Thursday, January 28, 2016

Pass4sure 640-722 Question Answer

Which three items do you need to establish a wireless connection to an enterprise wireless network? (Choose three.) .

A. SSID name
B. RF channel
C. RF signal
D. 802.1X/EAP credentials
E. pre-shared key
F. web page
G. WPA/WPA2 settings

Answer: A, C, D

Sunday, December 27, 2015

Pass4sure 640-722 Question Answer

What is an MBSSID?

A. a virtual AP configured on a physical AP that share a single physical device, which is one half-duplex radio
B. a set of physical APs configured in a BSA to form cells that are controlled by a single controller
C. the group of clients that are allowed to gain access to one or more SSIDs configured in an AP
D. the identified overlap area between two cells, which identifies the clients that are operating in that area at any given time

Answer: A

Which interface is considered a dynamic interface?

A. the virtual interface
B. the AP manager interface
C. the LAG interface
D. the management interface
E. the service port interface
F. a WLAN client data interface

Answer: F

Sunday, December 6, 2015

Pass4sure 640-722 Question Answer

What is the difference between the IEEE, the WiFi Alliance, and the FCC, ETSI, and TELEC?


A. The IEEE and FCC are responsible for the standards that apply to wireless networks. The WiFi Alliance, ETSI, and TELEC are the governmental agencies that regulate compliance with local standards.

B. The IEEE is responsible for Layer 1 and Layer 2 protocols. The WiFi Alliance is responsible for interoperability testing. The FCC, ETSI, and TELEC are responsible for radio frequency and transmission power-level regulations and standards in the U.S., Europe, and Japan.

C. The IEEE is responsible for Layer 1 and Layer 2 protocols. The FCC, ETSI, and TELEC are responsible for interoperability testing and compliance. The WiFi Alliance is responsible for radio frequency and transmission power-level regulations and standards on a global basis.

D. The IEEE and FCC are responsible for the Layer 3 protocol support and frequency and power-level regulations in the United States. ETSI and TELEC are responsible for frequency and power-level regulations in Europe and Japan. The WiFi Alliance is responsible to interoperability testing.

Answer: B

Monday, October 12, 2015

Pass4sure 640-722 Question Answer

Which governing body analyzes the applications and environments in which wireless networks are used?


A. EIRP
B. ETSI
C. FCC
D. IEEE
E. WiFi Alliance

Answer: D

 

Which statement about an infrastructure basic service set is true according to IEEE 802.11 specifications?


A. The set also is called an ad hoc network.
B. The BSSID is generated from the first wireless client that starts up in the IBSS.
C. The set enables the use of ESS.
D. No signals are relayed from one client to another client.

Answer: C

Tuesday, September 8, 2015

Pass4sure 640-722 Question Answer

The IEEE 802.11n standard provides 40-MHz channels, improved MAC efficiency, and MIMO. Which three elements define the 802.11n implementation of MIMO? (Choose three.) 

 

A. channel bonding
B. dynamic frequency selection
C. maximal ratio combining
D. packet aggregation
E. spatial multiplexing
F. transmit beam forming

Answer: C, E, F

 

 

 

Which two statements about WiMAX technology are true? (Choose two.) 


A. WiMAX is defined by 802.11i.
B. Typically, fixed WiMAX networks have a higher-gain directional antenna installed near the client.
C. WiMAX is capable of working as a long-range system over several miles.
D. WiMAX works only for licensed frequencies.

Answer: B, C

Thursday, July 9, 2015

Cisco is On an Acquisition Roll and it Just Bought One of its Vendors for $139 Million


