MENOG 18 Segment Routing Rasoul Mesghali CCIE#34938 Vahid

MENOG 18 Segment Routing Rasoul Mesghali CCIE#34938 Vahid Tavajjohi From HAMIM Corporation 1 Agenda Introduction Technology Overview Use Cases Closer look at the Control and Data Plane Traffic Protection Traffic engineering SRv6 2 MENOG 18 Introduction 3 MPLS Historical Perspective MPLS classic (LDP and RSVP-TE) control-plane was too complex and lacked scalability. LDP is redundant to the IGP and that it is better to distribute labels

bound to IGP signaled prefixes in the IGP itself rather than using an independent protocol (LDP) to do it. LDP-IGP synchronization issue, RFC 5443, RFC 6138 Overall, we would estimate that 10% of the SP market and likely 0% of the Enterprise market have used RSVP-TE and that among these deployments, the vast majority did it for FRR reasons. The point is to look at traditional technology (LDP/RSVP_TE) applicability in IP networks in 2018. Does it fit the needs of modern IP networks? 4 MPLS Historical Perspective In RSVP-TE and the classic MPLS TE The objective was to create circuits whose state would be signaled hop-by-hop along the circuit path. Bandwidth would be booked hop-by-hop. Each hops state would be updated. The available bandwidth of each link would be flooded throughout the domain using IGP to enable distributed TE computation. First, RSVP-TE is not ECMP-friendly. Second, to accurately book the used bandwidth, RSVP-TE requires all the IP traffic to run within so-called RSVP-TE tunnels. This leads to much complexity and lack of scale in practice. 5 1.network has enough capacity to accommodate without congestion traffic engineering to avoid congestion is not needed. It seems obvious to write it but as we will see further, this is not the case for an RSVP-TE network.

2.In the rare cases where the traffic is larger than expected or a non-expected failure occurs, congestion occurs and a traffic engineering solution may be needed. We write may because it depends on the capacity planning process. 3.Some other operators may not tolerate even these rare congestions and then require a tactical trafficengineering process. A tactical traffic-engineering solution is a solution that is used only when needed. 6 An analogy would be that one needs to wear his raincoat and boots every day while it rains only a few days a year. N2*K tunnels While no traffic engineering is required the classic RSVP TE solution is an always-on solution complexity and

limited scale, ofthe in the most likelyfor situation of an IP network, This is the reason the infamous full-mesh RSVP-TE classicalmost MPLS of TEthe solution always requires the IP tunnels. time, without anyall gain traffic to not be switched as IP, but as MPLS TE circuits. 7 Goals and Requirements Make things easier for operators

Improve scale, simplify operations Minimize introduction complexity/disruption Enhance service offering potential through programmability Leverage the efficient MPLS dataplane that we have today Push, swap, pop Maintain existing label structure Leverage all the services supported over MPLS Explicit routing, FRR, VPNv4/6, VPLS, L2VPN, etc IPv6 dataplane a must, and should share parity with MPLS 8 Operators Ask For Drastic LDP/RSVP Improvement Simplicity less protocols to operate less protocol interactions to troubleshoot avoid directed LDP sessions between core routers deliver automated FRR for any topology Scale avoid millions of labels in LDP database avoid millions of TE LSPs in the network avoid millions of tunnels to configure 9 Operators Ask For A Network Model Optimized For Application Interaction Applications must be able to interact with the network cloud based delivery internet of everything Programmatic interfaces and Orchestration Necessary but not sufficient

The network must respond to application interaction Rapidly-changing application requirements Virtualization Guaranteed SLA and Network Efficiency 10 Segment Routing Simple to deploy and operate Leverage MPLS services & hardware straightforward ISIS/OSPF extension to distribute labels LDP/RSVP not required Provide for optimum scalability, resiliency and virtualization SDN enabled simple network, highly programmable highly responsive 11 MENOG 18 Technology Overview 12 What is the meaning of Segment Routing? Segment 1 10 20 CE1

PE1 P2 10 P3 Segment 2 10 P5 P4 P6 PE2 P7 CE2 PE2 Segment 3 Default Cost is 100 13 SR in one Slide

