Segment Routing
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Transcript of Segment Routing
Segment Routing PONC – 2015, Herndon VA
draft-previdi-filsfils-isis-segment-routing-02
Craig Hill Distinguished SE U.S. Federal CCIE #1628 – [email protected]
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§ Balance of distributed intelligence and centralized optimization and programming § simplify the operation of MPLS (lower opex) § enable application-based service creation (new revenue) § enable scalable/reactive network programmability (SDN) § allow for better utilization of the installed infrastructure (lower capex) § apply to OTT, SP, Large Entreprises across WAN, DC, Access.
Segment Routing
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Segment Routing • Simple to deploy and operate
– Leverage existing MPLS forwarding, HW, and services – straight-forward ISIS/OSPF extension to distribute labels – LDP/RSVP not required – exponentially less state in the routing elements for TE – agnostic control-plane also applicable to IPv6
• Provide for optimum scalability, resiliency and virtualization • Tighter integration with application
– simpler network, highly programmable – highly responsive
The state is no longer in the network but in the packet
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Segment • Nodal segment
– a path (any path definition) to a node – represented by a unique global label within the ISIS domain (operator
configurable)
• Adjacency segment – a hop over an adjacent datalink to a neighbor – represented by a unique local label of the advertising node (system configured)
• Flooded and automatically computed by ISIS – SR subTLV for TLV 22 and 135
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§ Simple extension to let IGP install segments in the MPLS dataplane
§ Excellent Scale: a node installs N+A FIB entries § N node segments and A adjacency segments
IGP Segments
A B C
M N O
Z
D
P
Node segment to C
Node segment to Z
Adj Segment
Node segment to C
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Node Segment
• Z advertises a global node segment 16065 with its loopback – simple ISIS sub-TLV extension > default SRGB [16000, 23999] at all nodes is a request from all lead operators for operational
simplicity. The protocol and implementation allows for different SRGB at every node
• All remote nodes install in their FIB the node segment 16065 to Z
A B C
Z
D
16065
FEC Z push 16065
swap 16065 to 16065
swap 16065 to 16065
pop 16065
A packet injected anywhere with top segment 16065 will
reach Z via shortest-path
Packet to Z
Packet to Z
16065 Packet to
Z
16065 Packet to
Z
16065 Packet to
Z
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Node Segment
• ECMP – A node segment to 16078 distributes traffic across all ECMP paths to O
A B C
M N O
Z
D
P
16078
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Adjacency Segment
• C allocates a local segment 29003 and maps it to the instruction “complete the segment and forward along the interface CO”
• C advertises the adjacency segment in ISIS – simple sub-TLV extension
• C is the only node to install the adjacency segment in FIB
A B C
M N O
Z
D
P
Pop 29003
A packet injected at node C with segment
29003 is forced through datalink CO
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Label advertisement within ISIS
• Simple extension – One single 4-byte Segment sub-TLV
• Nodal segment: sub-TLV attached to leaf TLV – leaf is loopback
• Adjacency segment: sub-TLV attached to adjacency TLV
B C
O
D
C’s linkstate LSP advertises Leaf C/C with global nodal label 67 Adjacency CB with local label 9001 Adjacency CD with local label 9002 Adjacency CP with local label 9003
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Explicit path as Segment List
• ECMP – Node segment
• Per-flow state only at head-end – not at midpoints
• Source Routing – the path state is in the packet
header
A B C
M N O
Z
D
P
16078
Packet to Z 16065 16078
Packet to Z 16065
Packet to Z
Packet to Z 16065
Packet to Z 16065 16078 16072
Packet to Z 16065 16078 16072
16072 16072
16065
16065
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Verifying MPLS Forwarding RP/0/0/CPU0:xrvr-3#show mpls forwarding Local Outgoing Prefix Outgoing Next Hop Bytes Label Label or ID Interface Switched ------ ----------- ------------------ ------------ --------------- ------------ 16001 16001 No ID Gi0/0/0/0 10.0.0.1 0 16002 Exp-Null-v4 No ID Gi0/0/0/0 10.0.0.1 0 16004 Pop No ID Gi0/0/0/1 10.0.0.6 0 16005 16005 No ID Gi0/0/0/1 10.0.0.6 0 16010 16010 No ID Gi0/0/0/0 10.0.0.1 0 16010 No ID Gi0/0/0/1 10.0.0.6 0 24000 Pop No ID Gi0/0/0/0 10.0.0.1 0 24001 Pop No ID Gi0/0/0/1 10.0.0.6 0
Remote prefix-SID
Neighbor prefix-SID PHP on
Remote prefix-SIDs ECMP
R3 R2
R4 R5
Gi0/0/0/0
Gi0/0/0/1
R1
R10 Rn advertises prefix-SID 16000+n
Local Label == Outgoing Label
Neighbor prefix-SID Explicit-Null
Use-Cases and Benefits
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IPv4 MPLS Transport with IP FRR
• IPv4 over MPLS: the obvious way it should have been done – Just the IGP to operate – Sub50msec FRR integrated and automated
• Seamless migration – SR/LDP interworking
A B
M N
