices) plugged
Main Distribution Facility MDF/CDF/IDF
Room that contains the rack of equipment
Disadvantages of a routed backbone?
Routing takes more time than switching so: slower, more expensive, and require more management
Advantages of a routed backbone?
Segments the network and is managed by a different network manager
Multi-switch VLAN
Several switches are used to operate the VLAN Most commonly used in building backbone networks -- slowly starting to move to core backbone between buildings
network operating system (NOS)
Software that controls the network(one NOS for client and one for server)
When a frame arrives at a switch, what is stored from it along with the port it came in on? Source IP address. Source MAC address. Destination IP address. Destination MAC address.
Source MAC address.
What type of topology do BN uses?
Star topology It connects a series of LANs
Switched Ethernet has a _______________ logical topology and a ________________ physical topology: Bus, star. Bus, bus. Star, bus. Star, star
Star, star
Best Practice Design WAN
Start with more flexible packet switched services Once data needs are clear, move to cheaper dedicated circuit services NOTE: most companies still use VPN over a dedicated circuit so moving data is encrypted Low to Moderate Traffic(>10 Mbps) -packet switched- VPN over internet or frame relay High Traffic(10-50 Mbps) -packet switched-Ethernet, IP, or MPLS -Dedicated- T3 Very High Traffic(50 Mbps - 100 Gbps) -packet switched- Ethernet, IP, or MPLS -Dedicated - SONET
What is the best practice backbone design?
Switched backbone or VLAN distribution layer and routed in core layer
What types of backbones are typically used?
Switched backbones (Distribution layer) that use the same layer-2 switches as LANs
What operates the data-link layer?
Switches
Which of the following WAN services require translation or encapsulation into a new protocol? (check all that apply) T-Carrier SONET Frame Relay Ethernet Services MPLS BNC
T-Carrier SONET Frame Relay
Selecting the best WAN service depends on the data rates you anticipate between different campuses. Suppose, that your data rates will be very high because you need to move large data files across the network. Which of the following services would not meet your needs? T1 Ethernet Services MPLS SONET
T1
ABC Dollar is a growing retail store chain with 500 stores across the US. Most stores are relatively small stores located in small towns. The network will be used for real-time inventory updates and credit card transactions. What WAN would you recommend? (check all that apply) T3 Ethernet Services IP Services VPN over DSL
T3 Ethernet Services IP Services
Topology
The basic geometric layout of the network - the way in which the computers on the network are interconnected
Collision Detection (CD)
The capability of a layer 2 network protocol to know when two network nodes send data simultaneously, creating unreadable data.
What is each backbone connected to?
The router which is connected to a core router
Domain Controllers
The servers that contain the Active Directory databases. (like a DNS server)
Patch Cables
The very small cables used to connect devices in the rack
What do OC-1 and T3 have in common? They both run over twisted pair cables. They offer about the same data rate (44.376 Mbps and 51.84 Mbps). They both run over fiber optic cables. Nothing, the are completely different services.
They offer about the same data rate (44.376 Mbps and 51.84 Mbps).
what is not true about the traditional network design process? It follows a very structured systems analysis and design process. A precise estimate of the amount of data that each user will send and receive is developed. This process is cheap and fast. The suggested circuits must support the estimated traffic plus a modest increase in traffic.
This process is cheap and fast.
When would you use a routed backbone?
To connect different buildings on the same enterprise campus backbone network
Each computer must be physically connected by network circuits to the other computers in the network.
True
VLAN switches are a special combination of layer-2 switches and routers.
True
VLANs are networks in which computers are assigned to LAN segments by software rather than by hardware.
True
a Request for Proposal (RFP) specifies what equipment, software, and services are desired and asks vendors to provide their best prices.
True
the key concept in the building-block process is that using a few standard components throughout the network is cheaper in the long run than to use a variety of different components to build different parts of the network.
True
What do backbone network (BN) switches do?
Use the mac address to forward packets between network segments They learn addresses by reading the source and destination addresses
Chassis Switch
Used instead of a rack Enables users to plug modules directly into the switch They are used because they are flexible and easier to upgrade the switch
Routed Backbone (Subnetted backbones)
Used routers to connect to different LANs/subnets
When are routed backbones often used?
