Saturday, April 30, 2011

Sample IPv6 Addressing/Dimensioning Plan for ISPs

This is a high level summary of an IPv6 addressing & dimensioning plan for mid-sized service providers. Obviously it doesn't apply to all cases, but i hope other people will find it useful too.

First you define 3 levels of PoPs (Points of Presence), depending on number of customers and address consumption:

  • Level-1 PoP (Large)
  • Level-2 PoP (Medium)
  • Level-3 PoP (Small)
Then you define 2 types of customers:
  • Residential
  • Business

General rules
  • Keep the boundary on /32,/40,/48,/56,/64,/128 for easier management.
  • Avoid hex letters (A,B,C,D,E,F) on infrastructure addresses, at least until you run out of numbers.
  • Keep infrastructure addresses in a single block for easier ACL management.
  • Loopbacks, Management, Internal can be contained in a single /41, leaving Public on the other /41. 
  • Keep customer addresses in a single block per PoP for easier route aggregation.
  • Too much aggregation won't help you much in case of multiple internet exits.

Each ISP gets at least a /32 from its RIR. A sample dimensioning could be the following:

1 x /32
  • 1 x /40 : Infrastructure Addresses
    • 1 x /48 for all PoPs : Loopbacks & Management
      • 1 x /56 for all PoPs : Loopbacks
        • 1 x /64 per Loopback Category
          • 1 x /128 per Loopback Interface
      • 1 x /56 per PoP : Management
        • 1 x /64 per Management LAN
    • 1 x /48 for all PoPs : Reserved
    • 1 x /48 per PoP : Internal Networks
      • X1 x /56 : Routers P2P Links
        • 1 x /64 per Routers P2P Link 
      • X2 x /56 : Routers LANs
        • 1 x /64 per Routers LAN
      • X3 x /56 : Hosts LANs
        • 1 x /64 per Hosts LAN
      • X4 x /56 : Servers LANs
        • 1 x /64 per Servers LAN
      • X5 x /56 : Other
        • 1 x /64 per Other
    • 1 x /48 per PoP : Public Networks
      •  X1 x /56 : Routers P2P Links
        • 1 x /64 per Routers P2P Link 
      •  X2 x /56 : Routers LANs
        • 1 x /64 per Routers LAN 
      •  X3 x /56 : Hosts LANs
        • 1 x /64 per Hosts LAN 
      •  X4 x /56 : Servers LANs
        • 1 x /64 per Servers LAN 
      • X5 x /56 : Other
        • 1 x /64 per Other
  • A x /40 : Level-1 PoP Customers
    • N1 x /40 per PoP : Business Customers
      • 1 x /48 per Large Customer
      • 1 x /56 per Small Customer
    • N2 x /40 per PoP : Residential Customers
      • 1 x /56 per Customer LAN
      • 1 x /64 per Customer WAN
  • B x /40 : Level-2 PoP Customers
    •  M1 x /40 per PoP : Business Customers
      •  1 x /48 per Large Customer
      •  1 x /56 per Small Customer
    •  M2 x /40 per PoP : Residential Customers
      •  1 x /56 per Customer LAN
      •  1 x /64 per Customer WAN
  • C x /40 : Level-3 PoP Customers
    •  L1 x /40 per PoP : Business Customers
      •  1 x /48 per Large Customer
      •  1 x /56 per Small Customer
    •  L2 x /40 per PoP : Residential Customers
      •  1 x /56 per Customer LAN
      •  1 x /64 per Customer WAN
  • D x /40 : Reserved

Calculations

A,B,C depend on the total number of /40 per type of PoP (A>B>C).
N1,N2,M1,M2,L1,L2 depend on the number of customers per type of PoP (N1>M1>L1 & N2>M2>L2)

The summary of (N1 x /40) + (N2 x /40) for all Level-1 PoPs equals to A x /40.
The summary of (M1 x /40) + (M2 x /40) for all Level-2 PoPs equals to B x /40.
The summary of (L1 x /40) + (L2 x /40) for all Level-3 PoPs equals to C x /40.

Notes

The above plan is based on what i believe to be current best practices and recommendations for a specific type of service provider. Some things will change, as they changed in the past:

  1. Initially a /48 was recommended for all sites in the general case (RFC 3177), now it's per case (RFC 6177).
  2. Some years ago a /127 was not recommended for p2p links (RFC 3627), now /127 came back into surface (RFC 6164).
  3. Currently only /64 is used by SLAAC (RFC 4862), but someone though something longer would be better (draft-yhb-6man-slaac-improvement).

I am sure we'll see a lot of changes in the following months/years regarding the length of prefixes in IPv6. I just hope we don't have to move to something new with more than 128 bits.

5 comments:

  1. For the Residential LAN wouldn't be also an option to allocate 1 x /64 ? This will be of course kinda of one subnet for the LAN interface which hosts connected to that interface will acquire the prefix and with SAA will have its IP.

    Of course If the residential LAN will need more than one subnet then a /56 will be enough!

    ReplyDelete
  2. Sure, a /64 will be fine for the majority of subscribers. But as new services come out and more devices get activated, you'll probably need to separate them in the home network.

    ReplyDelete
  3. Well, yes, but there is only 1/8 of ipv6 address space used or planned to be used. When it's not enough or we eventually waste it like ipv4, the second eighth would be like another ipv6 address space and that could be segmented better. IPv4 didn't have that feature :).

    ReplyDelete
  4. can you briefly draw the diagram ?

    Because ............ I'd very want to know about it !

    ReplyDelete
  5. Can you draw a network diagram on how this plan would look like ?

    u can use IOU/GNS3/PacketTracer

    thanks

    ReplyDelete

 
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