Segment Routing Traffic Engineering Diptanshu Singh Why Traffic

Segment Routing Traffic Engineering Diptanshu Singh

Why Traffic Engineering ? • High bandwidth paths • Low Latency paths • Disjoint paths • Avoid resources o avoid low bandwidth links o avoid high utilized links • Optimize Network Capacity • Ad-Hoc o Calendaring 2

Distributed or Centralized computing ? Policy Single-Domain Multi-Domain Reachability IGP’s Centralized Low Latency Distributed or Centralized Disjoin from same node Distributed or Centralized Centralized Low Priority TBD Centralized Disjoin from different node Avoiding resources Capacity optimization Others… 3

High level Architecture • PCE controller LSP-DB PCEP • • TED SR PCE have multi-domain topology view --feed via BGP-LS from multiple domains Stateful PCE with native SRTE algorithms. PCEP Messages: • PCEP Request (PCC -> PCE) • PCEP Reply (PCE -> PCC) • PCC Report (PCC -> PCE) • PCE Update (PCE -> PCC) • PCE Initiate (PCE -> PCC) BGP-LS Router PCC Area Y Router Area X Router Area Z Router 4

SR Basics: Binding Segment • Binding Segment represents a tunnel at SR • The Binding Segment is a local segment – Has local significance • A Binding-Segment ID identifies a SRTE Policy – Each SRTE Policy is associated 1 -for-1 with a Binding-SID • Packets received with Binding-SID as top label are steered into the SRTE Policy associated with the Binding-SID – Binding-SID label is popped, SRTE Policy’s SID list is pushed 5

SR Basics: Binding Segment • Binding-SID use-case examples: – Label stack “compression”: nesting and stitching SRTE Policies – BGP SRTE Dynamic: use local Binding-SID(later) PCEP Request Could you provide me the ERO for AC 1? 3 PCEP Reply - 17001, 4001 - Instead of 17001, 17002, 17003, 17004 TOR DC IP PCE controller 2 1 PCC Report - 17002, 17003, 17004 - Binding SID 4001 WAN Headend AC 1 4001 IP 17004 Unicast-SID 17002 17003 Unicast-SID 17001 IP 4001 17001 IP 17004 17003 17002 Unicast-SID 17003 IP 17004 IP Unicast-SID 17004 6

Segment Routing Traffic Engineering: On Demand Next Hop • BGP SR-TE dynamic • HA with PCE SR controller • 7

On demand SR Next Hop Service Orchestrator Hint: 1. PCE collect topology and SID via BGP LS 2. Including ip address and SID PCE controller BGP Route Reflector BGP Link State ABR 1 To. R 1 DC To. R 2 Unicast-SID 16002 Unicast-SID 17003 Anycast-SID 18002 Unicast-SID 17001 Anycast-SID 18001 Unicast-SID 16001 ISIS SR 2 SRGB 16000 -16999 ABR 3 WAN ABR 2 Unicast-SID 17002 Anycast-SID 18001 Unicast-SID 16001 ISIS SR 1 SRGB 17 k-18 k AC 1 Access ABR 4 Unicast-SID 17004 Anycast-SID 18002 ISIS SR 3 SRGB 16000 -16999 AC 2 Unicast-SID 16002 8

On demand SR Next Hop Service Orchestrator Hint: 1. PCE collect topology and SID via BGP LS 2. Service Orchestrator to configure service PCE controller BGP Route Reflector XML YANG: - PW-123 from To. R 1 to AC 1 ABR 1 To. R 1 DC To. R 2 Unicast-SID 16002 Unicast SID 17003 Anycast SID 18002 Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 XML YANG: - PW-123 from AC 1 to To. R 1 ABR 3 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 Unicast-SID 16001 AC 1 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 9

On demand SR Next Hop Service Orchestrator PCE controller Do I have LSP to AC 1 ? BGP Route Reflector ABR 1 To. R 1 DC To. R 2 Unicast-SID 16002 Unicast SID 17003 Anycast SID 18002 Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 Hint: 1. PCE collect topology and SID via BGP LS 2. NMS/OSS to configure service 3. To. R 1 check if he has LSP to AC 1 Yes -> use it No -> next slide ABR 3 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 Unicast-SID 16001 AC 1 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 10

On demand SR Next Hop Service Orchestrator PCE controller PCEP request - Could you provide me the ERO to reach AC 1 ? 1 2 BGP Route Reflector PCEP reply - ERO is: 18001, 18002, 16001 3 ABR 1 DC To. R 2 Unicast-SID 16002 Unicast SID 17003 Anycast SID 18002 Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 To. R 1 Hint: 1. PCE collect topology and SID via BGP LS 2. Service Orchestrator to configure service 3. To. R 1 check if he has LSP to AC 1 4. To. R 1 request LSP to PCE ABR 3 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 Unicast-SID 16001 AC 1 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 11

