Design of IPv6 on GÉANT
Since Q2 2003, the GÉANT network has incorporated a dual-stack backbone in order to be able to deliver both IPv4 and IPv6 services. This section presents the IPv6 technical design, addressing plan and routing policy deployed over the network.
GÉANT Design
Based on the GÉANT set up, the decision was taken to build a fully-meshed BGP dual-stack network. For that purpose, an IGP protocol that could handle IPv4 and IPv6 was needed. GÉANT was initially implemented with OSPFv2, which supports only IPv4. In the first week of December 2002, we successfully introduced IS-IS in the core, and discarded OSPF. The results of this migration and IPv6 lab testing can be found on the IGP migration page.
NREN Connections
Connecting NRENs to IPv6 services on GÉANT requires the setting up of a second E-BGP v6 peer running on a parallel TCP session in addition to the existing E-BGP v4 connection. This IPv6 E-BGP peer can take place on the native access or via a tunnel if the NREN's access router is not IPv6-capable.
Another option - having only one TCP handling both IPv4 AFI and IPv6 AFI - was studied before deciding the final GÉANT topology. However, it was discarded due to the complexity of the configuration. This solution has the advantage of having only one TCP/BGP session per peer, but the IPv6 address is derived from IPv4 address, making the set-up more complex.
GÉANT IPv6 Routing Policy
The IPv6 routing policy between GÉANT and the NRENs is very similar to the one in place for IPv4, but a cautious approach has been adopted with regard to the type and length of prefixes GÉANT receives: only prefix lengths in the range /19 to /35 are accepted. This policy is based on existing guidelines to LIRs for IPv6 assignments to its customers, drawn from RIPE (ripe-267) and RFC documents (RFC3177). The maximum prefix length permitted is derived from the minimum allocation from RIRs to LIRs - /35 in the past, now /32.
Below you can find more details about the route exchange with NRENs.
Routes Accepted From NRENs
GÉANT accepts:
- NREN prefixes from /19 to /32 based on a prefix list
- Prefix 2002::/16 is accepted from NRENs
GÉANT does not accept 6bone prefixes.
GÉANT does not announce NRENs' routes that are tagged geant-dws-block 20965:7000 to commercial providers.
Routes announced to NRENs
- GÉANT originates sTLA 2001:0798/32
- GÉANT announces routes tagged geant-nrn
- Other Research and Education Networks
- Commercial routes from Global Crossing and Telia
Further details are available in the Routing Plan via the links alongside.
GÉANT Addressing Plan
DANTE obtained from RIPE the address space 2001:0798::/32. From that address space we allocated:
- 6NET - address space 2001:0798:0000::/35
- GÉANT - address space 2001:0798:2000::/35.
After internal discussions within the GEANTv6 task force, we decided to address the core network based on the address space 2001:0798:2000::/40.
The trunks in this addressing plan received /126 subnets' length. We decided to implement a subnet of /126 length rather than /64 to avoid the assignment and waste of 2^64 addresses per point-to-point link.
Most of the accesses are addressed in /126 too, since GEANT offers a /126 subnet from its address space to the NREN for configuring it. However, if the NREN prefers to implement its connection with other prefix lenght, the prefix is derived from the NREN space.
For more information, see the IETF recommendations and RIPE mailing list archives (available via the links on the right).
The remaining allocations and core addressing can be found in the Addressing Plan (also linked alongside).
Monitoring IPv6 in GEANT
Since IPv6 became operational in October 2003, IPv6 service has been monitored by the GÉANT NOC in order to provide a service similar to IPv4. Due to the lack of MIB values for IPv6, IPv6 traffic is monitored in the NREN access links with firewall counters which gather the amount of traffic.
IPv6 statistics are available to GÉANT NRENs only, via the network monitoring tools and monthly service reports.
