1. Per-MS Prefix Model for IPv6 in WiMAX by Frank Xia Behcet Sarikaya Raj Patil Presented by Jonne Soininen

2. Sept. 12-13, 20062 OUTLINE Introduction Per-MN subnet prefix model Issues Conclusions

3. Sept. 12-13, 20063 AR Physical Link: Ethernet, Optical, Frame- relay, etc. These are physical interfaces on the router An AR normally has a limited number of physical interfaces available for connectivity Virtual Link vs Physical Link Host AR MN BS Virtual Link: A link that does not directly map to a physical interface Dynamic behavior: When an MS is connected to an AR, the link is up. When an MS detaches from the AR, the link is deleted Capacity: Hundreds and thousands of MNs connect to AR, and each MN has at least a link From the IP layer perspective, there is no difference between physical and virtual links

4. Sept. 12-13, 20064 Implementation of Virtual Link 1.Each MN has one or more virtual links, such as link1 and link2 2.Each link has one or more CIDs/Tunnels. For example, link 1 has several CIDs, while link 2 only has one CID 3.The virtual link illustrated with dotted lines consists of two segments. The MN-BS segment is the air interface part, and is identified by CID (IEEE.16). The BS-AR segment can be a wired or wireless link. GRE tunnels on a per MS basis are established between the BS and AR. 4.In the BS, there is a mapping between CID and Tunnel ID. MN BSAR CID1Tunnel 1 CID nTunnel n link 1 link 2 Mapping CID2Tunnel 2 link 1 link 2

5. Sept. 12-13, 20065 PREFIX ASSIGNMENT Fast Router Discovery As soon as a virtual link becomes active, an AR sends an unsolicited RA Solicited Router Advertisement The AR responds with an RA when it receive a RS via a virtual link. Periodic Router Advertisements When a virtual link is active, periodic router advertisement SHOULD be sent by the AR. – Note: Periodic RAs should be dealt as a deployment option. They may be dropped by the AR if necessary.

6. Sept. 12-13, 20066 NEIGHBOR DISCOVERY Neighbor: An AR is the only neighbor for an MN on a link NS/NA/RS/RA: As per RFC2461, No modification or adaptation is necessary Stateless Address Autoconfiguration: As per RFC2462, No modification or adaptation is necessary DAD: There is very low address duplication possibility; Optimistic DAD as per RFC4429 is preferable

7. Sept. 12-13, 20067 INFORMATION MODEL Each MN and AR have a virtual link information table which includes the following elements virtual link ID Each MN has one or more virtual links connected to an AR Prefixes One or more prefixes assigned to the link for address configuration or renumbering CIDs Tunnel between BS and AR can be viewed as the extension of CID. These CIDs/tunnels compose the virtual link Optional items MTU and other items can be included

8. Sept. 12-13, 20068 DORMANT MODE OPERATION Efficient Dormant Mode: Link-local multicast is limited since the only nodes on the link are the MN and the AR Virtual link maintenance when an MN is dormant: When an MS becomes dormant, the MS and AR delete all existing CIDs/tunnels, while other attributes of the links entry including prefixes are kept unchanged, When the MS becomes active again, new CIDs/tunnel are created and the link table updated

9. Sept. 12-13, 20069 ISSUES RAISED Per MN prefix, how to manage the prefixes? MN mobility can cause route flip? Are there enough prefixes?

10. Sept. 12-13, 200610 Concern 1: Prefix Management AR DHCP Server MS AR DHCP client DHCP relay 2) Relay-forward (Solicit) 3)Relay-reply (Advertise) 4)Relay-forward (Request) 5)Relay-reply (Reply) 8) MLD Join 1)Network Entry and Authentication 6)Transport connection (Virtual Link )established 7) Router Advertise 9) DAD Procedure DHCP server is responsible for the prefix allocation and release

11. Sept. 12-13, 200611 Concern 2: Route Flip AR should broadcast the prefixes (MNs route information) dynamically upstream – Many MNs so high broadcast traffic MN leaves the ASN and this causes route flip too frequently Route Aggregation solves both problems. For example, each AR can be assigned a /48 prefix, while an MS' /64 prefix is derived from the /48 prefix extension.

12. Sept. 12-13, 200612 Concern 3: Enough Prefixes There is a detailed analysis in section 2.3.1 of RFC 3314 A total of 490 trillion (490x10^12) /64 prefixes can be assigned. This translates into around 80,000 prefixes per person on the earth today

13. Sept. 12-13, 200613 CONCLUSIONS Per-MN (or per-MS) prefix model fits naturally to p-t-p links Prefixes can be managed using DHCP There are enough prefixes (address depletion is not a concern) No impact to host stacks if the shared prefix model is adopted in the future