Forum-Compliant ATM LAN Emulation Device Driver

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The Forum-Compliant ATM LAN Emulation (LANE) device driver allows communications applications and access methods that would normally operate over local area network (LAN) attachments to operate over high-speed ATM networks.

This ATM LANE function supports LAN Emulation Client (LEC) as specified in The ATM Forum Technical Committee LAN Emulation Over ATM Version 1.0, as well as MPOA Client (MPC) through a subset of ATM Forum LAN Emulation Over ATM Version 2 - LUNI Specification, and ATM Forum Multi-Protocol Over ATM Version 1.0.

The ATM LANE device driver emulates the operation of Standard Ethernet, IEEE 802.3 Ethernet, and IEEE 802.5 Token Ring LANs. It encapsulates each LAN packet and transfers its LAN data over an ATM network at up to OC12 speeds (622 megabits per second). This data can also be bridged transparently to a traditional LAN with ATM/LAN bridges such as the IBM® 2216.

Each LEC participates in an emulated LAN containing additional functions such as:

  • A LAN Emulation Configuration Server (LECS) that provides automated configuration of the LEC's operational attributes.
  • A LAN Emulation Server (LES) that provides address resolution
  • A Broadcast and Unknown Server (BUS) that distributes packets sent to a broadcast address or packets sent without knowing the ATM address of the remote station (for example, whenever an ARP response has not been received yet).

There is always at least one ATM switch and a possibility of additional switches, bridges, or concentrators.

ATM supports UNI3.0, UNI3.1, and UNI4.0 signalling.

In support of Ethernet jumbo frames, LE Clients can be configured with maximum frame size values greater than 1516 bytes. Supported forum values are: 1516, 4544, 9234, and 18190.

Incoming Add Party requests are supported for the Control Distribute and Multicast Forward Virtual Circuits (VCs). This allows multiple LE clients to be open concurrently on the same ELAN without additional hardware.

LANE and MPOA are both enabled for IPV4 TCP checksum offload. Transmit offload is automatically enabled when it is supported by the adapter. Receive offload is configured by using the rx_checksum attribute. The NDD_CHECKSUM_OFFLOAD device driver flag is set to indicate general offload capability and also indicates that transmit offload is operational.

Transmit offload of IP-fragmented TCP packets is not supported. Transmit packets that MPOA needs to fragment are offloaded in the MPOA software, instead of in the adapter. UDP offloading is also not supported.

The ATM LANE device driver is a dynamically loadable device driver. Each LE Client or MPOA Client is configurable by the operator, and the LANE driver is loaded into the system as part of that configuration process. If an LE Client or MPOA Client has already been configured, the LANE driver is automatically reloaded at reboot time as part of the system configuration process.

The interface to the ATM LANE device driver is through kernel services known as Network Services.

Interfacing to the ATM LANE device driver is achieved by calling the device driver's entry points for opening the device, closing the device, transmitting data, and issuing device control commands, just as you would interface to any of the Common Data Link Interface (CDLI) LAN device drivers.

The ATM LANE device driver interfaces with all hardware-level ATM device drivers that support CDLI, ATM Call Management, and ATM Signaling.