Used to connect different buildings on the same enterprise campus backbone network
Layer-2 switch
Uses MAC addresses from the NICs to decide where to forward frames Hardware-based
Single-switch VLAN
VLAN operates only inside one switch Software is used to assign computers attached to the switch to different VLAN segments
VLANs vs Routers
VLANs create multiple subnets inside the switch Routers create subnets between switches
McWansey & Company is a consulting firm with offices in five cities across upstate New York. A typical office has 5-7 employees. The network will typically be used to exchange Word and PPT files. What WAN would you recommend? T3 VPN over DSL Ethernet Services IP Services
VPN over DSL
what are the three components of the network architecture that make up the enterprise edge?
WAN, internet access, e-commerce edge
Security for wireless ethernet
WEP, WPA, 802.11i, MAC address filtering, *wardriving
When would you use a switched backbone?
When network admins want to spread the traffic around the network more efficiently and where network capacity is not tied to physical location
Best Practice LAN design
Wired Ethernet (LAN) -100 Base T or 1000 Base T over Cat5e -Cable Plan: follow logical and physical design Wireless Ethernet (WLAN) -802.11 ac -Switch (all access points connected to) supports POE (so can have electricity) -Site Survey: must do to know where to put AP *^usually not all same size NW traffic (people, furniture, etc. absorbing the signal) *^need to know if the radio frequencies from access point will reach the client computers -Traffic travels in 3D - horizontally and vertically *^Can go across multiple floors in a building so need to know the access points won't cause a collision
Suppose you bring your laptop into a room with a 802.11ac wireless access point running at 300 Mbps that is connected into a 100Base-T switch which leads to the backbone. Your friend has connected her laptop via a Cat 5 cable to the switch. If you are the only computer using the AP: Your throughput will be about the same as hers. Your throughput will be faster than hers. Your throughput will be slower than hers. We don't know because we don't have sufficient information to make a decision.
Your throughput will be about the same as hers.
Suppose you bring your laptop into a room with a 802.11ac wireless access point running at 300 Mbps that is connected into a 100Base-T switch which leads to the backbone. Your friend has connected her laptop via a Cat 5 cable to the switch. If there are 20 computers using the AP: Your throughput will be faster than hers. Your throughput will be about the same as hers. Your throughput will be slower than hers. We don't know because we don't have sufficient informaiton to make a decision.
Your throughput will be slower than hers.
active scanning
a NIC transmits a special frame called probe frame on all active channels on its frequency range.
the main output of the needs analysis is:
a logical network design
wardriving
a malicious activity driving through a neighborhood with a wireless-enabled notebook computer goal of locating homes and businesses that have wireless networks in order to gain access to them
Thelogical and physical topologies ofWi-Fi are the same as those of hub-based Ethernet:
a physical star and a logical bus.
what are the three layers, also the first three components, of the network architecture?
access, distribution, and core layers
what is the proper placement of the organization's servers (eg., database servers, email servers)
all servers should be in the organization's data center
omnidirectional antennas
antenna transmits in all directions simultaneously
why is designing circuits for WAN more difficult than for LAN?
because LAN circuits come in standard sizes (e.g., 100 Mbps or 1 Gpbs). This is not true for WAN circuits that offer many more choices in standard sizes and it is much more difficult to estimate circuit loading for many users than it is for one user.