24001 Adj-SID Label 16007 Prefix-SID Label Service: L3VPN,L2VPN,6PE,6 VPE 16099 CE1 PE1 24001 16007 16007 P1 Prefix-SIDs are global Labels Adj-SIDs are local labels P2 Adj Label 24001 Segment 1 24001

P5 Prefix-SID Loopback0 Label 16099 P4 P3 Segment 2 16007 P6 PE2 P7 Segment 3 Deviate from shortest path-Source Routing: Traffic Engineering based on SR Prefix-SID Loopback0 Label 16007 16007 CE2 PE2

Default: PHP at each segment 14 Lets take a closer look 15 Source Routing the source chooses a path and encodes it in the packet header as an ordered list of segments the rest of the network executes the encoded instructions (In Stack of labels/IPv6 EH) Segment: an identifier for any type of instruction forwarding or service Forwarding state (segment) is established by IGP LDP and RSVP-TE are not required Agnostic to forwarding data plane: IPv6 or MPLS MPLS Data plane is leveraged without any modification push, swap and pop: all that we need segment = label 16 Segment Routing Overview MPLS: an ordered list of segments is represented as a stack of labels Control Plane Routing protocols with extensions

(IS-IS,OSPF, BGP) IPv6: an ordered list of segments is encoded in a routing extension header This presentation: MPLS data plane Segment Label Basic building blocks distributed by the IGP or BGP SDN controller Data Plane MPLS (segment ID = label) IPv6 (segment ID = V6 address) Paths options Dynamic (SPT computation) Explicit (expressed in the packet) Strict or loose path 17 Global and Local Segments Global Segment Any node in SR domain understands associated instruction Each node in SR domain installs the associated instruction in its

forwarding table MPLS: global label value in Segment Routing Global Block (SRGB) Local Segment Only originating node understands associated instruction MPLS: locally allocated label 18 Global Segments Global Label Indexes Global Segments always distributed as a label range (SRGB) + Index Index must be unique in Segment Routing Domain Best practice: same SRGB on all nodes Global model, requested by all operators Global Segments are global label values, simplifying network operations Default SRGB: 16,000 23,999 Other vendors also use this label range 19 Types of Segment 20 IGP Segment Two Basic building blocks distributed by IGP: -Prefix Segment -Adjacency Segment Prefix-SID (Node-SID)

Segment Segment 1 1 Segment 1 1 Segment Segment 2 2 Segment Segment 3 3 Segment 1 1 Segment Segment

4 4 Adjacency-SID Segment Segment 21 IGP Prefix Segment Node-SID 1 1 5 5 16006 16006 16006 Shortest-path to the IGP prefix Equal Cost Multipath (ECMP)aware 16006 2 2 6 6

Distributed by ISIS/OSPF 16006 1.1.1.6/32 Global Segment Label = 16000 + Index Advertised as index 16005 1 1 5 5 1.1.1.5/32 16005 16005 Default SRGB 16000-23,999 7 7 16005 2 2 7 7

16005 6 6 22 Node Segment FEC Z swap 16065swap 16065 push 16065 to 16065 to 16065 A A B B C C pop 16065 D D E E 16065 A packet injected anywhere with top label 16065 will reach E via shortestpath

E advertises its node segment Simple ISIS/OSPF sub-TLV extension All remote nodes install the node segment to E in the MPLS Data Plane 23 Node Segment FEC Z swap 16065swap 16065 push 16065 to 16065 to 16065 A A Packet to E C C B B pop 16065 D D 16065 16065

16065 E E Packet to E Packet to E Packet to E Packet to E 16065 A packet injected anywhere with top label 16065 will reach E via shortestpath E advertises its node segment simple ISIS sub-TLV extension and OSPF All remote nodes install the node segment to E in the MPLS dataplane 24 Adjacency Segment Adj to 7

1 1 5 5 Adj to 6 7 7 24056 2 2 24057 6 6 A packet injected at node 5 with label 24056 is forced through datalink 5-6 C allocates a local label and forward on the IGP adjacency C advertises the adjacency label Distributed by OSPF/ISIS simple sub-TLV extension (https://datatracker.ietf.org/doc/draft-ietf-isis-segment-routing-extensions/) https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-codepoints.xhtml C is the only node to install the adjacency segment in MPLS dataplane

