1. MPLS in Mobile Backhaul
MR-234
Luyuan Fang Issue 2
Broadband Forum Ambassador May 2010
Cisco Systems
Doug Hunt
Broadband Forum Ambassador
Alcatel-Lucent
2. Agenda
1. Introduction to the Broadband Forum
2. MPLS in Mobile Backhaul
Issues, trends and enablers of the transition to IP/MPLS in evolving
backhaul architectures
3. MPLS Basics
MPLS fit and operation in the mobile backhaul network and the
support of end-to-end SLAs, QoS, and high availability features
4. MPLS Pseudowires
For legacy network migration (TDM and ATM), LTE support (IP/
Ethernet) and their operation in MPLS backhaul networks
5. MPLS OAM and Protection
Operations, Administration and Management (OAM) capabilities of IP/
MPLS backhaul networks
11. Packet Synchronization and Timing
12. MPLS Mobile Backhaul Initiative – MMBI
13. Summary
2
3. MPLS in Mobile Backhaul Tutorial
Contributors
Matthew Bocci – Alcatel-Lucent
Rao Cherukuri – Juniper Networks
Dave Christophe – Alcatel-Lucent
Sultan Dawood – Cisco Systems
Doug Hunt – Alcatel-Lucent
Fabien Le Clech – France Telecom
Drew Rexrode – Verizon
Nikhil Shah – Juniper Networks
Dave Sinicrope – Ericsson
3
4. We are the United Broadband Forum
http://www.broadband-forum.org
The Broadband Forum is the central organization driving
broadband solutions and empowering converged packet
networks worldwide to better meet the needs of vendors,
service providers and their customers.
We develop multi-service broadband packet networking
specifications addressing interoperability, architecture and
management. Our work enables home, business and
converged broadband services, encompassing customer,
access and backbone networks.
4
5. The BroadbandSuite
Goals and Focus
The BroadbandSuite is broken down into three major domains:
BroadbandManagement
– Goal – enhance network management capabilities and enable an
intelligent, programmable control layer that unifies diverse networks
– Focus - empower service providers to deliver and efficiently maintain
personalized services that enhance the subscriber experience
BroadbandNetwork
– Goal - establish network architecture specifications to support current
and emerging services and applications
– Focus - deliver access, aggregation and core specifications that
provide inherent interoperability, quality, scalability and resiliency
capabilities from end-to-end
BroadbandUser
– Goal - Define unified networking standards by establishing a common
set of CPE capabilities within the business, home and mobile
environments
– Focus - Simplify the service delivery process by developing common
devices’ identification, activation, configuration and maintenance
specifications
5
broadband-forum.org
6. Broadband Forum Scope
PARTNER
APPLICATION
Management Quality of Experience IDENTITY
TR-069 (CWMP) TR-069 ACS
FUNCTION Identity, Accounting and Policy
Operations and Network Management
DSL Quality Management BILLING
PARTNER
CONTROL TR-126 IPTV TR-176 DSL OSS
FUNCTION Quality of Experience Profiles for IPTV
CWMP
TR-069
Network TR-144 Multi Service Requirements
Multi-Service Core
Edge
Aggregation
Access
VoD
SIP
TV
Content Network P2P E-FTTx
TR-101, TR-156 GPON
IP/MPLS Ethernet EPON
Aggregation
DSL
Mobile Network
SGW
RNC
BSC
Multi Service Architecture & Requirements Certification, Test and Interoperability
6
broadband-forum.org
7. We don’t work alone
Coordinated industry efforts maximize value with minimum overlap
7
broadband-forum.org
8. MPLS in Mobile Backhaul
Issues, trends and
enablers of the
transition to IP/MPLS
in evolving backhaul
architectures
9. State of the Market
Voice and text messages drive majority of current
revenue
– Price competition Declining average
– Reduction or flattening of growth in revenue per user
minutes per subscriber in markets (ARPU)
such as North America
– Subscribers granted ability to customize phones
Initial 4G (LTE/WiMAX) trials/deployments
– Significantly expand data capacity to enable new devices,
services and applications ARPU growth
– 1st generation wireless network built as a data network
– Focus on reducing cost per bit
9
11. Data revenue for mobile operators
Mobile Data revenue (as % of total ARPU) is growing
Mobile broadband data traffic is growing much faster than
corresponding revenue growth
11
12. From 2G/3G to LTE: Towards all-IP, simplified
network architecture
2G/3G Broadband Forum focus
areas for backhaul Softswitch
GMSC MGW PSTN
CDMA / EVDO Circuit Switched
Core (Voice)
Other
GSM / GPRS Voice MSC mobile
networks
EDGE Channels BTS
IP channel BSC / RNC
UMTS Internet
Node B Packet Switched
HSPA Core
VPN
SGSN GGSN
PDSN HA
New, all-IP mobile core network introduced with LTE
What is EPC ? End-to-end IP
Clear delineation of control plane and data plane
LTE+EPC
Simplified architecture: flat-IP architecture with a single core
IP channel Evolved Packet Core
eNode B
(eNB)
(All-IP)
Transport (backhaul
and backbone)
Evolved Packet Core = end-to-end IP transformation of mobile core
12
13. State of market : LTE
Large number of cell sites will support mix of 2G, 3G and 4G (LTE/WiMAX)
RAN types
Worldwide LTE subscribers will cross 200 millions by 2014
Source: Infonetics, Q3. 2009, ABI research
13
14. Backhaul connections Growth
(By Technology Type)
Worldwide Mobile Backhaul
New Connectivity by Technology
Operators migrating mobile
backhaul to converged, packet-
based architectures
Microwave used extensively in
Europe and Asia
Multiple options for
backhaul transport
Varies based on geography,
availability, volume, inter/
intra carrier relationships
Source: Infonetics, 2008
14
15. Business and technical Drivers for Mobile
backhaul evolution
Expense of the Mobile backhaul is sizable
portion of overall OPEX of Mobile operator
Fix the legacy backhaul bottleneck (Scale)
Solution need to support co-existence of 2G, 3G
and 4G base stations on the same cell site.