cut-through switching
begins the forwarding process before it has received the entire frame
another term that describes the core layer is:
campus backbone
star
centralAP towhich all computers direct their transmissions
lightweight directory access protocol (LDAP)
client computer sends a message to the ADS domain controller with this when it wants to access available resources
Components in a LAN
clients, servers, NICs, network circuits, hubs, switches, access points, and network operating system
AP's enable
computers close to each other to communicate
Network hubs and switches
connect network cables (like with a plug) act as repeaters(bc attenuation)
Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
contention-based media access control technique used by ethernet "wait until the circuit is free and then transmit"
3 modes of Switch Operations
cut through switching store and forward switching fragment free switching
how to find the increment
decimal value of the last possible "1" bit in binary
Improving LAN Performance Demand
decrease demand i. Understand NW traffic *Application Layer protocols 🡪 need to know what kind of packets are traveling on the NW and if they are moving large amounts of data across the NW ii. Shift demand from WLAN to LAN *Because LAN is star and WLAN is bus technology iii. Limit use of Applications *Ex: OU Wi-Fi doesn't allow TOR to be used
Improving LAN Performance Devices
enhance performance i. Upgrade AP ii. Wireless LAN Controller (WLC): device plugged into distribution layer switch that manages access points *All logic for the access points comes from this *Help with AP functionality iii. Upgrade servers
Hub-based Ethernet
ethernets logical topology when hubs are used all computers connected to one half duplex circuit running the length of the network
1000base-F Ethernet standard
fiber optic cables or ethernet but mostly fiber optic 1, 10, 40, 100 GbE
NOS Server Software enables
file server, print server, or database server to operate. replaces existing OS acts as the application software by executing the requests sent to it by the clients
fragment-free switching
frames retransmitted once the header (first 64 bytes) is received and has no errors Compromise between store and forward and cut-through
What technologies are part of the access layer (LAN).
hub, switch, and access point *not a router
Improving LAN Performance Circuits
increase circuit capacity i. Upgrade circuits to 1 Gbps ii. Upgrade/add Aps iii. NW segmentation - More subnets with different SSID's *Ex: OU Wi-Fi - has own subnet with own SSID and security restrictions (user authentication and MAC address filtering) vs. OU Guest - own subnet and SSID No restrictions iv. Add new Switches - so can add more AP's and then more users on NW
Wi-Fi Protected Access (WPA)
key is changed for every frame that is transmitted to the client
Bus Topology
lone half duplex circuit running the length of the network
802.11i (WPA2)
master key client and AP negotiate a new key Uses AES (Advanced Encryption Standard)
Point Coordination Function (PCF)
media access control (MAC) technique used in IEEE 802.11 based WLANs, including Wi-Fi relies on an access point to coordinate the communication within the network process -request to send(RTS) -clear to send(CTS)
user profile in a Network profile
needed for each person who uses the LAN
NOS Client Software
performs the functions associated with the data link and the network layers and must interact with the application software and the computer's own operating system.
NOS Server Software
performs the functions associated with the data link, network, and application layers and usually the computer's own operating system.
Connect point where a cable can be plugged in
port(all have unique numbers)
Access Point(AP)
radio transceiver that plays the same role as a hub or switch in wired Ethernet LANs.
store and forward switching
receives the entire frame before forwarding
Distributed Coordination Function (DCF)
relies on the ability of computers to physically listen before they transmit Process: -Listen -no one transmitting? then transmit -listen while transmitting -if collision stop transmitting and issue a jamming signal -wait random amount of time and start at 1
10base-T Ethernet standard
revolutionized ethernet and made it most popular LAN in world *100Base - T and 1000Base -T most common today
scanning
searching for an available AP
Switched Backbones
segmenting in HW Most common type of BN in distribution layer Topology - STAR In the Distribution and Access Layer All LAN switches are Dual homed so uses Spanning Tree Protocol(STP) to fix redundancy
collision domain
shared multipoint circuit in a hub that computers take turns using
collision
simultaneous transmission of frames that collide and destroy each other
SOHO
small office/home office
network profile
specifies what resources on each server are available on the network for use by other computers and which devices or people are allowed what access to the network
Forwarding Table
table lists the ethernet address of the computer connected to each port on the switch
bus
the radio frequencies are shared
AP's don't interfere with each other because
transmitted at different frequencies using a channel
servers should never be placed on a WLAN
true
WLAN frame layout with IEEE 802.11x
types of wireless ethernet
Most wired LANs built with
unshielded twisted-pair (UTP) cable, shielded twisted-pair (STP) cable, or fiber-optic cable.
Wireless LANs(WLAN)
use radio transmissions to send data between NICI and Access Point(AP)
Wireless Equivalent Privacy (WEP)
user ID and password required The oldest and weakest form of wireless encryption.
A LAN provides network access to
users, data center, and e commerce edge
Frames
what flow into the bus and then to all computers on the LAN
Network Interface Card (NIC)
wired network - physically connects computer to network wireless networks - radio transmitter that sends and receives messages on a specific radio frequency
Active Directory Service (ADS)
works in much the same manner as TCP/IP's DNS service