25 Datalink and Bundle Pop 9003 9001 switches on blue member Pop 9001 A A B B Pop 9002 Pop 9003 9002 switches on green member 9003 load-balances on any member of the adj Adjacency segment represents a specific datalink to an adjacent node Adjacency segment represents a set of datalinks to the adjacent node 26 A path with Adjacency Segments 9105 9107 9107 9101

9103 9103 9105 9105 9105 9107 9103 9101 1 1 9105 3 3 5 5 9105 9107 7 7 2 2

7 7 4 4 9103 Source routing along any explicit path stack of adjacency labels SR provides for entire path control 9103 6 6 9105 9105 9105 27 Combining Segments Prefix-SID Adj-SID Steer traffic on any path through the network Path is specified by list of segments in packet header, a stack of labels No path is signaled

No per-flow state is created For IGP single protocol, for BGP AF LS 16007 16007 24078 24078 24078 16011 16011 16011 Packet to Z Packet to Z Packet to Z 16007 1 1 16007 5 5 9 9

7 24078 3 3 6 6 8 8 11 10 16011 16011 16011 Packet to Z 16011 Packet to Z Packet to Z 28 Labeling Which prefixes? GE 0/0/0/0 P1 P2

P3 Prefix attached to P4 10.20.34.0/24 P4 Outgoing label in CEF? Entry in LFIB? Prefix-SID P4 (10.100.1.4/32) Y Prefix-SID P4 without Node flag (10.100.3.4/32) Y loopback prefix without prefix-sid (10.100.4.4/32) N link prefix connected to P4 (10.1.45.0/24) N So, this is the equivalent of LDP label prefix filtering: only assigning/advertising labels to /32 prefixes (loopback prefixes, used by service, (e.g. L3VPN), so BGP next hop IP addresses) Traffic to link prefixes is not labeled! 29

Data Data 7 7 Data Data R1 SID: 1 46 46 Explicit loose path for low latency app 4 4 7 7 Dynamic path R5 SID: 5 R3 SID: 3 Explicit path R7 SID: 7 High cost

Low latency R2 SID: 2 R4 SID: 4 Adj SID: 46 R6 SID: 6 SID: Segment ID No LDP, no RSVP-TE 30 Any-Cast SID for Node Redundancy A group of Nodes share the same SID Work as a Single router, single Label Same Prefix advertised by multiple nodes traffic forwarded to one of AnycastPrefix-SID based on best IGP Path if primary node fails,traffic is auto rerouted to other node 200 70 Packet 10 Application ABR Protection Seamless MPLS

ASBR inter-AS protection 200 70 70 Packet Packet Anycast SID: 200 Packet 200 70 Packet 30 40 70 90 20 50 60 80

31 Binding-SID BSID: BSID: 30410 30410 1 2 3 410 SID: SID: 30710 30710 5 4 16003 14 All Nodes SRGB [16000-23999] Prefix-SID NodeX: 1600X Binding-SID X->Y: 300XY 6

7 9 8 10 16006 16004 16004 30410 30410 Node 10 Node 10 16007 16007 16009 30410 30710 30710

30710 16010 16010 Node 10 Node 10 Node 10 Node 10 Node 10 Node 10 Node 10 Binding-SIDs can be used in the following cases: Multi-Domain (inter-domain, inter-autonomous system) Large-Scale within a single domain Label stack compression BGP SR-TE Dynamic Stitching SR-TE Polices Using Binding SID

32 BGP Prefix Segment Shortest-Path to the BGP Prefix Global 16000 + Index Node SID: 16001 12 10 Signaled by BGP 1 13 3 11 14 BGP-Connections 33 BGP Peering Segment Egress Peering Engineering 16001 30012 BGP-Peering-SID 18005 30012

Packet 18005 Packet 12 10 18005 Packet BGP-Peering-SID SID: 30012 Node SID: 16001 1 Packet 2 13 5 3 11 7 5.5.5.5/32 Node SID: 18005

