MB86977 Datasheet, PDF (10/30 Pages) Fujitsu Component Limited. – IP PACKET FORWARDING ENGINE

MB86977
s FUNCTIONAL DESCRIPTION
1. FEF Engine-NAT/IP forwarding function
The FEF Engine-NAT/IP forwarding macro accelerates NAT transformation and IP forwarding through hardware,
eliminating the use of software, i.e. host processing. Up to 128 NAT/IP forwarding connections, each defined by
the parameters set in the NAT/IP forwarding table, can be configured. These connections are the transmission
paths that connect the WAN and D.M.Z. interfaces, the WAN and LAN interfaces, and the D.M.Z. and LAN
interfaces-all at full wire speed.
The IP forwarding and NAT operations are briefly explained below.
• IP Forwarding
When both the destination and source IP addresses of an input packet matches one of the entries in the NAT/
IP forwarding table, the packet is forwarded through hardware to the destination interface indicated by the
matching entry. This transmission does not require host processing and is performed at full wire speed. If there
is no entry in the NAT/IP forwarding table that matches both IP addresses (destination and source IP address)
of the input packet, the packet is sent to the host through the host interface.
Described below is the operation performed on the packet when IP Forwarding is being applied:
• MAC address replacement
• TTL subtraction
• IP header checksum recalculation
• Ethernet frame CRC recalculation
• Transmission from the destination interface indicated
As for IP forwarding, both IPv4 and IPv6 type packets can be processed.
• NAT
When the destination and source IP addresses and the destination and source TCP/UDP port numbers of an
input packet matches one of the entries in the NAT/IP forwarding table, the hardware translates the address,
replaces the port numbers, and forwards the packet to the destination interface, all according to the parameters
defined by the matching entry. This transmission does not require host processing and is performed at full wire
speed. If there is no entry in the NAT/IP forwarding table that matches both IP addresses (destination and source
IP address) and both TCP/UDP port numbers of the input packet, the packet is sent to the host through the host
interface.
Described below is the operation performed on the packet when NAT is being applied:
• MAC address replacement
• TTL subtraction
• IP address replacement
• IP header checksum recalculation
• TCP/UDP port number replacement
• TCP/UDP header checksum recalculation
• Ethernet frame CRC recalculation
• Transmission from the destination interface indicated
As for NAT, only IPv4 type packets can be processed.
AH and ESP input packets are not subject to NAT translations.These types of packets are sent to the host through
the host interface.
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