Da t a pl a n e f o r SUBSCRIBER GATEWAY OVERVIEW & CHALLENGES - PowerPoint PPT Presentation

Da t a pl a n e f o r SUBSCRIBER GATEWAY OVERVIEW & CHALLENGES Natarajan Venkataraman, Principal Engineer, Ericsson India

Su bsc r iber Ga t ew a y › Entity at edge of access-aggregation network / mobile RAN network › Provides Internet access to subscribers › Enables ISPs to monitor usage for charging › Primary Role –AAA: Authenticate, Authorize subscribers and Account their traffic (for charging etc.) –Provide IP-address to subscribers –Provide various services as per SLA › Example Nodes –BNG / BRAS: Fixed broadband –P-Gateway: Mobile broadband › In talk we will take the BNG as a representative of a subscriber gateway Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 2

Depl o ymen t Po in t s - BNG Can be at edge Can be at edge of of aggregation access network network SUBSCRI BERS Access Aggregation Core Network Network SUBSCRI BNG BERS BNG SUBSCRI BERS Higher scale but Lower scale but lower throughput per higher throughput per subscriber subscriber Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 3

Su bsc r iber Ga t ew a y a n d Su ppo r t No d es WIFI PCRF/ DHCP AP/AC ACCT AAA Server AGGR ROUTER OLT SUBS AGGR CORE ROUTER ROUTER GW DSLAM Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 4

Desir ed Ch a r a c t er ist ic s › Good packet throughput (like any router) › High session setup / teardown rate (sessions/sec) › High subscriber scale –At each dataplane and at system level › Rich services, service orchestration › Session survivability support Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 5

Da t a pl a n e - Co n t r o l Pl a n e In t er a c t io n › Continuous session signaling packet transfer between control plane and dataplane › Continuous provisioning messages and responses between control plane and dataplane › Continuous session keep-alives with subscribers › Continuous push of statistics counters from dataplane to control plane and thence to accounting servers › Loss of these will be impactful  Poor product perception –Low session setup rates, Session flaps, Subscriber dissatisfaction, Revenue loss Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 6

Ser v ic e Pr o v isio n in g › Services made available to a subscriber can change at any time –Pre-paid model: Once limit is reached, service needs to be deactivated –Value-added services: Subscribers can purchase at anytime and expect instant activation –Time-based services: Increase in bandwidth or usage during peak / off-peak hours › Service changes are communicated to subscriber gateway via policy control nodes › Results in reprovisioning of an active packet processing chain for subscriber –Will such reprovisioning result in temporary traffic impact? –Can services be added / removed with minimal to nil hit? Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 7

Co n c ept u a l Da t a pl a n e Rx / Tx can be via ++ Services ACL To control To control tunnels plane plane Ingress Signalling Subscriber Signalling SUBSCRI Services RX ++ Traffic Traffic Traffic BERS Route Access / Aggr Detection Detection Detection (ACL/QoS/…) Network Internet SUBSCRI BERS Egress Subscriber Q Services TX ++ Traffic Route Detection (ACL/QoS/…) Signalling SUBSCRI Hierarchical BERS Traffic Queuing Injection Services ACL ++ From control plane Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 8

Typic a l Da t a pl a n e Design Reinject after tunnel decap may be needed if load- balancer @ Rx is used H-QoS can become To control plane From control plane a throughput bottleneck Packet Processing (if no LB @ Rx) Queuing / Scheduling Packet Processing Reorder RX TX (+LB) Packet Processing Queues for tunnels would Packet Processing Need to need a reinject back to prioritize packet processing Drops between CP and line traffic Differing service needs, tunnel encap / decap, mean higher variation in packet arrival rate at reorder / queue stage (Larger reorder queues) Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 9

Sc a l e - Memo r y Impl ic a t io n s › Large number of statistics – both to be collected and pushed periodically –Session level counters –Counters for each service › Large number of /32 (v4) [or /128 (v6)] routes –1 per subscriber: IPv4 (/32 routes) –2 or 3 per subscriber: IPv6 (Covers link-local, IA-PD and IA-NA routes) › Link-local and IA-NA would be /128 routes › Large number of QoS policers / meters –Each session (and each service as well) would need to be rate-limited as per SLA › Thus, multiple policers / meters per subscriber Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 10

Sc a l e – Timer Impl ic a t io n s › Session timers include –Protocol (keep-alive) timers –Idleness detection timers –Session lifetime timers › Higher scale can result in many timers firing simultaneously › Offloading of protocol timers to dataplane can increase responsiveness –Lowers burden on control plane –Lowers traffic between dataplane & control plane –BUT: Impacts dataplane throughput traffic! Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 11

Qo S Aspec t s › Since we create / remove subscriber sessions continuously, the H-QoS scheduler cone is dynamic and changes constantly › Bandwidth oversubscription is required –Cannot ensure no oversubscription via configuration › Memory requirement can be huge –But can result in packet buffers sitting in queues and starving the pipeline Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 12

NFV IMpl ic a t io n s › Backplane (chassis terminology) –Path between dataplane and control plane –As mentioned earlier, design of this path is critical for effective functionality › We saw that certain kinds of traffic cannot be lost –Backplane QoS is an essential characteristic of subscriber gateway dataplane › Fabric (chassis terminology) –Path between dataplane and service plane –In chassis systems, designed to be high throughput and near lossless –Subscriber gateway requires the essential properties of chassis fabric to be mimic-ed › Loss of fabric traffic also results in poor SLA adherence Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 13

NFV Impl ic a t io n s › Subscriber traffic likely to be carried over L2-over-L3 tunnels –Optimizing dataplane for tunnels may become the common case! › Service plane via separate service VMs –Packet processing at subscriber gateway can become simpler – hence faster –Service chain support in the dataplane › Subscriber gateway can just add service chain tags in its dataplane or interact with SDN controller to setup service chain paths Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 14