Stream Control Transmission Protocol(SCTP))

1.1.1 Challenges of Packetizing and Unpacketizing Algorithms

Different types of operands are inserted in packets. System is calculated on data type and pushed data to the best fitting in the packet as shown in Figure 3.8. When it finds error, how many times need for retrying on erroneous data? System tries three times and after the failed operation is identified. Sometimes the last packet of operation partially packetizing is not full and loses some memory. So the best fitting packetizing is more needed.

Figure 3.8: TCP header and payload size in a packet [58].

All data needs unpack and calculation of packet loss and looking for the overhead are complex. Sometimes we find the undetectable errors of packetizing and unpacketizing algorithms. Minimum and maximum length of a packet header is 20 byte to 60 byte respectively as shown in Figure 3.9. The TCP packet size is 1500~1450 byte. The maximum TCP packet size is 64K (65535 bytes) but it is not used in network. The maximum transmission unit (MTU) for Ethernet is 1500 bytes for an instance. If the size of data is more than 1450 byte, then it splits more than 2 packets.

1.1.2 A Typical Data Structure of TCP Packet

When synchronous (SYN) bit is active, TCP data is synchronized as a binary stream of file as shown in Figure 3.9. Sequence numbers are used to identify which data has been dispatched and accepted. Acknowledge (ACK) bit is used for acknowledgment from the server [19] [58].

Figure 3.9: A typical data structure of TCP packet [58].

When all data are received in server, the finish (FIN) bit is active. In payload, S= segment1, segment 2 …… segment(i) is the set of segments in packet (p0, p1, p2 … ) and all of them have same size. Here D₁, D₂ ….. , D_k+1, D_k+2… D_2k, D_2k+1, D_2k+2…. D_3k… are the set of n data that is needed to be packed in the segments of the packets. When a segment is full, a new segment is created. Packet is full by segments and a new packet is created. For this reason the TCP frame is discovered for resending error data. We find TCP non-jumbo frame size ≤ 1500. Multiple packets are contained in frames e.g. jumbo frame size is 9 kilo byte long. Number of data per segment defines segment size divided to data size. Data are inserted in a packet depending on packet size divided by size of data type. If the TCP packet size is 1500 ~ 1450 byte, then six packets are inserted in jumbo frame of payload [19] [58].

Figure 3.10 shows that clients send multiple packets to server and server receives the packets. These packets are stored in a queue of server according to the sequence numbers. Server processes packets in order of sequence number from the queue.

Figure 3.10 Window size is defined between sender and receiver [58].

1.1.3 A Typical Block Diagram of Frame

The internet protocol (IPv4) structure is shown in Figure 3.11. The IPv4 indicates the version 4 and it can host up to addresses. But it has some reserved bits that will be used in future technology. The frame format consists of IPv4 header, frame header, payload and trailer. The payload consists of packets (P0, P1 …P (B-1)). If a TCP packet grasps 0 byte of data, then it would be at least 40 + 1=41 bytes that can send 0 byte over TCP packet. Hexadecimal codes of payload data are stored in a trailer and compared with main data after receiving [19] [58]. Now trailer is used for error detection using the CRC method. However our proposed EFT uses ED algorithm to detect the errors.

Figure 3.11: A typical block diagram of frame format [58].

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