Bit Shifting For Virtual Trunks; Virtual Trunk Bandwidth; Virtual Trunk Connection Channels; Table 25-2 Bit Shifting For Virtual Trunking - Cisco BPX-BXM-155-8DX Installation And Configuration Manual

Chapter 25 Configuring BXM Virtual Trunks
Because the BNI cards use a Strata-UNI format across a virtual trunk, BNI virtual trunks are not
compatible with BXM/UXM virtual trunks which use either the standard UNI or NNI cell header
formats. Therefore, BXM to BXM, UXM to UXM, and BXM to UXM virtual trunks are supported,
while BNI to BXM or BNI to UXM virtual trunks are not supported.

Figure 25-5 ATM Virtual Trunk Header Types

HCF

Bit Shifting for Virtual Trunks

The ATM-STI header uses four of the VPI bit spaces for additional control information. When the cell
is to be transferred across a public network, a shift of these bit spaces is performed to restore them to
their normal location so they can be used across a network expecting a standard header.
This bit shifting is shown in Table 25-2. A BNI in the Cisco subnetwork can interface to a BXM (port
configured for port mode) in the cloud. The BXM in the cloud is configured for no shift in this case.
A BXM in the Cisco subnetwork can interface to a BXM UNI port or other UNI port in the cloud. The
BXM in the cloud is configured for bit shifting as shown in Table 25-2.

Table 25-2 Bit Shifting for Virtual Trunking

Subnetwork
BXM
BNI

Virtual Trunk Bandwidth

The total bandwidth of all the virtual trunks in one port cannot exceed the maximum bandwidth of the
port. The trunk loading (load units) is maintained per virtual trunk, but the cumulative loading of all
virtual trunks on a port is restricted by the transmit and receive rates for the port.

Virtual Trunk Connection Channels

The total number of connection channels of all the virtual trunks in one port cannot exceed the
maximum number of connection channels of the card. The number of channels available is maintained
per virtual trunk
Release 9.3.0, Part Number 78-10674-01 Rev. D0, July 2001
00 PID
PID CID
CID PYLD
FST PTI
HEC
ATM-STI
FW Rev Shift
--
--
GFCI VPI
VPI VCI
VCI
VCI PTI
HEC
ATM-UNI
Cloud FW Rev
> BXM (port mode)
> BXM (port mode)
Cisco BPX 8600 Series Installation and Configuration
Connection Management
GFCI VPI
VPI VCI
VCI
FS (unused) PTI
HEC
Strata-UNI through cloud
Shift
Yes**
No
25-9