mpcp (multipoint control protocol) professor : ho-ting wu speaker : 簡睿毅
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MPCP (Multipoint Control protocol)
Professor : Ho-Ting Wu
Speaker : 簡睿毅
Outline
Overview EPON MPCP Summary
Outline
Overview EPON MPCP Summary
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
Overview EPON MPCP Summary
MPCP (Multipoint Control protocol)
Introduction Two mode of operation Discovery Protocol RTT (Round-trip time) measurement Messages Format Messages Operation MPCP-Goals
MPCP (Multipoint Control protocol)
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
MPCP (Multipoint Control protocol)
Introduction Two mode of operation Discovery Protocol RTT (Round-trip time) measurement Messages Format Messages Operation MPCP-Goals
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
MPCP (Multipoint Control protocol)
Introduction Two mode of operation Discovery Protocol RTT (Round-trip time) measurement Messages Format Messages Operation MPCP-Goals
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
MPCP (Multipoint Control protocol)
Introduction Two mode of operation Discovery Protocol RTT (Round-trip time) measurement Messages Format Messages Operation MPCP-Goals
RTT measurement
MPCP (Multipoint Control protocol)
Introduction Two mode of operation Discovery Protocol RTT (Round-trip time) measurement Messages Format Messages Operation MPCP-Goals
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
MPCP (Multipoint Control protocol)
Introduction Two mode of operation Discovery Protocol RTT (Round-trip time) measurement Messages Format Messages Operation MPCP-Goals
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)
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
REPORT Operation(3/3)
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 (Multipoint Control protocol)
Introduction Two mode of operation Discovery Protocol RTT (Round-trip time) measurement Messages Format Messages Operation MPCP-Goals
MPCP- Goals
Optimize Network Resources Address Service Provider Requirements
Outline
Overview EPON MPCP Summary
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