IP Family Selection for MIF Host Zhen Cao, Dapeng Liu China Mobile

Problem of IP Family Selection IPv6 or IPv4, this is a question IPv6 is naturally preferred over IPv4, but sometimes it is not optimal or even does not work through –Some OSes have 3484-alike policy table, but some do not (OSX) –Even 3484 may fail to work under certain situations

Problem #1: NAT64 or NAT44? Default address selection defined in RFC3484 will prefer IPv6 over IPv4 Is this optimal ? NAT64 over NAT44? –Yes, good to moving traffic to IPv6 –If no, how different policy is delivered to the host? EPS Non-3GPP GGSN/ PGW 3GPP Host v4-only server NAT64 NAT44 DNS64 IPv4 Beaer IPv6 Beaer Draft-behave-wing-dns64-config Draft-savolainen-mif-dns-server-selection

Problem #2: NAT46 or NAT464 Step 4: which A to return? –IPv4 mapped to the AAAA: NAT46, may fail due to ALG –Naturally returned A : NAT464 DNSV4 APPBIA/BIS Dual stack Server 1. DNS A Request 2. DNS A & AAAA Request 3. DNS A & AAAA Response 4. DNS A Response IPv4 PacketsIPv6 Packets

Problem #3: Source Address Selection: Self Assigned IPv4 or Net-assigned IPv4 If a mapped A is returned to the application, which source address is selected? –Network assigned IPv4 address (N4) communication failure –Self-assigned IPv4 address (S4), but the whats the scope of S4? Solution: define a proper scope for self-assigned and shared IPv4 address DNSV4 APPBIS 1. DNS A Request 2. DNS A & AAAA Request 3. DNS only AAAA Response 4. DNS A Response (B4) Dst: B4 Stack Src: S4 or N4? Dst: B4 IPv6 Packet

Proposal Adding text on IP family selection problem explicitly to the PS document: –Section 4.3 on address selection –The inconsistency of host's application IP family, interface address family and remote end's IP family makes the IP family selection problem complicated. Wrongly choosing the IP family will result into communication failure