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Multi-segment Pseudowires in Passive Optical Networks
Ruobin Zheng, [email protected] Hongyu Li, [email protected]
• Objective
• MPLS to Access and Challenges
• PW support in GPON systems
• Summary
Contents
Page 3
Objective
The objective of this draft is to provide the information of PW support in current GPON systems for mobile backhaul. �
Page 4
Scenario of GPON for 2G and 3G mobile backhaul
According to the Technical Specification of “MPLS in Mobile Backhaul Networks Framework and Requirements” from IP/MPLS Forum 20.0.0, GPON is considered as a alternative for 2G and 3G mobile backhaul.
With PW extension to ONU, e2e MPLS tunnel can be built between CSG and MASG for mobile backhaul.
OLT don’t need to be aware of TDM/ATM/SDH services and don’t need to support physical interfaces of E1/T1, NxDS0, POS/SDH, ATM, …
HDLC TNL
HDLC TNL
Mobile Aggregation Site Gateway
IP TNL
ATM TNL TDM TNL
IP TNL
ATM TNL
TDM TNL
Aggregation network
BS
Access network
xDSL, microwave,
Leased Line, GPON,
Pt-to-pt fiber
Access Node
Cell Site Gateway
Edge Node
IP/MPLS Core
mobile networ
k
Iur/R3
Abis A
Iub
Iub/R6/R2
Iub
Radio Contoller
Iu-CS Iu-PS
MPLS transport network
Gb Iu-PS
Iu-CS A Gb Abis MSC 3G
SGSN 3G SGSN 2G
MSC 2G
Abis Abis
Edge Node
Edge Node
Edge Node
Iub/R6/R2
R3 CSN WiMAX
R3
Source from “IP/MPLS Forum 20.0.0” �MPLS “edge”
Page 5
Complexity ONU is very cost-sensitive to routing protocols and dynamic label allocation
Is routing protocol necessary in GPON?
Provisioning difficulties
When MS-PW is implemented in a PON, there may be a very large number of PW T-PEs. If PW labels on ONUs are
provision d by NMS directly, it requires a network manager touching each ONU once for each PW, and there may be
very many PWs. This makes provisioning a heavy burden for the network manager.
Additionally, there must be a concern that the configuration at the ONU and the OLT will be inconsistent because for
any PW, both the ONU and the OLT must be configured.
ONTs may not be able to support SNMP.
Challenges for MPLS to GPON for mobile backhaul
3G core
RNC Node B
Native MPLS
MPLS “edge”
IP node
Routing
LSP label allocation
ISIS or OSPF
LDP LDP
PE P PE
PW label allocation targeted LDP
LDP
ISIS or OSPF
P
MS-PW
LDP
ISIS or OSPF
OLT ONU
IP static route RIPv2
Native MPLS requires IP routing and routers
everywhere �
S-PE
Page 6
PHY
MPLS backbone
BS CSG
ONU S-PE
Access Metro/Core
TDM/ATM/ETH
PW
GEM
PW
MPLS MPLS LSP
LINK
GEM port
PHY
GEM
PHY
MPLS
LINK
PHY PHY
PW
OLT
GEM port Spoke MPLS Hub
Network reference model for MS-PW over GPON
PW
Network is partitioned into access segments and Metro/Core segments in a hub & spoke topology. The OLT is recommended as a S-PE so that PWs can be optimized within each segments. “PW over GEM” is
recommended as per ITU-T G.984.3 in access segments providing generic transport of TDM/ATM/ETH traffic. All PW segments are of the same technology, which is packet encapsulated. It is only the tunneling technology
that changes at the S-PE. �
Page 7
MS-PW ONU AR(OLT)
IP node
3G core
RNC Node B
MASG
Routing
LSP label allocation
ISIS or OSPF
OMCI LDP
T-PE P T-PE
PW label allocation targeted LDP
LDP
ISIS or OSPF
P S-PE
LDP
OMCI
Simplify MPLS /PW operation in GPON by introducing semi-static configuration using extensions to
OMCI as per G.988 No routing protocol and dynamic label
allocation protocol needed in the access network �
MS-PW over GPON
ISIS or OSPF
PWE3/MPLS “edge”
Label Provisioning for PW over GPON
The ONT management and control interface (OMCI) is a management channel between the OLT and the ONUs.
