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  • 1. Efficient Mobile Backhaul with Carrier Ethernet Lubo Tancevski
  • 2. Agenda LTE Requirements Impact on Transport Networks: - OAM and Protection - QoS - Services - Synchronization - Security MPLS-TP for LTE backhaul Conclusions 2 | FutureNet 2010| May 2010
  • 3. LTE Transformation - Key Technology Shifts 2G/3G CS Core MSC PS Core GGSN BTS Backhaul RNC Internet (Ethernet/TDM/ATM) SGSN 1 2 3 4 5 6 Radio Mobility Backhaul transition RNC Bearer mobility MCS voice and SGSN CS and PS Intelligence placed in To IP/Ethernet collapse into packet mobility Collapse into a Pure data services the eNB the SGW collapse into Unified IP incl. VoIP Distributed and flat RNC control the SGW backbone Substantial increase New revenue IP Architecture collapse into SGSN control in traffic volume generating services the MME collapse into the MME LTE MME Multi-Media Services Service Backhaul aware and mobile aware PCRF (IP/Ethernet) IP network P-GW S-GW Cost optimization 3 | FutureNet 2010| May 2010
  • 4. Transport Requirements for LTE Node B BSC / IP RNC ATM Core TDM BTS Access ePC node Backhaul transport (MPLS-TP) (IP/MPLS) Aggregation S- GW MME Node B node eNB P- GW PCRF LTE will be introduced as a hotspot in existing 2G and 3G networks  variety of clients (TDM, ATM, IP/Ethernet)  Much higher traffic volumes from new data services (video, gaming, SMS) Transport network technology needed that:  Is multiservice  Has low cost per bit for wholesale transport of data services  Enables seamless transition from existing SONET/SDH to packet transport and features transport-grade operation in terms of protection and OAM  Interoperation with the IP/MPLS packet core MPLS-TP fulfills the above criteria 4 | FutureNet 2010| May 2010
  • 5. How is LTE affecting the Network requirements? Large amount of data traffic accentuates the need for efficient operation and favors L2 transport  Very fast protection switching and powerful OAM to minimize disruptions and downtime and facilitate troubleshooting and recovery; L2 transport for lowest-cost operation Distributed architecture and new functionalities increase the level of complexity  Increased security concerns; requirements for L2VPNs; comprehensive OAM to assist with network operation VoIP puts strong emphasis on controlled delay/jitter and resilience  requires OAM with performance monitoring of delay and jitter; strong QoS; fast protection switching with TE capability Support for new end user services brings additional requirements  Requires multicast/broadcast support; heightens security/privacy sensitivities for banking, location-based services; QoS requirements for video traffic; OAM with performance measurement for video traffic; interoperation with ePC for e2e support 5 | FutureNet 2010| May 2010
  • 6. S1-U interface S11 interface S1-MME interface Interconnection between Transport and ePC S5 interface X2 interface bearer MS-PW [Static/T-LDP] PCRF MPLS-TP IP/MPLS MME (L2VPN) (L3VPN) Transport S-GW ePC P-GW LSP [Static/GMPLS-RSVP-TE] LSP [Static] LSP [RSVP-TE/LDP] Flattening of the architectures drives similar requirements across the network  VPN support in both Transport and ePC  Bearer concept spans radio, S1 and S5 interface and needs to be provisioned in both Transport and ePC with similar parameters  Coordination required between S1 and S5 for support of services; coordinated support for handover MS-PW for e2e interoperation incl. monitoring and redundancy; Coordinated tunnel set up LTE requires stronger coordination between Transport and ePC than 2G/3G MPLS-TP facilitates coordinated set-up and interoperation 6 | FutureNet 2010| May 2010
  • 7. OAM Requirements Client monitoring (Y.1731) MS-PW monitoring LSP monitoring PCRF Tandem monitoring MME MPLS-TP IP/MPLS S-GW ePC P-GW Transport  Very fast fault detection to detect failures and assist in sub-50ms protection  Fault localization and notification to assist with troubleshooting complex network  Alarm issuance and suppression to simplify management and operation  Multi-level operation to isolate and monitor section of the network to assist with troubleshooting  Delay and loss measurement (on demand and continuous), to assists with SLA verification and detect causes of performance degradation MPLS-TP features comprehensive set of OAM tools meeting above requirements 7 | FutureNet 2010| May 2010
