Dale’s Web Log

Here are all the interesting links I found the last few days:

• EAR Series: 2RU Rack Mount Fiber Amplifiers - Rack Mount Fiber Amplifiers - Tags: rack.mount edfa optical amplifier
• NP3000PR Rackmount EDFA: Erbium Doped Fiber Amplifier: Rack Mount Chassis - Rackmount EDFA: Erbium Doped Fiber Amplifier: Rack Mount Chassis - Tags: rack.mount edfa optical amplifier
• Free Online Photo Editors - - Tags: design free software tools Web photo editor image
• Free Diet Plans at SparkPeople - Track your daily consumption and exercise goals for free. - Tags: health Diet Fitness exercise
• Hodges fund managers offer secrets of high returns - April 2, 2007 - - Tags: stock.tips

ANAHEIM, Calif. — OFC/NFOEC — If 100Gbps Ethernet gathers pace quickly enough, it might put a crimp in the lifespan of the 40Gbps generation.

That’s one possibility being discussed here at OFC/NFOEC, as industry executives wonder whether 40Gbps might see a shortened lifespan due to pressure from both 10- and 100Gbps alternatives.

“We see the 40Gbps deployment as more of a stepping stone,” says Saeid Aramideh, vice president of marketing for CoreOptics Inc. “Not that we have stopped our activity there, but certainly we see our future being 100Gbps-based. My personal belief is that with the coming of 100Gbps transmission in the WAN, the 40Gbps life cycle could be short-lived.”

Metro and long-haul 100Gbps deployments are years off — most sources are saying 2012; AT&T Inc. has suggested 2010 — while 40Gbps deployments are underway now. AT&T has lit its OC768 backbone, and here at OFC/NFOEC, Verizon Communications Inc. officials said they also plan to build a 40Gbps core.

But here’s the catch. It’s generally accepted that for 40Gbps sales to take off, enabling 40Gbps to usurp 10Gbps, the cost should be no more than 2 to 2.5 times as much as 10Gbps. So far, 40Gbps prices aren’t there.

“The cost economics of 10Gbps are so strong right now, it’s limiting 40Gbps to only those cases where they have to use it,” says Roy Rubenstein, research director with the transceiver market research firm, LightCounting . A typical, short-reach, 40Gbps transceiver can carry a $20,000 to $25,000 price tag, he notes.

So, if 100Gbps optics manage to catch up by costing, say, about five times as much as 10Gbps, could that cut short the 40Gbps generation? “Depending on where 40Gbps moves, you might see an intercept point with 100Gbps, but it’s too early to tell,” says Mike Ricci, a senior vice president at JDS Uniphase Corp.

What might make that intercept point possible is the amount of attention being lavished on 100Gbps transmission. The 100Gbps name-dropping at OFC/NFOEC includes prominent vendors such as Alcatel-Lucent, Infinera Corp, and CoreOptics customer Siemens Communications Group .

“There’s a window for 40Gbps. If people get the prices right, they can have a chance,” LightCounting’s Rubenstein says.

The optics vendors pushing 40Gbps don’t appear too worried, considering 100Gbps transmission is still pretty far from reality. “If there’s a need for 100Gbps, it’ll happen, but at this point I don’t see a significant threat to the investments made in 40Gbps,” says Ed Cornejo, director of product marketing at Opnext Inc.

That doesn’t mean Opnext is ignoring the next wave, as it’s already engaging in 100Gbps laser research in its lab. On a panel at Monday’s Optical Society of America Executive Forum, Opnext CEO Harry Bosco said the tough part, when it comes to transceivers, will be finding the chips to work at that speed.

And recent M&A activity shows confidence in the upcoming 40Gbps market. Two of this week’s acquisitions — Kailight Photonics Ltd. by Optium Corp., and Kodeos Communications Inc. by Finisar Corp. — “show people are getting serious about their 40Gbps portfolios,” Rubenstein says. Kailight is shipping 40Gbps modules, while Kodeos, more of a 10Gbps vendor, uses long-haul encoding techniques that could be useful at 40Gbps, he says.

— Craig Matsumoto, West Coast Editor, Light Reading

How Skype Works By Cedric Price

Skype is a software application that allows you to make free phone calls to more than 75 million people worldwide, and shockingly cheap calls to practically everywhere else on Earth! As a result of that, Skype has become the fastest growing service in the history of the Internet. Recently, the company was acquired by eBay, another step forward towards achieving the final goal of making Skype the world’s largest communication company.

