ATCN 2014: SDN - Mobility and SDN: Mobility Management and Mobile Networks Karin Anna Hummel, ETH Zurich (thanks to Vasileios Kotronis for some material) November 10, 2014 1
Locating and Connecting 2
Wireless Networks and Mobility The Internet WiMAX, etc. Source: dreamstime.com WLAN AP AP AP P-GW S-GW LTE cellular network 3
Issues in Wireless Networks Mobility management in IP networks traditionally does not separate control and data plan inefficient traffic management LTE networks require traffic to be sent to the P-GW in the core inefficient traffic management LTE radio access management is local no coordinated, global optimization possible Different wireless protocols available, but no seamless roaming between different wireless technologies Can SDN provide improvements and optimizations? 4
Literature Sources [SDCellular_2012] Towards Software Defined Cellular Networks. L.E. Li, Z.M. Mao, J. Rexford. Europ. Workshop on Software Defined Networks, 2012 [SoftCell_2013] SoftCell: scalable and flexible cellular core network architecture. Xin Jin, Li Erran Li, Laurent Vanbever, and Jennifer Rexford. 2013. [SoftRAN_2013] SoftRAN: Software Defined Radio Access Network. A. Gudipati, D. Perry, L.E. Li, S. Katti. HotSDN 2013 [DMM_2013] Software Defined Networking for Distributed Mobility Management. Y. Li, H. Wang, M. Liu, B. Zhang, H. Mao. Globecom 2013 Workshop [MMPerf_2014] Software Defined Networking to Improve Mobility Management Performance. M. Karimzadeh, A. Sperotto, A. Pras. AIMS 2014 [OpenFlow_2013] OpenFlow-enabled Mobile and Wireless Networks. Open Network Foundation Solution Brief, 2013 https://www.opennetworking.org/images/stories/downloads/sdn-resources/solution-briefs/sb-wireless-mobile.pdf 5
Outline Handling mobility in wireless networks Mobility management WLAN, cellular network Improvements of mobility management Distributed mobility management Improvements of the cellular network (LTE) Software defined RAN (Radio Access Network) SDN in the core network Integration of multiple wireless networks 6
Mobility Management and Handover Management of mobile device (user equipment, UE) Handover of UE from one stationary point (base station/enodeb, access point, S-GW or MSC, etc.) to the next Binding, update Lookup Base station Location database / location agent Search Transmission Central mobility anchor Mobile IP, GSM/3G/LTE Distributed mobility anchoring: e.g., Host Identity Protocol (HIP, RFC 4423, 5201): decouples locator and identification function of IP addresses 7
Ex. Mobility Management of Mobile IP Home agent (HA) Control plane : Care-of address (mobile host / foreign agent) is signalled to HA, update/binding Data plane : Tunnelling of data packets; source-ha-(fa)-mobile host Source Host Foreign Agent Mobile Host Mobile Host using DHCP Home Agent 8
Ex. Mobility Management in LTE GPRS tunnelling protocol GPRS tunnelling protocol P-GW S-GW HSS MME Data plane GPRS tunnelling: P-GW: Packet data network gateway S-GW: Serving gateway Control plane mobility management: HSS: Home subscription server MME: Mobility management entity : evolved base station Tracking area: known position of any UE, paging (cf. routing area/location area in 3G/2G) UE (user equipment) 9
SDN: Improving Mobility Management SDN: Making the control plane programmable (centralized), detaching control and data plane E.g. Use OpenFlow: Easy redirection of traffic flow irrespective of IP address of the mobile host makes IP translation obsolete [MMPerf_2014] Use the (OpenFlow) controllers to make distributed location updates easy changes in address space of mobile hosts [DMM_2013] 10
SDN and LTE: Improving Scalability in the Core Network 1/2 [SDCellular_2012, Softcell_2013] Problem: Cellular core networks are not scalable Processing overhead (of packets) and state at the core P-GW: content filtering, firewall, traffic optimization CENTRALIZED Variety of subscriber attributes: billing plan, roaming, phone model, etc. Variety of application types: video traffic (needs transcoding), Web traffic (needs caching), exemptions for user cap (bandwidth user may use) SoftCell SDN: functionality from the core to the edge Eliminate S-GW, P-GW functions middleboxes (virtualized) Overcome the inflexibility of LTE equipment (vendor-dependency) 11
SDN and LTE: Improving Scalability in the Core Network 2/2 [SDCellular_2012, Softcell_2013] Multi-dimensional aggregation: reducing size of tables in switches by combining IDs of policy, UE, base station Packet classification at the edge (base station) Piggy-packing classification Packet header Internet gateway just forwards Prototype based on Floodlight Open SDN controller Use of commodity switches 12
SoftCell Critiques? SoftCell Elements Controller Access switches (classification) Core switches Gateways (to the Internet) Middleboxes (packet processing) LTE Elements S-GW P-GW Mobility management Local anchor points at the access switch local agent Backup controller can contact local agents MME/HSS functionality? (if centralized, how does it differ?) Mobility management MME HSS 13
SDN and LTE: Soft Radio Access Network (RAN) RAN characteristics Dense deployment of small cells Limited spectrum No safe frequency reuse (clustering) [SoftRAN_2013] Main tasks within RAN Allocating radio resources GSM cells: cluster size of 7 Implementing (frequent) hand-over (small cells!) Managing interference, (tx power management) Load balancing between cells Complex LTE distributed control sub-optimal SoftRAN: An SD centralized control plane Abstraction of base stations: one virtual big base station Load balancing, interference management, global optimizations Local: Radio resource allocation (as long as tx power is coordinated) 14
SoftRAN [SoftRAN_2013] Critiques? Global state: appropriate area? Latency between controller and radio element: 5-10 ms [SoftRAN_2013] some (local) adaptations have to remain at the radio element 15
SDN: To Make Seamless Multi-homed Networking a Reality http://www.opennetsummit.org/archives/apr12/katti-wed-openradio.pdf 16
OpenRadio OpenRadio [http://snsg.stanford.edu/projects/openradio/] SDN is a natural way to abstract from the wireless network Hides network heterogeneity Hides network state Combine multiple access options OpenRadio built on DSP & ARM processor unit LTE, WiMAx enabled Wi-Fi: OpenWRT-based Network Layer: OpenFlow 17
OpenRoads (OpenFlow Wireless): https://www.youtube.com/watch?v=grskkgossz c#t=25 Thank you! November 10, 2014 ATCN 2014, SDN: Mobility and SDN 18