1. 4byte ASNs Test Scenarios
- 8th TWNIC OPM
2007/7/5, Taipei
許至凱
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2. Agenda
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4 bytes AS number overview
BGP capability in 4 bytes AS number
BGP attribute update
New BGP attribute
Testing scenarios
Reference
2

3. 4 bytes AS number overview
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Original ASN encoded
2 bytes
ASN pool: 0 ~ 65535
ASN expansion
4 bytes
ASN pool: 0 ~ 4294967295
M:N
M: 0 ~ 65535
N: 0 ~ 65535
2 bytes map to 4 bytes
0.0 ~ 0.65535
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4. BGP capability in 4 bytes AS number
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BGP Capability Advertisements
RFC2842
Capabilities Optional Parameter
BGP router supported 4 bytes ASN
Capability code: 65
Capability Length: 4
4

5. BGP attribute update
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AS_PATH attribute update
Original:
AS carried in this attribute is encoded as a 2
byte ASN
New:
AS carried in this attribute is encoded as a 4
byte ASN
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6. BGP attribute update
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AS_AGGREGATOR attribute update
Original:
AS carried in this attribute is encoded as a 2
byte ASN
New:
AS carried in this attribute is encoded as a 4
byte ASN
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7. New BGP attribute
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AS4_PATH
Optional transitive attribute
AS_PATH is “well-known mandatory” attribute
AS4_PATH semantics:
AS carried in this attribute is encoded as a 4
bytes entity
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8. New BGP attribute
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AS4_AGGREGATOR
Optional transitive attribute
AS_AGGREGATOR is “optional transitive”
attribute
AS4_AGGREGATOR semantics:
AS carried in this attribute is encoded as a 4
bytes entity
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9. Testing scenarios
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NEW AS_PATH testing
Peering with 4 bytes ASN is mappable to 2
bytes ASN
0.65000 0.65001
Peering with 4 bytes ASN is NOT mappable to
2 bytes ASN
0.65000 2.65001
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10. Testing scenarios
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AS4_PATH testing
Peering with 4 bytes ASN is mappable to 2
bytes ASN
65000 0.65001
Peering with 4 bytes ASN is NOT mappable to
2 bytes ASN
65000 2.65001
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11. Testing scenarios
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AS4_PATH testing
2 bytes ASN travel through 4 bytes ASN
65000 0.65001 65002
65000 2.65001 65002
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12. Testing scenarios
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AS4_PATH testing
4 bytes ASN travel through 2 bytes ASN
0.65000 65001 0.65002
2.65000 65001 2.65002
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13. Testing scenarios
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NEW AS_AGGREGATOR testing
0.65002
0.65000 0.65001
0.65003
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14. Testing scenarios
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AS4_AGGREGATOR testing
2 bytes ASN is aggregated via 4 bytes ASN
65002
65000 2.65001
65003
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15. Testing scenarios
http://www.seed.net.tw
AS4_AGGREGATOR testing
4 bytes ASN is aggregated via 2 bytes ASN
2.65002
0.65000 65001
2.65003
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16. Reference
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RFC1771
Y. Rekhter, T. Li, “A Border Gateway Protocol
4 (BGP-4)”, March 1995.
RFC4893
Q. Vohra, E. Chen, quot;BGP Support for Four-
octet AS Number Spacequot;, May 2007.
BGP support for 4-Byte AS Numbers -
Implementation Survey Report
Geoff Huston, Asia Pacific Network
Information Centre
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17. Questions & Comments?
sees your needs