Skype is easy to install and use. It allows its users to make crystal clear calls, regardless of their location, send instant messages, switch seamlessly between text and voice communication, make video calls, conference calls, transfer files, call landlines and cell phones for a fraction of the cost of a traditional call. Skype is truly making a revolution in the way we communicate.

But how does it actually work? This article focuses on describing the Skype network and the technology behind it.

Skype is a type of peer-to-peer Voice-Over-IP client, based on the Kazaa file sharing program. The developers of Skype claim that it provides better voice quality than similar applications like MSN and Yahoo Messenger. It also encrypts calls end-to-end.

There are two types of machines in the Skype network – ordinary host (Skype Client) and Super Node (SN). An ordinary host is the computer of a regular user who has the application installed and connects to the network in order to communicate with other users. The Super Nodes are the end-point of ordinary hosts in the network. In other words, ordinary hosts connect to the Super Nodes. Any computer with a public IP and proper hardware configuration can be a SN. An ordinary host must connect to a super node and must register itself with the Skype login server for a successful login. The Skype login server is the only central unit in the whole network. It stores the usernames and respective passwords of all Skype users. Nslookups have shown that this server is located in Denmark. All Super Nodes connect to the login server in attempt to verify the username password of the client. It stores your Skype Name, your e-mail address, and an encrypted representation of your password.

If you are a regular Skype user, then your computer is considered an ‘ordinary host’ that connects to a Super Node. The Super Nodes are servers, located in different parts of the world. But your Skype client, must know to which SN it has to connect. Therefore, every Skype client (SC) maintains a local table that contains the IPs and corresponding ports of Super Nodes. This is called a host cache and it stored in the Windows Registry of the given SC. So basically, every time you load up Skype, it reads the date from the host cache, takes the first IP and port from there and tries to connect to this SN. If the connection fails for some reason (the SN is offline; it is no longer part of the network, etc) then it reads the next line from the table. In case it fails to connect to any of the IPs listed, the Skype returns a login error upon start-up. Hence, the host cache must contain at least one valid entry in order for the application to connect to the network and work properly. Valid entry means an IP address and port number of an online Super Node. The path to the table in the Windows Registry is HKEY_CURRENT_USER / SOFTWARE / SKYPE / PHONE / LIB / CONNECTION / HOSTCACHE. You can verify that on your computer by opening the Start menu, then click Run and enter ‘regedit’, without the dashes. Of course, the exact path could be different in the next versions of the application.

As a concept, Super Nodes were introduced in the third-generation P2P networks. They allow improved search performance, reduced file-transfer latency, network scalability, and the ability to resume interrupted downloads and simultaneously download segments of one file from multiple peers. Basically, they help ordinary hosts connect to each other and guide efficiently the encrypted network traffic.

Super Nodes are also responsible for the ‘Global Indexing’. This technology enables you to search for other users in the network. The company guarantees that it will find a user if he has registered and has logged in during the last 72 hours.

A very interesting moment about the Skype network is that it ’self-modifiable’. If you have the application installed, your computer may turn into a Super Node, without you even knowing it, because those capabilities don’t have a noticeable impact on a computer’s performance. SNs basically store the addresses of up to several hundred Skype users, without carrying any voice, text or file-transfer data. In that manner, the more Skype users come online, the more supernodes become available to expand the capacity of the network.

Skype routes the traffic intelligently by choosing the optimum data transfer path. Since it uses either TCP or UDP protocol, it breaks the whole data stream into seperate packets, which can take different paths to the end destination. The final arrangement is done at the receiving end.

As far as safety and privacy are concerned, Skype uses Advanced Encryption Standard, known as Rijndel, used also by the U.S. Government organizations to protect sensitive data. Skype uses 256-bit encryption.

The programmers of Skype have implemented wideband codecs which allows it to maintain a good sound quality at a bandwidth of 32kb/s and allow frequencies between 5-8,000Hz to pass trough.

Your list of contacts, the application stores in the Windows Registry. This is called the Buddy list and once again, it is digitally encrypted. So, the list is local for every machine, or in other words, it’s not downloaded from the central server.

Let’s briefly describe the tasks of the Skype client. First it connects to the network. It then listens on particular ports for incoming calls, refreshes the host cache table, uses wideband codecs, maintains the buddy list, encrypts messages and determines if there is a firewall or not.

The login process:

The login process is the most important one and it consists of several phases. As mentioned, SC must connect to a valid SN in order to authenticate the username and password with the Central Server.