Future Proof: Path to 4G, Next Generation
Networks
Address network synchronization
15
16. LTE Deployment requires evolution of
backhaul transport
LTE+EPC
eNB
IP channel Evolved Packet Core
(All-IP)
eNB
Transport (backhaul
and backbone)
LTE is built on an all-IP flat architecture – compared to 3G and previous generations
of mobile technology it has
– A more direct data and control path between the mobile user and the core
network
– Base stations (called eNBs) with additional functionality – including direct
communication of client data and control plane traffic between eNBs
Transport Implications
– Favors more flexible backhaul mesh, such as architectures that do not need to
transverse the aggregation points
– To support transport of latency-sensitive traffic between eNBs, need a backhaul
architecture that minimizes latency
– MPLS at the aggregation points is one of the likely solutions to this challenge
16
17. LTE Deployment requires evolution of
backhaul transport (continued)
LTE+EPC
eNB
IP channel Evolved Packet Core
(All-IP)
eNB
Transport (backhaul
and backbone)
Flatter IP architecture requires smooth interworking between previously separate
mobile backhaul and backbone transport networks
– VPN scaling: LTE enabled eNB user plane by-passes RNC, connects directly to
PS-Core
– Scope of E2E network planning, traffic engineering, transport SLA monitoring
increases (e.g. high availability, stringent E2E QoS is no longer broken up into
segments with mobile NEs between each)
17
18. Why MPLS?
MPLS is THE unifying technology for various backhaul
types
MPLS is proven in Service Provider deployments
globally – it delivers on its promises
MPLS adds carrier-grade capabilities
– Scalability - millions of users/end points
– Resiliency - high availability including rapid restoration
– Manageability – ease of troubleshooting & provisioning
– Traffic Engineering plus QoS – predictable network behavior
– Multiservice – support for 2G, 3G ATM and IP RAN (e.g. LTE,
WiMAX) and co-existence with other types of traffic e.g.
residential
– Virtualization – VPNs to ensure separation of OAM from
signaling / bearer planes, partitioning of multi-operator traffic
18
19. Why IP/MPLS in Mobile Backhaul?
Backhaul requires co-existence of multiple transport options
– MPLS is proven mechanism to support ATM, TDM, Ethernet, HDLC emulation
(Pseudowires)
– Allows legacy RAN equipment to continue to be utilized (CAPEX protection)
while leveraging the advantages of new packet transport networks
Packet Backhaul needs to support multi-media traffic
– Voice/VoIP, Video, SMS,
– MPLS –TE enables advanced QoS capability
– Improved network utilization, Better ROI
Reliability is critical
– MPLS offers faster convergence and interoperable mechanisms for failure
detection and recovery
Backhaul is increasingly becoming a strategic asset
– MPLS at cell site enabled carriers to offer new revenue generating services (i.e.
L2/L3 VPNs)
IP/MPLS
Scalability Resiliency Multi-Service Manageability TE/QOS
19
20. Multi-phase MPLS migration into
RAN Transport
Phase 1 Radio Access Network IP/MPLS Backbone
Cell Site Hub MTSO
TDM Enet/PPP
T1/E1 T1/E1 Enet
Copper Copper Fiber
BSC RNC WAC
TDM/IP ATM/IP Enet
ATM PPP TDM ATM PPP Enet Converged
T1/E1 T1/E1 Aggregation SDH/SONET
Copper Copper via Fiber
IP/MPLS
2G – TDM/IP
3G – ATM/IP SDH/SONET Backbone
WiMAX - Enet
TDM ATM PPP Enet TDM ATM PPP Enet
LTE - Enet µwave (PDH channels) µwave (SDH ch)
Separate transmission
facilities for different ATM Central Aggregation,
Aggregation Consolidation,
technologies
Overlay Service Routing
MPLS “edge”
20
21. Multi-phase MPLS migration into
RAN Transport
Phase 2 Radio Access Network IP/MPLS Backbone
Cell Site Hub TDM ATM PPP Enet MTSO
MPLS
SDH/SONET
TDM Enet/PPP MPLS fiber
T1/E1 T1/E1
Aggregation BSC RNC WAC
Copper Copper TDM ATM PPP Enet
for all MPLS TDM/IP ATM/IP Enet
ATM PPP Technologies Ethernet Converged
T1/E1 T1/E1
Copper Copper
fiber IP/MPLS
2G – TDM/IP
3G – ATM/IP
Backbone
WiMAX - Enet
TDM ATM PPP Enet TDM ATM PPP Enet
LTE - Enet µwave (PDH channels) MPLS
Ethernet ch
Separate transmission µwave
facilities for different Central Aggregation,
Common facility for Consolidation,
technologies all traffic Service Routing
MPLS “edge”
21
22. Multi-phase MPLS migration into
RAN Transport
Phase 3 Radio Access Network IP/MPLS Backbone
Cell Site TDM ATM Enet IP Hub TDM ATM Enet MTSO
MPLS MPLS
SDH/SONET SDH/SONET
MPLS fiber MPLS fiber
Aggregation Aggregation BSC RNC WAC
TDM ATM Enet IP TDM ATM Enet
for all for all
MPLS MPLS TDM/IP ATM/IP Enet
Technologies Ethernet Technologies Ethernet Converged
fiber fiber IP/MPLS
2G – TDM/IP Backbone
3G – ATM/IP
WiMAX - Enet TDM ATM Enet IP TDM ATM Enet
LTE - Enet MPLS MPLS
Ethernet ch Ethernet ch
µwave µwave Router
Common facility for Common facility for
all traffic all traffic
MPLS “edge”