Cisco announced on that it was acquiring Carlsbad, California-based  for $139 million.
That sum includes cash for the company and "retention based incentives," for executives, Debbie Dunnam, Cisco senior VP of Global Customer Success said in a blog post.
Cisco had been a customer of since 2009 makes software that lets manufacturers easily keep track of their warranty customers and service agreements.
Its software does things like automatically send renewal notices, uncover items that customers bought that are not covered by their service plans, and so on. Its claim to fame is that it not only works for the manufacturer of the products, like Cisco, but can be used by the manufacturer's reseller partners. Cisco has a gazillion of those.
 Will be added to Cisco’s Global Customer Success (GCS) organization, the part of Cisco that was using. Its founder CEO, Scott Herron, said in a blog post that Cisco will not be shuttering the service for its own internal use. It will continue to support customers. Has customers such as Panasonic, CDW, and Ingram Micro. Lenovo, many others.
 Wasn’t exactly a startup. It was founded in 2004 and clicked along for a decade without taking VC money. In 2014, it raised $12 million from Kayne Partners.
This is the second acquisition from Cisco in as many weeks. Last week, Cisco bought another software company, OpenDNS, or $635 million.
A couple of years ago, outgoing Cisco CEO John Chambers made waves when he said Cisco wasn't going to buy any more US companies until the country changed the tax code to allow him to use Cisco's stockpile of overseas cash to pay for them, paying little-to-no taxes on that cash. US companies don't get taxed on overseas cash until they want to spend it at home on things like acquisitions or dividends, and then they are charged the full corporate rate of 35%. Chambers has been an outspoken critic of that tax policy.
Chambers never held to the threat, breaking it later that year to spend $2.7 billion buying security company Source Fire. But Cisco did continue to buy lots of overseas companies for a while.
That seems to have gone right out the window as of 2015.  So far this year, Cisco has bought five companies, all software companies (an area where Cisco sorely lacks homegrown expertise), all in the US.

Thursday, June 18, 2015

Apple to iOS Devs: IPv6-only Cell Service is Coming Soon, Get your Apps Ready


On the first day of its World Wide Developers Conference (WWDC), Apple presents its keynote, where it mostly unveils its consumer-facing plans. Later, when the pundits are taking their first jab at explaining what it all means, there's the Platforms State of the Union session. At 35 minutes in, Sebastien Marineau, Apple’s VP of Core OS, dropped the following bomb: "Because IPv6 support is so critical to ensuring your applications work across the world for every customer, we are making it an App Store submission requirement, starting with iOS 9."

However, on the last day of WWDC, there was a session that put the above statement in a somewhat different light. We'll get back to that because, in the mean time, I spent a larger part of the week than I'd like to admit testing whether various applications work over IPv6.

The current state of IPv6

My first reaction was "this means no more Skype under iOS 9." Which led to some back-and-forth about whether Skype works over an IPv6-only network. The easiest way to test this is to get rid of that old, rickety version 4 of the Internet Protocol—it only has four billion addresses!—simply by turning it off in the Network pane of the System Preferences on your Mac. If there's an IPv6 router present on your Ethernet or Wi-Fi network, your Mac will then configure an IPv6 address for itself—well, two, actually—and connect to the IPv6 Internet. If there's no IPv6 router present, at least your Mac will talk to other devices on the local network over IPv6, using "link local" addresses.

In this setup, many things will work just fine. You can reach the Apple, Microsoft, Google, Yahoo, Facebook, and Wikipedia websites using any current browser. If your mail server has IPv6, you can send and receive e-mail. Time Machine works, and you can sync your iPhone to iTunes over Wi-Fi. iTunes will stream audio (but not video) to an Apple TV.

However, there are many things that don't work. You can't reach any IPv4-only websites, such as support.apple.com or developer.apple.com. iCloud, Apple Maps, the iTunes/App Stores, iMessage, and iPhone call/SMS forwarding don't work. And Skype doesn't work: it runs, but it doesn't "see" any contacts and it complains about a lack of Internet connectivity when you try to make calls.

In the real world, of course, people don't go around turning off IPv4 on their Macs—and on iOS that's not even an option. A more realistic way to test IPv6-only is by connecting to a network that doesn't have IPv4 connectivity but does have IPv6 connectivity. This is surprisingly hard to achieve in practice, as every device that supports IPv6 also runs IPv4, and the old protocol usually can't be turned off. However, after getting an old Cisco router out of retirement, I was able to test this scenario.

The difference between this method and turning off IPv6 at the network interface level is that devices can still communicate using IPv4 over the local network. In this setup, I was able to use AirPlay streaming of video from iTunes on the Mac to the Apple TV, too. The Apple TV was also happy to connect to Netflix and YouTube, but most other channels and iTunes Store content weren't available. Interestingly, the weather app on the Apple Watch worked, but the weather (and sunrise/sunset) wouldn't show up on the watch face display Examcollection 640-722. On my iPhone, the Overcast and Pocket Casts podcast players couldn't sync with their servers. SMS forwarding, the App Store, and notifications also didn't work.

