http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode
ATM operates as a channel-based transport layer, using virtual circuits (VCs). This is encompassed in the concept of the Virtual Paths (VP) and Virtual Channels. Every ATM cell has an 8- or 12-bit Virtual Path Identifier (VPI) and 16-bit Virtual Channel Identifier (VCI) pair defined in its header. The VCI, together with the VPI, is used to identify the next destination of a cell as it passes through a series of ATM switches on its way to its destination. The length of the VPI varies according to whether the cell is sent on the user-network interface (on the edge of the network), or if it is sent on the network-network interface (inside the network).
As these cells traverse an ATM network, switching takes place by changing the VPI/VCI values (label swapping). Although the VPI/VCI values are not necessarily consistent from one end of the connection to the other, the concept of a circuit is consistent (unlike IP, where any given packet could get to its destination by a different route than the others).[8] ATM switches use the VPI/VCI fields to identify the Virtual Channel Link (VCL) of the next network that a cell needs to transit on its way to its final destination. The function of the VCI is similar to that of the data link connection identifier (DLCI) in frame relay and the Logical Channel Number & Logical Channel Group Number in X.25.
http://www.cisco.com/en/US/docs/routers/access/1800/1841/software/configuration/guide/ezvpn.html
Device(config-subif)# pvc 10/100 l2transport
why 100 ? (max, 2 的 16 次方）
why l2transport ?
- Q: Can any one tell me the exact difference between the commands L2transport and x-connect to create Vc for vpls/EoMPLS
- A: xconnect is the new command, l2transport is there for backwards compatibility.
Router#debug atm events (this is useful !!!)
Home modem config:
Q: I got my hands on an old DSL-300G D-link modem but the configuration requires the VPI and VCI values.
A: 0/35 setting is for any provider using Bell’s wholesale in Ontario/Quebec