A lot of us use Skype daily but have no idea about how it works. Here is a brief description of the Skype framework.
Skype employs a partially decentralized architecture – a mix of the peer-to-peer and client-server architectures. The client-server system is used for authentication while the peer-to-peer system is used for IP telephony, relaying, indexing peers and file transfers. On top of this is the Skype overlay network which users interact with directly, an overlay network is a virtual network that is formed above and independent of the underlying Internet protocol network.
Skype uses overlay networks to achieve the following:
1. It enables them to design and use their own proprietary protocols and application over the Internet. This enables Skype to encrypt all packet transmissions.
2. Redundant links between Skype peers guarantees robustness. This assures of end-to-end connection even when network resources are severely limited.
3. The peer-to-peer overlay model provides an elegant solution to the scalability challenge, given the huge number of interconnected nodes.
4. Skype uses its overlay network to circumvent problems arising from Network Address Translation traversal and bypass firewalls.
5. Routing and relaying are very flexible; protocols allow peers to autonomously set up links with the best nodes available.
6. The overlay allows Skype to store a lot of offline data in its peers leading to reduced storage infrastructure expenses.
7. Employing peer relays improves the quality of VoIP calls.
However the use of overlay networks can lead to serious security and privacy issues as users can use Skype to breach policy. Some possible reasons why organizations block Skype include the following:
1. There is no way to check user activity on the Skype; thus confidential information can be transferred through Skype. User communication is also encrypted, making it impossible to detect what information exchanges are going on.
2. Also, there is some speculation that Skype PCs can be used to launch denial-of-service attacks because viruses, spyware and malicious code can be transferred across its network. Skype can also become resource-intensive as any Skype user can unknowingly become a super-peer if he has access to enough computing resources.
Hopefully, you know more now about Skype.