Chapter 4. Managing The Network; Atm Connections; Tcp/Ip Over Atm - IBM 64-bit/66MHz PCI ATM MMF Installation And Using Manual

Chapter 4. Managing the Network

This chapter provides information to assist in creating and maintaining ATM networks.

ATM Connections

ATM networks use a virtual path identifier (VPI) and a virtual channel identifier (VCI).
VPI and VCI together identify connections in the ATM network. A VPI:VCI pair defines a
path between two nodes in an ATM network. The VPI field occupies 1 byte in the ATM
cell's 5-byte header, while the VCI field occupies 2 bytes in the ATM cell's 5-byte
header.
For the 64-bit/66MHz PCI ATM MMF Adapter, the value of VPI must be 0. The VCI
value can be between 0 and 127 decimal.
Although not required, VPI:VCI values are typically assigned symmetrically, that is, the
same values are reserved in both directions across the link. A link is the physical
medium of transmission, for example, a telephone wire or microwave beam. A link
connection includes the physical medium for transmission, the protocol, associated
devices and programming. A link connection is both logical and physical.
More than one virtual channel (VC) can be set up on the same link, but the VPI:VCI
must be different for each connection on the link. A permanent virtual channel (PVC) is
a static connection between two end stations and the ATM network. The PVC is created
by selecting a physical path from the end station through the switches to the other end
station. VPI:VCIs are assigned to establish the connection between the two end
stations. The PVC must be configured in each end station and in all switches included
in the connection.
An ATM switch automatically performs the following functions:
v Recognizes the source of the cell
v Changes VPI:VCI
v Determines the destination of the cell
v Transmits the cell to its destination

TCP/IP over ATM

Each ATM network interface can have an assigned IP (internet protocol) address. This
assigned network interface can have VPI:VCIs associated with it. This allows a TCP/IP
host, identified by its IP address, to communicate with multiple TCP/IP hosts on the
ATM network.
If your host has more than one IP address, (for example, one ATM interface and one
token-ring interface), you must add one network interface for each IP address. The
64-bit/66MHz PCI ATM MMF Adapter supports multiple network interfaces.
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