MPCP (Multipoint Control protocol)

1. MPCP (Multipoint Control protocol) Professor : Ho-Ting Wu Speaker : 簡睿毅

2. Outline • Overview EPON • MPCP • Summary

3. Outline • Overview EPON • MPCP • Summary

4. PON (Passive Optical Network ) • Features of a passive optical network: • an attractive solution to implement FTTB (fiber to the build) and FTTH (fiber to the home)access networks FTTH deployment scenarios • a point-to-multipoint optical network • only passive optical components: • Couplers and Splitters • two primary types of PON technologies: • ATM PON (APON) • Ethernet PON (EPON)

5. Architecture of PONs OLT: Optical Line Terminal ONU: Optical Network Unit

6. Ethernet PON • EPON started to be standardized by IEEE 802.3ah EFM since 2001 • Ethernet is a ubiquitous technology: deployed widely in LAN, MAN and WAN • Ethernet is more attractive to PON than ATM • high speed: up to 10 Gigabit/s • lower cost of Ethernet equipments than those of ATM • easier interoperability than that in ATM • lower overhead

7. Features of Ethernet PON • All data packets carried in EPON are encapsulated in Ethernet frames • Broadcasting in the downstream direction from the OLT to ONUs • Sharing the upstream channel capacity among ONUs • Collision will occur when different ONUs transmit data simultaneously • Method is needed for multiple access — Medium Access Control (MAC) protocols

8. Downstream traffic in EPON

9. Upstream traffic in EPON

10. Outline • Overview EPON • MPCP • Summary

11. MPCP (Multipoint Control protocol) • Introduction • Two mode of operation • Discovery Protocol • RTT (Round-trip time) measurement • Messages Format • Messages Operation • MPCP-Goals

12. MPCP (Multipoint Control protocol) • Introduction • Two mode of operation • Discovery Protocol • RTT (Round-trip time) measurement • Messages Format • Messages Operation • MPCP-Goals

13. Basic Characteristics • The Multi-Point Control Protocol (MPCP) specifies a control mechanism between a Master unit and Slaves units connected to a Point-to-Multi-Point (P2MP) segment to allow efficient transmission of data • MPCP is implemented in MAC Control layer • MPCP uses five MAC Control messages - GATE, REPORT, REGISTER_REQ,REGISTER,REGISTER_ACK

14. MPCP (Multipoint Control protocol) • Introduction • Two mode of operation • Discovery Protocol • RTT (Round-trip time) measurement • Messages Format • Messages Operation • MPCP-Goals

15. Two mode of operation • Auto Discovery mode - to detect newly connected ONUs and learn the round-trip delay and MAC address of that ONU • Normal mode - to assign transmission opportunities to all initialized ONUs

16. Auto Discovery mode (1/2) • OLT allocates an initialization slot, an interval of time when no previously initialized ONUs are allowed to transmit • OLT sends an initialization GATE message advertising the start time of the initialization slot and its length • Only un-initialized ONUs will respond to the initialization GATE message

17. Auto Discovery mode (2/2) • When the local clock located in the ONU reaches the start time of the initialization slot ,the ONU will transmit its own message (initialization REPORT) • When the OLT receives the REPORT from an un-initialized ONU, it learns its MAC address and round-trip time

18. MPCP (Multipoint Control protocol) • Introduction • Two mode of operation • Discovery Protocol • RTT (Round-trip time) measurement • Messages Format • Messages Operation • MPCP-Goals

19. Discovery Protocol • Four MAC control messages – Discovery GATE: Creates transmission opportunity for undiscovered devices – Register_Request: ONU response to “Discovery Gate” – Register: OLT response to Register_Request – Register_Ack: ONU response to Register • ONUs can wake-up Simultaneously – Protocol must deal with contention in Register_Requests • Multiple ONUs can potentially be registered within single Discovery time period

20. Auto Discovery

21. ONU Behavior During Discovery • At Power-up / Reset, an ONU enters Discovery State: – Undiscovered ONUs Await Reception of “Discovery Gate” message from OLT • Unregistered ONU responds only: – If received message’s Logical Link ID(LLID) matches discovery/default LLID and the grant type is discovery