Skype gets the fist IP from the host cache, sends it a UDP packet and waits for response. If there is no response after 5 seconds, it sends a TCP packet to the same IP. It tries to establish a TCP connection to the HC IP address and port 80 (HTTP port). If still unsuccessful, it tried to connect to IP address and port 443 (HTTPS port). If this does not work either, it reads the next address in the HC. If Skype is unable to connect to a SN, it will report a login failure.

The application comes with several build-in addresses of different nodes, called bootstrap super nodes.

If the connection attempt is successful, the client must authenticate the user name and password with the Skype login server, which holds all user names and passwords and makes sure they are unique across the whole network. When the application connects to an SN, it receives an up-to-date list of other active SNs, so it has the most current information.

The Media Transfer process:

The video/voice communication through SKype is established through UDP. The trick here is that quite often, one of the users is behind a firewall or a router, hence it doesn’t have a real IP address. But if both Skype clients are on real IPs, then the media traffic flows directly between them over UDP. The size of the voice packet is 67 bytes, which is actually the size of UDP payload. One second conversation results in roughly 140 voice packets being exchanged both ways, or 3-16 kilobytes/s.

If one of the callee or both of them do not have a public IP, then they send voice traffic to another online Skype node over UDP or TCP. The developers of Skype have preferred to use UDP for voice transmission as much as possible.

An interesting fact is that even if both sides are not speaking, voice packets will still be flowing between them. The purpose of these so called ’silent packages’ is to keep the connection alive.

Conclusion:

There are several factors responsible for the success of Skype. First of all, the voice quality is better compared to other applications. It works without a problem on computers with firewall. It is very easy to install and use. Skype’s security is also a big advantage. Everything that is being transferred across the network is being encrypted to ensure privacy. As a result of that, even if hackers intercept the data being transferred, they won’t be able to decode it.

The Skype application does not include any adware or spyware. But, there are cases when third parties have managed to add such functionalities (not only for Skype), so it’s really important that you download it from the right place. Therefore, do it either from the official website, or from respected sites as http://www.freesecuredownloads.com/skype/index.html.

For secure download, free of any adware or spyware, go to http://www.freesecuredownloads.com/skype/index.html

Article Source: http://EzineArticles.com/?expert=Cedric_Price
http://EzineArticles.com/?How-Skype-Works&id=496462

Here are all the interesting links I found the last few days:

• Blackboard @ FSU (campus.fsu.edu) - campus.fsu.edu provides the university community a secure environment for teaching and learning, participating in sponsored organizations, and using Secure Applications to transact University business - Tags: FSU FSUID
• Florida State University Registrar - FSU Transcripts - Tags: FSU Transcript
• FIT - Requesting Transcripts - - Tags: FIT Transcript
• University of Colorado at Boulder Telecommunications Program - MS in Telecommunications - Tags: masters.degree distance.learning
• Telecommunications Engineering Technology, Master of Science - The master of science degree in telecommunications engineering technology is offered by the department of electrical, computer, and telecommunications engineering technology. The program accommodates individuals with both technical and non-technical bacca - Tags: masters.degree telecommunications distance.learning
• ExceLight expands XFP Portfolio with long-reach transceiver - The SXP3101UL XFP can reliably transmit signals at distances of 120 km or more without the need for electronic dispersion compensation - Tags: laser xfp dispersion dispersion.compensation long-haul transceiver

In a paper delivered today at OFC/NFOEC 2007 in Anaheim, CA, Alcatel-Lucent describes how it has developed a tunable optical waveguide equalizing filter that is fabricated entirely in a CMOS manufacturing line, the same manufacturing technology that produces electronic integrated circuits. Alcatel-Lucent says its breakthrough technology “eliminates the package walls separating the photonic circuit from the electronic circuit,” thereby opening the door to new optical networking architectures.

While the electronics industry is a multibillion-dollar per year industry, the photonics industry remains essentially a boutique operation. Components are built on separately optimized material platforms, including lithium niobate (LiNbO3), indium phosphide (InP), and indium gallium arsenide (InGaAs). As a result, the photonics market is fractured; each material sees a portion of the market, and none of the materials enjoy the economies of scale inherent in the electronics world.

“What we can envisage,” says Alice White, vice president of enabling technologies at Alcatel-Lucent Bell Labs, “is a world in which these two worlds—electronics and photonics—come together seamlessly on a single platform.” Consider, for example, her recently purchased hybrid car. “This car chooses when to use the gas engine and when to use the electronic motor based on which is best, efficiency-wise and performance-wise,” she explains. “Sometimes it uses both together, but it does this seamlessly. We could imagine, down the road, a situation in which the electronics and photonics are on the same chip. And thinking about trying to do that gives us some real architecture and design advantages,” White notes.

