This document uses the following terms:
answer: A message that is sent in response to an offer that is received from an offerer.
caller: An endpoint that initiates a call to establish a media session.
candidate: A set of transport addresses that form an atomic unit for use with a media session. For example, in the case of Real-Time Transport Protocol (RTP) there are two transport addresses for each candidate, one for RTP and another for the Real-Time Transport Control Protocol (RTCP). A candidate has properties such as type, priority, foundation, and base.
candidate identifier: A random string that uniquely identifies a candidate.
Check List: An ordered list of candidate pairs that determines the order in which connectivity checks are performed for those candidate pairs.
component: A representation of a constituent transport address if a candidate consists of a set of transport addresses. For example, media streams that are based on the Real-Time Transfer Protocol (RTP) have two components, one for RTP and another for the Real-Time Transfer Control Protocol (RTCP).
component identifier: A simple integer that identifies each component in a candidate and increments by one for each component.
default candidate: A candidate that is designated for streaming media before connectivity checks can be finished. The candidate that is most likely to stream media to the remote endpoint successfully is designated as the default candidate.
fully qualified domain name (FQDN): An unambiguous domain name that gives an absolute location in the Domain Name System's (DNS) hierarchy tree, as defined in [RFC1035] section 3.1 and [RFC2181] section 11.
Internet Protocol version 6 (IPv6): A revised version of the Internet Protocol (IP) designed to address growth on the Internet. Improvements include a 128-bit IP address size, expanded routing capabilities, and support for authentication and privacy.
local candidate: A candidate whose transport addresses are local transport addresses.
local transport address: A transport address that is obtained by binding to a specific port from an IP address on the host computer. The IP address can be from physical interfaces or from logical interfaces such as Virtual Private Networks (VPNs).
NAT binding: The string representation of the protocol sequence, NetworkAddress, and optionally the endpoint. Also referred to as "string binding." For more information, see [C706] section "String Bindings."
peer-derived transport address: A derived transport address that is obtained from a connectivity check that is sent to a peer endpoint.
Real-Time Transport Control Protocol (RTCP): A network transport protocol that enables monitoring of Real-Time Transport Protocol (RTP) data delivery and provides minimal control and identification functionality, as described in [RFC3550].
Real-Time Transport Protocol (RTP): A network transport protocol that provides end-to-end transport functions that are suitable for applications that transmit real-time data, such as audio and video, as described in [RFC3550].
remote endpoint: See peer.
RTCP packet: A control packet consisting of a fixed header part similar to that of RTP packets, followed by structured elements that vary depending upon the RTCP packet type. Typically, multiple RTCP packets are sent together as a compound RTCP packet in a single packet of the underlying protocol; this is enabled by the length field in the fixed header of each RTCP packet. See [RFC3550] section 3.
Session Description Protocol (SDP): A protocol that is used for session announcement, session invitation, and other forms of multimedia session initiation. For more information see [MS-SDP] and [RFC3264].
Simple Traversal of UDP through NAT (STUN): A protocol that enables applications to discover the presence of and types of network address translations (NATs) and firewalls that exist between those applications and the Internet.
Transmission Control Protocol (TCP): A protocol used with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet. TCP handles keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet.
Traversal Using Relay NAT (TURN): A protocol that is used to allocate a public IP address and port on a globally reachable server for the purpose of relaying media from one endpoint to another endpoint.
TURN server: An endpoint that receives Traversal Using Relay NAT (TURN) request messages and sends TURN response messages. The protocol server acts as a data relay, receiving data on the public address that is allocated to a protocol client and forwarding that data to the client.
MAY, SHOULD, MUST, SHOULD NOT, MUST NOT: These terms (in all caps) are used as defined in [RFC2119]. All statements of optional behavior use either MAY, SHOULD, or SHOULD NOT.