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13.05.2014
Have you ever run in to a problem where you are attempting to troubleshoot a network connectivity issue with a network capture utility and seen only the 3 way handshake? It is relatively common knowledge that this will happen when TCP Chimney offload is enabled but disabling it via the registry or netsh sometimes doesn’t always resolve the problem.
The initial troubleshooting for this type of issue is to turn off TCP Chimney Offload via Netsh as follows.
Disabling Chimney with netsh and changed the registry values above will allow you to see all the traffic in most cases but not always. The configurable options available vary depending on how the vendor implements the driver for Windows.
TransportNetLib provides software API to utilize Network Coprocessor (NETCP) hardware accelerator functionality offered by Keystone devices. Packet DMA (PKTDMA) controller in NETCP peripheral enables transfers of data and control packets between NETCP and host. HPLIB (High Performance Lib): Low Overhead user mode library optimized for fast path applications. Note: The transport library is currently restricted to use in one user space process only. For the ingress traffic from network to host, NETCP allows classification lookup offload and policy checks before packets are redirected to application. The section includes more detailed description of various modules included in TransportNetLib.
API is used to return a piece of application-provided opaque data that has been stored in the netapi instance. The configuration APIs are used to insert and remove classification rules in the NETCP hardware lookup engines. Each configuration API returns a handle, Application Id (APPID), for further reference to corresponding NETCP rule. Inserts a MAC interface rule in the NETCP hardware lookup engines for packet classification through first level lookup. Inserts an IP address rule associated with a MAC interface along with optional IP qualifiers in the NETCP hardware lookup engine. Inserts a classifier rule in the NETCP hardware lookup engines which can be used to route a particular packet flow to a specific PKTIO channel. In this mode, the NETCP is setup to do IPSec processing as packets are received or transmitted. Module expands underlying CPPI hardware descriptors for optimal usage at application layer. In order to allow efficient zero copy operations the module introduces concept of zero buffer descriptors (BLD). In the example referred under Figure 4 for the split operation, module expects a packet descriptor (PD: TiPkt) with buffer and linked buffer descriptors (BD) in addition to a Buffer Less Descriptor (BLD). In the example referred under Figure 5 for the merge operation, module expects two separate Packet Descriptors. Module provides network adaptation layer, and abstracts NETCP access to all upper software layers in TransportNetLib package. IPSec Security parameters (Security Policy & Security association) are configured into Linux Kernel by an IKE protocol agent executing in the control plane.
IPSecMgr retrieves the security parameters from Linux Kernel & configure NETCP utilizing the services of NETCP configuration module (NWAL). The library provides optimal implementation for some of necessary helper functions required by Fast Path application running of cores to use TransportNetLib software efficiently.
Provides APIs for synchronization across multiple processes or threads running across SMP ARM processes. The HPLIB provides a set of cache APIs which are required for non-cache coherent memory architectures. API is used to schedule the calling thread to run on the specified core as specified by the CPU set, enables user space access to ARM system timer and the core performance monitor unit (PMU). HPLIB will implement a subset of LLD OSAL APIs as “static inline” functions to avoid the overhead of function calls.
The kernel module is responsible for obtaining a chunk of contiguous, cached memory for the user space transport library to use (from the Kernel Contiguous Memory Allocator a€“CMA).
The kernel module performs a custom mapping of the SOC Queue Manager Data Register space so that writes to hardware queues (Queue Push) can be made bufferable.


