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

MPCP (Multipoint Control protocol)

Professor : Ho-Ting Wu

Speaker : 簡睿毅

Outline

Overview EPON MPCP Summary

Outline


PON (Passive Optical Network )

Features of a passive optical network:– an attractive solution to implement FTTB (fiber to t

he build) and FTTH (fiber to the home)access net

works 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)

Architecture of PONs

(1) Tree Topology (2) Ring Topology

(3) Tree with Redundant Trunk (4) Bus Topology

OLT

ONU

ONU

ONU

ONU

OLT

ONU

ONUONU

ONU

OLT

ONU ONU

ONU ONU

OLT

ONU

ONU

ONU

ONU

OLT: Optical Line Terminal

ONU: Optical Network Unit

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

Features of Ethernet PON

All data packets carried in EPON are encapsulated in

Ethernet frames Broadcasting in the downstream direction from the O

LT to ONUs

Sharing the upstream channel capacity among ONUs – Collision will occur when different ONUs transmit data simultaneo

usly– Method is needed for multiple access — Medium Access Control

(MAC) protocols

Downstream traffic in EPON

Upstream traffic in EPON

Outline



Introduction Two mode of operation Discovery Protocol RTT (Round-trip time) measurement Messages Format Messages Operation MPCP-Goals



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



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

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

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



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

Auto Discovery

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

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

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

Resolving Discovery Contention

Some sort of randomization must be applied to ONU Register messages to minimize collisions



RTT measurement



Messages Format

OLTONU

GATE , REGISTER ONUOLT

REPORT , REGISTER_REQUEST , REGISTER_ACK

Used only during discovery processREGISTER , REGISTER_REQUEST , REGISTER_ACK

GATE/REPORT Behavior

Protocol layer conveys information- OLTONU 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



GATE Operation(1/2)

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

REPORT Operation(1/3)


REPORTs are generated in ONU MAC control client

- Indicate local conditions to OLT

REPORTs pass through the MAC-control REPORTs are optional


A REPORT message may contain queue reports

The OLT must process REPORT messages The OLT may consider the REPORT when all

ocating bandwidth The ONU must issue REPORTs periodically REPORT messages can be used with timesta

mps only



MPCP- Goals

Optimize Network Resources Address Service Provider Requirements

Outline


Point-to-Point Emulation (PtPE)

Shared-Medium Emulation (SME)

Combined PtPE and SME Mode

Summary

MPCP is compliant with deployed Ethernet by using P2P Emulation layer

An 802.3ah point-to-multipoint network is a layer2 domain with a Bridge at the OLT having a directlink to each ONU

Traditional Ethernet framing is maintained Peer-to-peer communications can be disabled atbridge

MPCP is confined to one sub-layer – MAC Control MPCP allows higher layer to implement various

DBA algorithms

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

Documents

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