IP/MPLS is agnostic to transmission techniques in Access
22
23. Mobile Backhaul Standards
Landscape
3GPP
– RAN definition and specification – definition of the RAN and its interfaces
Broadband Forum
– MMBI – architecture of mobile backhaul transport support with MPLS
– WT-145 – next generation broadband network architecture to support
mobile backhaul
– Certification – certification of MPLS technologies to support mobile
backhaul transport
– Tutorials and Marketing – education on MPLS in mobile backhaul
transport and issues
Metro Ethernet Forum
– MBH Phase I and II – Metro Ethernet services and interfaces required to
support mobile backhaul
– MBH Marketing and Tutorial – education on Ethernet in mobile backhaul
transport and issues
ITU-T SG 15
– Adaptive & Differential Clock Synchronization specification
23
24. What is MMBI ?
MPLS in Mobile Backhaul Initiative
– Work item embraced by the Broadband Forum
– Defining role IP/MPLS technologies in Mobile backhaul
(including LTE)
IP/MPLS Forum launched the industry wide
initiative in 2Q 2007 and the Broadband Forum
continues that work
– Framework and Requirements Technical Spec: IP/MPLS
Forum 20.0.0
– Detailed technical specs are ongoing work
– MPLS in Mobile Backhaul Certification Program
Pilot phase on TDM over MPLS complete
ATM over MPLS in development
Ethernet and IP over MPLS (future work item)
24
25. What MMBI aims to solve/facilitate ?
Faster mobile broadband deployment
– HSPA/HSPA+/LTE, EV-DO, LTE
Enhanced experience for mobile users with new data
services and application, along with voice
– Location based service, VoIP, gaming, etc
Future-proof investments
Improve mobile operator’s bottom line and simplify
operations
– Converging technology specific backhaul networks to single
multi-service packet infrastructure
– Based on proven benefits of IP/MPLS while leveraging cost-
benefits of Ethernet
25
26. MMBI Reference Architecture
(more on this later)
Access Aggregation Core
BS Cell Site
Gateway Mobile
Aggregation
Abis Site Gateway
TDM TNL MSC 2G
Edge RC A A
Access
Node
TDM TNL Abis Gb MSC 3G
Iub Access
network Iu-CS
ATM TNL
xDSL,
Node Edge S5/S8A
Node ATM TNL Iub IP/
microwave, Aggregation MPLS S5/S8A
Leased network Core PDN GW
Iub/S1 Line, Edge IP Iub/S1 mobile
IP
TNL
GPON, Node
Edge
TNL networ Gb
Optical Eth Node HDLC Abis Iu-CS k
TNL Iu-PS SGSN 2G
Abis Iu-PS
HDLC
TNL
MPLS transport network Iur SGSN 3G
MPLS PE function could be integrated into
RAN the BS (BTS/Node B/BS)/RC
Terminology WCDMA/ CDMA LTE Technology Data Services
UMTS 2000/1x
GSM/UMTS EDGE, GPRS, HSPA
Base Station Node-B BTS eNB
CDMA CDMA2000, 1xRTT,
Base Station Controller RNC BSC A GW
EV-DO
Circuit Edge devices MSC MSC -
Packet Edge devices SGSN, GGSN PDSN PDN GW 4G LTE
26
27. MPLS Basics
MPLS operation in the mobile
backhaul network
Support of end-to-end SLAs,
QoS, and high availability
features
28. MPLS Definition
Multiprotocol Label Switching (MPLS) is a network technology
that enables network operators to implement a variety of
advanced network features, both to serve their customers and to
enhance their own network utilization.
These features are a result of the transformation of the
connectionless per-hop behavior of an Internet Protocol (IP)
network into a connection-oriented forwarding along MPLS Label
Switched Paths (LSP).
MPLS operates over a range of devices such as routers,
switches, etc, using enhanced IP protocols and leveraging
Operations Administration and Management (OAM) systems
similar to those with IP
– MPLS can be viewed as an extension of IP, rather than its
replacement.
MPLS works with both IPv4 and IPv6
MPLS is currently being extended to provide additional packet
transport capabilities (MPLS-TP)
28
29. Label Switched Path (LSP)
LSP is the path followed by labelled packets that are assigned to
the same FEC
– Packets of similar characteristics are treated/forwarded in a similar
way
LSP
IP source IP destination
network network
MPLS
network
FEC is Forwarding Equivalence Class
– This class is formed based on the equivalence in forwarding,
• i.e., “forwarding equivalence” FEC-to-label binding mechanism
– Flow (stream, traffic trunk) of IP packets – forwarded over same LSP
– FEC-to-label binding mechanism binding is done once, at the ingress
29
30. Network Engineering vs. Traffic Engineering
Network Engineering
– "Put the bandwidth where the traffic is"
Physical cable deployment
Virtual connection provisioning
Traffic Engineering
– "Put the traffic where the bandwidth is"
On-line or off-line optimisation of routes
Ability to diversify routes
– Leverage knowledge of available resources in network
30
31. Providing Resiliency with MPLS
Lower Layers
– Partial or full mesh
– Automatic Protection Switching strategies of SONET/
SDH/WDM
MPLS Layer
– Outage
Protection and Re-routing procedures
– Administrative
Re-optimization and Preemption
IP Layer
– IGP convergence algorithms
IGP: Internal gateway protocol
31
32. Carrier-Grade IP/MPLS Protection
Restoration time
– Recovery times smaller than IGP convergence times. 50ms fail-over
possible.
– Failover transparent to edge service protection mechanisms
Resource efficiency
– Leverages statistical gains over use of optical or SDH/SONET layers
Service differentiation
– MPLS enables granular levels of protection. This helps service
differentiation (QoS, protection)
Node protection
– Service awareness assist in node protection or protection of layer 2
traffic
Robustness
– Route pinning avoids transient LSP behavior when SPF routing
changes
Interoperability
– MPLS provides standardized protection in multi-vendor environments
32 – RFC 4090: FRR extensions to RSVP
33. MPLS Pseudowires
For legacy network
migration (TDM and ATM),
LTE support (IP/Ethernet)
and their operation in MPLS
backhaul networks
34. What is PWE3?
PWE3 – “Pseudowire Emulation Edge-to-
Edge” – IETF Working Group assigned to
study carriage of “Legacy and New Services”
over MPLS
Protocol encapsulations can be carried over
MPLS
– Legacy Services under consideration are:
FR, ATM, SONET & SDH, DS0, DS1, DS3, …
– And new services such as:
Ethernet, VLANs, etc.
