Add IPv6 presentation.

2021-05-17-ipv6/ipv6.txt

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+IPv6
+
+1. Network layers and IP
+2. Routing and subnets
+3. Problems with IPv4
+4. Solutions of IPv6
+5. SLAAC
+6. IPv4 in IPv6
+
+Under:
+Link-layer, MAC (Ethernet, Wi-Fi)
+Intra-network communication
+
+Upper:
+Transport-layer, TCP / UDP
+Data communication
+
+Middle:
+Internet layer, IPv4/6
+Inter-network communication
+
+2. Routing and subnets
+
+CIDR notation:
+192.168.0.0/24 - 192.168.0.XX
+
+2a0d:d9c0:1234:abcd:5678:cdef:1234:4567/64
+2a0d:d9c0:1234:abcd:xxxx:xxxx:xxxx:xxxx
+
+192.168.0.0/24 to 192.168.1.0/24
+2a0d:d9c0::/64 to 2a0d:d9c1::/64
+
+3. Problems with IPv4
+
+Not enough (public) addresses!
+
+Private subnets allow extension through NAT
+
+192.168.0.0/16 behind 45.134.135.1
+
+Problems: state, complexity...
+And *still* not enough addresses!
+
+4. Solutions of IPv6
+
+Many, many, *many* more addresses
+Every device has an address, no NAT
+Enough for everyone.
+
+(security: NAT does not provide security.
+Proper firewalling does.)
+
+Otherwise, nothing basic really changes
+Devices have an IPv6, talk to others over link-layer
+Same difference!
+
+5. SLAAC
+StateLess Address AutoConfiguration
+
+Usually, in IPv4, DHCP
+Requires manual configuration
+
+In IPv6, equivalent is SLAAC
+* MAC addresses to autoconfigure address in a subnet
+* Device Address Duplication built-in checks
+* More work for the routers
+
+Router Advertisements, Router Solicitation
+Neighbor Advertisements, Neighbor Solicitation
+
+2a0d:d9c0:1234:5678::/64 + MAC address =>
+2a0d:d9c0:1234:5678:224:81ff:fe7d:da46
+
+6. IPv4 in IPv6
+
+Same technique as SLAAC: encode IPv4 in IPv6 /64
+2a0d:d9c0:1234:5678:192.168.42.42
+
+We can use a translation service to provide IPv4 connectivity to IPv6 hosts.
+NAT-like: IPv6 can initiate to IPv4, not the other way around.