PE2 PE1
All VPN services ride on the prefix segment to PE2
Any service resolving on IGP IPv4 Prefix SID
- Internet
- VPNv4 - 6PE - PW
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SDN WAN Orchestration Platform
• Application platform for placing traffic demands and paths across an IP/MPLS WAN
• North-Bound API: Java/REST
• South-Bound (Bi-Directional): BGP-LS (update link-state TO controller), stateful PCEP (programs network elements FROM controller), Netc/YANG
• Intelligent collector, planner, and optimizer engine and can leverage “what if” exercises for load placement
• Multi-vendor enabled & extensible
• Leverages OpenDaylight Infrastructure with “WAN Orchestration” applications (uses REST to controller)
Collector Programming
Application Engine
WAN
Databases
MATE Apps
Client Apps
Cross Domain Orchestration
APIs
IP/MPLS Segment Routing Multi-
Layer
SDN WAN
BGP-LS PCEP
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Centralized Traffic Engineering
2G from A to Z please
Link CD is full, I cannot use the shortest-path 65 straight to Z
16065
FULL
16065
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Centralized Traffic Engineering
Path ABCOPZ is ok. I account the BW. Then I steer the traffic on this path
FULL 16066
16065 16068
• Highly programmable and responsive to rapid changes – perfect support for centralized optimization efficiency, if required
Tunnel AZ onto {66, 68, 65}
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Disjoint TE Service • A to Z any plane
– IGP shortest-path – PrefixSID of Z (65)
• A to Z via blue plane – SRTE policy pushes one additional
segment “Blue Anycast” (111)
• Benefits – ECMP – No hop-by-hop signalling load and delay – No midpoint state
Beta Available
16065 pkt
16065 pkt
16111
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Latency TE Service
• Data from Tokyo to Brussels – IGP shortest-path via US, higher and cheaper capacity – PrefixSID of Brussels
• Voice from Tokyo to Brussels – SRTE policy pushes one additional segment “Russia Anycast” – Low-latency path
• Benefits – ECMP – Availability of the anycast segment against node failure – No hop-by-hop signalling load and delay – No midpoint state
Node segment to Brussels Node segment to Russia
Brussels pkt
Data
Brussels pkt
Russia
Voice
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§ SR flows can be auto-routed over existing RSVP-TE tunnels
SR and RSVP co-existence Service A over SR
FCS in June
SR only
SR and RSVP-TE
RSVP-TE only
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Topology-Independent LFA
• 100%-coverage • 50-msec • Link and Node protection • Automated and Simple to operate and understand • Prevents transient congestion and suboptimal routing – leverages the post-convergence path, planned to carry the traffic
• Incremental deployment – applicable to primary IP, LDP and SR traffic
Beta available
Industry Acceptance & Standardization
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§ Fundamental to the velocity and success
§ Significant commitment § technical transparency § multi-vendor commitment § beta and poc
§ Many more operators now involved
§ Deployments in a few months
Strong Operator Partnership
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IETF
• Working-Group is created • Use-Case is WG status • Architecture is WG status • Protocol Extension is WG status • ~ 25 drafts maintained by SR team Over 50% are WG status Over 75% have a Cisco implementation
www.segment-routing.net
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Segment Routing Header
• Segment Routing introduces a new Routing Header Type: – The Segment Routing Header (SRH) – Contains the list of segments the packet should
traverse – VERY close to what already specified in RFC2460 – Changes are introduced for: > Better flexibility > Addressing security concerns raised by RFC5095
• Two SR-IPv6 drafts: – draft-previdi-6man-segment-routing-header – draft-martin-spring-segment-routing-ipv6-use-cases
S. Previdi, Ed. C. Filsfils Cisco Systems, Inc. B. Field Comcast I. Leung Rogers Communications March 5, 2014
IPv6 Segment Routing Header (SRH)
draft-previdi-6man-segment-routing-header-00
J. Brzozowski J. Leddy Comcast I. Leung Rogers Communications S. Previdi M. Townsley C. Martin C. Filsfils R. Maglione Cisco Systems March 5, 2014
IPv6 Segment Routing Use Cases
draft-martin-spring-segment-routing-ipv6-use-cases-00
Conclusion
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§ Leverage MPLS dataplane and services § Drastically improve MPLS control-plane while enabling new services
§ Simplicity, Scale, Functionality, Centralized Optimization and Programmability
§ Strong operator adoption and tight involvement
§ Innovation and Standardization
§ Aggressive productization by Cisco
§ PoC and Beta code available
Segment Routing
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§ http://www.segment-routing.net/
Stay Informed
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Get involved
• All of these use-cases are either FCS or beta available • Leverage dcloud.cisco.com virtual labs • Get involved and provide ideas and requirements • SR is operator driven • Your help is key
Thank you.