IOCTL to return the physical address of the contiguous memory block that has been allocated for user space transport.
Sideband mode data operations are made through PKTIO channels created by NETAPI to send data to NETCP crypto and to receive crypto results.
Packet arrives as normal packet as shown with an AppId meta data tag indicating that a MAC rule or IP rule has matched (it is possible to set up a classifier to match specifically on ESP protocol as well, in which case the AppId would reflect the classifier match). The Application is then required to figure out that this is an IPSec packet and identify security context to use. Once the security context has been found, the packet must be sent to the PKTIO: NETCP_SB_TX channel previously opened. After processing by the NETCP crypto hardware, the decrypted packet will arrive on the PKTIO channel for NETCP_SB_RX, and its associated callback (this channel must be in the list of channels polled obviously). The metadata will also include a pointer to the authentication tag and the length of the tag. In order to encrypt and addition of the authentication tag for a packet during transmit, the sequence is similar to the receive steps.
The (encrypted) packet can then be transmitted to the network as in the case for normal packets.
In any of these cases, the AppId in the metadata returned with the packet will indicate either the Id of the SA (if no policy was matched) or the ID of the policy if a policy is matched. Inflow packets are transmitted using the same PKTIO: NETCP_TX transmit channel as non-IPSec packets. Figure 8 provides breakdown of different steps for outgoing packets with hardware offload being enabled for IPSec packets. The mcsdk_linux_3_00_00_10 and later releases provide an integrated linux-software development kit environment.
Transport-SDK software includes source code for Low Level software modules supporting ARM target. Note: Due to an issue with legacy drivers that expect a contiguous, un-cached DDR area for shared buffers, patches in the kernel that enable continguous, cached DDR that is (hw maintained) coherent with external DMA may be disabled by default in some releases.
Navigate to System Type --->TI KeyStone Implementations and select MPAX based coherency support, exit and save configuration. Note one thing that the ipsecmgr_module will “load” if it is built against the kernel build from the KDIR directory and that kernel is running on the EVM. Transport Library applications may be run in a mode of Linux, known as Low Overhead Linux (LOL), where a subset of  the multi-core ARM15s present on Keystone2 SOCs are dedicated to just the application. The net_test  example programs have configuration via net_test_config file to control how threads are assigned to cores. Please refer to TransportNetLib Test Users Guide for an details about sample test applications being provide with this release. This user space application executes on the ARM and is responsible for detecting IPSEC Security Association and Policy configuration from the Linux Kernel.
Once the kernel detects these entries, they can be offloaded to NETCP (hardware) crypto for IPSEC packet processing using the command shell application described below. To get the sp_id required for the ipsecmgr_cmd_shell, enter the commands below on the daemon (example with k2h). Note: The device tree changes below aren't necessary if using the default TI MCSDK release images. You may also need to look at the features related to TCP Chimney offload available on the Network card. Many network cards have features including Receive Side Scaling, TCP Checksum Offload and TCP Large Send Offload. Refer to the vendor’s documentation for specific information on how to disable offload features. Purpose of this document is to introduce system level details and is intended for software application developers using the TransportNetLib software package. In order to get additional details for the device and peripherals refer URL and reference documentation.
Individual packets to NETCP contain data in containers called descriptors which can be moved between hardware queues.
Both PKTDMA and QMSS are central part of the Multicore Navigator functionality available in keystone devices.
TransportNetLib software available in MCSDK provides highly optimized platform abstraction to application leveraging various hardware offload features supported by NETCP peripheral.


Figure 2 provides an overview of NETCP offload functionality for packets received from network. In addition it allows flexible redirection of packets out of a specific Gigabit Ethernet port. SAs are IPSec security contexts defining uni-directional secure path (tunnel or transport).In addition the security policy API allows configuration to enable policy check for incoming packet at NETCP. In this mode, for receive, IPSec packets will be delivered to the host in the normal manner (via PKTIO ) with an AppId matching an IP configuration, or even just matching a MAC interface in the case that the IP has not been configured into NETCP.
If these APIs are used, then a scheduler instance is required for each thread (ideally one thread per core but this can be also used with multiple threads per core). At the end of the split, module returns pointer to two separate Packet descriptors to the application which is split based on the size configured by application.
At the end of the merge operation a single packet descriptor is returned back which merges both packet descriptors.
Each heap has a specific set of properties and can be used by applications to have buffers & descriptors residing in different memory regions with different properties etc. IPSec security policies & associations for the data plane (also referred to as Fast Path) can be offloaded to NETCP for HW acceleration using this interface. For coherent memory architectures, these cache primitives are not required as cache coherency functionality is handled by the hardware. Currently, these APIs will be provided for QMSS and CPPI LLDs and focus on API’s which get invoked in the data path, such as APIs which perform virtual to physical and physical virtual address translations for buffers and descriptors. This is essentially the packet length (not including Ethernet checksum) minus the Ethernet header and outer IP header.
This environment, once setup, can be used to compile TransportNetLib libraries and test applications. Please note your installation path as this is required to update the TransportNetLib setup environment build script.
This results in a user space transport library that is functional but Not performance optimized.
The variable is “KDIR” and this will need to point to the location where the linux-keystone directory is installed(linux-keystone is the top level directory from where the kernel is built). The kernel boot line command parameter, isolcpus, can be used to isolate one or more ARM15 cores from general SMP balancing and kernel scheduling algorithms. To avoid such a situation, we can assign certain IRQs to subset of ARM15 cores (referred to as slow path core), freeing up other cores to more efficiently run user space applications.
To access these options, choose the configure button on the general tab of the adapters properties. Disabling the offload features of the network card will allow you to view all of the traffic in many cases where disabling the scalable network pack features in the OS doesn’t work. The document includes brief overview of APIs exposed by each module for illustration purpose and is subjected to modifications. Figure 3 illustrates detailed steps involved in the packet transmission path while enabling the offload functionality.
If not used, then application can invoke individual library poll routine directly from their main processing loop.
In the case of non blocking mode, application can invoke separate poll routine to retrieve the status of configuration request to NETCP. To enable full performance for user space transport, the kernel must be rebuilt as shown below so that continguous, cached and DMA-coherent memory is available to user space.
You should refer to the vendor’s documentation for specific steps on how to disable these features.
PKTDMA flows can be configured by the host to specify the buffers and descriptors for the packets forwarded by NETCP peripheral.
Additional steps from application would only require preparation of command label which is attached to the packet during transmission.
The scheduler interface allows for configuration to callback functions to perform periodic housekeeping functions based on number of poll cycles.




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