14 AS1 Pop and Forward to the BGP Peer Local Signaled by BGP-LS (Topology Information) to the controller Local Segment- Like an adjacency SID external to the IGP Dynamically allocated but persistent AS2 34 WAN Controller SR PCE Collects via BGP-LS IGP Segments BGP Segments Topology SR PCE BGP-LS Collects information from network BGP-LS 12

10 1 2 13 5 3 7 5.5.5.5/32 Node SID: 18005 11 14 IGP-1 IGP-2 35 An end-to-end path as a list of segment Controller learn the SR SR PCE PCE PCEP,Netconf, BGP

network topology and usage dynamically Controller calculate the optimized path for different applications: low latency, or high bandwidth Controller just program a list of the labels on the source routers. The rest of the network is not aware: no signaling, no state information simple and Scalable 12 {16001, 16002, 124, 147} 10 Node SID: 16001 1 13 {16002, 124,

147} Node SID: 16002 Adj SID: 124 4 2 50 Low latency {147} Low bandwidth {124, 147} Peering SID: 147 7 3 11 5 High latency High bandwidth 14 IGP-1

IGP-2 BGP-Peer Default ISIS cost metric: 10 36 37 MENOG 18 Segment Routing Segment Routing Global Block 38 Segment Routing Global Block (SRGB) Segment Routing Global Block Range of labels reserved for Segment Routing Global Segments Default SRGB is 16,000 23,999 A prefix-SID is advertised as a domain-wide unique index The Prefix-SID index points to a unique label within the SRGB Index is zero based, i.e. first index = 0 Label = Prefix-SID index + SRGB base

E.g. Prefix 1.1.1.65/32 with prefix-SID index 65 gets label 16065 index 65 --> SID is 16000 + 65 =16065 Multiple IGP instances can use the same SRGB or use different non-overlapping SRGBs 39 1 2 3 4 Recommended Recommended SRGB SRGB allocation: allocation: Same Same SRGB SRGB for for all all 16000 16004 16000 Idx 4 16004 23999

23999 24000 24000 16000 Idx 4 Same Same SRGB SRGB for for all: all: Simple Simple Predictable Predictable 23999 easier easier to to troubleshoot troubleshoot 24000 simplifies Programming simplifies SDN SDN Programming 24004 Idx 4 31999 SRGB

16000-2399 1048575 SRGB 16000-2399 1048575 SRGB 1048575 24000-31999 40 MENOG 18 Segment Routing IGP Control and Date Plane 41 MPLS Control and Forwarding Operation with Segment Routing Services PE-1 MP-BGP PE-2 IPv4 VPN IPv4 IPv6

LDP RSVP BGP IPv6 VPN VPWS VPLS Packet Transport Static IS-IS IGP PE-1 PE-2 MPLS Forwarding OSPF No changes to control or forwarding plane IGP label distribution for IPv4 and IPv6. Forwarding plane remains the same 42

SR IS-IS Control Plane overview IPv4 and IPv6 control plane Level 1, level 2 and multi-level routing Prefix Segment ID (Prefix-SID) for host prefixes on loopback interfaces Adjacency SIDs for adjacencies Prefix-to-SID mapping advertisements (mapping server) MPLS penultimate hop popping (PHP) and explicit-null label signaling 43 ISIS TLV Extensions SR for IS-IS introduces support for the following (sub-)TLVs: SR Capability sub-TLV (2) IS-IS Router Capability TLV (242) Prefix-SID sub-TLV (3) Extended IP reachability TLV (135) Prefix-SID sub-TLV (3) IPv6 IP reachability TLV (236) Prefix-SID sub-TLV (3) Multitopology IPv6 IP reachability TLV (237) Prefix-SID sub-TLV (3) SID/Label Binding TLV (149) Adjacency-SID sub-TLV (31) Extended IS Reachability TLV (22) LAN-Adjacency-SID sub-TLV (32) Extended IS Reachability TLV (22) Adjacency-SID sub-TLV (31) Multitopology IS Reachability TLV (222) LAN-Adjacency-SID sub-TLV (32) Multitopology IS Reachability TLV (222) SID/Label Binding TLV (149) Implementation based on draft-ietf-isis-segment-routing-extensions

