The QOS features mentioned in this section only apply to the Customer’s LAN and private WAN (i.e. MPLS) networks. Internet connections do not apply or use any QOS features, since US laws prohibit the preferential treatment of traffic on Internet connections.
Voice, as a class of IP network traffic, has strict requirements concerning packet loss, delay, and delay variation (also known as jitter) to maintain high voice quality. To meet the requirements for voice traffic, many vendor solutions includes the following QOS features:
· Traffic classification
· Queuing
· Traffic shaping
· Compressed Real-Time Transport Protocol (CRTP)*
· Transmission Control Protocol (TCP) header compression*
46Labs monitors and sizes the Network to Network Interfaces (NNIs) (the connections between the MPLS, Internet, and the PSTN network) to ensure there is never any oversubscription. However, in MPLS networks the Provider Edge (PE) to Customer Edge (CE) MPLS connections are a common place where oversubscription can occur. The proper QOS configuration of the PE and CE routers is often the most important consideration in maintaining high voice quality on MPLS networks.
46Labs recommends that the Peeredge Switchess follow the industry best practice design approach and mark all SIP signaling traffic with a Differentiated Services Code Point (DSCP) marking of 24 (PHB CS3) and all RTP/SRTP traffic with a DSCP marking of 46 (PHB EF).