DESIRE II

1
DESIRE II

• 2nd Web Cache Managers Workshop
• Budapest, 2-3 March 2000
• http//www.desire.org/

2
Cost Benefit Analysis - take 2

• TOP-LEVEL CACHES
• dos donts
• Ton.Verschuren_at_SURFnet.NL

3
Contents

• Ways to add a top-level cache to your mesh
• Case 1 SURFnet
• Case 2 JAnet
• Conclusions

4
Extending your mesh with a TL-cache

• 3 models
• 2nd-level cache
• 2nd-level cache with billing for international
  traffic
• combination of 1st-level and 2nd-level cache

5
Pros of TL-caches

• increased (national) hit rate
• routing options for web traffic (DiffServ,
  CAR/WFQ, or dedicated link)
• access control charging possible
• identify sites that could benefit greatly from
  mirroring(and other monitoring options)
• give the right example for your customers

6
Cons of TL-caches

• could be single-point-of-failure
• huge (distributed) system
• who pays?

7
TL-cache rule of thumb

• Is a TL-cache efficient for you?
• Can it attract enough traffic?
• Is the hit rate high enough?
• Caching mesh cost-benefit analysis from Desire
  1http//www.surfnet.nl/innovatie/desire1/deliver
  /WP4/D4-2.html

8
Case 1 SURFnet

• Model 2nd-level cache only

9
Case 1 SURFnet (contd)

• Data from 4Q98
• External connectivity

10
Case 1 SURFnet (contd)

• Cost of bandwidth
• Ratio NL Europe USA 1 11
  15
• Usage pattern
• Ratio NL Europe USA 1 2
  3
• Savings formula
• S(r) H C(r) / Tr route (NL, EU, US)H
  volume of hits (in bits)C cost of route
  (bandwidth only)T period in seconds

11
Case 1 SURFnet (contd)

• Savings of the TL-cache in 4Q98

12
Case 1 SURFnet (contd)

• Reduction ltlt 1
• Conclusion exit top-level cache
• Why are the results so bad?
• 35 clients is just too few!
• DisclaimerThere are lies, damn lies, and
  statistics.

13
Case 1 SURFnet (contd)
14
Case 2 JAnet

• Model 2nd-level cache
• And charging for transatlantic traffic between
  6-1 hrs!except when via JAnet cache.

15
Case 2 JAnet (contd)
16
Case 2 Janet (contd)

• 160 1st-level caches connected
• JWCS 1.5 TB storage (40 machines in 2 locations)
• combined 1st-level caches 6 TB storage
• 500 GB per day thruput 100 GB from US 25 of
  all US web traffic!
• Hit rate 25-30 overall mesh 50-60
• Charging ? 30 / GB
• Saving ? 1000 per day (? 400,000 per year)
• Costs less than savings!
• See http//wwwcache.ja.net/

17
Conclusions

• When you are thinking about extending your mesh
  with a top-level cache
• choose a model
• ensure you have enough 1st-level caches
• carrot or stick?
• Keep your service in sync with bandwidth upgrades
• Decide what intercache communication to use.
• Evaluate your service periodically.