Telugu Aunty Boothu Kathalu

ఆంటీ తో మంచం మీద ఒక రాత్రి, The transport layer must deal with the imperfections of the network layer service. There are three types of imperfections that must be considered by the transport layer : Segments can be corrupted by transmission errors Segments can be lost Segments can be reordered or duplicated To deal with these types of imperfections, transport protocols rely on different types of mechanisms. The first problem is transmission errors. The segments sent by a transport entity is processed by the network and datalink layers and finally transmitted by the physical layer. All of these layers are imperfect. For example, the physical layer may be affected by different types of errors : random isolated errors where the value of a single bit has been modified due to a transmission error random burst errors where the values of n consecutive bits have been changed due to transmission errors random bit creations and random bit removals where bits have been added or removed due to transmission errors The only solution to protect against transmission errors is to add redundancy to the segments that are sent. Information Theory defines two mechanisms that can be used to transmit information over a transmission channel affected by random errors. These two mechanisms add redundancy to the information sent, to allow the receiver to detect or sometimes even correct transmission errors. A detailed discussion of these mechanisms is outside the scope of this chapter, but it is useful to consider a simple mechanism to understand its operation and its limitations. Information theory defines coding schemes. There are different types of coding schemes, but let us focus on coding schemes that operate on binary strings. A coding scheme is a function that maps information encoded as a string of m bits into a string of n bits. The simplest coding scheme is the even parity coding. This coding scheme takes an m bits source string and produces an m+1 bits coded string where the first m bits of the coded string are the bits of the source string and the last bit of the coded string is chosen such that the coded string will always contain an even number of bits set.