Introduction to Segment Routing Ismail Ali Technical Consultant (Cisco Systems (M) Sdn Bhd)

1. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 1Cisco Confidential 1© 2013 Cisco and/or its affiliates. All rights reserved.
Ismail Ali
Technical Consultant, Cisco Systems Malaysia

2. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2
• Introduction
• Incremental Deployment Use Cases
• Standardization
• Conclusion

3. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3

4. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4
• Source Routing: source chooses a path and encodes it in packet header as an
ordered list of segments.
• Segment: an identifier for any type of instruction
Service
Context
Locator
IGP-­based forwarding construct
BGP-­based forwarding construct
Local value or Global Index
Segment = Instructions such as
"go to node N using the shortest path"

5. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5
• MPLS: an ordered list of segments is
represented as a stack of labels
SR re-­uses MPLS data plane without any
change
• IPv6: an ordered list of segments is
represented as a routing extension
header
This presentation focuses on
MPLS data plane
IPv6 IPv6
IPv6
Control
Plane
IPv4
MPLS
Data
Plane

6. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6
• Locally significant to node allocating it
• Node processes SID and switches packet
towards adjacency
• Advertised as an absolute value
• Globally significant within SR domain
• All nodes switch packet towards prefix/node
via shortest path
• Advertised as a relative (index) value
• Make use of a per-­node reserved block (SR
Global Block or SRGB)
B C
N O
Z
D
P
A
9101
9105
9107
9103
9105
B C
N O
Z
D
P
A
65
65
65 65
Prefix/Node SID Adjacency SID

7. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7
D
(php)
7
A B
C D
E
103
103
Payload Payload
201
202
Payload
202
201
202
Payload
202
Payload Payload
C D
A B
E
202
202
201
102
202
Payload
A B
102
C D
E
202
Payload
202
Payload
C E C D EB C D
(php)
EB
Node Path Adjacency Path Combined Path

8. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8
• Efficient packet networks leverage ecmp-­aware
shortest-­path!
node segment!
• Simplicity
one less protocol to operate
No complex LDP/ISIS synchronization to troubleshoot
8
A B
M N
PE2PE1
All VPN services ride on the node segment
to PE2

9. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9

10. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10
• Tokyo to Brussels
data: via US: cheap capacity
VoIP: via Russia: low latency
• CoS-­based TE with SR
IGP metric set such as
Tokyo to Russia: via Russia
Tokyo to Brussels: via US
Russia to Brussels: via Europe
Anycast segment “Russia” advertised by Russia core routers
• Tokyo CoS-­based policy
Data and Brussels: push the node segment to Brussels
VoIP and Brussels: push the anycast node to Russia, push Brussels
10
Node segment to Brussels
Node segment to Russia

11. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11
• For Traffic Engineering
• or for OAM
11
B C
N O
Z
D
P
A
9101
9105
9107
9103
9105
9101
9101
9105
9107
9103
9105
9101

12. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12
12
Path ABCOPZ is ok. I account the BW.
Then I steer the traffic on this path
FULL
66
65
68
Tunnel AZ onto
{66, 68, 65}
The network is simple, highly programmable and responsive to rapid changes
2G from A to Z please

13. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13
Definition
Applications express
requirements –
bandwidth, latency,
SLAs
SDN controllers are capable of
collecting data from the network
– topology, link states, link
utilization, …
Applications are mapped to a path
defined by a list of segments
The network only maintains segments
No application state
Segment
Routing
SDN
Controller
Applications
1
2
3

14. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14
• Applications program
the network on a per-­
flow basis
• End-­to-­End policy
DC, WAN, AGG, PEER
• Millions of flows
No per-­flow midpoint state
No reclassification at
boundaries
• Simple
BGP and ISIS/OSPF
DC (or AGG)
10
11
12
13
14
2 4
6 5
7
Default ISIS cost metric: 10
Default Latency metric: 10
50
WAN
3
1
PEER
Low Lat, Low BW
High-BW to 7
for application …
Push
{16001,
16005}
High Lat, High BW

15. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 15
• Automated 50msec FRR
DC (or AGG)
10
11
12
13
14
2 4
6 5
7
Default ISIS cost metric: 10
Default Latency metric: 10
50
WAN
3
1
PEER
Low Lat, Low BW
High-BW to 7
for application …
Push
{16001,
16005}
High Lat, High BW

16. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16
• Any policy can be
programmed by the
application
• The network scaling and
simplicity is preserved
DC (or AGG)
10
11
12
13
14
2 4
6 5
7
Default ISIS cost metric: 10
Default Latency metric: 10
50
WAN
8
8
PEER
Low Lat, Low BW
High-BW to 7
Load-share across DC edges
for application …
Push
{16008,
16005}
High Lat, High BW

17. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17
• Any policy can be
programmed by the
application
• The network scaling and
simplicity is preserved
DC (or AGG)
10
11
12
13
14
2 4
6 5
7
Default ISIS cost metric: 10
Default Latency metric: 10
50
WAN
3
1
PEER
Low Lat, Low BW
Low-Latency to 7,
DC Plane 0 only
for application …
Push
{16010,
16001,
200,
147}
High Lat, High BW

18. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 18
• Any policy can be
programmed by the
application
• The network scaling and
simplicity is preserved
DC (or AGG)
10
11
12
13
14
2 4
6 5
7
Default ISIS cost metric: 10
Default Latency metric: 10
50
WAN
3
1
PEER
Low Lat, Low BW
High-BW to 7,
1st VNF at 14
2nd
VNF at 6
for application …
Push
{16014,
301,
16003,
16006,
302,
16005}
High Lat, High BW

19. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 19
Adding value at your own pace
Enable Segment Routing on the network (Software only)
Insert Orchestration, SDN controller
Connect with Cisco’s
and third party VNFs
Network Simplification
Network Resiliency
End-­User Experience
Network Optimization
Service Velocity
E2E Application Control
Benefits

20. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 20Cisco Confidential 20© 2013 Cisco and/or its affiliates. All rights reserved.

21. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 21
• Control plane scale and complexity
• Many protocols
• Many encapsulations
• Many bugs
• Forwarding plane capacity
• Lots of growth == lots of stress

22. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 22
• Peering -­-­-­ want programmatic control over policy
• Massively Scaled Datacenters (even more protocols,
high device and link counts, commodity hardware,
greater vendor diversity, legacy applications)
• Inter-­DC vs External workloads
Latency-­sensitive vs bulk
Scheduled vs unscheduled

23. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 23
• Reduced complexity
Protocol counts
Fewer protocols == less code == fewer bugs
Amount of distributed control plane state
Unified forwarding plane (analog of BGP is the Better IGP )
• Maintain healthy vendor diversity
• Want to (eventually and incrementally) enable software control
Leverage our in-­house software (and networking) expertise
Re-­use ongoing controller and TE work
Don’t want another new parallel network

24. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 24
• Well-­understood forwarding plane (MPLS)
• Encourages sensible engineering tradeoffs
• Possibility of removing some distributed signaling protocols
• Removes per-­tunnel state from the core
• Gets us closer to a static core, significantly quieter control plane
• Good interop with existing protocols
Safe incremental deployment
• SDN with standards-­based interfaces
Segments are defined at a useful level of abstraction for composition
Anycast is also useful

25. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 25
• Autopilot for orchestration
• SWAN for TE
• BGP-­LS for topology and SR label discovery
• BGP-­LU for creating tunnels
Widely supported, so we can impose on the non-­SR edge
Single label (but can hack w/Route Resolution)
Label stacks would be nicer
Can scale with indirection and vanilla BGP
Non-­standard use of RFC 3107, maybe we can do better
• BGP prefix SID’s for the MSDC
• EPE scenario for peering
BMP for route collection

26. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 26
• Built out a full emulation of core network using VM’s running early
vendor(s) code
Fantastic tool, please more fidelity.
• Modeled the entire control plane w/MPLS forwarding
Obviously slower in the forwarding plane
• Very basic controller driving BGP-­LU via REST

27. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 27
• Investigated several use cases:
Basic forwarding over an SR routed network
Traffic steering
EPE
Vendor interop
Server-­to-­server
• Found a few bugs and interop issues
Mostly design/use cases.
• Management is on the thin side
Still awkward to see some SR state
Not quite fully integrated

28. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 28

29. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 29
• IETF standardization in SPRING working
group
• Protocol extensions progressing in multiple
groups
IS-­IS
OSPF
PCE
IDR
6MAN
• Broad vendor and customer support
Sample IETF Documents
Segment Routing Architecture
(draft-­ietf-­spring-­segment-­routing)
Problem Statement and Requirements
(draft-­ietf-­spring-­problem-­statement)
IPv6 SPRING Use Cases
(draft-­ietf-­spring-­ipv6-­use-­cases)
Segment Routing Use Cases
(draft-­filsfils-­spring-­segment-­routing-­use-­cases)
Topology Independent Fast Reroute using Segment Routing
(draft-­francois-­spring-­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)
Close to 30 IETF drafts in progress

30. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 30
• Strong commitment for standardization and
multi-­vendor support
• SPRING Working-­Group
• All key documents are WG-­status
• Over 25 drafts maintained by SR team
Over 50% are WG status
Over 75% have a Cisco implementation
• Several interop reports are available
www.segment-routing.net
tools.ietf.org/wg/spring/

31. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 31
• Fundamental to the velocity and success
• Over 30 operators involved
• Technology tailored to solve real
requirements
Tactical: solve long-­reported issues
Strategic: key architecture for long-­term evolution

32. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 32
• Platforms: ASR9000, CRS-­1/CRS-­3, WAE (shipping)
• IS-­IS IPv4 (shipping)
Node/Adjacency SID advertisement
LDP interworking (mapping server/client)
Traffic protection (topology independent LFA link protection)
• OSPFv2 (shipping)
Node SID advertisement
Traffic protection (LFA)
• Upcoming
IS-­IS / OSPFv2 parity
SR Traffic Engineering (manual provisioning and PCEP)
OAM (Ping/Trace)

33. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 33

34. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 34
• Simple routing extensions to implement source routing
• Packet path determined by prepended segment identifiers (one or more)
• Data plane agnostic (MPLS, IPv6)
• Network scalability and agility by reducing network state and simplifying control plane
• Traffic protection with 100% coverage with more optimal routing
• Interworking capabilities with LDP-­only devices
34

35. © 2013 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 35
Thank you.
http://tools.ietf.org/wg/spring/
http://www.segment-­routing.net/