34
35. MPLS Pseudowire
Reference Model
Native Emulated Service
Pseudowire (PW) (forward)
MPLS Tunnel LSP (forward)
AC AC
CE1 PE1 IP/MPLS Network PE2 CE2
MPLS Tunnel LSP (backward)
Pseudowire (backward)
AC: Attachment Circuit ATM, Ethernet , FR, IP, TDM, etc Attachment
CE: Customer Edge Circuit (AC)
PE: Provider Edge - Same at each end
35
36. MPLS Point-to-Point Services
Label Stacking
Tunnel PW VC Encaps
Header Layer 2 payload
Header Information
1 2 3
Three Layers of Encapsulation
1) LSP Tunnel Header: Contains information needed to
transport the PDU across the IP / MPLS network
2) Pseudowire Header: Used to distinguish individual PWs
within a single tunnel
3) Emulated VC Encapsulation: Contains the information about
the enclosed PDU (known as Control Word)
LSP Tunnel Header determines path through network
Pseudowire Header identifies VLAN, VPN, or
connection at the end point
All services look like a Virtual Circuit to MPLS network
36
38. Encapsulation Methods for Transport of
Ethernet over MPLS Networks
4 octets 4 octets 4 octets
Tunnel PW Control
Header Header Word Payload (Ethernet/802.3 PDU)
bits 4 12 16
Set to 0 to 0000 Reserved Sequence Number
signify PW
data Control Word (use is optional)
Enables transport of an Ethernet/802.3 PDU across a MPLS network
Ethernet PDU consists of the Destination Address, Source Address, Length/Type,
MAC Client Data and padding
Ethernet PW operates in one of two modes:
– Raw mode: If there is a 802.1Q VLAN tag in a frame, it is passed transparently by network
– Tagged mode: Each frame must contain at least one 802.1Q VLAN tag which PW termination
points have an agreement (signaled or manually configured) on how to process tag
Optional Control Word allows:
– Sequence number to guarantee order of frames – use is optional
RFC 4448
38
39. ATM Cell Mode Encapsulation for
Transport over MPLS
4 octets 4 octets 4 octets
52 octets 52 octets
Tunnel PW Control ATM cell #1 ATM cell #2
Header Header word minus FCS minus FCS …
bits 4 4 4 6 16
0000 Flags Res Length Sequence Number
Control Word
N-to-One Cell Mode Multiple Cell Encapsulation
2 modes relevant to backhaul: Control Word (optional)
– One-to-One Cell Mode - maps VPI VCI PTI C
one ATM VCC (or VPC) to one PW ATM Payload (48 bytes)
– N-to-One Cell Mode - maps one or “ “
more ATM VCCs (or VPCs) to one VPI VCI PTI C
PW (shown above); only required
ATM Payload (48 bytes)
mode for ATM support “ “
Ingress performs no reassembly
Control word is optional: If used, Flag and Length bits are not used
39 RFC 4717
40. Structure-Agnostic TDM Encapsulation for
Transport over MPLS (SAToP)
4 octets 4 octets 4 octets
Tunnel PW Control
Header Header Word Fixed RTP Header* TDM Payload
2 2 * Optional see RFC 3550
bits 4 1 1 6 16
0000 L R RSV FRG Length Sequence Number
SAToP Control Word
Structure agnostic transport for TDM (T1, E1, T3 and E3) bit streams
– Ignores structure imposed by standard TDM framing
– Used in applications where PEs do not need to interpret TDM data or
participate in TDM signaling
SAToP Control Word allows:
– Detection of packet loss or mis-ordering
– Differentiation between MPLS and AC problems as causes for emulated
service outages
– Conservation of MPLS network bandwidth by not transferring invalid data
(AIS)
– Signaling of faults detected at PW egress to the PW ingress
40 RFC 4553
41. PW Control Plane
PWs have a control plane that signals binding of PW label to the PW FEC
PE MPLS PE
Tunnel LSP
Layer 2 Pseudowire Layer 2
AC AC
CE CE
Payload
(L2 protocol)
Ethernet Targeted LDP
ATM PW Label Inner Label
TDM, etc LSP Label Outer Label
RSVP-TE or LDP
MPLS Label Stack
PW Setup and Maintenance: IETF RFC 4447
41
42. MPLS Pseudowires for Backhaul
2G
BTS L2 AC
MPLS RAN MTSO
PE L2 AC
3G Pseudowire
Node B Cell-
Tunnel
site
LSP
PE PW frame
4G payload
(L2 protocol)
eNB, BS PW Label Inner Label
T-LSP Label Outer Label
MPLS Label Stack
Pseudowires
– Emulate a native layer 2 service, such as Ethernet, TDM, ATM VC/VP,
FR VC, etc
Many PWs carried across MPLS network in a tunnel LSP
– PWs can utilise features of the MPLS network for resiliency, QoS, etc
42
43. Multi-Segment PW for Backhaul
Cell Site Ethernet, TDM, ATM MS-PW
2G
BTS
MPLS Aggregation
MPLS
3G
Access Pseudowires
Node B
Tunnel LSP T-PE
S-PE
4G
Hub MTSO
eNB, BS
T-PE
A static or dynamically configured set of two or more contiguous PW segments
that behave and function as a single point-to-point PW
Enables:
Scalability – to hundreds of base stations connecting to RNC/BSC site
Multi-domain operation – including multi-provider backhaul networks
Multi-technology operation – leverage mechanisms from non-MPLS access
infrastructures
43
44. MPLS OAM and Protection
Operations,
Administration and
Management (OAM)
capabilities of IP/MPLS
mobile backhaul networks
45. MPLS for Backhaul: OAM Requirements
OAM needed for reactive & proactive network
maintenance
– Quick detection and localization of a defect
– Proactive connectivity verification and performance
monitoring
OAM tools have a cost and revenue impact to Service Level
carriers e.g ATM OAM, MAC-Ping
– Reduce troubleshooting time and therefore reduce
VLL / PW Level
OPEX e.g VCCV, PW status
– Enable delivery of high-margin premium services
which require a short restoration time Tunnel LSP Level
Top level requirements e.g LSP ping
– Provide/co-ordinate OAM at relevant levels in IP/
MPLS network
– Proactive and reactive mechanisms, independent at all
levels
45
46. OAM and Service Assurance: Mobile Backhaul
Test Service Latency, Jitter, Packet
Loss and Round-trip Delay Operator GUI
Schedule a Suite of Tests at
Monitor Alerts for Potential OAM
Notification Service Activation or Time of Day
SLA Violation
Calculate SLA Automate On-Demand Test
Performance Metrics Suites from Fault Notification
OAM
Notification
(flat file)
OSS
2G
BTS
MPLS RAN MTSO
PE
3G L2 AC Pseudowires L2 AC
Node B
Cell-site Tunnel LSP
PE
4G