44 SR OSPF Control Plane overview SR OSPF Control Plane Overview OSPFv2 control plane Multi-area IPv4 Prefix Segment ID (Prefix-SID) for host prefixes on loopback interfaces Adjacency SIDs for adjacencies MPLS penultimate hop popping (PHP) and explicit-null label signaling 45 OSPF Extensions OSPF adds to the Router Information Opaque LSA (type 4): SR-Algorithm TLV (8) SID/Label Range TLV (9) OSPF defines new Opaque LSAs to advertise the SIDs OSPFv2 Extended Prefix Opaque LSA (type 7) >OSPFv2 Extended Prefix TLV (1) Prefix SID Sub-TLV (2) OSPFv2 Extended Link Opaque LSA (type 8) >OSPFv2 Extended Link TLV (1) Adj-SID Sub-TLV (2) LAN Adj-SID Sub-TLV (3) Implementation is based on draft-ietf-ospf-prefix-link-attr and draft-ietf-ospf-segment-routingextensions 46 TLV 22 TLV 135 47

TLV 242 48 TLV 135 Sub-TLV 3 Prefix-SID SID-Index 16 49 TLV 22 Sub-TLV 32 LAN-Adj-SID LAN-Adj-SID 24001 50 MENOG 18 Use Cases 51 Unified MPLS Provisioning

EPN 5.0 Metro Fabric Netconf Yang Netconf Yang PCE Programmability L2/L3VPN Services Intra-Domain CP FRR or TE Intra-Domain CP LDP BGP BGP-LU LDP BGP BGP-LU RSVP LDP

BGP IGP IGP With With SR SR IGP IGP With With SR SR IGP Do More With Less 52 IPv4/v6 VPN/Service transport 5 5 7 7 VPN VPN Packet to Z Packet to Z

5 7 VPN Packet to Z Site-1 VPN 3 2 PE-1 VPN Packet to Z 5 4 5 IGP only No LDP, No RSVP-TEVPN Packet to Z ECMP multi-hop shortest-path 6 Site-2

VPN 7 7 5 7 PE-7 PHP 5 Packet to Z 7 7 VPN VPN Packet to Z Packet to Z 53 MENOG 18 Internetworking With LDP 54

Simplest Migration: LDP to SR Initial state: All nodes run LDP, not SR Step1: All nodes are upgraded to SR in no particular order Default label imposition preference = LDP Leave defaultsegment-routing LDP label imposition sr-prefer segment-routing mpls mpls sr-prefer preference LDP SR LDP+SR 3 LDP SR LDP+SR 4 LDP SR LDP+SR 1 Step2: All PEs are configured to prefer SR Label imposition in no particular order Step3: LDP is removed from the nodes in the network in no particular order Final State: All nodes run SR,Not LDP

SR LDP+SR LDP SR LDP 5 2 6 SR LDP LDP+SR LDP SR LDP+SR LDP Domain 55 1 2 4 3 5 segment-routing

segment-routing mpls mpls sr-prefer sr-prefer SRGB Local/in lblOut lbl 16000 16005 Local/in lblOut lbl 16000 16005 16005 23999 23999 24000 24000 24001 24002 Local/in lblOut lbl 16000 16000

24005 16005 pop 23999 23999 32011 24000 24000 24001 24003 24005 segment-routing segment-routing mpls mpls (defualt) (defualt) Local/in lblOut lbl pop 16005 31999 56 LDP/SR Interworking - LDP to SR

When a node is LDP capable but its next-hop along the SPT to the destination is not LDP capable no LDP outgoing label In this case, the LDP LSP is connected to the prefix segment C installs the following LDP-to-SR FIB entry: incoming label: label bound by LDP for FEC Z outgoing label: prefix segment bound to Z outgoing interface: D SR LDP This entry is derived and installed automatically , no config required A B Prefix Z C Out Label (LDP), Interface Input label(LDP) 16, 0

32 D Z Out Label (SID), Interface 16006, 1 57 1.1.1.5/32 lbl 90100 1 1.1.1.5/32 90007 2 4 3 LDP 1.1.1.5/32 5 SR

SID 16005 Local/in lblOut lbl 24000 90100 90008 Local/in lblOut lbl 24000 Local/in lblOut lbl 16000 90007 90100 16005 31999 LDP LDP LSP LSP Copy SGB Local/in lblOut lbl 16005 16005

