 Hello and welcome to the session on stream control transmission protocol that is SCTP. At the end of this session students will be able to introduce the SCTP as a new transport layer protocol. Students will be able to identify SCTP services and compare them with TCP. Here figure shows the new transport layer protocol called SCTP. SCTP is designed as a general purpose transport layer protocol that can be handled multimedia and stream traffic which are growing every day on the internet. Strip control transmission protocol is a new reliable message oriented transport layer protocol. Figure shows the relationship of SCTP to the other protocols in the internet protocol suit. SCTP lies between the application layer and the network layer and serves as the intermediary between the application programs and the network operations. SCTP however is mostly designed for the internet applications that have recently been introduced. These new applications such as IUA use ISDN or IP, M2UA and M3UA which is operated on telephone signaling, H.248 which is a media gateway control, H.323 which is IP Telephony and SIP that is IP Telephony. They all need a more sophisticated service than TCP can provide. SCTP provides this enhanced performance and reliability. Here we concisely compare UDP, TCP and SCTP. UDP is a message oriented protocol. A process delivers a message to UDP which is encapsulated in a user datagram and sent over the network. UDP preserves the message boundaries. Each message is independent from any other message. This is desirable feature when we are dealing with applications such as IP Telephony and transmission of real-time data. However, UDP is unreliable. The sender cannot know the destiny of message send. A message can be lost, duplicated or received out of order. UDP also lacks some other features such as congestion control and flow control needed for a transport layer protocol. TCP is a byte oriented protocol. It receives a message or messages from a process, stores them as a stream of bytes and sends them in segments. There is no preservation of the message boundaries. However, TCP is a reliable protocol. The duplicate segments are detected, the loss segments are resented and the bytes are delivered to the end process in order. TCP also has congestion control and flow control mechanisms. SCTP combines the best features of UDP and TCP. SCTP is a reliable message oriented protocol. It preserves the message boundaries and at the same time detect lost data, duplicate data and out of order data. It also has congestion control and flow control mechanisms. SCTP has other innovative features which are unavailable in UDP and TCP. SCTP is a message oriented reliable protocol that combines the best features of UDP and TCP. There are services offered by SCTP to the application layer processes. Process to process communication. SCTP uses all well-known ports in the TCP space. Table shows list of some extra ports numbers used by SCTP, multiple streams. We know that TCP is a stream oriented protocol. Each connection between a TCP client and a TCP server involves one single stream. The problem with this approach is that loss at any point in the stream blocks the delivery of the rest of the data. This can be acceptable when we are transferring text. It is not when we are sending real-time data such as audio or video. SCTP allows multi-stream service in each connection which is called association in SCTP terminology. If one of the streams is blocked, the other streams can still deliver their data. The idea is similar to the multiple lanes of highway. Each lane can be used for a different type of traffic. For example, one lane can be used for regular traffic, another for carpools. If the traffic is blocked for regular vehicles, carpool vehicles can still reach their destinations. Here the figure shows the idea of multiple stream delivery, multi-homing. A TCP connection involves one source and one destination IP address. This means that even if the sender or receiver is a multi-home host that is connected to more than one physical address with multiple IP addresses, only one of these IP addresses per end can be utilized during the connection. And SCTP association on the other hand supports multi-homing service. The sending and receiving hosts can define multiple IP addresses in each end for an association. In this fault tolerant approach, when one path fails, another interface can be used for data delivery without interruption. This fault tolerant feature is very helpful when we are sending and receiving real time payload such as internet telephony. Here the figure shows the idea of multi-homing. In the figure, the client is connected to two local networks with two IP addresses. The server is also connected to two networks with two IP addresses. The client and server can make an association using four different pairs of IP addresses. However, here you have to note that in the current implementation of TCP, only one pair of IP addresses can be chosen for normal communication. The alternative is used if the main choice fails. Since in other words, at present, SCTP does not allow load sharing between different paths. SCTP association allows multiple IP addresses for each end. Here pause the video, think and answer. A connection in TCP, SCTP is called an association. The answer is B, full duplex communication. Like TCP, SCTP offers full duplex service when data can flow in both directions at the same time. Each SCTP then has ascending and receiving buffer and packets are sent in both directions. Connection oriented service, like TCP, SCTP is a connection oriented protocol. However, in SCTP, a connection is called an association. When a process at a site A wants to send and receive data from another process at site B, the following occurs. The first one is that the two SCTP establish an association between each other. The second step is that data are exchanged in both directions. And the third step is that the association is terminated. Reliable service, SCTP like TCP is a reliable transport protocol. It uses an acknowledgement mechanism to check the safe and sound arrival of data. Here is the reference. Thank you.