How Skype Architecture Works

Posted by Mark Gillett, CVP Skype Product Engineering & Operations
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In recent days, we have seen media reports that we believe are inaccurate and could mislead Skype users regarding our approach to user safety and privacy. I would like to clarify a few details.

We are still deeply moved by the loyalty that we see among our users around the world. Every day we work to create the best product for communication at a distance. We want Skype to be a reliable, fast and easy-to-use tool, and in most cases it will be free. It is used by mothers and fathers, teachers, military personnel, children, brothers and sisters, grandparents, lovers and old friends around the world. Our growth over the past nine years shows that we are on the right track, and we say to the entire community of our users: “Thank you.” We are honored to serve 250 million users every month, and to provide 115 million minutes of conversations between people only in the last quarter. We believe that communication is one of the basic human needs and,

Of course, this does not happen by magic. Ensuring the accessibility of such a connection for everyone is a difficult technical task. This requires investment, innovation and the desire to use all new technologies and opportunities. In addition to the need to solve the problems of expanding the scale and providing a reliable connection and a product that people would like, we, working on a global scale, understand that we are very responsible. We strive to do this well: both in terms of providing a phenomenal communication experience for all users, and in terms of responsible behavior as a member of the global community.

Despite our efforts, some media have recently published publications that suggest that Skype is acting inappropriately, based on ulterior motives, against the interests of our users. It is difficult to assume something less consistent with the philosophy of Skype.

Let me state some of the statements made in the press and provide the facts in response.

It has been suggested that Skype made changes to the network architecture at the request of Microsoft in order to provide law enforcement authorities with greater access to our users ’communications.

Wrong .

The architecture of Skype is based on our commitment to providing the best product for our users. Skype began the process of developing and moving supernodes to cloud servers long before Microsoft acquired it. Skype first deployed these “mega-super nodes” in the cloud to increase the reliability of Skype software and services in December 2010. These sites were hosted on Skype’s own data centers and on third-party infrastructure (Amazon EC2), and more recently, on Microsoft data centers. This step was taken in order to improve Skype, primarily to increase the reliability of the platform and increase the speed with which we can respond to problems. This step also gives us the opportunity to quickly introduce new interesting features that allow us to make communication fuller and richer in the future.

At the beginning of this year, we completed the migration of our super nodes to Microsoft data centers, and now we can get the degree of reliability and support that other Microsoft cloud products use, such as Xbox Live, Bing, SkyDrive, Hotmail and Office 365. This creates real benefits for our users and contributes to our ability to scale Skype.

It was suggested that Skype had recently changed its position and policy regarding cooperation with law enforcement agencies.

Wrong .

The transition to our own super nodes was not planned to facilitate the access of law enforcement agencies to the communication of our users. The law enforcement team responsible for responding to requests from law enforcement has existed on Skype since 2005. While we are really focused on creating the best product for our users, we also consider ensuring its safety for all fundamental to the quality of the product. Our position has always been reduced to the fact that, in cases where law enforcement agencies follow the appropriate legal procedures, we respond to their requests in accordance with the law and within the framework of what is technically feasible. We have rules posted on our main site.which provide additional information to our position on this issue.

It has been suggested that as a result of recent architecture changes, Skype has been able to track and record audio and video calls from our users.

Wrong .

Switching to the internal hosting of “super nodes” does not provide for monitoring and recording calls. “Super nodes” help Skype customers find each other on the network so that they can connect to make a Skype call. Simply put, supernodes act as a distributed directory of Skype users. Calls from Skype to Skype do not go through our data centers and “super nodes” do not participate in the transfer of audio or video between Skype clients.

These calls continue to be established directly between the Skype nodes (clients) participating in the conversation. In some cases, Skype uses servers to assist in making calls: for example, the server is used to notify the client that a new call is being initiated with him, and where the full Skype application is not running (for example, the device is suspended, “sleeps” or requires notification of an incoming call for activation), as well as in group video calls, where the server aggregates media streams (video) from several clients and sends them to clients, which may not have sufficient bandwidth to establish Connections with all the participants.

We believe that servers are the best way to solve these technical problems, as well as provide maximum convenience for our users.

As before, SkypeOut calls and incoming phone calls to Skype online numbers (calls connecting Skype with public telephone networks) go through the gateways of our partners, as this is necessary in order to connect them to a traditional telephone network.

It has been suggested that the changes we made were made to facilitate law enforcement access to Skype instant messaging.

Wrong .

We have made improvements to our software and infrastructure to improve usability and reliability. Point.

In order to ensure the delivery and synchronization of instant messages between multiple devices, as well as to control the delivery of messages between users located behind some firewalls that do not allow direct connection between clients, some messages are stored temporarily on ours (Skype / Microsoft) servers for immediate or subsequent delivery to the user.

As I said above, if law enforcement agencies, following the appropriate procedures, request access to messages temporarily stored on our servers, we will need to provide it. I must repeat, we will do this only if the law requires it, and if it is technically feasible.

Some commentators have suggested that Skype has ceased to protect the communication of its users.


Skype software autonomously applies encryption to Skype-to-Skype calls between computers, smartphones and other mobile devices that have the full version of the Skype application , as it always has been. This has not changed. Only the Skype version distributed in China through our joint venture with contains a chat filter in accordance with local laws .

As I said at the very beginning, our users and their amenities are our top priorities.

We have an amazingly loyal community of users from around the world, and we believe that our users deserve the very best products we can create.

Every day we help Skype users contact their loved ones wherever they are - in Moscow, Miami or Mumbai, and what platform they use - PC, iPhone, TV, Windows Phone, Mac or Android. We constantly strive to develop and implement an effective, safe, reliable and yet easy-to-use communication system. We hope you continue to love Skype.

Thank you for your continued support, loyalty to our products and love for Skype.

- Mark

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