???? 90007 16005 pop 23999 24000 58 LDP/SR Interworking - SR to LDP When a node is SR capable but its next-hop along the SPT to the destination is not SR capable no SR outgoing label available In this case, the prefix segment is connected to the LDP LSP Any node on the SR/LDP border installs SR-to-LDP FIB entry(ies) SR A Prefix Z B Out Label (SID), Interface ?, 0 LDP

C D Input Label(SID) Out Label (LDP), Interface ? 16, 1 Z 16006 59 LDP/SR Interworking - Mapping Server A wants to send traffic to Z, but Z is not SR-capable, Z does not advertise any prefixSID which label does A have to use? The Mapping Server advertises the SID mappings for the non-SR routers for example, it advertises that Z is 16066 A and B install a normal SR prefix segment for 16066 C realizes that its next hop along the SPT to Z is not SR capable hence C installs an SR-to-LDP FIB entry incoming label: prefix-SID bound to Z (16066) outgoing label: LDP binding from D for FEC Z

A sends a frame to Z with a single label: 16006 A Prefix Z SR LDP Z(16006) B Out Label (SID), Interface 16006, 0 C D Input Label(SID) Out Label (LDP), Interface 16006 16, 1

Z 60 Mapping-Server 1.1.1.5/32 lbl 90090 2 1 1.1.1.5/32 Imp-null 5 4 3 SR LDP 1.1.1.5 Local/in lblOut lbl 16000 Local/in lblOut lbl 16000 Local/in lblOut lbl

16000 23999 16005 16005 23999 pop 16005 ? 90090 pop 90090 pop Cop Cop yy NA 90090 16005 Local/in lblOut lbl

23999 61 90002 90090 MENOG 18 Traffic Protection 62 Classic Per-Prefix LFA disadvantages Classic LFA has disadvantages: Incomplete coverage, topology dependent Not always providing most optimal backup path Topology Independent LFA (TI-LFA) solves these issues 63 Classic LFA Rules 64 Classic LFA has partial coverage Classic LFA is topology dependent: not all topologies provide LFA for all destinations Depends on network topology and metrics E.g. Node6 is not an LFA for Dest1 1 (Node5) on Node2, packets would loop since Node6

uses Node2 to reach Dest1 (Node5) Node2 does not have an LFA for this destination (no backup path in topology) Topology Independent LFA (TI-LFA) provides 100% coverage Dest-1 5 2 6 X 20 3 7 5 Dest-2 Default Metric : 10 Initial Classic LFA FRR TI-LFA FRR Post-Convergence 65 Classic LFA and suboptimal path Classic LFA may provide a suboptimal FRR

backup path: This backup path may not be planned for capacity, e.g. P node 2 would use PE4 to protect a core link, while a common planning rule is to avoid using 1 Edge nodes for transit traffic Additional case specific LFA configuration would be needed to avoid selecting undesired backup paths Operator would prefer to use the postconvergence path as FRR backup path, aligned with the regular IGP convergence TI-LFA uses the post-convergence path as FRR backup path PE-4 Dest-1 100 100 2 6 X 5

3 7 5 Dest-2 Default Metric : 10 Initial Classic LFA FRR TI-LFA FRR 66 Post-Convergence TI-LFA Zero-Segment Example TI-LFA for link R1R2 on R1 Prefix-SID Z Calculate LFA(s) Packet to Z - Compute post-convergence SPT - Encode post-convergence path in a SID-list P-Space - In this example R1 forwards Prefix-SID Z the packets towards R5 A Z 1 2

1000 Packet to Z 5 Packet to Z 4 3 Q-Space Default metric: 10 67 TI-LFA Single-Segment Example TI-LFA for link R1R2 on R1 Prefix-SID Z - Compute post-convergence SPTPacket to Z - Encode post-convergence path in a SID-list - In this example R1 imposes the SID-list and Prefix-SID (R4) Prefix-SID Z sends packets towards R5 A Z 1 2

