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

Natarajan Venkataraman, Principal Engineer, Ericsson India

Da t a pl a n e f o r SUBSCRIBER GATEWAY

OVERVIEW & CHALLENGES

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 2

› 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

Su bsc r iber Ga t ew a y

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 3

Depl o ymen t Po in t s - BNG

Access Network

Aggregation Network

Core

Lower scale but higher throughput per subscriber Higher scale but lower throughput per subscriber Can be at edge of access network Can be at edge

• f aggregation

network

BNG BNG

SUBSCRI BERS SUBSCRI BERS SUBSCRI BERS

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 4

Su bsc r iber Ga t ew a y a n d Su ppo r t No d es

SUBS GW

AGGR ROUTER CORE ROUTER

PCRF/ AAA

ACCT

DSLAM

OLT

WIFI AP/AC

AGGR ROUTER

DHCP Server

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 5

› 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

Desir ed Ch a r a c t er ist ic s

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 6

› 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

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

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 7

› 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?

Ser v ic e Pr o v isio n in g

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 8

Co n c ept u a l Da t a pl a n e

RX

Subscriber Traffic Detection

Signalling Traffic Detection

To control plane

Ingress Services (ACL/QoS/…)

Route

Egress Services (ACL/QoS/…)

TX ++ ++

ACL ++ Services ACL ++ Services

Route

Subscriber Traffic Detection

Signalling Traffic Injection

From control plane

Q

Hierarchical Queuing

Signalling Traffic Detection

To control plane

Rx / Tx can be via tunnels

SUBSCRI BERS SUBSCRI BERS SUBSCRI BERS

Internet

Access / Aggr Network

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 9

Typic a l Da t a pl a n e Design

RX (+LB) Packet Processing Packet Processing Packet Processing Packet Processing

Reorder (if no LB @ Rx)

Queuing / Scheduling TX From control plane To control plane Drops

Need to prioritize 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) H-QoS can become a throughput bottleneck Queues for tunnels would need a reinject back to packet processing Reinject after tunnel decap may be needed if load- balancer @ Rx is used

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 10

› 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

Sc a l e - Memo r y Impl ic a t io n s

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 11

› 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!

Sc a l e – Timer Impl ic a t io n s

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 12

› 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

Qo S Aspec t s

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 13

› 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

NFV IMpl ic a t io n s

Dataplane for Subscriber Management - Requirements and Challenges | 2017-03-30 | Page 14

› 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

NFV Impl ic a t io n s