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Controlling Traffic Offloading Using Neighbor Discovery Protocol

Controlling Traffic Offloading Using Neighbor Discovery Protocol. IETF#80 Mif WG, 28-March-2011 draft-korhonen-mif-ra-offload-01 Jouni Korhonen Teemu Savolainen. Background. Current default address selection prefers IPv6 over IPv4 (default policy table on RFC3484).

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Controlling Traffic Offloading Using Neighbor Discovery Protocol

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  1. Controlling Traffic Offloading Using Neighbor Discovery Protocol IETF#80 Mif WG, 28-March-2011 draft-korhonen-mif-ra-offload-01 JouniKorhonen TeemuSavolainen

  2. Background • Current default address selection prefers IPv6 over IPv4 (default policy table on RFC3484). • A Mif host may have IPv6 enabled on a more 'expensive’ access (e.g. cellular) and a 'cheaper' access (e.g. Wi-Fi) may only have IPv4. • There might be a need for a network managed solution to “guide” MIF hosts to prefer IPv4 in communication instead of IPv6 – or prefer ‘cheaper’ accesses over ‘expensive’ accesses. • DHCPv6 is not always preferred or available, thus consider also Neighbor Discovery Protocol as a ‘command channel’. • RFC4191 not always usable: e.g. no support for IPv4 traffic.

  3. Illustration oftypicalsetup Dual-stack destination Internet IPv4 route IPv6 route Router (e.g. PDN GW) IPv4 WLAN Dual-Stack cellular • RA with: • prefer IPv4 over IPv6 • don’t prefer this interface’s default IPv4 gateway

  4. Solution proposal (experimental) • A new option to Router Advertisement, which tells the network side address family preferences to the Mif host: • Coexists with RFC4191. • If present -> set new priorities; if absent -> not used and remove possible previous priorities. • Lower-than-IPv4 Preference -> prefer any address than IPv6 tied to this interface, if just available.. • Default IPv4 Gateway Preference -> use other interface for IPv4 traffic, if just available.. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length=1 |L|D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Gateway | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  5. Solution proposal cont’d • The new option effectively affects/modifies the source address selection Rule 3: • The addresses SA and SB have the same scope. • If Lower_than_IPv4(SA) == true and No_specific_routes(D) == true, then mark SA temporarily as "deprecated”. • If Lower_than_IPv4(SB) == true and No_specific_routes(D) == true, then mark SB temporarily as "deprecated”. • If one of the two source addresses is "preferred" and one of them is "deprecated" (in the [RFC4862] sense), then prefer the one that is "preferred.” • Similar modification also concerns the destination address selection Rule 3 when checking whether a candidate source address for a given destination is deprecated. • Do not modify ‘policy table’ as those changes are not trivially tied to a specific interfaces..

  6. Next steps and summary • There is still verifications to do: • Implement and test how well it actually performs, especially against RFC4191. [IPv6 offloading works rather nicely using just RFC4191 – tested already..] • Race conditions.. • A lightweight approach for on-demand access and address selection prioritization controlled from the network side: • One interface can be ‘selected’ as the commanding interface.. • Unfortunately has an end host impact..

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