Transcript mif-6

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?
DNS64
NAT44
3GPP
IPv4 Beaer
EPS
Host
Non-3GPP
v4-only
server
GGSN/
PGW
IPv6 Beaer
NAT64
Draft-behave-wing-dns64-config
Draft-savolainen-mif-dns-server-selection
Problem #2: NAT46 or NAT464
V4 APP
BIA/BIS
DNS
Dual stack
Server
1. DNS A Request
2. DNS A & AAAA Request
3. DNS A & AAAA Response
4. DNS A Response
IPv4 Packets
IPv6 Packets
• Step 4: which “A” to return?
– IPv4 mapped to the AAAA: NAT46, may fail due to ALG
– Naturally returned A : NAT464
Problem #3: Source Address Selection: Self
Assigned IPv4 or Net-assigned IPv4
V4 APP
Stack
BIS
DNS
1. DNS A Request
2. DNS A & AAAA Request
3. DNS only AAAA Response
4. DNS A Response (B4)
Dst: B4
•
Src: S4 or N4?
Dst: B4
IPv6 Packet
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 what’s the scope of S4?
•
Solution: define a proper scope for self-assigned and shared IPv4 address
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