Samsung Ubigate iBG1000, Руководство пользователя

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CHAPTER 3. Software Overview
3-10
© SAMSUNG Electronics Co., Ltd.
Packet Forwarding Plane
The Router Subsystem is a software-based router that can flexibly support a
variety of routing protocols. Packet headers may be examined and modified as
required to support routing between links supporting different protocols.
Received packets are moved into the main memory by the source interface
using DMA. The routing processor on the main board examines each packet
header in the main memory, makes the routing decision, modifies the packet
as required, and inserts the packet into the transmit queue for the appropriate
destination. The destination interface then copies the packet from main
memory using DMA and transmits the packet.
Packet data is stored in data buffers that are separate from the descriptor
structures used by the source and destination DMA Controllers. This allows
the processor to get a packet ready for transmission without copying it from
one buffer to another.
The forwarding plane consists of the following software components:
 Layer 2 Forwarding component: This component performs layer 2
forwarding functions such as VLAN trunking.

Layer 3 Forwarding component: This component performs IPv4 unicast,
and IPv4 multicast forwarding functions.
 Firewall/VPN component: This component performs the firewall and IPSec
based VPN functions in conjunction with Layer 3 Forwarding component.

ACL component: This component performs ACL based stateless firewall
function for packets received on the WAN and main board Fast Ethernet
interfaces.
 QoS component: This component performs the QoS functions for packets
received from WAN interfaces as well as packets transmitted to WAN
interfaces.
 Tunneling component: This component performs the GRE and IPIP
tunneling functions.