G.984.4 and G.988 extends the functions that can be configured using OMCI to include MPLS and MPLS PW termination points at an ONT. This allows seamless integration of MPLS and MPLS PW services with a PON.
Making use of a GPON management protocol (OMCI) helps to reduce the labor of configuration simplify and speed up the PW provision procedure to a great extent avoid the potential inconsistence or mismatch between ONUs and OLT notify to S-PE (which is the OLT) of the status of the AC at the T-PE (which is the ONU).
It can be applied when SNMP is not support by ONTs.
Page 8
There is a trend that operators are deploying MPLS and PWE3 in access networks, especially
in an access network of G-PON or NG-GPON. However, IP routing and routing protocol challenge the scalability and complexity of the
access network (e.g. PON). With OMCI for PW operation and PW over GPON, no need for full IP/MPLS stack in GPON
ONUs. Thus keep PON simple and cost-effective.
Summary
PON
Access router (OLT)
NG-GPON
ONU
MPLS edge
Aggregation network � MPLS in GPON
BS BS
Data Plane
PW over GPON for multiple services
Management Plane
OMCI for label provisioning
Thank you
Page 10
G.984.4 and G.988 extends the functions that can be configured using OMCI to include MPLS and MPLS PW termination points at an ONT. This allows seamless integration of MPLS and MPLS PW services with a PON.
Dynamic Control Plane of native MPLS
PE Auto-Discovery
Signaling for PW
VPN
Pro
toco
ls
T-LDP
BGP-AD
Signaling for LSP
Multicast signaling
Tunn
el L
SP P
roto
cols
Topology Discovery
Physical links Ethernet, etc.
mLDP or PIM
LDP
IGP(ISIS/OSPF)
Node Registration
Semi-static PW configuration
Semi-static LSP configuration
Tree Topology
Physical links
PON or Eth. OMCI
Semi-static Label Provisioning
One Simplification
for all
One Simplification for All The ONT management and control interface (OMCI) is a management channel between the OLT and the ONUs that supports Ethernet, equipment, subscriber interface, and subscriber feature management.
OMCI specifies the managed entities of a protocol-independent management information base (MIB) module that models the resources and services in an ONU. Through standardized OMCI signalling, OLT builds up its management bonds with ONUs automatically.
OMCI is standardized in G.984.4 and G.988.
Page 11
SNMP-based Provisioning vs. OMCI-based Provisioning Problems of SNMP-based provisioning
When MS-PW is implemented in a PON, there may be a very large number of PW T-PEs. If PW labels on ONUs are provision d by NMS directly, it requires a network manager touching
each ONU once for each PW, and there may be very many PWs. This makes provisioning a heavy burden for the network manager.
Additionally, there must be a concern that the configuration at the ONU and the OLT will be inconsistent because for any PW, both the ONU and the OLT must be configured.
ONTs may not be able to support SNMP. Benefit of OMCI-based provisioning
reduce the labor of configuration simplify and speed up the PW provision procedure to a great extent
When using OMCI to provision PWs on ONU, the network manager only needs to send all configurations to the OLT, which will send all parameters to ONUs automatically through OMCI. There is no need to touch each ONU.
avoid the potential inconsistence or mismatch between ONUs and OLT Through standardized OMCI signalling, OLT builds up its management bonds with ONUs
automatically. OMCI can act as a signaling mechanism between ONU and OLT, which enables the ONU to
notify AC status to OLT. It can be applied when SNMP is not support by ONTs.
Page 12
Multi-service support in GPON systems
• Multi-service support means multiple transport modes in current GPON system. • high OPEX: operational difficulty and management complexity • high cost of access router (NG-OLT) with a whole bunch of physical interfaces: E1/T1, NxDS0, POS/SDH, ATM, ETH …
GPON MAC
SDH ETH IP MPLS TDM
GEM GEM GEM GEM GEM
Service layer ATM
GEM
TDM
PW
ATM Service layer ETH …
GEM GPON MAC
• The trend is that PW layer functions as an uniform transport layer for multiple services. • OMCI is extended for semi-static configuration of PWs. • It can greatly reduce the operational difficulty and management complexity and keeps ONU simple and cost-effective.