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A virtual private network (VPN) extends a private network across a public network, such as the Internet. It enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network, and thus benefit from the functionality, security and management policies of the private network. A VPN is created by establishing a virtual point-to-point connection through the use of dedicated connections, virtual tunneling protocols, or traffic encryption.
A VPN spanning the Internet is similar to a wide area network (WAN). From a user perspective, the extended network resources are accessed in the same way as resources available within the private network. Traditional VPNs are characterized by a point-to-point topology, and they do not tend to support or connect broadcast. Therefore, communication, software, and networking, which are based on OSI layer 2 and broadcast packets, such as NetBIOS used in Windows networking, may not be fully supported or work exactly as they would on a local area network (LAN). VPN variants, such as Virtual Private LAN Service (VPLS), and layer 2 tunneling protocols, are designed to overcome this limitation.
VPNs can allow employees to securely access a corporate intranet while travelling outside the office. Similarly, VPNs can securely connect geographically separated offices of an organization, creating one cohesive network. VPN technology is also used by individual Internet users to secure their wireless transactions, to circumvent geo-restrictions and censorship, and to connect to proxy servers for the purpose of protecting personal identity and location
(b) Data Link Layer deals with error control. Data link layer adds reliability to physical layer by adding mechanisms to detect and retransmit lost or damaged frames. Also uses a mechanism to prevent duplication of frames. Also uses a mechanism to prevent duplication of frames.
Error Control bits are added to the form in the TRAILER.
(ii) Transport layer is also responsible for the Error Control. Error control is performed end-to-end. This layer makes sure that entire message reaches Rx Transport layer w/o error. Error can be a result of Lost, damaged or duplicated data and usually Re Tx is done.
Presentation Layer is concerned with Syntax and Semantics of info exchange between two systems. This Layer Encrypt, Encode and compress data and also perform Decryption, Decoding and Decompressing Data process
Transport Layer in OSI model functions as a link between user support layers and network support layers
In signal processing, data compression, source coding, or bit-rate reduction involves encoding information using fewer bits than the original representation. Compression can be either lossy or lossless. Lossless compression reduces bits by identifying and eliminating statistical redundancy. No information is lost in lossless compression. Lossy compressionreduces bits by identifying unnecessary information and removing it. The process of reducing the size of a data file is referred to as data compression. In the context of data transmission, it is called source coding (encoding done at the source of the data before it is stored or transmitted) in opposition to channel coding.
Compression is useful because it helps reduce resource usage, such as data storage space or transmission capacity. Because compressed data must be decompressed to use, this extra processing imposes computational or other costs through decompression; this situation is far from being a free lunch. Data compression is subject to a space–time complexity trade-off. For instance, a compression scheme for video may require expensive hardware for the video to be decompressed fast enough to be viewed as it is being decompressed, and the option to decompress the video in full before watching it may be inconvenient or require additional storage. The design of data compression schemes involves trade-offs among various factors, including the degree of compression, the amount of distortion introduced (when using lossy data compression), and the computational resources required to compress and decompress the data
cs601 assignment solution
For Hybrid Topologies see Lecture # 6 Page no 34 (Handouts). You will come to know what is required to implement.