Packet to Z P-Space Prefix-SID Z 5 Packet to Z Packet to Z 4 3 Q-Space Default metric: 10 68 TI-LFA Double-Segment Example Prefix-SID Z Packet to Z TI-LFA for link R1R2 on R1 - Compute post-convergence SPT - Encode post-convergence path in a SID-list Prefix-SID (R4) Adj-SID (R4-R3) Prefix-SID Z A Z

1 2 Packet to Z P-Space Prefix-SID Z 5 Packet to Z Packet to Z - In this example R1 imposes the SIDlist and sends packets towards R5 4 Adj-SID (R4-R3) Prefix-SID Z 3 1000 Q-Space Default metric: 10 Packet to Z 69

TI-LFA for LDP Traffic LDP (1,Z) Packet to Z A Z 1 2 Packet to Z LDP (5,4) Adj-SID (R4-R3) Prefix-SID Z P-Space Prefix-SID Z 5 Packet to Z Packet to Z 4 Adj-SID (R4-R3) Prefix-SID Z 3

1000 Q-Space Default metric: 10 Packet to Z 70 MENOG 18 Traffic Engineering 71 RSVP-TE Little deployment and many issues Not scalable Core states in kn2 No inter-domain Complex configuration Tunnel interfaces Complex steering PBR, autoroute Does not support ECMP 72 SRTE Simple, Automated and Scalable No core state: 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

SDN Controller for compute Binding-SID (BSID) for scale Lots of Functionality Designed with lead operators along their use-cases Provides explicit routing Supports constraint-based routing Supports centralized admission control No RSVP-TE to establish LSPs Uses existing ISIS / OSPF extensions to advertise link attributes Supports ECMP Disjoint Path 73 RR SR PCE 1.1.1.10 BGP BGP-LS 1.1.1.3 PCEP 16003 PCC 3 PCEP 1.1.1.2 11 10

1.1.1.5 16005 5 BGP 1.1.1.7 16007PCC VRF Blue 7 PCEP T:30 BGP 1.1.1.22 PCC 16022 22 BGP PCEP 1.1.1.21 Domain-2 14 ISI-S/SR Domain-1 13 ISI-S/SR

2 1.1.1.11 1.1.1.9 16009 9 Router-id of NodeX: 1.1.1.X Domain-1 Prefix-SID index of NodeX: X ISI-S/SR Link address XY: 99.X.Y.X/24 with X < Y Adj-SID XY: 240XY 21 1.1.1.23 PCC 16023 T:30 23 VRF Blue Default IGP Metric: I:10 Domain-2 Default TE Metric: T:10 TE Metric used to express latency ISI-S/SR

74 MAP: MAP: PCreq/reply Community (100:777) means MAP 1.1.1.21/32 in vrf BLUE must receive Community (100:777) meansTE Metric MAP:: to 1.1.1.21/32 COMPUTE: minimize Node22 in vrf BLUE must receive minimize TE Metric and low latency SR TE Metric and minimize low latency service service tag tag with with

compute at PCE community (100:777) RR compute at PCE community RESULT : SID list: OIF: to3 (100:777) PCE VPN Label : 99999 VPN Label : 99999 11 10 BGP: 1.1.1.21/32 via 21 BSID: 30022 5 3

2 13 VRF Blue 7 T:30 22 21 14 9 T:30 23 VRF Blue Automated Automated Steering Steering uses uses color color extended extended communities communities and and nexthop nexthop to

to match match with with the the color color and and end-point end-point of of an an SR SR Policy Policy E.g. BGP route 2/8 E.g. BGP route 2/8 with with nexthop nexthop 1.1.1.1 1.1.1.1 and and color color 100 100 will be steered into an SR Policy with color 100 and

will be steered into an SR Policy with color 100 and end-point end-point 1.1.1.1 1.1.1.1 If no such SR Policy exists, it can be instantiated automatically If no such SR Policy exists, it can be instantiated automatically (ODN) (ODN) 75 MENOG 18 SRv6 76 SRv6 for underlay SRv6 RSVPfor forUnderlay FRR/TE Horrendous states in k*N^2

Simplification, FRR,scaling TE, SDN IPv6 for reach 77 Opportunity for further simplification NSH for NFV UDP+VxLAN Overlay SRv6 for Underlay Additional Protocol and State Additional Protocol just for tenant ID Simplification, FRR, TE, SDN IPv6 for reach Multiplicity of protocols and states hinder network economics 78 IPV6 Header Next Header (NH) Indicate what comes next 79 NH=IPv6 NH=IPv4 80

