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1 Cutouts Are Bad http://bill.herrin.us/network/201010-cutout s.ppt

Cutouts Are Bad

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Cutouts Are Bad. http://bill.herrin.us/network/201010-cutouts.ppt. What is a Cutout?. What’s wrong with Cutouts?. You gain nothing – multihomed orgs cost just as many routing slots and IP addresses using Cutouts as they do using RIR addresses. - PowerPoint PPT Presentation

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Page 1: Cutouts Are Bad

1

Cutouts Are Bad

• http://bill.herrin.us/network/201010-cutouts.ppt

Page 2: Cutouts Are Bad

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What is a Cutout?

207.199.128.0/18 - ISP

207.199.136.0/23 – multihomed customer

ISP’s large IPv4 blockAnnounced via BGP to ISP’s peers and upstream transits

Multihomed customer’s Cutout block – announced via BGP to several ISPs

Page 3: Cutouts Are Bad

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What’s wrong with Cutouts?

•You gain nothing – multihomed orgs cost just as many routing slots and IP addresses using Cutouts as they do using RIR addresses.

•Disaggregation for Traffic Engineering (TE) indistinguishable from Cutouts

•TE costs you a lot of money

Page 4: Cutouts Are Bad

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The other guy’s TE costs you money!

• CIDR Report 9/24/2010

•ASnum   NetsNow NetsAggr NetGain   % Table   337009   208022  128987  38.3% All ASes

AS6389     3779      282   3497  92.5%  BellSouthAS4323     4468     1924   2544  56.9%  twtelecomAS19262   1819      285   1534  84.3%  Verizon

• Four cents per BGP route per router per year.

• $0.04 x 128,987 x your 100 routers = half a million bucks

• $0.04 x 128,987 x 150,000 BGP routers worldwide = $775 million per year to carry all that TE.

Page 5: Cutouts Are Bad

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The Traffic Engineering Cutout Problem

207.199.128.0/18 - ISP

207.199.128.0/20 – TE preference to receive via a particular upstream

207.199.136.0/23 – multihomed customer

Must carry the /18 route

The /20 is discardable, particularly if the ISP is distant. System remains reachable regardless.

The /23 must be carried – you won’t always and may never be able to reach it via the /18.

But how do you configure YOUR router to tell the difference between THEIR /20 and /23?

Page 6: Cutouts Are Bad

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What’s wrong with Cutouts?

•Your customers hate it too.

•Renumbering manpower costs money

•Multihomed orgs tend to run valuable systems

•Outages from renumbering issues are expensive

Page 7: Cutouts Are Bad

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CutoutsBad Today

Bad Tomorrow

Page 8: Cutouts Are Bad

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Future Tech: map-encap

• IRTF Routing Research Group trying to make your routers less expensive.

• “Map-encap” creates a second tier routing system using dynamic tunnels – cheap.

Page 9: Cutouts Are Bad

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Future Tech: map-encap

Internet

Origin

BGP Router

Encapsulator

ISP A

ISP B

Decapsulator

Decapsulator

Destination

Send to: 198.51.100.7

192.0.2.0/24

203.0.113.0/24203.0.113.45

192.0.2.12

198.51.100.7

Page 10: Cutouts Are Bad

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Cutouts Break Map-Encap

Internet

Origin

BGP Router

Encapsulator

ISP A

ISP B

Decapsulator

Decapsulator

Destination

Send to: 198.51.100.7

192.0.2.0/24

198.51.100.0/24198.51.100.1

192.0.2.12

198.51.100.7

X

Page 11: Cutouts Are Bad

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What’s the solution?

•Stop requiring small multihomed orgs to use cutouts.

•Don’t allow cutouts to enter use in IPv6.

•Let multihoming with BGP qualify an org for an ARIN direct assignment. Period.

Page 12: Cutouts Are Bad

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Conclusion

• Cutouts are Bad.

• Cutouts waste our money.

• Cutouts kill tech that would save us money.

• Let’s fix ARIN policy so we can stop using them.

• http://bill.herrin.us/network/201010-cutouts.ppt

• http://bill.herrin.us/network/bgpcost.html