eNB, BS
46
47. Service-Aware OAM Toolkit
Cell Site VLL / PW Level Service Level
e.g BFD, VCCV, PW status e.g ATM OAM, SDP-Ping
2G
BTS
MPLS Aggregation
MPLS
3G Access Pseudowires
Node B
Tunnel LSP
4G Hub MTSO
eNB, BS Tunnel / LSP Level
e.g LSP Ping & Traceroute
Quickly isolate and troubleshoot faults to reduce MTTR
Tool set for reactive & proactive network operation and maintenance
Defect detection, proactive connectivity verification, and performance monitoring
Provide/co-ordinate OAM at relevant levels in IP/MPLS network
– Services Level: Eth CFM, Eth EFM, ATM, FR loopback, SAA
– Tunnel LSP Level: LSP ping and LSP Traceroute
– Pseudowire Level: PW Status, VCCV-BFD, VCCV-Ping, mapping to Ethernet, TDM, ATM
notifications
MPLS is currently being extended to provide additional packet transport capabilities (MPLS-TP)
47 for performance monitoring, path segment monitoring and alarm suppression
48. LSP Ping
LSP Ping is MPLS specific variation of traditional ICMP ping/traceroute
ad hoc tool
– Ping is simple e2e loopback
– Traceroute uses TTL to incrementally verify path
Ping paradigm useful for craftsperson initiated testing
– TELNET/CLI
LSP Ping is augmented with a number of TLVs processed by the receiver
to extend functionality
As LSP is unidirectional, and Ping is bi-directional, LSP Ping is
augmented with options for distinguishing real problems from return path
problems
48
49. Bidirectional Forwarding Detection (BFD)
Simple, fixed-field, hello protocol
– Easily implemented in hardware
– Very useful as a fault-detection mechanism
Nodes transmit BFD packets periodically over respective
directions of a path
If a node stops receiving BFD packets some component of the
bidirectional path is assumed to have failed
Applicable to tunnel end-points
49
50. Virtual Circuit Connection Verification
(VCCV)
2G
BTS PE1 PSN PE2
4G-3G-2G
3G Node B A GW/
Attachment Pseudowire Attachment HBSC/RNC
4G Circuit
Complex
eNB, BS Circuit
Mechanism for connectivity verification of PW
Multiple PSN tunnel types
– MPLS, IPSec, L2TP, GRE,…
Motivation
– One tunnel can serve many pseudo-wires
– MPLS LSP ping is sufficient to monitor the PSN tunnel (PE-PE
connectivity), but not PWs inside of tunnel
Features
– Works over MPLS or IP networks
– In-band CV via control word flag or out-of-band option by inserting router
alert label between tunnel and PW labels
– Works with BFD, ICMP Ping and/or LSP ping
50
51. PW Status Signaling
AC defect PW status: AC RX fault AC defect
2G PSN
BTS PE1 PE2 4G-3G-2G
A GW/
3G Node B HBSC/RNC
Attachment Pseudowire Attachment Complex
4G
eNB, BS Circuit Circuit
PWs have OAM capabilities to signal defect notifications:
Defect status mapped between AC and PW in the PE
PW status signaling propagates defect notifications along PW
- Extension to T-LDP signaling
51
52. PW Status Signaling: Multi-segment PWs
2G
PW Status
BTS MPLS Aggregation
MPLS
Access Pseudowires
3G
Node B Tunnel LSP
S-PE T-PE
4G Hub MTSO
eNB, BS
T-PE
Cell Site
PW status signaling also works for MS-PWs
S-PEs:
– Transparently pass remote defect notifications
– Generate notifications of local defects
52
53. MPLS Network Reliability
Both node level and network level recovery are required
3G
active
Node B
A GW/
RNC
Ethernet
standby
4G ATM (IMA)
MPLS RAN
eNB, BS
Network Level Recovery
Node Level Recovery Dual-homing w/o RSTP
Non-stop routing for ALL protocols (LDP, MPLS FRR
OSPF, IS-IS, BGP, multicast, PIM-SM) MPLS Standby Secondary
Non-Stop Service for ALL services (VPLS, Sub 50 ms restoration
VLL, IP-VPN, IES, multicast) End-to-end path protection
MPLS extensions to include
additional approaches
53
54. Network Level Redundancy for PWs
AC redundancy protocol drives Active/standby state of
forwarding state of PWs/PEs LAG/APS sub-groups
reflected in PW status
3G
Node B
active
PW status A GW/
Ethernet RNC
4G ATM (IMA)
MPLS RAN standby
eNB, BS
Forwarding direction AC redundancy:
determined by PW state MC – APS
MC - LAG
Protects against PE and AC failures
PE configured with multiple pseudowires per service with multiple end-
points
Local precedence indicates primary PW for forwarding if multiple PWs are
operationally UP
PW status exchanged end-to-end to notify PEs of operational state of both
PWs & ports / attachment circuits (PW Status Notification).
draft-ietf-pwe3-pw-redundancy & draft-ietf-pwe3-redundancy-bit
54
56. The Need for Synchronization in
Mobile Networks
RNC
RNC
NobeB
1: Radio Framing Mobile Core
Accuracy NodeB Network(s)
eNB or BS A GW
2 : Handoff
Control 3 : Backhaul
eNB or BS Transport Reliability
Synchronization is vital across many elements in the
mobile network
In the Radio Access Network (RAN), the need is
focused in three principal areas
56
57. Radio Framing Accuracy
In Time Division Duplexing (TDD), the base station clocks must be
time synchronized to ensure no overlap of their transmissions within
the TDD frames
– Ensuring synchronization allows for tighter accuracies and reduced
guard-bands to ensure high bandwidth utilization
In Frequency Division Duplexing (FDD) centre frequencies must be
accurate for receivers to lock
57
58. Handoff Control For Reliable Mobility
Performance
Synchronization is vital to ensure service continuity
(i.e successful handoff)
Studies have shown significant reduction in call drops when
good synchronization is in place; enhanced QoE
58
59. Backhaul Transport Reliability
Backhaul network
eNB/BS/ A GW/
NodeB/BTS X RNC/
BSC
TCP end-to-end windowed transmission
Wander and Jitter in the Backhaul and Aggregation Network can
cause underflows and overflows
Slips in the PDH framing will cause bit errors leading to packet
rejections
Packet rejections lead to retransmissions and major perceptible
slow down in TCP windowed sessions
59
60. Clock distribution methods
Physical layer clock
– Using synchronous TDM interfaces, e.g. PDH/SDH
– Using synchronous Ethernet as per G.8261/G.8262, and G.
