Feature Description
The Transactional Rule Matching (TRM) feature enables the Enhanced Charging Service (ECS) to bypass per-packet rule matching on a transaction once the transaction is fully classified. This enables ECS to better utilize CPU resources and accomodate additional throughput for the system, thus improving the overall performance.
A transaction for TRM can be defined as the entire UDP flow, the ACK of the 3-way handshake to the FIN/RST of a TCP flow, or the HTTP request to the next HTTP request, or HTTP request to the FIN/RST for the final request of the flow. The TRM feature can perform rule matching on IP L4 rules (UDP, TCP), HTTP, and HTTPS.
Fastpath
The Fastpath feature can be used to reduce the overall system performance impact as a large amount of data packet is consumed through the ECS data path. The Fastpath feature introduces an alternate ECS data path (Fastpath) with limited supported features. By limiting the supported features, Fastpath eliminates the overhead of packets being subjected to the large number of feature-based conditional checks in ECS.
Fastpath does not replace the existing data path, and works in parallel with the existing ECS data path. The Fastpath feature is part of the Transactional Rule Matching (TRM) feature and requires TRM to be enabled.
 Important |
From 16.0 release, Transactional Rule Matching and Fastpath functionalities have been merged, and will be governed only by the transactional-rule-matching keyword alone. The fastpath keyword independently can no longer be used to turn on or turn off this functionality. |
Feature Support
The following table provides information on the supported and unsupported features of Fastpath. Features that are listed under the Optimized column in the table below indicate that the features are directly supported by Fastpath. Features that are listed under the Eligible column in the table below indicate that a flow requiring the feature does not prevent it from taking advantage of Fastpath. Features that are listed under the unsupported column in the table below indicate that all packets in the flow that belong to the feature is not supported for Fastpath and will take the existing ECS data path.
Important |
The TRM feature is supported in SSI platform; earlier it was restricted only to ASR 5500. |
Important |
MVG is not supported. For more information, contact your Cisco account representative. |
|
Feature |
Fastpath Optimized |
Fastpath Eligible |
Unsupported |
|---|---|---|---|
|
Url Redirect |
— |
Yes |
— |
|
Charging Bucket Maintenance |
— |
Yes |
— |
|
ITC/BW control |
— |
Yes |
— |
|
Next Hop |
— |
Yes |
— |
|
TCP State based rules |
— |
Yes |
— |
|
Post-processing Rules |
— |
Yes |
— |
|
Flow limit - Discard/Redirect/Terminate-Flow/Terminate-Session |
— |
Yes |
— |
|
DSCP / IP TOS |
— |
Yes |
— |
|
ICSR |
— |
Yes |
— |
|
Session Recovery |
— |
Yes |
— |
|
Content Filtering (CF) Static |
— |
— |
Yes |
|
CF Dynamic |
— |
— |
Yes |
|
Socket Migration |
— |
— |
Yes |
|
Blacklisting |
— |
Yes |
— |
|
ICAP |
— |
— |
Yes |
|
NAT |
Yes |
— |
— |
|
SFW |
— |
— |
Yes |
|
Video transrating |
— |
— |
Yes |
|
MVG CAE Readdressing |
— |
— |
Yes |
|
MVG Pacing |
— |
— |
Yes |
|
MVG Link Monitoring |
— |
— |
Yes |
|
MVG Header Insertion |
— |
— |
Yes |
|
ADC/P2P Refer to the Note below this table. |
— |
Yes |
— |
|
SIP-ALG (App Layer Gateway) |
— |
— |
Yes |
|
H323 - ALG |
— |
— |
Yes |
|
DCCA |
— |
Yes |
— |
|
IPv6 |
Yes |
— |
— |
|
Flow Readdress |
— |
— |
Yes |
|
Idle-timeout handling |
Yes |
— |
— |
|
Connection termination (2MSL) |
— |
Yes |
— |
|
TCP Proxy |
— |
— |
Yes |
|
QOS |
— |
Yes |
— |
|
Lawful Intercept |
— |
Yes |
— |
|
HTTP/HTTPS |
— |
Yes |
— |
|
Non HTTP L7 protocols |
— |
— |
Yes |
|
NON UDP/TCP flows |
— |
— |
Yes |
|
Tethering detection |
— |
— |
Yes |
|
Gx |
— |
Yes |
— |
|
Gy |
— |
Yes |
— |
|
HEE |
— |
Yes |
— |
|
Radius |
— |
Yes |
— |
|
Diameter |
— |
Yes |
— |
|
L4 checksum |
— |
— |
Yes |
|
TCP link monitoring |
— |
— |
Yes |
|
Header enrichment |
— |
— |
Yes |
|
Wimax Hotlining |
— |
— |
Yes |
|
Parsing Error Detection Denial |
— |
— |
Yes |
|
IP only Byte Counting/Charging |
Yes |
— |
— |
|
DNS Snoop |
— |
Yes |
— |
|
ICMP |
— |
— |
Yes |
|
Data Record generation |
— |
Yes |
— |
|
Fair Usage |
— |
Yes |
— |
|
SPI |
Yes |
— |
— |
Important |
Note that all ADC protocols are not Fastpath eligible. Refer to the ADC Administration Guide for more information. |
Even when a flow is supported for Fastpath, some packets for the flow are not eligible to be processed in Fastpath. When a packet is not eligible, the packet is processed in the existing ECS data path. The following table provides information on the packet-level support in Fastpath:
|
Packet Handling Feature |
Fastpath Eligible |
No Support |
|---|---|---|
|
Valid UDP/TCP in order pkts |
Yes |
— |
|
OOO Packet handling |
— |
Yes |
|
TCP Retransmissions |
Yes |
— |
|
IP Fragmentation |
— |
Yes |
|
TCP Handshaking |
— |
Yes |
|
TCP Termination |
— |
Yes |
|
First packet of Flow |
— |
Yes |
|
Gx Rule Update |
— |
Yes |
|
Invalid L3/L4 packet |
Yes |
— |
|
Packet already queued |
— |
Yes |
Limitations and Dependencies
The following are limitations to the TRM feature:
-
TRM is supported only on the ASR 5500 platform.
-
TRM is limited to flows with no protocol routing rules with the exception of HTTP and HTTPS flows. All other flows are not supported and TRM does not have any impact on other flows.
-
When TRM is enabled, the following functionalities are affected:
-
Per direction rule matching.
-
TCP state rules for the duration of the TRM transaction.
-
Configuring delay charging when the TRM feature is enabled impacts only packets outside transaction boundaries. All packets within the transaction boundary will be applied to the application (i.e. HTTP).
-
-
Once a flow is classified to a ruledef (first packet in flow for UDP or the first data packet after the 3-way handshake for a TCP flow), TRM will attempt to use that matched rule for the duration of the transaction. This might result in the ruledefs such as those with mid-transaction TCP states or packet direction to be ignored for the flow.
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