  • 8. Protection, Client protection and Dual Homing eNB Access node Access node Aggregation node Aggregation node S-GW eNB to access node Transport Network Transport node to S-GW  Typically several  Mesh and rings  Redundancy in case of S-GW failure as well as cables or, less  Failure detection dual-homed links frequently, several through OAM (MPLS-  Failure Detection fibers TP) through 802.1ag  Failure detection CFM/Y.1731; also  Sub-50ms protection Physical LOS through 802.3ah EFM switching (linear and  Detection through /802.1ag/Y.1731; also ring) MPLS-TP OAM possible physical LOS  1+1, 1:1, 1:N, bi-  VRRP and MC-LAG  Protection through directional operation  L2VPN and MAC re- link aggregation  Local and e2e learning protection 8 | FutureNet 2010| May 2010
  • 9. QOS: the bearer concept GBR bearer Non-GBR bearer EndPoints transport ePC UE Radio S1 S-GW S5 P-GW bearer bearer bearer A bearer provides same packet treatment to the flows from UE to P-GW (includes radio, S1, and S5 interface) Guaranteed Bit Rate bearer is characterized by Guaranteed Bit Rate (GBR) and Maximum Bit Rate (MBR) and guarantees no packet loss due to congestion Non-Guaranteed Bit Rate bearer offers no guarantees and is the default Flows mapped to bearers based on demands  Each flow characterized by QoS Class Identifier QCI and Allocation and Retention Priority ARP (for establishment and handover) 9 | FutureNet 2010| May 2010
  • 10. QOS Mapping NOTE: The mapping is configurable by operators. Application layer QoS (QCI) eNodeB P-GW Signalling, RT/NRT traffic, OM data mapping Transport (S1) + S5 signal/PTRAU UDP/TCP UDP/TCP IP QoS DSCP marking, DiffServ IP IP L2/3 Data link layer L2 mapping Physical layer Physical layer Physical layer Data link layer QoS -PPP priority: MC-PPP -Ethernet QoS: IEEE802.1p/q In Transport (S1 interface) L2 operation per class of service following MEF 22 (less than 9 CoS)  Bearers mapped on class of service depending on their requirements  QoS determined by p-bits, that could be further mapped into MPLS-TP EXP bits H-QoS needed on the P-GW 10 | FutureNet 2010| May 2010
  • 11. Requirements for Multi-Point Operation New services introduce requirements for the S1 interfaces  Multicasting support for video: -> E-LAN or E-TEE  VoIP and data/web: -> E-LINE  Handover through X2 interfaces with direct communications between eNBs  E-LAN (preferred) or E-LINE Architectural requirements for multipoint connections -> L2VPN required  S1-Flex  S-GWs pools and MME pools; load balancing  MME and control signaling - idle mode tracking and paging; connect set-up MPLS-TP efficiently supports LTE services  Support for MEF requirements and specifications  Full flexibility of operation with L2VPNs 11 | FutureNet 2010| May 2010
  • 12. S1-U interface S11 interface S1-MME interface Services for LTE S5 interface X2 interface E-LAN for X2 E-TREE for S1 MME EPC Transport S-GW PCRF P-GW X2 interface defined for handover S1 interfaces carry traffic to/from the between eNBs S-GW  Low bandwidth, low delay requirements  UL point to point  Up to 16 X2 interfaces, (depending on  DL could be point to point or could be the density of the coverage) point-to-multipoint (video, gaming) Could be realized by E-LAN or E-LINE Could be realized by E-LAN, E-TREE or E-LINE 12 | FutureNet 2010| May 2010
  • 13. Tracking Area, S-GW Service Area and MME Pool Area MME Pool Area S-GW service area S-GW MME Pool S-GW service area S-GW MME Pool Area S-GW service area PCRF Tracking area MME Pool P-GW Tracking area S-GW Pool Tracking Area, S-GW Serving Area and MME Pool Area are important architectural elements in LTE  L2VPNs can be set-up per each or combination of them 13 | FutureNet 2010| May 2010