8264 for ESMC/SSM
– External Timing Interface
GPS synchronization
Clock distribution over packet network
– IEEE 1588-2008 – ITU-T Q13/SG15 currently developing an
IEEE Std 1588-2008 "telecom profile" for frequency distribution
– NTP – The IETF is currently developing NTPv4*
Adaptive & Differential Clock Synchronization
Multiple methods might be deployed in a network
*Note: NTPv3 requires equipment with high quality oscillators
60
62. MMBI Scope
MPLS technology to transport mobile traffic (user plane and
control plane) over access, aggregation and core networks
4G (LTE), 3G, 2.5G and 2G networks, including evolution
RAN and Core equipments with range of physical interfaces (e.g.
FE, GE, E1/T1, STM1/OC-3, DSL, etc.) and technologies (PDH,
SDH/SONET, ATM and ATM/IMA, PPP, FR, Ethernet, etc.),
either directly attached or through an intervening access network
Different kinds of access transmission technologies: pt-to-pt
access (xDSL, microwave, P2P Fiber), pt-to-mp access (GPON)
Address coexistence of legacy and next generation mobile
equipment in the same network infrastructure.
Support a smooth migration strategy for network operators as
newer TNLs (Transport Network Layers) are introduced and
legacy TNLs are phased out
62
63. MMBI Scope (continued)
MPLS facilities in Access and/or Aggregation networks leased
from a third party, and which may be shared by more than one
mobile operator
Converged access/aggregation network supporting both
wireline, e.g. residential and enterprise, and wireless services.
QoS for support of distinct service types (e.g. real-time services
and associated delay and jitter requirements)
Support for clock distribution to the base stations, including
frequency, phase and time synchronization
Resiliency capabilities, including failover times appropriate for
wireless backhaul networks. E.g. dual attachment at the BSC/
RNC and methods for failover.
OAM mechanisms
63
64. Multiple TNLs – Successive Generations of
Mobile Architecture
Network Specification Transport Network
Layer (TNL)
GSM/GPRS/EDGE TDM, IP*
(2G/2.5G)
UMTS R3, R99/R4 ATM
R99/R5, R6, R7 ATM
IP
CDMA 1x-RTT IS-2000 HDLC or TDM
CDMA 1x EV-DO IS-856 IP
LTE R9, R10 IP
64 *Note: some 2G and 2.5G equipment can be upgraded to use an IP TNL
65. MMBI Architecture and Use Cases
Deployment Scenarios -- Location for MPLS functions is intended
to be flexible
– MPLS interworking functions could be located either:
In the edge node, or
in the access node, or
in the access gateway or
directly integrated into the base station.
TNL (Transport Network Layer) Scenarios – Support for a range
of access technologies at base stations and controller elements
– Case 1: TDM TNL
Base stations and controller elements communicating using TDM bit
streams
– Case 2: ATM TNL
Base stations and controller elements communicating using ATM cells
– Case 3: IP TNL
Base stations and controller communicating using IP packets
– Case 4: HDLC TNL
Base stations and controller elements communicating using HDLC-
encoded bit streams (e.g. CDMA)
65
66. Typical 2G and 3G RAN Topology
Star topology enabling communication from BS to
Controller and from Controller to BS
Centralized topology
66
67. Typical LTE RAN Topology
Star topology enabling communication from BS to aGW
and communication from aGW to BS.
Neighboring any-to-any topology enabling communication
between BSs
Flat topology
67
69. Generic TNL Protocol Stack – 2G/3G Architecture:
Example of SS-PW Deployment
TNL TNL TNL TNL
TNL PW TNL PW TNL PW
LSP LSP LSP LSP LSP LSP LSP
L2 L2 L2 L2 L2 L2 L2
L1 L1 L1 L1
L1 L1 L1 L1 L1 L1 L1 L1
MPLS network
PE Access P Aggregation P PE
network network TNL PW
BS RC
TDM CSG MPLS MPLS MASG TDM
ATM Access ATM
Ethernet Node Node Node Ethernet
PW extends from PE to PE
– Each TNL Type supported by corresponding TNL PW
– In deployment scenario shown, PW extends from Cell Site Gateway
(CSG) to Mobile Aggregation Site Gateway (MASG)
69
70. Generic TNL Protocol Stack – 2G/3G Architecture:
Example of MS-PW Deployment
TNL TNL TNL TNL
TNL PW TNL PW TNL PW TNL PW TNL PW
LSP LSP LSP LSP LSP LSP
L2 L2 L2 L2 L2
L1 L1 L1 L1
L1 L1 L1 L1 L1 L1
MPLS network
T-PE Access S-PE Aggregation T-PE
network network TNL PW
BS RC
TDM CSG MASG TDM
ATM Access MPLS ATM
Ethernet Node Ethernet
PW extends from T-PE to T-PE; switched at S-PE
– Each TNL Type supported by corresponding TNL PW
– In deployment scenario shown, PW extends from Cell Site Gateway
(CSG) to Mobile Aggregation Site Gateway (MASG)
70
71. MMBI: Timing deployment scenarios
Access Aggregation
BTS / Node B CSG BTS / Node B MASG MSC 2G
A
BNG 2 G -3 G MSC 3G
Access Edge
Gateway Access BS C / RNC A / MPLS
Node Node
TNL Complex Gb Core Iu-CS
TNL
mobile
Aggregation network
BTS / Node B network
Access network Iu - CS Gb
Iu - PS
xDSL,
Iu - PS SGSN 2G
microwave,
