L2TP is a tunnelling protocol for layer 2 (data link layer) of the OSI model. The send/receive port number forpackets additionally indicates which tunnelling protocol the packets are using.If the port number is changed by the dynamic NAPT (IP masquerade) feature, the information that indicatesthe tunnelling protocol will be lost, and end-to-end communication will be impossible.To allow end-to-end communication, specified packets from a specified device are allowed to pass throughthe WAN–LAN boundary without having their port number changed.Conditions• Communication across the WAN–LAN boundary is subject to the following conditions.a. Access from a LAC*2 on the LAN side to the LENS*1 on the WAN side:– Operate according to the dynamic NAPT settingsb. Access from a LAC*2 on the WAN side to the LENS*1 on the LAN side:– Only 1 LENS*1 can be installed on the LAN side.– The L2TP tunnel is established from the WAN side.– The L2TP tunnel’s first packet can be sent from either the LAN side or the WAN side.– You must set the LAN-side LENS’s IP address.*1 LENS: L2TP Network Server*2 LAC: L2TP Access ConcentratorPC Programming Manual References27.11 Router Configuration—VPN—[3-3] Pass Through8.6.22 Quality of Service (QoS)DescriptionThis PBX supports the following QoS (Quality of Service) mechanisms.You can enable and disable the QoS feature and configure the specific QoS settings.Setting DescriptionQoS Service Priority controlAuto QoS VoIP Automatically prioritise VoIP packets (SIP, H.323, MGCP,RTP)Upstream Bandwidth Set a limit on the number of frames sent of a specified typeIf the WAN line is narrow, sending packets at the link up-speed can cause overflow at the exit point (modem,etc.) and result in packet loss. To avoid this, the sending bandwidth should be restricted to match the speedof the WAN line.This, combined with priority control can allow efficient communication.Conditions• Only PQ*1 is supported for priority control. WRR*2 and SP*3+WRR*4 are not supported.Installation Manual 3938.6.22 Quality of Service (QoS)