On demand SR Next Hop Hint: 1. PCE collect topology and SID via BGP LS 2. Service Orchestrator to configure service 3. To. R 1 check if he has LSP to AC 1 4. To. R 1 request LSP to PCE 5. To. R 1 report service state to orchestrator Service Orchestrator PCE controller BGP Route Reflector XML YANG notification: - PW-123 is UP Ethernet ABR 1 To. R 1 Ethernet To. R 2 Unicast-SID 16002 Unicast-SID 17003 Anycast-SID 18002 Unicast-SID 17001 Anycast-SID 18001 Unicast-SID 16001 PW 16001 DC 18002 18001 ABR 2 Unicast-SID 17002 Anycast-SID 18001 Unicast-SID 16001 ABR 3 Ethernet PW 16001 WAN 18002 AC 1 Ethernet ABR 4 Unicast-SID 17004 Anycast-SID 18002 Etherne PW 16001 Access AC 2 Unicast-SID 16002 12

ODN with policy Service Orchestrator Hint: 1. PCE collect topology and SID via BGP LS 2. Service Orchestrator to configure service PCE controller BGP Route Reflector XML YANG: - PW-123 from To. R 1 to AC 1 - PW-124 from To. R 2 to AC 2 - Policy: Disjoin GID 123 ABR 1 To. R 1 DC To. R 2 Unicast-SID 16002 Unicast SID 17003 Anycast SID 18002 Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 XML YANG: - PW-123 from AC 1 to To. R 1 - PW-124 from AC 2 to To. R 2 - Policy: Disjoin GID 123 ABR 3 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 Unicast-SID 16001 AC 1 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 13

ODN with policy Service Orchestrator PCE controller PCEP request - Could you provide me the ERO to reach AC 1 ? BGP Route Reflector - Policies are G-ID 123 PCEP request - Could you provide me the ERO to reach AC 2 ? 1 - Policies are G-ID 123 2 Unicast-SID 16001 DC To. R 2 Unicast-SID 16002 Unicast SID 17003 Anycast SID 18002 Unicast SID 17001 Anycast SID 18001 ABR 1 To. R 1 Hint: 1. PCE collect topology and SID via BGP LS 2. Service Orchestrator to configure service 3. To. R 1 and To. R 2 check if they has LSP to AC 1 and AC 2 respectively. 4. To. R 1 and To. R 2 request LSP to PCE ABR 3 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 Unicast-SID 16001 AC 1 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 14

ODN with policy (Cont) Hint: 1. PCE collect topology and SID via BGP LS 2. Service Orchestrator to configure service 3. To. R 1 and To. R 2 check if they has LSP to AC 1 and AC 2 respectively. 4. To. R 1 and To. R 2 request LSP to PCE 5. PCE sees the same Disjoint ID and computes two Disjoint paths Service Orchestrator PCE controller 3 4 PCEP reply - ERO is: 17001, 17003, 16001 PCEP reply - ERO is: 17002, 17004, 16002 ABR 1 To. R 2 Ethernet Unicast-SID 16002 Unicast SID 17003 Anycast SID 18002 Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 Ethernet BGP Route Reflector PW PW 16001 DC 16002 17003 17004 17001 ABR 3 Ethernet PW 16001 WAN Unicast SID 17002 Anycast SID 18001 AC 1 Ethernet 17003 PW ABR 4 Ethernet PW 16002 16001 Access ABR 2 17002 Unicast-SID 16001 17004 Ethernet Unicast SID 17004 Anycast SID 18002 AC 2 PW 16002 Unicast-SID 16002 15

On demand steering for BGP services Hint: 1. Isolated domains with no redistribution. 2. CPE send BGP update for prefix X and add LL community ex: 100: 777 Technical name: BGP SR-TE dynamic PCE controller BGP Route Reflector BGP-LS Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 CPE 1 DC Unicast-SID 16002 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 Unicast-SID 16001 AC 1 ABR 3 ABR 1 To. R 2 Unicast SID 17003 BGP-LS Anycast SID 18002 CPE 2 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 16

On demand steering for BGP services Hint: 1. Isolated domains with no redistribution. 2. CPE send BGP update for prefix X and add LL community ex: 100: 777 Technical name: BGP SR-TE dynamic PCE controller BGP Route Reflector Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 CPE 1 DC Unicast-SID 16002 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 NLRI: 1. 1/32 Community: 100: 777 Unicast-SID 16001 AC 1 ABR 3 ABR 1 To. R 2 Unicast SID 17003 Anycast SID 18002 CPE 2 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 17