But the situation where computing devices only have IPv6 connectivity, with no way to reach the IPv4 Internet, is pretty far-fetched. In a blog post earlier this week, Geoff Huston, chief scientist at APNIC,deducted points because Apple isn't implementing any technologies that bridge the gap between IPv4 and IPv6. He wrote:
IPv4 is not going away any time soon, and for some years to come it’s not the IPv6-only networks that will provide services to customers. It’s just not quite there yet. For years to come we need to operate the Internet in a mode that supports IPv6 and IPv4 together in Dual Stack mode. The operational premise for today’s devices and apps is simple: 'Do IPv6 if you can, and fall back to IPv4 if you must.' So how well is Apple doing in a dual stack world? Not as well as I would want.
Huston points out that Android supports a technology called 464XLAT. 464XLAT allows IPv4 apps to talk to IPv4 servers over IPv6 networks by having the phone translate the application's network requests from IPv4 to IPv6. Then, at the edge of the IPv6 network, a NAT64 device translates the IPv6 packets back to IPv4 and sends them on their way to the server.

What’s actually happening

So why wouldn't Apple go this route? During the "Your App and Next Generation Networks" session on Friday morning, Prabhakar Lakhera took the stage and clarified what's going on. He explained in a bit more detail what Apple's considerations with IPv6 on iOS 9 are. Lakhera referred to the fact that there are pretty much no IPv4 addresses left and that the big cellular carriers really don't want to continue running IPv4 and IPv6 side by side in dual stack configuration—apparently, IPv6-only cellular service is coming. Soon.


The way Apple is addressing that situation is to make sure that all iOS apps support IPv6. However, many servers are still IPv4-only. To reach those, the cellular networks are going to deploy NAT64 translators. NAT64 allows IPv6 applications to access IPv4 servers. Without these translators, IPv6 applications ask the DNS for IPv6 addresses to connect to, but obviously IPv4-only servers don't have IPv6 addresses, so a regular DNS server then returns an empty list of IPv6 addresses, leaving the application all dressed up with nowhere to go.

A DNS64 server, on the other hand, creates a "synthetic" IPv6 address that the application can use. The packets sent to those addresses end up at the NAT64 translator, which recovers the IPv4 address of the intended destination using the IPv6 address created by the DNS64 and translates the packet from IPv6 to IPv4.

In the presence of DNS64+NAT64, most of the applications that wouldn't work in my IPv6-only test setup will work fine because it ensures that IPv6 software can reach IPv4 servers.

So 464XLAT and DNS64+NAT64 achieve the same result, but there is a fundamental difference: 464XLAT also works for applications that only support IPv4, while DNS64+NAT64 expects applications to talk IPv6 to the network. So applications that work over DNS64+NAT64 are ready for the IPv4 to be turned off at some point, while 464XLAT kicks that particular can down the road.
To allow iOS developers to test whether their applications work through NAT64, Apple has included a DNS64+NAT64 implementation in the seeds of OS X 10.11, which can be enabled by first option-clicking the Share pane in the System Preferences and then option-clicking the Internet Sharing service. After that, a "Create NAT64 Network" option appears.

The main reasons why applications only work over IPv4 are the use of the ancient Unix get host byname() family of system calls and "pre-flight checks" that try to determine whether the system has a connection to the Internet by looking for an IPv4 address or if address 0.0.0.0 can be reached. These issues are usually easy enough to fix—70 percent of current iOS apps already work over IPv6 today.

Things only get complex for applications that need to interact with the network on a lower level, such as VoIP applications like Skype. Such apps need to figure out how to connect two client devices that are probably behind NATs and firewalls—more challenging than simply looking up a server address.
iOS developers should definitely check out the presentation, and it's highly recommended for non-developers with an interest in networking, too, with Stuart Cheshire explaining how to remove network performance bottlenecks that aren't caused by a lack of raw bandwidth. This includes whyCoDel is the bee's knees and that Apple is enabling Explicit Congestion Notification (ECN) in iOS 9 and OS X 10.11.