3Com 7600 manual LEC Parameters, Flush protocol, Be set by management, 6LEC Operational Parameters

12-16CHAPTER 12: ATM, LAN EMULATION, AND VIRTUAL LANS

Flush protocol

According to the previous section, a unicast frame can be sent to a destination LEC over two VCC paths: a data-direct VCC or a multicast-send VCC via the BUS. Since a frame transmitted over a data-direct VCC may arrive sooner, switching between the two VCC paths during transmission can cause the frames to be received out-of-order at the destination LEC. The flush protocol is provided to ensure the correct order of delivery of unicast data frames at all times. The transmitting LEC establishes a dialog with the destination LEC to make sure that all traffic on the first VCC has been processed (flushed) before transmitting on the second VCC.

Multicast Frames LECs may wish to send frames to a multicast MAC address, and/or they may wish to receive frames addressed to a given MAC address. In order to send frames to a multicast MAC address, the LEC sends the frames on the multicast-send VCC to the BUS. The LEC will also be able to receive flooded unicast frames and broadcast and multicast frames on the multicast-forward VCC from the BUS.

Control Information In addition, the LE implementation of the 7600 Card complies with the on Data VCs standard and requires that control information be carried in-band on data

VCs (Flush, Ready frames) and be identified by a special frame header (LECID field). The 7600 Card can extract these frames from the data as well as generate control frames as required.

LEC Statistics Statistical information can be displayed about different types of data-frame traffic through the LEC (see “Display LEC Statistics” on page 8-2). The operator can also display statistics on the various types of control-frames in and out of the LEC (see “Display LEC Control-frame Statistics” on page 8-14)

LEC Parameters		The following LEC parameters govern the operation of the LEC; most can
		be set by management:
Table 12-6LEC Operational Parameters
Parameter	Description		Minimum	Default	Maximum
Control-timeout	Time out period used for timing out most		10 seconds	120 seconds	300 seconds
	request/response control frame interactions.