Cabletron Systems 7C04-R, 7C03 manual Interface, AAL Type

ATM Configuration

The remainder of the window contains a list box which displays the following information about each of the currently configured PVCs; use the scroll bar to the right of the list to view additional connections, if necessary:

Interface

The device interface on which the PVC was configured. Index numbers are assigned in an XXXXYY format, where X = slot index times 10,000, and Y = port index; note that the redundant interfaces on each 7A06-01 NIM share a single IF index, and changes in the active interface will be transparent to this window.

VPI

Displays the Virtual Path Identifier assigned to the connection; current versions of 7A06-01 firmware allow values from 0–3. Virtual Path Identifiers are used to group virtual connections, allowing for channel trunking between ATM switches. Each VPI can be configured to carry many different channels (designated by VCIs) between two points.

VCI

Displays the Virtual Channel Identifier assigned to the connection; allowable values are 0–1023 for each VPI. Each assigned VCI must be unique within its defined VPI: for example, you can assign a VCI of 14 as many as four times: once with a VPI of 0, once with a VPI of 1, and so on. Remember, it is the combined VPI and VCI designations assigned to a channel that creates the grouping of virtual connections.

AAL Type

This field indicates which AAL protocol type is currently in use on the Virtual Channel Circuit (VCC). An instance of this object only exists when the local VCL end-point is also the VCC end-point, and the ATM Adaptation Layer (AAL) is in use. The ATM Adaptation Layer maps user, control, and management data into or out of the information field of ATM cells of a virtual connection. The possible Protocol Type Values are:

•1 (AAL1) — this protocol is used in Constant Bit Rate (CBR) services, which require information to be transferred at a constant rate after the virtual connection has been established.

•34 (AAL3/4) — the protocol used for connectionless or connection-oriented transfer of data which may be sensitive to loss but not to delay.

•5 (AAL5) — the protocol used for connection-oriented data transfer that requires better error detection than available with AAL 3/4. (Note, however, that the AAL5 protocol itself does not support multiplexing.)

•other — which may indicate a user-defined AAL type.

•unknown — which indicates that the AAL type cannot be determined.

Accessing the AToM MIB Window 5-3