22. OLT Behavior During Discovery • OLT Must Periodically Reserve Time Periods for Discovery –The Frequency of discovery windows can be chosen for desired overhead • Since Undiscovered ONU Addresses are Unknown – “Discovery Gates” are broadcast to all ONUs

23. Failure Modes • OLT assumes ONU is unregistered if: – REGISTER_ACK message wasn’t received at the first grant opportunity – ONU responds to “Discovery GATE” messages • ONU assumes it is unregistered if: – After sending a REGISTER_REQUEST message, it receives a “Discovery GATE” before receiving a REGISTER message – After sending a REGISTER_ACK message, it receives a “Discovery GATE” before receiving a “Normal GATE” message

24. Resolving Discovery Contention • Some sort of randomization must be applied to ONU Register messages to minimize collisions

25. MPCP (Multipoint Control protocol) • Introduction • Two mode of operation • Discovery Protocol • RTT (Round-trip time) measurement • Messages Format • Messages Operation • MPCP-Goals

26. RTT measurement

27. MPCP (Multipoint Control protocol) • Introduction • Two mode of operation • Discovery Protocol • RTT (Round-trip time) measurement • Messages Format • Messages Operation • MPCP-Goals

28. Messages Format • OLTONU GATE , REGISTER • ONUOLT REPORT , REGISTER_REQUEST , REGISTER_ACK • Used only during discovery process REGISTER,REGISTER_REQUEST , REGISTER_ACK

29. GATE/REPORT Behavior • Protocol layer conveys information - OLTONU bandwidth assignment - ONU OLT bandwidth request • Service layer sitting above makes decisions - OLT bandwidth allocation - ONU bandwidth utilization • OLT sends GATE messages to ONU and guarantees no overlaps

30. MPCP (Multipoint Control protocol) • Introduction • Two mode of operation • Discovery Protocol • RTT (Round-trip time) measurement • Messages Format • Messages Operation • MPCP-Goals

31. GATE Operation(1/2)

32. GATE Operation(2/2) • ONU transmits only during the time indicated in the GATE • ONU MAC-control enables PHY transmission at the start of a GATE duration and disables it at the end of the GATE duration • GATE messages can be used with timestamps only

34. REPORT Operation(1/3)

35. REPORT Operation(2/3) • REPORTs are generated in ONU MAC control client - Indicate local conditions to OLT • REPORTs pass through the MAC-control • REPORTs are optional

36. REPORT Operation(3/3) • A REPORT message may contain queue reports • The OLT must process REPORT messages • The OLT may consider the REPORT when allocating bandwidth • The ONU must issue REPORTs periodically • REPORT messages can be used with timestamps only

38. MPCP (Multipoint Control protocol) • Introduction • Two mode of operation • Discovery Protocol • RTT (Round-trip time) measurement • Messages Format • Messages Operation • MPCP-Goals

39. MPCP- Goals • Optimize Network Resources • Address Service Provider Requirements

40. Outline • Overview EPON • MPCP • Summary

41. Point-to-Point Emulation (PtPE)

42. Shared-Medium Emulation (SME)

43. Combined PtPE and SME Mode

44. Summary • MPCP is compliant with deployed Ethernet by using P2P Emulation layer • An 802.3ah point-to-multipoint network is a layer 2 domain with a Bridge at the OLT having a direct link to each ONU • Traditional Ethernet framing is maintained Peer-to-peer communications can be disabled at bridge • MPCP is confined to one sub-layer – MAC Control • MPCP allows higher layer to implement various DBA algorithms

45. Reference • Ethernet Passive Optical Network (EPON) Glen Kramer, University of California, Davis Biswanath Mukherjee, University of California, Davis Ariel Maislos, Passave Networks, Israel • Supporting differentiated classes of service in Ethernet passive optical networks Glen Kramer and Biswanath Mukherjee , University of California, Davis Sudhir Dixit and Yinghua Ye , Center, 5 Wayside Road, Burlington Ryan Hirth , Communications, 755 Baywood Drive, Petaluma