Public User Services on a Metro Ethernet Network
In Figure 10-7, the digital subscriber line access multiplexers (DSLAMs) support multiple permanent virtual channels (PVCs) so that a same user can use multiple services, such as High-Speed Internet (HSI), Internet Protocol Television (IPTV), and voice over IP (VoIP).
The carrier assigns different PVCs and VLAN ranges to HSI, IPTV, and VoIP services, as described in Table 10-5.
Service |
VLAN Range |
|---|---|
HSI |
101 to 300 |
VoIP |
301 to 500 |
IPTV |
501 to 700 |
A user accesses the VoIP service. When a VoIP packet reaches a DSLAM through a specified PVC, the DSLAM marks the packet with a VLAN in the VLAN range mapped to the PVC, such as 301. When the VoIP packet reaches the UPE, the UPE tags the packets with an outer VLAN ID mapping the VoIP VLAN ID range, such as 2000. The inner VLAN ID represents user information and the outer VLAN ID represents service information and the location of the DSLAM (packets from different DSLAMs are tagged with different outer VLAN IDs). When the packet reaches the NPE indicated by the outer VLAN tag, the VLAN tag is terminated on the QinQ termination sub-interface. According to the core network configuration, the packet is forwarded on the IP network or enters the corresponding VPN.
HSI and IPTV services are processed in the same manner, except that VLAN tags of HSI services are terminated on a broadband remote access server (BRAS).
The NPE can perform HQoS scheduling based on double tags and generate a DHCP binding table to avoid network attacks. In addition, the NPE can implement DHCP authentication based on double tags or other information. You can also configure VRRP on QinQ termination sub-interfaces to ensure service reliability.