Overview of SCTP: Definition, Functions, and Restrictions

Definition of SCTP

What is SCTP? SCTP is the abbreviation of the Stream Control Transmission Protocol, which is an Internet protocol suite in the transport layer of a computer network communication protocol. SCTP is at the same level as User Datagram Protocol (UDP) and Transmission Control Protocol (TCP), the latter provides transport layer functions for many Internet applications.

Functions of SCTP

The following are the functions of SCTP. If you are interested in the content, you can continue to read.

• Transferring data in blocks in independent streams eliminates unnecessary line header blocking.
• Improved error detection is suitable for jumbo Ethernet frames.
• Path selection and monitoring function used to select the main data transmission path and test the connectivity of the transmission path.
• Verification and confirmation mechanisms prevent flooding attacks and provide notification of duplicate or missing data blocks.
• Multi-homing support, where one or two endpoints of the connection can contain multiple IP addresses. This allows transparent failover between redundant network paths.

SCTP can transmit signaling messages between signaling system 7 (SS7) of 3G mobile networks through M3UA, M2UA, or SUA. SCTP provides reliable and safe transmission, minimizes end-to-end delay, and shortens failover time in the event of network failures, orderly and out-of-order transmissions.

Restrictions of SCTP

SCTP has the following restrictions and limitations.

IP Address

• Up to eight source IP addresses and eight destination IP addresses are allowed in SCTP communication.
• It only supports static IP NAT. The incoming interface packets must belong to the same area.

Policies

• After deleting the policy, related sessions and associations will be cleared.
• It does not support dynamic strategies. You must configure all policies for SCTP sessions.
• You cannot use the application protocol to ignore the option to configure the application in the security policy to allow SCTP ALG communication.
• You configure one policy to allow SCTP communication from all client IPs to all server IPs, and another policy is configured to allow SCTP communication from server IP to client IP.

Rate Limiting

• Any changes in the rate limit configuration will not affect subsequent traffic of existing associations.
• Limit the rate of up to 80 addresses in a configuration file.
• An address in a configuration file can limit the rate of up to 10 protocols.
• The supported protocol decimal value is 0 to 63.

SCTP Configuration File Controls SCTP Enable/Disable

• If no configuration file is attached to the policy, the SCTP packet will be forwarded without inspection.
• If SCTP is disabled, all associations will be deleted, and subsequent SCTP packets will be delivered or discarded according to the policy.
• If a configuration file with only nat option is attached to the policy, only SCTP packets matching the policy will be NATed.
• If SCTP is enabled, all existing SCTP sessions must be cleared, otherwise, the traffic matching the old sessions will be forwarded without any checks from the SCTP module.

Why Is SCTP Better for LTE

In LTE, it is more reasonable to use SCTP as a standard protocol instead of TCP and UDP, because it is more flexible, safe, and fast. As more and more people rely on mobile data and use high-bandwidth applications such as video conferencing, it is necessary to make all the necessary improvements at the telecom provider level to meet this demand.

In terms of software, compared with TCP, SCTP can handle multiple simultaneous streams and multiplexed streams, while TCP can only process one data stream for each end-to-end connection.

SCTP is used to carry telecommunication signaling through IP. However, unlike TCP, which uses a byte stream interface (and therefore has a byte limit), SCTP is used as a data stream and can even be used with multiple streams sending multiple messages called blocks.

SCTP provides greater flexibility in certain applications that require continuous data exchange (such as VoIP) since SCTP runs in streams instead of bytes.

Final Words

It’s time to conclude. From this post, you can know what VLSM is and what the difference between it and FLSM is. Besides, you can learn the procedure of implementing VLSM. I believe that this post is helpful to you.