TCP vs SCTP

TCP (Transmission Control Protocol) has been around for quite some time and it has provided us with the protocol to move data from one point to another in our computer networks. Despite its success, TCP also has many limitations. SCTP (Stream Control Transmission Protocol) does everything that TCP does while adding new features that TCP doesn’t have.

The first feature that SCTP adds to the mix is multi-homing. Multi-homing allows the two endpoints of a connection to declare multiple interfaces (IP addresses). Providing and alternate route for the data in case the current interface in use fails for some reason. The transfer from one interface to another is seamless; therefore the connection is not interrupted.

The second feature is multi-streaming. Rather than use a single stream of data, SCTP can create multiple streams that can be used independently. This doesn’t really improve the speed of the medium but it allows the data to arrive concurrently; minimizing the wait time for pages to completely load. This feature also prevents control packets from getting blocked by data packets, like what usually happens in TCP; thereby improving data control.

TCP is very vulnerable to denial of service attacks, which locks up the resources of the server and prevents others from using it. Rather than TCP’s 3-way handshake initiation, SCTP uses a 4-way handshake that allocates resources near the end of the entire handshake. Because of this, SCTP s not vulnerable to DoS attacks.

Data in TCP comes in packets. Packets have a specific size and a long stream would be divided to fit while short ones are spliced together. This means that message framing must be provided at the application layer to fully identify separate messages. SCTP implements message framing and each message would always have the same size when it comes out as it came in.

Lastly, SCTP has made delivery ordering optional. Delivery ordering is necessary in many instances. That’s why it is mandatory in TCP. But in certain cases where ordering is not needed, resources can be freed by disabling this capability. SCTP provides flexibility to suite each situation with optional ordered delivery.

SCTP is, in many ways, superior to TCP. But due to our long term use of TCP, it is quite hard to transition to the superior one. Nonetheless, the advantages of SCTP would gradually draw attention and users.

Summary:

1. SCTP is better at multi-homing than TCP
2. SCTP has multi-streaming while TCP doesn’t
3. SCTP has initiation protection while TCP doesn’t
4. SCTP has message framing while TCP doesn’t
5. Ordered delivery is optional with SCTP but not with TCP

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