  • 14. S1-U interface S11 interface S1-MME interface S1-Flex S5 interface X2 interface MME Pool S-GW 1 L2VPN100 PCRF S-GW 2 P-GW S-GW 3 Each eNB needs to have a connectivity to several S-GWs and MMEs:  UE connect procedure  Change of MME during handoff/roaming or load balancing For the connect procedure MME selects an S-GW out of many available S-GWs  selection based on location, or based on low probability for changing S-GW MME can initiate load balancing  initiate load balancing by S1 bearer release with TAU load balancing.  Establishment of a new S1 bearer to a new S-GW  MME can initiate an S1 overload and specify new S-GW L2VPNs facilitate operation 14 | FutureNet 2010| May 2010
  • 15. Synchronization requirements: what is important? Frequency Synchronization  Always required  All BS types: Macro, Micro, Pico, Femto  3GPP values: Wide Area BS 0.05 ppm, Medium Range BS 0.1 ppm, Local Area BS 0.1 ppm  Single value so far for LTE: Max 50 ppb (ref. 3GPP 36.104 section 6.5.1) Time Synchronization (same frame start-time among BS) required if  TDD mode, whatever the BS type (macro, femto etc.)  FDD mode, in case one of the following features are used (NA for femto)  eMBMS/COMP/network MIMO  HO eHRPD / LTE 1588 and Synchronous Ethernet Requirement on every transport node 15 | FutureNet 2010| May 2010
  • 16. Synchronization distribution  IEEE1588v2  GPS  1588 Master server could be co-  Receiver inside the eNB. located with the MME or transport  interface RS422 networks will provide time  Frequency & Phase synchronization to eNB via specific 1pps + ToD connector  Synchronous Ethernet  Transport network has its own  Requires Layer 1 clock tree through master and server all Ethernet devices between clock master and eNB’s.  Recommended clock delivery over IP networks  Synchronous Ethernet supporting intermediate nodes  External Timing Port  High stability internal clock: optional Synchronous Ethernet Sync Ethernet clock master GPS Ethernet MME PCRF S-GW P-GW 1588v2 1588v2 client IEEE1588v2 Precision Time server Protocol 16 | FutureNet 2010| May 2010
  • 17. IPSec tunnel Tunnel endpoints Security LSP Security of heightened concern in LTE because of location-based services and because of the distribution of the role of RNC Especially concern in the case of mobile backhaul providers Several technologies could be used depending on the required level of security:  Radius/EAP  IPSec for S1 and (less likely) for X2  Tunnels and 802.1X for X2 or as an alternative to IPSec for S1 Un-trusted Trusted Transport ePC MME Security S-GW eNB GW PCRF P-GW 17 | FutureNet 2010| May 2010
  • 18. MPLS-TP MPLS-TP will enable efficient packet transport by transport profiling of IP/MPLS  Basic MPLS constructs (PW, LSP, tunnel…) assuring seamless interconnection with IP/MPLS  Comprehensive multi-level OAM in the data plane only with fast failure detection, fault localization, alarms and suppression, performance monitoring and tandem connection monitoring  Separation of the control and data plane and operation through control plane, and through NMS without any control plane support  Fast protection switching in the data plane with support from OAM  IP-less and IP-based mode of operation in the data plane Joint work by ITU-T and IETF ensuring convergence of transport and routing specs  ITU-T TMPLS G.81xx specs available; further TMPLS standardization stopped and ITU-T will align existing G.81xx specs to the MPLS-TP RFCs when completed MPLS-TP can provide very efficient backhaul for LTE 18 | FutureNet 2010| May 2010
  • 19. Conclusions LTE brings profound changes:  Transition to all-packet services including VoIP  Much increased data rates up to 300Mb/s  Flat IP and distributed architecture The transport infrastructure needs to support LTE as well as existing 2G and 3G LTE has major impact in the following areas:  Support for Services  Synchronization  QoS  OAM and Resilience  Security  Interoperation with packet core MPLS-TP is shown to be good candidate for LTE transport 19 | FutureNet 2010| May 2010
  • 20. www.alcatel-lucent.com www.alcatel-lucent.com 20 | FutureNet 2010| May 2010