The purpose is to avoid the drop in TCP congestion window size which takes some

The purpose is to avoid the drop in tcp congestion

This preview shows page 9 - 10 out of 10 pages.

callee, silence packets were still sent. The purpose is to avoid the drop in TCP congestion window size, which takes some RTT (round-trip time) to reach the maximum level again. 4.6 Security Security in VoIP Security, especially in a converged voice and data network, is a high priority. Proper mechanisms are needed to protect the voice communications elements and to prevent unauthorized users and hackers from accessing the network. Basically there are two major solutions for achieving some degree of protection goals: IP security [10] is one solution on network layer that can be applied for securing IP Telephony networks; on higher layers (transport and application layer) , a firewall may provide different security services depending on the layers on which it has functionality: network, transport or application layer. Security in Skype Skype is encrypted end-to-end because it uses the public Internet to transport voice calls and text messages and sometimes these calls are routed through other peers. Skype encryption ensures that no other party can eavesdrop on call or read instant messages. As claimed on Skype’s homepage, Skype uses AES (Advanced Encryption Standard) to protect sensitive information. Skype uses 256-bit encryption in order to actively encrypt the data in each Skype call or instant message. Skype uses 1024 bit RSA to negotiate symmetric AES keys. User public keys are certified by the Skype server at login using 1536 or 2048-bit RSA certificates. This scenario is supposed like this: before A wants to send message to B, A sends its certification which is encrypted with Skype server’s private key to B first. B can decrypt the certification and read the public key of A. Then A encrypts AES key with its private key and sends it to B. While B knows A’s public key, he can read the AES key and use it to transfer messages with A.
Image of page 9
INFOTECH Seminar Advanced Communication Services (ACS), 2005 10 5. Conclusion Skype is a successful combination of several technologies with high potential as it has many advantages compared to traditional VoIP: much better voice quality, ability to traverse the NAT and firewalls, encrypted media channel, ability to scale up to handle large-scale connection-oriented real-time services such as voice, etc. However Skype’s achievement is because that on the basis of p2p overlay networks, it makes use of several great technologies and integrates them very skillfully. For instance, Skype possibly uses a variant of the STUN (discuss in part 4.1) to determine the NAT and firewall it is behind. The p2p networks have a flat architecture, and avoid employing central components. This results to that there are heavy software based DSP operations at Skype clients, including codecs, mixer and fancy echo cancellation. However it will make the person-to-person communication easier, which is the original purpose of the Internet.
Image of page 10

You've reached the end of your free preview.

Want to read all 10 pages?

  • Spring '16

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask ( soon) You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors