Planet Networking & Communication wgsw-28040 User Manual page 106

User's Manual of WGSW-28040
Frame Income
Income Frame is tagged Income Frame is untagged
Frame Leave
Leave port is tagged Frame remains tagged Tag is inserted
Leave port is untagged Tag is removed Frame remain untagged
Table 4-5-1: Ingress / Egress Port with VLAN VID Tag / Untag Table
■ IEEE 802.1Q Tunneling (Q-in-Q)
IEEE 802.1Q Tunneling (QinQ) is designed for service providers carrying traffic for multiple customers across their networks.
QinQ tunneling is used to maintain customer-specific VLAN and Layer 2 protocol configurations even when different customers
use the same internal VLAN IDs. This is accomplished by inserting Service Provider VLAN (SPVLAN) tags into the customer's
frames when they enter the service provider's network, and then stripping the tags when the frames leave the network.
A service provider's customers may have specific requirements for their internal VLAN IDs and number of VLANs supported.
VLAN ranges required by different customers in the same service-provider network might easily overlap, and traffic passing
through the infrastructure might be mixed. Assigning a unique range of VLAN IDs to each customer would restrict customer
configurations, require intensive processing of VLAN mapping tables, and could easily exceed the maximum VLAN limit of
4096.
The Managed Switch supports multiple VLAN tags and can therefore be used in MAN applications as a provider bridge,
aggregating traffic from numerous independent customer LANs into the MAN (Metro Access Network) space. One of the
purposes of the provider bridge is to recognize and use VLAN tags so that the VLANs in the MAN space can be used
independent of the customers' VLANs. This is accomplished by adding a VLAN tag with a MAN-related VID for frames entering
the MAN. When leaving the MAN, the tag is stripped and the original VLAN tag with the customer-related VID is again available.
This provides a tunneling mechanism to connect remote costumer VLANs through a common MAN space without interfering
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