Brocade Communications Systems ServerIron ADX 12.4.00 Service Manual download pdf (Page 17)

ServerIron ADX NAT64 Configuration Guide 5

53-1002444-02

NAT64 and NAT46 implementation details

DRAFT: BROCADE CONFIDENTIAL

NAT64 full-sized packet handling

NAT64 full-sized packet handling enables full-sized packets from the IPv4 host to be split into

multiple packets for the IPv6 client. This functionality is needed because an IPv4 header is 20

bytes in length and an IPv6 header (along with extension headers if applicable) is greater than or

equal to 40 bytes.

If the ServerIron ADX receives a full-sized packet (total length of IPv4 packet equal to the MTU) on

the IPv4 side, when it translates the IPv4 header to the IPv6 header, the total length of the IP

packet may exceed the MTU of the IPv6 side, so this full-sized packet must be split into two IPv6

fragments before being sent to the IPv6 host. The head fragment size will be equal to the IPv6-side

MTU and the non-head fragment size will be equal to the original packet size minus the first

fragment size.

NAT64 fragmentation support

NAT64 fragmentation handling enables the ServerIron ADX to convert an IPv4 fragmented packet

to an IPv6 fragmented packet and vice versa. The fragmentation formats are different for IPv4 and

IPv6.

For the IPv6 to IPv4 direction, the ServerIron ADX:

• Strips off the IPv6 fragment ed header

• Extracts the information stored in it

• Populates the fragment ID, offset, and flags of the IPv4 header

For the IPv4 to IPv6 direction, the ServerIron ADX:

• Extracts information stored in the IPv4 header

• Creates and populates the IPv6 fragmented header

host precedence violation (code 14) communication with destination

administratively prohibited (code 1)

precedence cutoff in effect (code 15) communication with destination

administratively prohibited (code 1)

Time Exceeded (Type 11) Time Exceeded (Type 3)

Code remains same from ICMPv4

Destination Unreachable (Type 3)

destination protocol unreachable (code

Parameter Problem (Type 4)

unrecognized Next Header type encountered

(code 1)

Parameter problem: bad IP header (Type 12)

pointer indicates the error (code 0)

Parameter Problem (Type 4)

Any other parameter problem

Echo Request (Type 8) Echo Request (Type 128)

Echo Reply (Type 0) Echo Reply (Type 129)

TABLE 2 ICMPv4 to ICMPv6 message translation (Continued)

ICMPv4 message type ICMPv6 message type

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 148 149

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Brocade Communications Systems ServerIron ADX 12.4.00 Service Manual Page 17

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