Network protocols

Roc needs several network protocols to deliver data between the sender and the receiver.

Roc doesn’t invent new protocols. Instead, it relies on existing open standards to take advantage of their careful design and potential interoperability with other software. Roc implements all protocols by itself, for two reasons. First, not all protocols have a suitable open implementation. Second, the protocol support is tightly integrated into the Roc pipeline and it would be hard to employ a stand-alone implementation.

Although Roc is designed to support arbitrary protocols, so far all supported protocols are RTP-based. RTP by itself is very basic but also very extensible. To employ RTP, one needs to select an RTP profile and, if necessary, some RTP extensions. Roc employs RTP Audio/Video Profile which specifies how to stream audio and video using RTP. Roc also employs FEC Framework, which specifies how to incorporate various FEC schemes into RTP.

Note that employing FEC Framework increases the service quality but also breaks interoperability with RTP implementations that are not aware of this extension. If you need compatibility with such applications, you should disable FEC in Roc

Roc also employs various RTCP extensions to exchange non-media reports between sender and receiver. Usually this doesn’t break interoperability with implementations that don’t support extensions, however some features may not work with such implementations (e.g. sender-side latency tuning).

Here is the full list of the network protocols implemented by Roc:

RFC

Name

Comment

RFC 3550

RTP: A Transport Protocol for Real-Time Applications

Basic RTP and RTCP

RFC 3551

RTP Profile for Audio and Video Conferences with Minimal Control

RTP AVPF (Audio/Video Profile)

RFC 3611

RTP Control Protocol Extended Reports

RTCP XR
(supported blocks: DLRR, RRTR)

RFC 6776

Measurement Identity and Information Reporting Using a Source Description (SDES) Item and an RTCP Extended Report (XR) Block

RTCP XR Measurement Information Block

RFC 6843

RTP Control Protocol (RTCP) Extended Report (XR) Block for Delay Metric Reporting

RTCP XR Delay Metrics Block

RFC 6363

Forward Error Correction (FEC) Framework

FECFRAME

RFC 6865

Simple Reed-Solomon Forward Error Correction (FEC) Scheme for FECFRAME

Reed-Solomon FEC Scheme

RFC 6816

Simple Low-Density Parity Check (LDPC) Staircase Forward Error Correction (FEC) Scheme for FECFRAME

LDPC-Staircase FEC Scheme