On demand steering for BGP services Hint: 1. CPE send BGP update for prefix X and add LL community 2. AC 1 PE announce VPN prefix X with LL community Technical name: BGP SR-TE dynamic PCE controller BGP Route Reflector NLRI: 1. 1/32 Community: 100: 777 CPE 1 DC Unicast-SID 16002 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 Unicast-SID 16001 AC 1 ABR 3 ABR 1 To. R 2 Unicast SID 17003 Anycast SID 18002 Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 CPE 2 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 18

On demand steering for BGP services Technical name: BGP SR-TE dynamic PCEP request - Could you provide me the ERO to reach AC 1 ? - Policy is LL 1 2 To. R 1 BGP Route Reflector PCEP reply - ERO is: 17001, 17003, 16001 3 Unicast-SID 16002 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 Unicast-SID 16001 AC 1 ABR 3 ABR 1 DC To. R 2 Unicast SID 17003 Anycast SID 18002 Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 CPE 1 PCE controller Hint: 1. CPE send BGP update for prefix X and add LL community 2. AC 1 PE announce VPN prefix X with LL community 3. On demand Next Hop LL to PCE controller 4. Install explicit path for prefix X in VRF CPE 2 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 19

– Binding-SID (e. g. 24006): push {Label 17001, Label 17003, Label 16001} • TE provides the Binding-SID BGP FIB: 1. 1/32; NH: AC 1 Received VPN label: L_VPN Community 100: 777 Binding Label: 24006 TE • TE installs SRTE Policy in SRTE Policy to AC 1: SID List {17001, 17003, 16001}, OIF 3 Binding Label: 24006 FIB On demand steering for BGP services Local label: 24006 out label: POP OIF: SRTE; Label stack {17001 17003 16001} of the SRTE Policy to BGP 20

– 1. 1/32 via 24006 – Push VPN label and steer in SRTE Policy • TE installs SRTE in FIB BGP • RIB installs in FIB: 1. 1/32; NH: AC 1 Received VPN label: L_VPN Community 100: 777 Binding Label: 24006 TE On demand steering for BGP services SRTE Policy to AC 1: SID List {17001, 17003, 16001}, OIF 3 Binding Label: 24006 • BGP, RIB and FIB aware of FIB BSID 1. 1/32; recursion-via-label L_VPN, NH via 24006 Local label: 24006 out label: POP OIF: SRTE; Label stack {17001 17003 16001} 21

PCE HA 5 PCE 2 Secondary PCE 1 Primary 2 3 4 7 1 CPE 1 DC To. R 2 Unicast-SID 16002 Unicast SID 17003 Anycast SID 18002 WAN ABR 2 Unicast SID 17002 Anycast SID 18001 Unicast-SID 16001 AC 1 ABR 3 ABR 1 To. R 1 6: wait for some timer BGP Route Reflector Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 1. Service Provisioned via Overlay RR, Orchestrator 2. Request via PCEP to PCE primary with TE policy 3. PCE replies with ERO 17001, 17003, 16001 4. To. R 1 Reports to PCE Primary and Secondary via PCC Report 5. Primary PCE fails 6. To. R 1 waits for some time 7. To. R 1 Reports PCE 2 of becoming master CPE 2 Access ABR 4 Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 22

ODN HA model • • SR-PCE not to be considered as a Single “god” box SR-PCE is closer to RR Different TOR’s can use different pairs of SR-PCE SR PCE preference can be either based on proximity or service Service Orchestrator CPE 1 To. R 1 PCEP Unicast-SID 16002 BGP LS PCE ABR 1 RR DC To. R 2 Unicast SID 17003 Anycast SID 18002 Unicast SID 17001 Anycast SID 18001 Unicast-SID 16001 PCE ABR 3 RR Unicast SID 17002 Anycast SID 18001 PCEP AC 1 CPE 2 Access WAN PCE ABR 2 RR Unicast-SID 16001 PCE ABR 4 RR Unicast SID 17004 Anycast SID 18002 AC 2 Unicast-SID 16002 23

Thank you.

References • http: //www. segment-routing. net/ • Current IETF Drafts for SR: • http: //www. segment-routing. net/home/ietf • PCEP Extensions for Segment Routing • https: //tools. ietf. org/html/draft-ietf-pce-segment-routing-06 • Binding SID • https: //tools. ietf. org/html/draft-sivabalan-pce-binding-label-sid-00 • Anycast Segments in MPLS based Segment Routing • https: //tools. ietf. org/html/draft-psarkar-spring-mpls-anycast-segments-01 • BGP Link-State extensions for Segment Routing https: //tools. ietf. org/html/draft-gredler-idr-bgp-ls-segment-routing-ext-01 25