Of course, White and her team have gone beyond just thinking about it. They say they have developed a CMOS-compatible tunable optical equalizer that leverages inherent advantages from both the electronic and photonic worlds.

The research is funded by the Defense Advanced Research Projects Agency’s (DARPA’s) EPIC Program, or Electronic and Photonic Integrated Circuits Program. Alcatel-Lucent Bell Labs’ partners on the project include BAE Systems, which provides the CMOS foundry; MIT; Cornell University; and Applied Wave Research, a computer-aided design (CAD) vendor.

As dictated by DARPA’s EPIC Program, all deliverables have to be made in a commercial foundry. And while she admits that this was a formidable challenge, White also notes, “The fact that we can do it makes this all the more interesting. It really leapfrogs the tech transfer issue.”

Silicon-based tunable optical equalizer

Bell Labs says its zero/pole filters enable network operators to clean signals within a transmission channel on the silicon chip—either directly or by modifying the signal in anticipation of later distortion—as well as balance the power of different transmission channels. The key to the demonstration is a new control configuration that uses a single voltage to adjust the signal equalization and an innovative new architecture to realize complex responses in a low-order filter.

The base structure of the filter is a Mach-Zehnder interferometer. The filter itself is symmetric; light comes into the filter and is split among two ring resonators on the upper arm of the filter and two ring resonators on the lower arm. “What the rings do is create a nonlinear response in frequency,” explains Doug Gill, MTS, Integrated Photonics Research, Alcatel-Lucent Bell Labs. “The resonance makes the phase change in a very nonlinear way. We control how sharply that phase changes and where the phase change is located in frequency space. We call it ‘The Dance of the Resonances.’ We align them and tune them to get the response that we want,” he says.

At the output of the filter, the light from the two arms interferes constructively and destructively to get the desired type of magnitude response. “But,” says Gill, “you can also get the type of phase response that you want, and that’s why this filter can compensate both for intensity distortion across the profile of the channel and phase distortion across the profile of the channel.”

Sanjay Patel, technical manager of Integrated Photonics Research at Ball Labs says the team purposely selected a filter design for its first implementation of the technology in part because optical loss has historically been an issue. Silicon, by contrast, is a high index contrast material, which has enabled Bell Labs to make very tight bends and create an optical circuit that is much smaller than, say, a planar lightwave circuit (PLC)-based device. “It is about a factor of twenty smaller,” Patel reports.

Moreover, he asserts, using a combination of silicon and optics gives you “the advantage of doing the optical compensation ranges in compact form factors with electronic assist. So you kind of get the best of all worlds, and you can say, ‘I know where optics provides an advantage, and I know where electronics provides an advantage.’ I can seamlessly move between the two and complement the necessary strengths that both of these bring to the area of dispersion compensation, just as an example,” he adds.

Particularly in the case of dispersion compensation, there are advantages to doing that in the optical domain, notes Gill. When you go into the electrical domain, you lose the phase information of the signal. “So here is an example of where there is an inherent advantage of doing that particular process in the optical domain,” Gill says. “And then you can have the support of the electronics around that process to add electronic dispersion compensation on top to whatever degree might be necessary.”

While generally available technologies are not expected for 3 to 5 years, synergistically combining such optical filters with on-chip electronic circuits can provide a commercially viable path to providing reconfigurable, low-cost, low-power-consumption devices that could fit into small-form-factor pluggable modules, say Bell Labs representatives. These new devices also are ideal for dual-use applications in systems that route data over both electronic and optical networks, depending on the most appropriate delivery and/or transport format.

Eliminating walls

At the end of the day, says Bell Labs, this announcement is about tearing down the barriers between electronics and photonics that exist both in the physical world and in the mindset of network engineers. “What we’re trying to do here is stop that [mentality of] ‘Do it electronically’ or ‘Do it photonically,’” says White. “Instead, let’s just say, ‘In this particular functionality, what makes the most sense?’ And then not have a package wall separating the photonic circuit from the electronic circuit.”

Every time you have a package wall, adds Gill, you increase the cost and size of the device, and you introduce constraints on design. “When you have a package wall, you have to have some common standard mating characteristic between the various packages. Eliminating those package walls opens up new dimensions in component design.”

“We’re really thinking about these things in terms of not a fight between electronics and optics but a collaboration,” muses Patel. “There are synergies.”