Chapter 14 Adsl - ZyXEL Communications IES4005M User Manual

C 1 4
HAPTER
ADSL
Use these commands to configure ATM virtual circuits (VCs) on DSL ports. You can then use the
commands in other chapters to apply settings like QoS, Transparent LAN Service (VLAN TLS), VLAN
translation and aggregation, transparent VLAN, and VLAN trunking to the virtual circuits.
ATM
Asynchronous Transfer Mode (ATM) is a networking technology that provides high-speed data
transfer. ATM uses fixed-size packets of information called cells. With ATM, a high QoS (Quality of
Service) can be guaranteed.
Permanent Virtual Circuits
A Permanent Virtual Circuit (PVC) is a logical point-to-point circuit between sites. PVCs are low-
delay circuits because routing decisions do not need to be made along the way. Permanent means
that the circuit is pre-programmed by the carrier as a path through the network. It does not need
to be set up or torn down for each session. PVCs are also called virtual channels.
The system can handle multiple IEEE 802.1p priority queues on a single PVC. You can also define up
to eight PVCs on a DSL port and use them for different services or levels of service. You set the
PVID that is assigned to untagged frames received on each channel. You also set an IEEE 802.1p
priority for each of the PVIDs. In this way you can assign different priorities to different channels
(and consequently the services that get carried on them or the subscribers that use them).
For example, you want to give high priority to voice service on one of the ADSL ports. First
configure a static VLAN on the system for voice on the port. Then do the following:
• Configure a channel on the port for voice service.
• Set the channel to use the PVID of the static VLAN you configured.
• Assign the channel a high priority.
LLC
LLC is a type of encapsulation where one VC (Virtual Circuit) carries multiple protocols with each
packet header containing protocol identifying information. Despite the extra bandwidth and
processing overhead, this method may be advantageous if it is not practical to have a separate VC
for each carried protocol, for example, if charging heavily depends on the number of simultaneous
VCs.
VC Mux
VC Mux is a type of encapsulation where, by prior mutual agreement, each protocol is assigned to a
specific virtual circuit, for example, VC1 carries IP, VC2 carries IPX, and so on. VC-based
125
IES4005M User's Guide