V6100 and V7122 User Guide 267RTP NO-OPThis feature complies with the IETF’s draft-wing-avt-rtp-noop-03.txt titled ‘A No-Op PayloadFormat for RTP’.The IETF document defines a no-op payload format for RTP. This can be used to verify RTPconnectivity and to keep NAT bindings and Firewall pinholes open. The draft defines theRTP payload as dynamic. 3Com’ default payload type is 120.Users can control activation of the RTP No-Op Packets by setting the parameterRTPNoOpEnable.Receipt of No-Op is always supported. If RTP No-Op packet transmission is activated, users can control the time interval inwhich the No_Op packets are sent in the case of silence (no RTP traffic). This isperformed using parameter RTPNoOpInterval. Users can control the payload type with which the No_Op packets are sent. This isperformed using parameter RTPNoOpPayloadType.Point-to-Point Protocol over Ethernet (PPPoE)PPPoE is a method of sending the Point-to-Point Protocol over Ethernet network.Point-to-Point Protocol (PPP) OverviewPoint-to-Point Protocol (PPP) provides a method of transmitting data over serial point-to-point links. The protocol defines establishing, configuring and testing the data link connectionand the network protocol.The PPP standard describes a state machine used to establish a valid connection betweentwo hosts over a serial connection. There are three major stages described, helping toestablish a network layer (such as an IP) connection over the point-to-point link: LCP (LinkConfiguration Protocol) Authentication and NCP (Network Control Protocol). Once thenetwork protocol is configured, the two hosts can communicate, sending network layerprotocol (such as IP) over the PPP connection (a small PPP header is added at thebeginning of each packet).At the initial phase, the hosts use LCP (link configuration protocol) to negotiate for linkcharacteristic and parameters. Packets sent in this phase have two octets of ‘PPP header’followed by LCP message with variable length. Various parameters and options arenegotiable at this phase, including MRU (maximum receive unit), Authentication Protocol,and others.
