Foundry NetIron M2404C and M2404F Metro Access Switches
Configuring TLS (Rev. 03)
Transparent LAN Services (TLS)
© 2008 Foundry Networks, Inc.
Page 4 of 16
Figure 2: IP Packet Frame Format with the Additional TLS Tag Header
Overview
TLS implies Layer 2 connectivity offered by a service provider to multiple customer sites in a
manner that is transparent to the Customer Edge (CE) devices.
The device is positioned on the edge of the provider network. It is connected to CE switches, and
interfaces to the provider network.
To provide TLS, Ethernet frames originated by the source CE switch are received at the Provider
Edge (PE) switch, encapsulated and transported across the provider network, where the PE switch
removes the encapsulation and delivers the unmodified frame to the destination CE switch (see
Figure 3
).
Figure 3: TLS Implementation
The 802.1Q VLAN-ID tag (VID) in the user’s traffic is transparent to switches. This allows all the
CE switches to behave as if attached to a shared LAN.
Three types of ports are defined in the network switches deployed by the service provider:
•
Residential port
– A port that is connected to a user that does not participate in the TLS.
Packets that are transmitted through this port have no added tag.
•
Access (user) port
– A port that is connected to a user. Packets that are transmitted through this
port have no added tag.
•
Core (uplink) port
– A port that is connected to the service provider’s network. All packets
that are transmitted through this port are either control packets or packets with an additional
tag.