Leased Line,
PRC SGSN 3G
GPON,
via Optical Eth
GPS
(a 1 )
(a2 )
(a3 )
(a4 )
PHY clock (b )
PKT clock
(c)
(d )
71
72. IP transformation in mobile networks
with evolution to LTE
CS Core
TODAY
Backhaul (TDM/ATM) PS Core
Node B
RNC SGSN GGSN
1 2 3 4 5 6 7
Radio Backhaul RNC bearer MCS voice and
intelligence transition mobility CS and PS Best effort
SGSN packet evolve into a Internet
moving to to IP/ evolves to to
mobility evolves unified all-IP
eNodeB Ethernet the SGW e2e QoS
into the SGW domain
RNC control SGSN control
distributed into evolves into
the MME/eNB the MME
LTE Multimedia
Services
Backhaul (IP/Ethernet) PCRF
MME
Service and mobile aware
eNB SGW all-IP network
PDN GW
72
73. LTE Evolved Packet System (EPS)
Backhaul (IP TNL Application)
UE EUTRAN EPC Applications
IMS Apps
eNB S10 HSS
MME S6a PCRF Rx
X2
S1-MME S11 Gx
S5/S8 SGi
eNB S-GW P-GW PDN
S1-U
S5
The Evolved Packet System consists of the following sub-systems:
• User Equipment (UE) which includes specialized security cards often identified as part of the
EUTRAN (detail not shown)
• Evolved UTRAN (EUTRAN) which consists of the evolved Node B (eNB)
• Evolved Packet Core (EPC) which includes the following nodes:
− Serving Gateway (S-GW) which serves as a mobility anchor for inter-eNB handover
− PDN Gateway (P-GW) which is the cross-technology mobility anchor in the EPS
− The Mobility Management Entity (MME) which handles authentication and signaling for
connection and mobility management
− The Policy and Charging Rules Function (PCRF) supports per session QoS and associated billing
• Applications include IMS as well as non-IMS
− UEs signal directly to the applications
73 HSS: Home Subscriber Server
74. Evolved Packet Core: Overview of components
and functionality
eNodeB: Policy, Charging & Rules Function
all radio access functions Network control of Service Data Flow (SDF)
detection, gating, QoS & flow based charging
Radio admission control
Dynamic policy decision on service data flow
Scheduling of UL and DL data
treatment in the PCEF (xGW)
Scheduling and transmission of Authorizes QoS resources
paging and system broadcast
IP header compression (PDCP) PCRF
Outer-ARQ (RLC)
Policy
Decisions PDN Gateway
IP anchor point for bearers
UE IP address allocation
Per-user based packet filtering
Connectivity to packet data network
Mobility Management Entity Serving Gateway
Authentication Local mobility anchor for inter-eNB handovers
Tracking area list management Mobility anchoring for inter-3GPP handovers
Idle mode UE reachability Idle mode DL packet buffering
S-GW/PDN-GW selection Lawful interception
Inter core network node signaling for Packet routing and forwarding
mobility between 2G/3G and LTE
74 Bearer management functions
75. MMBI Reference Architecture - LTE
Flat Topology RANs using IP TNL:
Network Specification TNL
HSPA+ flat 3GPP R7 IP
LTE 3GPP R8
MPLS provides two solutions that can be applied
to combination of any-to-any and star topologies:
– Layer 2 VPNs e.g. VPLS
– Layer 3 VPNs e.g. BGP IP/VPNs RFC 4364
75
76. MMBI Reference Architecture – VPLS Use Cases
Access Aggregation Core
Cell SIte
Gateway Mobile
(CSG) Aggregation
Site Gateway
(MASG)
BS1 Edge aGW
CSG1 Node
S1 S3/S4
Access Access S5/S8a SGSN
IP TNL
network Node Edge IP/MPLS
Node IP TNL
S1 Core S5/S8a
BS2 Aggregation
CSG2 S3/S4 network PDN GW
S1 network
IP TNL
S6a
S6a
Edge HSS
BS3 Node
CSG3
S1 Access
IP TNL network
L2VPN MPLS transport network solutions aGW
MPLS PE function could be
CSG1 integrated into the aGW
CSG2 Ethernet VPLS (MME GW, S - GW, ASN GW)
CSG3
CSG1 VPLS
CSG2 Ethernet VPLS
CSG3
Eth PW
CSG1 VPLS
CSG2 Full mesh VSI
CSG3
Spoke PWs
CSG1 H - VPLS H-VPLS Note: BS supports Ethernet interface.
CSG2
CSG3 One Cell Site Gateway can connect
multiple BS.
76
77. MMBI Reference Architecture – L3VPN Use
Cases
Access Aggregation
Cell SIte Core
Gateway Mobile
(CSG) Aggregation
Site Gateway
(MASG)
BS1 Edge aGW
CSG1 Node S3/S4
S1 SGSN
Access Access
IP TNL S5/S8a
network Node Edge
Node IP/MPLS S5/S8a
IP TNL S1
BS2 Aggregation Core PDN GW
CSG2 S3/S4 network
S1 network S6a
IP TNL
S6a HSS
Edge
BS3 Node
CSG3
S1 Access
IP TNL network
L3VPN MPLS transport network solutions aGW MPLS PE function could be
integrated into the aGW
CSG1
CSG2 L3VPN (MME GW, S - GW, ASN GW)
IP
CSG3
CSG1 L3VPN
CSG2 IP L3VPN
CSG3 MPLS
CSG1 VRF
CSG2 L3VPN
CSG3
Note: BS supports Ethernet interface.
One Cell Site Gateway can connect
multiple BS.
77
78. Abstract Test Suite for TDMoMPLS
TDMoMPLS
– 46 Test Cases
Additional 11 Synchronization Test Cases
The Abstract Test Suite for TDM Services over MPLS describes test
procedures based on the requirements for encapsulating TDM signals
over MPLS networks and distributing timing using pseudo-wires over a
MPLS network. Test cases in this specification are defined for T1, E1,
T3 and E3 services.
