Consideration and proposal of laser on/off time for 10G EPON

Transcription

1 Consideration and proposal of laser on/off time for 0G EPON Ken-Ichi Suzuki Akihiro Otaka Junichi Kani November 007 NTT Access Network Service Systems Laboratories, NTT corporation

2 Background We should consider remaining issues including upstream overhead length for 0G EPON. In G EPON, the burst overhead consists of a constant length of 0 ns (Ton+Toff) and a variable length less than 83 ns (Sync time = Treceiver_setting + Tcdr + Tcode_group_align ). Sync time Grant length Idle Upstream burst signal and timing parameters

3 Observation In 00-00, IEEE 80.3ah had no experience with burst mode optics and has selected conservative values for T on and T off which would allow continuous-mode optics be used in burst-mode operation. Since 003, the optics continuously became faster and faster. No transceivers deployed today require 5 ns on/off time. Because laser turns on very fast, many commerciallydeployed systems set SyncTime=0, because OLT receiver can synchronize during the 5 ns allocated for T on. Allocating constant 5 ns for T on and 5 ns for T off wastes significant amount of bandwidth. 3

4 Proposal We propose definitions of T on and T off be variables while their default values remain 5 ns in Section..5. of IEEE std Currently, OLT maintains ONU-specific parameter (RTT) used in calculating grant start time. Currently, OLT does not preclude SyncTime to be ONU-specific. Adding ONU-specific T on and T off is not a burden on the OLT. Current grant calculation GrantStartTime[n] = RxTime RTT[n] GrantLength[n] = T on + SyncTime[n?] + DataSize + T off Proposed grant calculation GrantStartTime[n] = RxTime RTT[n] GrantLength[n] = T on [n] + SyncTime[n?] + DataSize + T off [n]

5 Options There are two options to make T on and T off adjustable Method : MPCP Handshake Add additional fields to REGISTER_REQ and REGISTER messages ONU informs OLT about its actual T on and T off in REGISTER_REQ message. OLT echoes T on and T off that it will assume in the REGISTER message. Same method as ONU uses to announce Pending Grants value to the OLT. Method : OAM Query Add alaserontime and alaserofftime MIB variables. OLT starts with allocating 5 ns for T on and T off. OLT uses OAM messages to get the actual T on and T off from the ONU. After receiving the actual T on and T off values, the OLT starts allocating ONU-specific T on and T off in the grant length. With both methods, ONU always allocates its actual on/off times and does not need to have logic to adjust times based on its state. 5

6 Proposal for REGISTER_REQ T on and T off field We propose to add -byte field to REGISTER_REQ The field carries the actual T on and T off values used by the actual laser in the given ONU. The OLT confirms (echoes) these values in a REGISTER message. This is the same handshake as used for delivering Pending Grants value from ONU to OLT After sending REGISTER, OLT starts allocating ONUspecific T on and T off in grant length. Existing REGISTER_REQ Destination Address Source Address Length/Type = Opcode = 00-0 Timestamp Flags Pending grants Discovery Information Pad/Reserved FCS 37 Proposed REGISTER_REQ Destination Address Source Address Length/Type = Opcode = 00-0 Timestamp Flags Pending grants Discovery Information Laser Turn On Time Laser Turn Off Time Pad/Reserved FCS 35

7 Proposal for REGISTER T on and T off field We propose we add -byte field to REGISTER message. Existing REGISTER Proposed REGISTER The field echoes T on and T off values received from the ONU. Destination Address Source Address Length/Type = Opcode = Destination Address Source Address Length/Type = Opcode = Timestamp Timestamp Assigned port Assigned port Flags Flags Sync Time Sync Time Echoed pending grants Echoed pending grants Pad/Reserved 3 Echoed Laser On Time FCS Echoed Laser Off Time Pad/Reserved 3 FCS 7

8 Pros and Cons Method : MPCP handshake Method : OAM Query Pros Efficient from the start - all grants are allocated by the OLT with the actual T on and T off No modifications to state machines in Clause. Cons Changes to MPCP messages (changes to state machines in Clause ). OLT will issue a number of grants with default T on and T off (5 ns) until it queries the ONU s MIB. ONUs with faster lasers may be getting extra bandwidth for a while 8

9 Straw Poll #5 I support Adjustable (ONU-specific) Laser On and Laser Off times for only 0G EPON (PR and PRX). Yes: 33 No: 0 No opinion: 9

10 Straw Poll # Adjustable (ONU-specific) Laser On and Laser Off times should use: A) Modified REGISTER_REQ and REGISTER messages 8 B) OAM messages 0 No opinion 9 0

11 Motion #0 Accept as a baseline proposal for MPCP handshake-based adjustable Laser On and Laser Off times for 0G EPON using modified REGISTER_REQ and REGISTER messages shown in pages and 7 of 3av_07_suzuki_.pdf. Moved by: Ken-Ichi Suzuki Seconded by: Bidyut Parruck Yes: 33 No: 0 Abstain: 3 Number in the room: 37 Technical, required 75% Motion passed