Gigabit-capable Passive Optical Networks

APPENDIX II

PLOAM MESSAGES

The PLOAM channel comprises a small set of relatively simple messages, with the idea that they can be supported in fairly low-level firmware, if not actually in hardware. They are used for low-level negotiations between OLT and ONU, including ONU discovery when no higher level (OMCI) management channel is available.

Many of the PLOAM messages are elaborated in the various sections where they are key actors; this appendix is dedicated to the nuts and bolts. As we have done before, we describe G.987 XG-PON and G.984 G-PON separately: there is some overlap, but not enough to combine the descriptions.

II.1 PLOAM MESSAGES IN G.987 XG-PON

The PLOAM message in G.987 XG-PON is 48 bytes long. With a history of ATM in the original world of B-PON, there was concern that 48-byte messages might be mistaken as a retrograde step, but 48 was the correct size for the messages that needed to be defined, and 48 bytes it is. Variable-length messages were considered but rejected because fixed-length messages are easier to parse and the difference in efficiency is inconsequential.

As illustrated in Figure all G.987 XG-PON PLOAM messages have the same structure.

Figure II.1 G.987 XG-PON generic PLOAM message.

ONU-ID The ONU-ID consumes 2 bytes of the generic PLOAM message. The first 6 bits are zero padding; the 10-bit ONU-ID occupies the least significant end of the field. The ...