NH=Routing Extension Generic routing extension header Defined in RFC 2460 Next Header: UDP, TCP, IPv6 Hdr Ext Len: Any IPv6 device can skip this header Segments Left: Ignore extension header if equal to 0 Routing Type field: > 0 Source Route (deprecated since 2007) > 1 Nimrod (deprecated since 2009) > 2 Mobility (RFC 6275) > 3 RPL Source Route (RFC 6554) > 4 Segment Routing 81 NH=SRv6 NH=43,Type=4 82 NH=43 Routing Extension RT = 4 Segment-List 83

MENOG 18 SRH Processing 84 Source Node 1 A1:: Segment List [ ] is the LAST segment Segment List [ ] is the FIRST segment Segments Left is set to First Segment is set to IP DA is set to the first segment Packet is send according to the IP DA Normal IPv6 forwarding SA = A1::, DA = A2:: SR Hdr ( A4::, A3::, A2:: ) SL=2 3 A3:: 4 A4:: Payload

IPv6 Hdr Segment list in reversed order of the path IPv6 Hdr SR Hdr Source node is SR-capable SR Header (SRH) is created with 2 A2:: Version Traffic Class Payload Length FlowLabel Label Flow Next = 43 Hop Limit Source Address = A1:: Destination Address = A2:: Next Header Len= 6 First = 2

Flags Type = 4 SL = 2 TAG Segment List [ 0 ] = A4:: Segment List [ 1 ] = A3:: Segment List [ 2 ] = A2:: Payload 85 Non-SR Transit Node 1 A1:: Plain IPv6 forwarding Solely based on IPv6 DA No SRH inspection or update IPv6 Hdr SA = A1::, DA = A2:: SR Hdr ( A4::, A3::, A2:: ) SL=2 2 A2::

3 A3:: 4 A4:: Payload 86 SR Segment Endpoints SR Endpoints: SR-capable nodes whose address is in the IP DA SR Endpoints inspect the SRH and do: A A1:: 2 A2:: IPv6 Hdr 3 A3:: 4 A4:: SA = A1::, DA = A3:: SR Hdr ( A4::, A3::, A2:: ) SL=1 Payload

SR Hdr Decrement Segments Left ( -1 ) Update DA with Segment List [ Segments Left ] Forward according to the new IP DA IPv6 Hdr IF Segments Left > 0, THEN Version Traffic Class Payload Length FlowLabel Label Flow Next = 43 Hop Limit Source Address = A1:: Destination Address = A3:: Next Header Len= 6 First = 2 Flags

Type = 4 SL = 1 TAG Segment List [ 0 ] = A4:: Segment List [ 1 ] = A3:: Segment List [ 2 ] = A2:: Payload 87 SR Segment Endpoints SR Endpoints: SR-capable nodes whose address is in the IP DA SR Endpoints inspect the SRH and do: 1 A1:: 2 A2:: 3 A3:: IPv6 Hdr 4 A4:: SA = A1::, DA = A4:: SR Hdr ( A4::, A3::, A2:: ) SL=0 Payload

ELSE (Segments Left = 0) Remove the IP and SR header Process the payload: Inner IP: Lookup DA and forward Standard IPv6 processing TCP / UDP: Send to socket The final destination does not have to be SR-capable. SR Hdr Decrement Segments Left ( -1 ) Update DA with Segment List [ Segments Left ] Forward according to the new IP DA IPv6 Hdr IF Segments Left > 0, THEN Version Traffic Class Payload Length FlowLabel Label Flow Next = 43 Hop Limit

Source Address = A1:: Destination Address = A4:: Next Header Len= 6 First = 2 Flags Type = 4 SL = 0 TAG Segment List [ 0 ] = A4:: Segment List [ 1 ] = A3:: Segment List [ 2 ] = A2:: Payload 88 Deployments around the world Bell in Canada Orange Microsoft SoftBank Alibaba Vodafone Comcast China Unicom 89

Deployments in IRAN IRAN TIC new Network is going to be implemented based on SR 90

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