IPSA offloads flow-based enhanced pattern matching to CPx processors

IPSA offloads enhanced pattern matching operations required for flow-based content processing to CP8 and CP9 Content Processors. IPSA offloads enhanced pattern matching for NTurbo firewall sessions and firewall sessions that are not offloaded to NP processors. When IPSA is turned on, flow-based pattern databases are compiled and downloaded to the content processors from the IPS engine and IPS database. Flow-based pattern matching requests are redirected to the CP hardware reducing the load on the FortiGate CPU and accelerating pattern matching.

 

IF IPSA is supported on your FortiGate unit, you can use the following command to configure it:

config ips global

set cp-accel-mode {advanced | basic | none}

end

basic offloads basic pattern matching. advanced offloads more types of pattern matching resulting in higher throughput than basic mode. advanced is only available on FortiGate models with two or more CP8s or one or more CP9s. If the cp-accel-mode option is not available, then your FortiGate does not support IPSA.

On FortiGates with one CP8, the default cp-accel-mode is basic. Setting the mode to advanced does not change the types of pattern matching that are offloaded.

On FortiGates with two or more CP8s or one or more CP9s the default cp-accel-mode is advanced. You can set the mode to basic to offload fewer types of pattern matching.

 

NP6 Acceleration

NP6 network processors provide fastpath acceleration by offloading communication sessions from the FortiGate CPU. When the first packet of a new session is received by an interface connected to an NP6 processor, just like any session connecting with any FortiGate interface, the session is forwarded to the FortiGate CPU where it is matched with a security policy. If the session is accepted by a security policy and if the session can be offloaded its session key is copied to the NP6 processor that received the packet. All of the rest of the packets in the session are intercepted by the NP6 processor and fast-pathed out of the FortiGate unit to their destination without ever passing through the FortiGate CPU. The result is enhanced network performance provided by the NP6 processor plus the network processing load is removed from the CPU. In addition the NP6 processor can handle some CPU intensive tasks, like IPsec VPN encryption/decryption.

Session keys (and IPsec SA keys) are stored in the memory of the NP6 processor that is connected to the interface that received the packet that started the session. All sessions are fast-pathed and accelerated, even if they exit the FortiGate unit through an interface connected to another NP6. There is no dependence on getting the right pair of interfaces since the offloading is done by the receiving NP6.

The key to making this possible is an Integrated Switch Fabric (ISF) that connects the NP6s and the FortiGate unit interfaces together. Many FortiGate units with NP6 processors also have an ISF. The ISF allows any port connectivity. All ports and NP6s can communicate with each other over the ISF. There are no special ingress and egress fast path requirements as long as traffic enters and exits on interfaces connected to the same ISF.

Some FortiGate units, such as the FortiGate-1000D include multiple NP6 processors that are not connected by an ISF. Because the ISF is not present fast path acceleration is supported only between interfaces connected to the same NP6 processor. Since the ISF introduces some latency, models with no ISF provide low-latency network acceleration between network interfaces connected to the same NP6 processor.

 

There are at least two limitations to keep in mind:

• The capacity of each NP6 processor. An individual NP6 processor can support between 10 and 16 million sessions. This number is limited by the amount of memory the processor has. Once an NP6 processor hits its session limit, sessions that are over the limit are sent to the CPU. You can avoid this problem by as much as possible distributing incoming sessions evenly among the NP6 processors. To be able to do this you need to be aware of which interfaces connect to which NP6 processors and distribute incoming traffic accordingly.
• Some FortiGate units may use some NP6 processors for special functions. For example, ports 25 to 32 of the FortiGate-3700D can be used for low latency offloading.

 

NP6 session fast path requirements

 

NP6 processors can offload the following traffic and services:

• IPv4 and IPv6 traffic and NAT64 and NAT46 traffic (as well as IPv4 and IPv6 versions of the following traffic types where appropriate)
• Link aggregation (LAG) (IEEE 802.3ad) traffic (see Increasing NP6 offloading capacity using link aggregation groups (LAGs) on page 1211)
• TCP, UDP, ICMP and SCTP traffic
• IPsec VPN traffic, and offloading of IPsec encryption/decryption (including SHA2-256 and SHA2-512)
• IPsec traffic that passes through a FortiGate without being unencrypted.
• Anomaly-based intrusion prevention, checksum offload and packet defragmentation
• SIT and IPv6 Tunnelling sessions
• Multicast traffic (including Multicast over IPsec)
• CAPWAP and wireless bridge traffic tunnel encapsulation to enable line rate wireless forwarding from FortiAP devices
• Traffic shaping and priority queuing for both shared and per IP traffic shaping.
• Syn proxying
• Inter-VDOM link traffic

Sessions that are offloaded must be fast path ready. For a session to be fast path ready it must meet the following criteria:

• Layer 2 type/length must be 0x0800 for IPv4 or 0x86dd for IPv6 (IEEE 802.1q VLAN specification is supported)
• Layer 3 protocol can be IPv4 or IPv6
• Layer 4 protocol can be UDP, TCP, ICMP, or SCTP
• In most cases, Layer 3 / Layer 4 header or content modification sessions that require a session helper can be offloaded.
• Local host traffic (originated by the FortiGate unit) can be offloaded
• If the FortiGate supports, NTurbo sessions can be offloaded if they are accepted by firewall policies that include IPS, Application Control, CASI, flow-based antivirus, or flow-based web filtering.

Offloading Application layer content modification is not supported. This means that sessions are not offloaded if they are accepted by firewall policies that include proxy-based virus scanning, proxy-based web filtering, DNS filtering, DLP, Anti-Spam, VoIP, ICAP, Web Application Firewall, or Proxy options.

If you disable anomaly checks by Intrusion Prevention (IPS), you can still enable hard- ware accelerated anomaly checks using the  fp-anomaly field of the config system interface CLI command. See Configuring individual NP6 pro- cessors on page 1215.

If a session is not fast path ready, the FortiGate unit will not send the session key or IPsec SA key to the NP6 processor. Without the session key, all session key lookup by a network processor for incoming packets of that session fails, causing all session packets to be sent to the FortiGate unit’s main processing resources, and processed at normal speeds.

If a session is fast path ready, the FortiGate unit will send the session key or IPsec SA key to the network processor. Session key or IPsec SA key lookups then succeed for subsequent packets from the known session or IPsec SA.

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