BGP Peering Engineering
Automation challenges and enablers
Cloud & Virtualization GroupCamilo Cardona (camcardo@cisco.com), Paolo Lucente (plucente@cisco.com)
November 2015v5.1

Introduction• Inter-domain traffic includes all traffic crossing the boundary ofnetworks• BGP is used to exchange reachability information among networks• Inter-domain traffic engineering has been historically hard:§ Control traffic to meet objectives§ Estimate the effects of changes• We describe these problems and discuss potential solutions• Main objective being (semi-)automation© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

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FocusNeighboring ASes
Observed backbone
RR

AS2

R2IngressTraffic

R3

R1AS1R4AS3AS5R5AS4© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential3Some high-level use-cases• Design/architectural/business:§ Simulate optimal placement of interconnects§ Simulate impact of interconnect failures• Operational:§ Simulate impact of (BGP policy) changes without disrupting live traffic© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

4Egress / Ingress differences• Egress and ingress traffic are differently managed• Egress traffic:§ Operators have control on the paths they would like to use for their traffic• Ingress traffic:§ Depends on how the other networks decide§ Operators can try to influence the decision of others© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

5Egress traffic• Routers decide the best path using the BGP decision process• Operators change attributes of the paths to reflect their policy• The typical egress TE process consists in tweaking attributes to steer

traffic as desired• Old problem:§ Feamster et al. “Guidelines for interdomain traffic engineering”. CCR. 2003.
§ Nanog presentations (e.g. Wepman, 2004; Roisman, 2009; etc.)• Proposed workflow: collection, simulation, optimization, deployment© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

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EPE Challenges: Collection• Requires the collection of different sources of data:§ BGP paths, traffic, policy• Over time mostly non-standard or mature APIs:§ BGP paths (BGP Add-Path, BMP)
§ Traffic (Netflow/IPFIX, sFlow)§ Policy (Tail-f, Openconfig project)

Collection

Simulation

Optimization

Deployment© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

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EPE Challenges: Simulation• What-if scenarios hard to simulate• BGP decision process is complex:§ RRs add a level of complexity§ Not always deterministic§ Proper network design• Focus on the important prefixes§ Identify importance, ie. by service or by IP prefixes/paths making more traffic§ Prioritize or exclude

Collection

Simulation

Optimization

Deployment© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

8EPE Challenges: Optimization• Not easy to move traffic in a granular way:
§ Changing LP, MED changes everything§ Need to include IGP into account§ iBGP policies are typically not desirable• Complex metrics:§ For example: latency, bit-miles calculations§ No standard way to include in the optimization process

Collection

Simulation

Optimization

Deployment© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

9EPE Challenges: Deployment• Alternatives to deploy:§ Operate changes (ie. policies) at network edges§ Injection of best paths via a BGP controller• Using controllers to operate changes:§ Collection would be similar§ Southbound interface might vary (BGP itself, Openflow, etc.)§ Segment Routing as a solutionCollection

Simulation

Optimization

Deployment© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

10Segment Routing: very quick intro (1/3)• Segment Routing uses Segment IDs to identify links (or services)• MPLS or IPv6 to define the labels• Ingress routers and can use SR to control internal path and externalpath• Filsfils et al. “The Segment Routing Architecture”. Globecomm. 2015.
• For inter-domain traffic, SR allows for granularly steering traffic

without being impacted by IGP or other metrics© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential11Segment Routing: very quick intro (2/3)© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

12Segment Routing: very quick intro (3/3)© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

13Ingress traffic• An operator attempts to attract traffic over specific links• Complex by design: the Internet is formed by networks with different

policies:§ Conflicts could be unsolvable§ Some Content providers don’t even use BGP to select a source and path

• Proposed workflow: deployment, collection, assessment, negotiation© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

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Ingress: Deploy• Different tools can be used to influence other ASNs:§ AS-Path prepending§ MEDs, Communities§ Prefix de-aggregation or hiding• Other routers paradigms such as LISP provide more direct ways ofinfluencing the inbound path:§ But policies would still prevail

Deployment

Collection

Assessment

Negotiation© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

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Ingress: Collect, Assess, Negotiate• Collect:§ Similar to the egress case
§ External data might be useful• Assess:§ Keep track of the implemented mechanism. Ensure that it works• Negotiate:§ Talk to your neighbors. They might be willing to cooperate

Deployment

Collection

AssessmentNegotiation© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

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Conclusions and closing words• Take control of your data
• Security was not discussed, but it is an important issue:§ New data to monitor§ more decisions to make§ (Discard a route with problems or lower its preference?)© 2014 Cisco and/or its affiliates. All rights reserved. Cisco Confidential

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