Segment Routing in SP Networks - ptnog.pt€¦ · Segment Routing Architecture...

Paulo ValenteSP Systems Engineer, CCIE #134566.June.2019

PTNOG::3Segment Routing in SP Networks

© 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public

Access

Aggregation

Challenges of Todays Service Creation

2

HW Appliances

Legacy Central Office

Metro Network Domain Core Network Domain Data Center Domain

Limited Cross-domain Automation

Centralized Delivery of Services

VNF

IPMPLS

L2VPN

Ethernet

L3VPN VXLAN

E2E service provisioning is lengthy and complex:ü Multiple network domains under different management teamsü Manual operationsü Heterogeneous Underlay and Overlay networks

VNF


From Unified MPLS to Segment RoutingProtocol stack and network simplification

Domain 1 Domain 2 Domain 3

LDP

RSVP

IGP

BGP-LU

LDP

Intra-Domain CP

Protection FRR/TE

Inter-Domain Connectivity

L2/L3VPN Services

Unified MPLSEPN 4.0

BGP

L2/L3 VPN

IGP IGP IGPLDP LDP LDP

BGP-LU

RSVP-TE RSVP-TE RSVP-TE

IGP+Segment Routing

Inter-Domain Connectivity with SLATraffic Engineering

Protection FRR – TI-LFA Intra -Domain CP

L2/L3VPN EVPN

Segment RoutingStateless Fabric

BGP

3


Unified “Stateless Fabric” for Service Creation

4

Cloud Scale NetworkingCentral Office

Metro Network Core and Peering Network Network Data CenterAccess

Compute Leaf Spine

Virtualize

Transform the CO into a data center to enable distributed service delivery and speed up service creation

Simplify

Unified underlay and overlay networks with segment routing and EVPN

VNF VNF

VNF

VNF

BGP VPN

IGP Segment Routing

Automate

E2E Cross-domain automation with model-driven programmability and streaming telemetry

Controller


Intent Based Network Virtualization

5

Cloud Scale NetworkingCentral Office

Metro Network Core and Peering Network Network Data CenterAccess

Compute Leaf Spine

Virtualize

Single infrastructure for different SLA and forwarding requirements

Simplify

Simplified intent based steering, per destination, per flow

VNF

VNF

VNF

VNF

BGP VPN

IGP Segment Routing

Automate

Model driven, Multi Domain Path Computation, Intent aware forwarding and protection.

Controller

uRLLCmMTC

High BandwidthEncrypted

Low Delay


Years

2013 2014 2015 2016 2017 2018 2019

Segment Routing Customer Adoption

Planning Production

First public SegmentRouting Presentation(MPLS-WC)

FCS (IOS-XR)

First SR live Deployment(15 months after FCS)

IEFT SPRING Working Group

Significant MomentumWorldwide

6

6


Segment Routing Standardization

IETF standardization in SPRING working group

First RFC document - RFC 7855 (May 2016)

Protocol extensions progressing in multiple groups• IS-IS• OSPF• PCE• IDR• 6MAN• BESS

Broad vendor support

Strong customer adoption and support• WEB, SP, Enterprise

7

Sample IETF Documents

Problem Statement and Requirements(RFC 7855)

Segment Routing Architecture(draft-ietf-spring-segment-routing)

IPv6 SPRING Use Cases (draft-ietf-spring-ipv6-use-cases)

Segment Routing with MPLS data plane(draft-ietf-spring-segment-routing-mpls)

Topology Independent Fast Reroute using Segment Routing(draft-bashandy-rtgwg-segment-routing-ti-lfa)

IS-IS Extensions for Segment Routing(draft-ietf-isis-segment-routing-extensions)

OSPF Extensions for Segment Routing(draft-ietf-ospf-segment-routing-extensions)

PCEP Extensions for Segment Routing(draft-ietf-pce-segment-routing)

40+ IETF drafts in progress

https://tools.ietf.org/html/rfc7855

http://tools.ietf.org/html/draft-ietf-spring-segment-routing

http://tools.ietf.org/html/draft-ietf-spring-ipv6-use-cases

https://tools.ietf.org/html/draft-ietf-spring-segment-routing-mpls-04

https://tools.ietf.org/html/draft-bashandy-rtgwg-segment-routing-ti-lfa-00

http://tools.ietf.org/html/draft-ietf-isis-segment-routing-extensions

http://tools.ietf.org/html/draft-ietf-ospf-segment-routing-extensions

http://datatracker.ietf.org/doc/draft-ietf-pce-segment-routing/

Segment Routing adoption

Simplified

Web / OTT

Service Providers

Enterprise

Segment RoutingThe “state” is in the packet

Seattle

New-York

Barcelona

Mexico

Madrid

Toronto LondonSegment Routing

MEXMAD

BCN

MAD

BCNBCN

1. A unique and global luggage tag is attached to the luggage with the list of stops to the final destination

2. At each stop, the luggage is simply routed to the next hop listed on the luggage tag

Path can be controlledSimple and scalableRESULT:

Intent – Route the luggage to Barcelona via Mexico and Madrid

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Path expressed in the packet DataDynamic path

Explicit path

Paths optionsDynamic

(Headend computation)Explicit

(Operator / Controller)

Control PlaneRouting protocols with

extensions(IS-IS,OSPF, BGP)

SDN controller

Data PlaneMPLS

(segment labels)IPv6

(+SR header)

Segment Routing

10

An IP and MPLS source-routing architecture that seeks the right balance between distributed intelligence and centralized

optimization


Segment Routing – Forwarding PlaneMPLS

A list of segments represented as a one or a stack of labels

IPv6A list of segments encoded directly in the IPv6 extension header

11© 2019 Cisco and/or its affiliates. All rights reserved. Cisco Public


Label 2

Label 3

Label 4

Label 1Active Segment

MPLS header

payload

Segment Routing Segments – MPLSThe active segment is on the top

Label 2

Label 3

Label 4

Active Segment

MPLS header

payload

Label 3

Label 4

Active Segment

MPLS header

payload

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Locator 1 Function 1




Active

IPv6 header

Segment Routing Header

payload

Segment Routing Segments – IPv6Active segment is copied in the destination address

DestinationAddress

2





Active

IPv6 header


payload

DestinationAddress

1





Active

IPv6 header


payload

DestinationAddress

0

13


Multiple Prefix SIDs for the same end-pointfor different intent

• Operator-defined custom IGP algorithm leveraging dedicated Prefix-SIDs set

• Example:• Operator configure pref-SID 16004

associated to Loopback 0

• Operator defines Flex-Algo 128 as “minimize delay metric”

• Prefix SID flex-algo 128 17004 associated to Loopback 0

• For each destination two different SIDs are installed in FIB

5 1

6 7

8 7

2

4

3

IGP: 100 IGP: 100 Loopback0Default Algo 0Prefix SID: 16004 Metric IGP

5 1

6 7

8 7

2

4

3

D: 1 D: 1 Loopback0Algo 128Prefix SID: 17004Metric Delay

Default IGP metric: 10Default IGP metric: 10

14


Flex Algo properties

15

One single SID even for complex intente.g. Low Latency, exclude/include affinity..

Protected path stays in Flex Algo virtual topologyTI-LFA aware


Circuit Optimization vs SR OptimizationIntent: path to 3 avoid links RED

2

15 3

6

8 9

2

4

15 3

6

7

8 9

SR-native algo is needed!No more circuit!

Recognized Innovation - Sigcomm 2015SID List: {7, 3}

ECMP, minimized SID list, IP-optimized

Classic TE algorithm is not efficient!!Need to specify all hops: {4, 5, 7, 3}

No ECMP, Old algorithm and technology , ATM optimized

pkt1600316007

pkt

16003

pkt

With SR we can do much better

4 7

16

Automated Steering


SR Policy IdentificationAn SR Policy is uniquely identified by a tuple

(end-point and color)End-point: the destination of the SR PolicyColor: a numerical value to differentiate multiple SRTE Policies between the

same pair of nodes

1

2

3

6

4

5

SR Policy

(green, 6)Color: greenEnd-point: 6

18


SR Policy Color

For the same end-point different colors for different SLAe.g.• Green = Low Latency• Blue = High Bandwidth

Enable Auto Steering• Policy color to match BGP ext. community color• color extended community is specified in RFC 5512

1

2

3

6

4

5

green, 6

blue, 6

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SR Policy Binding SID

• A binding SID is associated to every SR policy • Programmed in the headend FIB• Explicitly configured or dynamically allocated• Enable Traffic Steering in a SR policy

• Packet received with Binding-SID as top label is steered into the SRTE Policy associated with the Binding-SID

• Binding-SID label is popped, SRTE Policy’s SID list is pushed

1

2

3

6

4

5

SR Policy

(green, 6)Color: greenEnd-point: 6

Binding SID:99000SID list 4,6

pkt99000

pkt1600616004

pkt16004

pkt

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Segment Routing - Automated Steering (AS)Steer traffic into SR Policy based on destination - color

BGP signaled routes: IPv4, VPNv4, EVPN• End-pont = BGP Next Hop• Route color = SR policy color

1

2

3

6

4

5

Traffic for 10.10.10.1 – NH 6

and 20.20.20.1 - NH 6

RR

20.20.20.0/2410.10.10.0/24

10.10.10.0/24 NH=6 color=GREEN20.20.20.0/24 NH=6 color=BLUE

Automated steering directs traffic based on

destination/colors Route policy to advertise routes with

specific color

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Conclusion

Simple, Automated and Scalable• No state in the network: state in the packet header• No tunnel interface: “SR Policy”• No head-end a-priori configuration: on-demand policy instantiation• No head-end a-priori steering: automated steering

Multi-Domain• SR Path Computation Element (SR-PCE) for compute

Flexible AlgorithmSpecific metric (e.g. delay) Specific TopologyTI-LFA traffic stay in Flex Algo topologySingle label per intent

Lots of Functionality and flexibility• Designed with lead operators along their use-cases

22


5G Technology Innovations

CUPS: Control/User Plane Separation

Cloud RAN – Fronthaul/Midhaul

Multi-Access Edge Computing Network Slicing

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• Ability to run multiple logical networks as virtually independent business operations

• Simultaneous support strict SLA reqs & best effort traffic over same infra.