– An overview of the different groups of requirements that compose the TDM
circuit emulation
Services over MPLS is provided as follows:
Packet format and encapsulation layer
Usage of optional RTP header
Structure-agnostic emulation
Structure-aware emulation
Packetization and depacketization
TDMoMPLS defects
Performance monitoring
Synchronization distribution and performance (Normative Annex)
78
79. Abstract Test Suite for ATMoMPLS
ATMoMPLS
– Draft
– Currently 50 Test Cases
The Abstract Test Suite for ATM over MPLS
describes test procedures based on requirements for
encapsulating Asynchronous Transfer Mode (ATM)
over MPLS networks.
– An overview of the different groups of requirements that
compose the Abstract Test Suite for ATMoMPLS is
provided as follows:
Packet format and encapsulation
OAM - Fault & Performance management
QOS Mapping
Synchronization (ref: ATS for TDMoMPLS Annex S)
79
81. Certification Benefits
Service Provider community
– Vendor meets requirements
– Potential savings of resources
Vendor community
– Marketing tool
– Shortening test cycle
– Carefully written test cases, better specifications
User community
– Purchase equipment with confidence
81
83. MPLS in Mobile Backhaul: Critical
Success Factors
Backhaul transformation is essential for
2G/3G (scalability and cost reduction) and
evolution to a LTE all IP flat architecture
Co-existence of multiple transport options
(ATM, TDM, Ethernet) for investment
protection
Carrier Grade IP/MPLS services
– High Availability
– Fast reconvergence
Efficient End-to-End Management and
OAM for rapid mass deployment
Scalability to large numbers of cell sites
Base Station synchronization
– Carrier frequency accuracy of 50 PPB
for LTE, WiMAX, GSM/W, CDMA
– Need to preserve synchronization & timing
with Carrier Ethernet transport
83
84. Focus from the Broadband Forum
Rapid growth in mobile backhaul bandwidth demand
– Scaling the backhaul in TDM way for all traffic is expensive
– Industry is shifting towards IP based networks
Can migrate entire mobile RAN OR
Hybrid model - Use MPLS for the data traffic and voice remains on
TDM
IP/MPLS offers many benefits and has been deployed globally in
mobile core. Similar drivers apply to backhaul.
Standards for backhaul transport - leaning towards IP
In recent years, the Broadband Forum has published
implementation agreements to facilitate the migration of ATM and
TDM to MPLS-based infrastructure
Broadband Forum aims to complement the cost benefits of Ethernet
with the proven track record of MPLS for building converged,
reliable and QoS-aware mobile grade infrastructure.
84
85. Broadband Forum Mobile Backhaul
work in progress
Technical Specifications for MPLS Based Mobile Backhaul
Networks for LTE (WT-221)
Technical Specifications for MPLS Based Mobile Backhaul
Networks for 2G & 3G (WT-222)
Equipment Requirements for MPLS over Aggregated Interfaces
– e.g., MPLS over Ethernet LAG (WT-223)
MPLS in Carrier Ethernet Networks – network architecture for
providing carrier Ethernet services (WT-224)
Abstract Test Suite for ATM over MPLS – Certification testing
(WT-225)
85
86. Related Standards Organizations and
Consortiums
3GPP: http://www.3gpp.org
Broadband Forum: http://www.broadband-forum.org
IEEE: http://www.ieee.org
IETF: http://www.ietf.org
ITU-T SG 15: http://www.itu.int/ITU-T/studygroups/com15/index.asp
Metro Ethernet Forum (MEF): http://metroethernetforum.org
Next Generation Mobile Network Initiative (NGMN):
http://www.ngmn.org
WiMAX Forum: http://www.wimaxforum.org
86
87. Thank you for attending the
MPLS in Mobile Backhaul Tutorial
The Broadband Forum is a non-profit
corporation organized to create guidelines for
broadband network system development and
deployment. This Broadband Forum For more information,
educational presentation has been approved by
members of the Forum. This Broadband Forum visit us at http://
educational presentation is not binding on the www.broadband-forum.org
Broadband Forum, any of its members, or any
developer or service provider. This Broadband
Forum educational presentation is subject to
change, but only with approval of members of
the Forum. This educational presentation is
copyrighted by the Broadband Forum, and all
rights are reserved. Portions of this educational
presentation may be copyrighted by Broadband
Forum members or external sources.
88. Abbreviations
2G – Second generation mobile network MGW – Message gateway
3G – Third generation mobile network MMBI – MPLS in mobile backhaul initiative
4G – Fourth generation mobile network MME – Mobility management entity
AG – Access gateway MPLS – Multiprotocol label switching
aGW– Access gateway MPLS-TP – MPLS Transport Profile
ASN – Access service node MSC – Mobile switching center
BS – Base station MTSO – Mobile telephone switching office
BSC – Base station controller Node B – Base station transceiver with UMTS/WCDMA
BTS – Base transceiver station PCRF – Policy and charging function
CDMA – Code division multiple access PDN – Packet data network
CS – Circuit switched PDSN – Packet data serving node
CSG – Cell site gateway P-GW – PDN gateway
EDGE – Enhance data rates for GSM evolution PS – Packet switched
eNB - – 4G/LTE base station PW – Pseudowire
eNode B – 4G/LTE base station RAN – Radio access network
EPC – Evolved packet core RNC – Radio network controller
EUTRAN – Evolved UTRAN RSVP – Resource reservation protocol
EV-DO – Evolution data optimized SGSN – Serving GPRS support node
FEC – Forwarding equivalence class S-GW – Serving gateway
FRR – Fast re-route TE – Traffic engineering
GGSN – Gateway GPRS support node TNL – Transport network layer
GPRS – General packet radio service UE – User equipment
GSM – Global system for mobile communications UMB – Ultra mobile broadband
GW – Gateway UMTS – Universal mobile telecommunications system
HSPA – High speed packet access VLAN – Virtual local area network
HSS – Home subscriber server VPN – Virtual private network
LSP – Label switched path WAC – WiMAX wireless access controller
LTE – Long term evolution WiMAX – Worldwide interoperability for microwave access
MASG – Mobile aggregation site gateway
88
