TFRC

This document specifies an update to the round-trip time (RTT) estimation algorithm used for TFRC (TCP-Friendly Rate Control) congestion control by the Datagram Congestion Control Protocol (DCCP). It updates specifications for the CCID-3 and CCID-4 Congestion Control IDs of DCCP.

The update addresses parameter-estimation problems occurring with TFRC-based DCCP congestion control. It uses a recommendation made in the original TFRC specification to avoid the inherent problems of receiver-based RTT sampling, by utilising higher-accuracy RTT samples already available at the sender.

It is integrated into the feature set of DCCP as an end-to-end negotiable extension. [STANDARDS-TRACK]

This document specifies a profile for Congestion Control Identifier 4, the small-packet variant of TCP-Friendly Rate Control (TFRC), in the Datagram Congestion Control Protocol (DCCP). CCID 4 is for experimental use, and uses TFRC-SP (RFC 4828), a variant of TFRC designed for applications that send small packets. CCID 4 is considered experimental because TFRC-SP is itself experimental, and is not proposed for widespread deployment in the global Internet at this time. The goal for TFRC-SP is to achieve roughly the same bandwidth in bits per second (bps) as a TCP flow using packets of up to 1500 bytes but experiencing the same level of congestion. CCID 4 is for use for senders that send small packets and would like a TCP- friendly sending rate, possibly with Explicit Congestion Notification (ECN), while minimizing abrupt rate changes. This memo defines an Experimental Protocol for the Internet community.

This document specifies TCP Friendly Rate Control (TFRC). TFRC is a congestion control mechanism for unicast flows operating in a best-effort Internet environment. It is reasonably fair when competing for bandwidth with TCP flows, but has a much lower variation of throughput over time compared with TCP, making it more suitable for applications such as streaming media where a relatively smooth sending rate is of importance.

This document obsoletes RFC 3448 and updates RFC 4342. [STANDARDS-TRACK]

This document proposes a mechanism for further experimentation, but not for widespread deployment at this time in the global Internet.

TCP-Friendly Rate Control (TFRC) is a congestion control mechanism for unicast flows operating in a best-effort Internet environment (RFC 3448). TFRC was intended for applications that use a fixed packet size, and was designed to be reasonably fair when competing for bandwidth with TCP connections using the same packet size. This document proposes TFRC-SP, a Small-Packet (SP) variant of TFRC, that is designed for applications that send small packets. The design goal for TFRC-SP is to achieve the same bandwidth in bps (bits per second) as a TCP flow using packets of up to 1500 bytes. TFRC-SP enforces a minimum interval of 10 ms between data packets to prevent a single flow from sending small packets arbitrarily frequently.

Flows using TFRC-SP compete reasonably fairly with large-packet TCP and TFRC flows in environments where large-packet flows and small-packet flows experience similar packet drop rates. However, in environments where small-packet flows experience lower packet drop rates than large-packet flows (e.g., with Drop-Tail queues in units of bytes), TFRC-SP can receive considerably more than its share of the bandwidth. This memo defines an Experimental Protocol for the Internet community.

This document contains the profile for Congestion Control Identifier 3, TCP-Friendly Rate Control (TFRC), in the Datagram Congestion Control Protocol (DCCP). CCID 3 should be used by senders that want a TCP-friendly sending rate, possibly with Explicit Congestion Notification (ECN), while minimizing abrupt rate changes. [STANDARDS-TRACK]