4 byte AS number workshop material

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It is the training material in 4 byte AS number migration training course. Date: Nov. 18, 2009. Location: National Taiwan Normal University.

Transcript of 4 byte AS number workshop material

  • 1. 4-Byte AS Number Workshop

2. Agenda

  • 4-byte ASN recap
  • Workshop environment introduction
    • IOS Route-Reflector
    • IOS Confederation
    • JUNOS Route-Reflector
    • JUNOS Confederation
  • 4-byte ASN in a 2-byte ASN BGP domain
  • Add 4-byte ASN ready router in a BGP domain
  • 4-byte ASN BGP policy discussion
  • Q&A

3. 4-byte ASN recap

  • Changes in BGP 4-byte AS:
    • New BGP capability advertisement
      • Capability code: 65
      • Capability length: 4
    • Attribute update
      • AS_PATH attribute carry 4 byte AS
      • AGGREGATOR attribute carry 4 byte AS
    • New attribute
      • Add AS4_PATH attribute
        • optional, transitive
        • Construct from AS_PATH attribute by 4-byte AS enabled router when face to 2-byte AS only router
      • Add AS4_AGGREGATOR attribute
        • optional, transitive
        • Construct from AGGREGATOR attribute by 4-byte AS enabled router when face to 2-byte AS only router

4. 4-byte ASN recap

  • Limitations:
    • NEW BGP speaker need a 2-byte AS to peer with the OLD BGP speaker.
      • No-mappable 4-byte AS can use 23456 as 2-byte AS
    • AS4_PATH is not compatible with:
      • AS_CONFED_SEQUENCE
      • AS_CONFED_SET
      • Must use mappable 4 byte member ASN during the migration
        • i.e. 0.64512 ~ 0.65535
  • Other considerations
    • BGP community handling
      • Current AS encoding method in BGP community should be updated
      • ref: draft-rekhter-as4octet-ext-community-03.txt
    • Netflow statistics
      • Netflow version 9 support 4-byte AS number

5. 4-byte ASN recap

          • From 4-Byte AS Numbers, The view from the Old BGP world, p21 by Geoff Huston, APNIC

6.

  • AS4_PATH example
    • 193.5.68.0/23
    • Attribute Type/Length/Value
      • Attribute Type (2 octets)
        • 0xe0 =>optional, transitive
        • 0x11 =>AS4_PATH (TYPE CODE 17)
      • Attribute Length (Variable)
      • AS Path Segments (Variable), which includes
        • Segment Type (1 octet)
          • 0x02 =>AS Sequence
        • Segment Length (1 octet)
          • 0x03 =>AS numbers in the AS Sequence
        • Value (Variable)
          • 0x00 00 1a ae => 6830 (The AS who generated the AS4_PATH)
          • 0x00 00 22 36 => 8758
          • 0x00 03 00 0d => 3.13

4-byte ASN recap 7.

  • AS4_PATH example
    • 195.47.195.0/24
    • Attribute Type/Length/Value
      • Attribute Type (2 octets)
        • 0xe0 =>optional, transitive
        • 0x11 =>AS4_PATH (TYPE CODE 17)
      • Attribute Length (Variable)
      • AS Path Segments (Variable), which includes
        • Segment Type (1 octet)
          • 0x02 =>AS Sequence
        • Segment Length (1 octet)
          • 0x01=>AS numbers in the AS Sequence
        • Value (Variable)
          • 0x00 03 00 10 => 3.16 (The AS who generated the AS4_PATH)

4-byte ASN recap 8.

  • AS4_PATH example
    • 2001:7fb:ff00::/48
    • Attribute Type/Length/Value
      • Attribute Type (2 octets)
        • 0xe0 =>optional, transitive
        • 0x11 =>AS4_PATH (TYPE CODE 17)
      • Attribute Length (Variable)
      • AS Path Segments (Variable), which includes
        • Segment Type (1 octet)
          • 0x02 =>AS Sequence
        • Segment Length (1 octet)
          • 0x03=>AS numbers in the AS Sequence
        • Value (Variable)
          • 0x00 00 04 65 => 1125 (The AS who generated the AS4_PATH)
          • 0x00 03 00 05 => 3.5
          • 0x00 00 31 6e => 12654

4-byte ASN recap 9.

          • From 4-Byte AS Numbers, The view from the Old BGP world, p23 by Geoff Huston, APNIC

4-byte ASN recap 10.

          • From 4-Byte AS Numbers, The view from the Old BGP world, p24 by Geoff Huston, APNIC

4-byte ASN recap 11. 4-byte ASN recap

  • ASDOT
    • Split the ASN into two 16bits numbers
    • ex. 65600 is 1.64 in 2-byte representation
      • 65600 is 65536*1 + 64
    • Difficult to handle in regular expressions
  • ASPLAIN
    • Just like regular 2-byte AS, but extending to 32 bits
    • ex. 65600
  • ASPLAIN and ASDOT in the workshop
    • AS66000 -> AS 1.464
    • AS67000 -> AS 1.1464
    • AS68000 -> AS 1.2464
    • AS69000 -> AS 1.3464

12. Workshop environment introduction 4-Byte AS Transit ISP/IX ISP customer Regular ISP 2-Byte AS Transit ISP/IX ISP customer ISP customer Regular ISP ISP customer ISP customer ISP customer 13. Workshop environment introduction IOS Route-Reflector AS69000 AS100 AS101 AS68101 AS67101 AS66101 F1/0 FE1/0 FE1/1 FE1/0 FE1/0 eBGP eBGP iBGP R# 2-byte available only R# 4-byte available Login: guest Password: guest enable: admin Transit Interface IP 10.100.AS#.R#/16 10.69.AS#.R#/16 ISP Interface IP 10.AS#.R#R#.R#/24 ISP Loopback IP 10.AS#.0.R#/32 172.101.6.0/24 172.101.66.0/24 172.101.7.0/24 172.101.8.0/24 172.101.68.0/24 F1/0 2.2/16 4.4/16 R2 R4 F1/1 F1/1 R1 R3 R2 R4 R5 R6 R7 R8 F1/0 F2/0 F2/0 F1/1 F2/1 F2/0 F2/1 F1/0 F1/1 F2/1 F2/0 F1/0 F1/1 F1/1 F1/0 F2/1 F2/0 F2/1 10.101/16 10.169/24 14. Workshop environment introduction IOS Confederation AS69000 AS100 AS102 AS68102 AS67102 AS66102 F1/0 FE1/0 FE1/1 FE1/0 FE1/0 eBGP eBGP iB