• Solution with Virtualisation, SDN control and overall Orchestration from E2E of Access, Transport and Mobile Core Network

5G Technology InnovationNetwork Slicing NGMN, 5G whitepaper

Slice#1_SLA1

Slice#2_SLA2

Slice#3_SLA3

SR_tunnel2 SR_tunnel2

SDN Controller

Orchestration

RAN EPC

SDN Controller

SDN Controller

• Programmability of transport network for dynamic and flexible service creation

• Automation to compute the best path and guarantee the SLA throughout service lifetime

• Independent traffic flows with specific SLAs

• Scalable, Reliable, Simple

• Statistical multiplexing for efficient network resources

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IPv6 provides reachability

Supports 5G growth and scale

5G

5G

5G

IoT services

Source Address

Destination Address

IPv6

Metro/Core Network

IP

4G

xDSLFTTH

Cable

LegacyDC

Supports container adoption formicro-services

Next-Gen Data Center

Micro-services

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• Simplicity• Protocol elimination

• SLA• FRR and TE

• SDN• SR is de-facto SDN architecture

• Overlay

• NFV• 5G Slicing

SRv6 – Segment Routing & IPv6

IPv6 for reachability

SR for anything else

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• SRv6 SIDs are 128-bit addresses• Locator: most significant bits are used to route the segment to its parent node• Function: least significant bits identify the action to be performed on the parent node

• Argument [optional]: Last bits can be used as a local function argument

• Flexible bit-length allocation• Segment format is local knowledge on the parent node

• SIDs have to be specifically enabled as such on their parent node• A local address is not by default a local SID• A local SID does not have to be associated with an interface

Network as a ComputerSRv6 Network instruction

Locator Function Argument1111 : 2222 : 3333 : 4444 : 5555 : 6666 : 7777 : 8888

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Next Segment










Next Segment





Locator 1 Function 1Locator 3 Function 3




Next Segment









SRv6 for anything

Optimized for HW processinge.g. Underlay & Tenant use-cases

Optimized for SW processinge.g. NFV, Container, Micro-Service

Metadata TLV

Segments Left




TAG

31


• Services are expressed with segments• Flexible• Scalable• Stateless

Packets from are steered through a sequence of services on their way to the server

Network as a Computer Service Chaining with SRv6

S1 S2 S3 DSR: 〈S1, S2, S3, D〉

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SR-UnAware VNFs:• Application is not aware of SR at all • Leverage VPP as a vm/container vSwitch to do SRv6

processing

Service Programming with SRv6

SR-Aware VNFs:• Leverage SRv6 Kernel support to create smarter applications • SERA: SR-Aware Firewall (extension to iptables)

Types of VNFs

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• A3::A32 means• App in Container 32• @ node A3::/64

• Stateless • NSH creates per-chain state

in the fabric• SR does not

• App is SR aware or not

Service ChainingIntegrated NFV

1

2

4

V/64

3

T/64

4

App 76VM

Server 5

5

3 App 32Container

Server 3IPv6 Hdr SA = A1::0, DA = A3::A32

Payload

IPv6 Hdr SA = T::1, DA = V::2

SR Hdr < A3::A32, A4::0, A5::A76, A2::C4 >


Payload

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• Integrated with underlay SLA


1

2

4

V/64

3

T/64

4

App 76VM

Server 5

5

3 App 32Container

Server 3

IPv6 Hdr SA = A1::0, DA = A4::0

Payload


SR Hdr < A3::A32, A4::0, A5::A76, A2::C4 >

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• A5::A76 means• App in VM 76• @ node A5::/64

• Stateless • NSH creates per-chain state

in the fabric• SR does not

• App is SR aware or not


1

2

4

V/64

3

T/64

4

App 76VM

Server 5

5

3 App 32Container

Server 3

IPv6 Hdr SA = A1::0, DA = A5::A76

Payload


SR Hdr < A3::A32, A4::0, A5::A76, A2::C4 >

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• Integrated with Overlay


1

2

4

V/64

3

T/64

4

App 76VM

Server 5

5

3 App 32Container

Server 3

IPv6 Hdr SA = A1::0, DA = A2::C4

Payload


SR Hdr < A3::A32, A4::0, A5::A76, A2::C4 >


Payload

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• Well-progressed standardization• IETF: draft-ietf-dmm-srv6-mobile-uplane-01• 3GPP: Accepted study item in CT4 (#29.892) – starts July

• SRv6 an alternative to GTP-U• Removing the per-session tunneling has obvious benefits• Optimal data path (ultra-low latency)• Integrated service chaining (allows for NFVs for security, billing, ...)

• Native support for network slicing• Achieved either via a centralized SDN solution or via SR TE with IGP FlexAlg• Optimal resource utilization

SRv6 in Mobile

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