Editing Voice over IP (section)

===Layer 2===
Several protocols are used in the [[data link layer]] and [[physical layer]] for quality-of-service mechanisms that help VoIP applications work well even in the presence of [[network congestion]]. Some examples include:
* [[IEEE 802.11e]] is an approved amendment to the [[IEEE 802.11]] standard that defines a set of quality-of-service enhancements for wireless LAN applications through modifications to the [[media access control]] (MAC) layer. The standard is considered of critical importance for delay-sensitive applications, such as voice over wireless IP.
* [[IEEE 802.1p]] defines 8 different classes of service (including one dedicated to voice) for traffic on layer-2 wired [[Ethernet]].
* The [[ITU-T]] [[G.hn]] standard, which provides a way to create a high-speed (up to 1 gigabit per second) [[Local area network]] (LAN) using existing home wiring ([[Power line communication|power lines]], phone lines and [[Ethernet over coax|coaxial cables]]). G.hn provides QoS by means of Contention-Free Transmission Opportunities (CFTXOPs) which are allocated to flows (such as a VoIP call) that require QoS and which have negotiated a ''contract'' with the network controllers.