These instructions are intended to help you start using the Endace DAG cards. They are not endorsed by Endace, and if you’re stuck then you should refer to their manuals or contact their technical support people (who are quite helpful). These instructions are based on the DAG7.5G4 PCI Express card.

Interface Modules (SFPs)

Endace only support the Finisar SFPs. Others do work, and I’ve used a Cisco 10/100/1000 SFP that was borrowed from the IT department.

The DAG cards do not support 100BASE-FX SFPs – the only fibre interfaces supported are 1000BASE-X. If you need to monitor 100Mb/s fibre links then you will need a media converter, but any timing measurements need to take into account the latency of the media converter (which are often two port switches).

Basic Capture

If all you want to do is capture frames then set the card up as receive only, fix the ports to the correct rate and you’re done. Most of the time auto-negotiation of duplex works fine, but things do get messy with taps and half duplex devices.

dagconfig default Resets the card to default values

dagconfig 100 rxonly mem=128:0 Sets all ports to 100Mb/s and allocates all the memory to a single receive stream

Now it is time to capture some frames. dagsnap does this for you, but a trap is that it can also store data that has arrived in the meantime. The dagbits command can be used to clean the buffer out first.

The verbose (-v) option of dagsnap shows the total accumulated data, how much of the buffer memory is used and the incoming data rate (in that order). The recording time is specified with the –s option and output file with the –o option. A 15 minute capture to example.erf would be:

dagbits –d0 –cv –S2 Runs for two seconds and clears the buffer

dagsnap –s 900 –v –o example.erf Runs for 900 seconds and saves into example.erf

Viewing Files

Wireshark is a very easy way of viewing ERF files since it supports them directly. Converting the ERF file to a PCAP file with dagconvert reduces the time stamp accuracy. If you capture from multiple ports at once all the frames end up in one file, but the receive interface is stored in the ERF header. Adding a custom column to Wireshark that has the custom field erf.flags.cap makes it very clear where the frames came from. Colour coding based on the interface also helps.

enter image description here

Filtered Capture

Sometimes there is more happening on the network than you care about. DSM filtering is a nice way of doing this, but you need to use DSM firmware. The factory firmware in the DAG7.5G4 is edag75g4pci_dsm_v2_2, and this supports DSM. The latest version is edag75g4pci_bfs_v2_4 and this doesn’t support DSM. If you have upgraded to a new version and want to enable DSM then run dagreset

A DSM filter file is an XML file with special tags. Check the Endace documentation (EDM04-07 dsm_loader User Guide) for details. I want to capture data only if the Ethertype is 0x88BA, so my filter file is:

<?xml version="1.0"?>
<dsm-config version="1.0">
    <!-- SV filter -->
           <ethertype hex="true">88BA</ethertype>
            <ethertype hex="true">88BA</ethertype>

Two filters are needed to ensure frames that are tagged with 802.1Q are also captured. Filters can be set up for particular source or destination addresses too.

The capture process is just like a simple capture, but dsm_loader is run first

dsm_loader -f filter.xml dagbits -d0 -cv 
                 -S2 dagsnap -v -s 15 -o capture_file.erf

The only way of going back to the user/updated firmware is to reboot the computer.

Transmitting Data

The DAG7.5G4 is capable of transmitting and receiving data at the same time. There are some extra setup steps required though. These involve setting up the buffer memory and disabling receive for an interface or two. The data to be transmitted needs to be prepared properly.

The DAG card transmits ERF files, and this means it can transmit from multiple interfaces. The simplest way is to replay a captured file, but you can also convert a PCAP file to ERF and specify which interface should be used. A trap is that the ERF data needs to be aligned to 64 byte boundaries, and this is managed by dagconvert. I haven’t replayed ERF captures, so this example will take some synthetic PCAP data.

To convert input_file.pcap to output_file.erf, with interface 1 (the second port) to be used, run:

dagconvert -i input_file.pcap -o output_file.erf -T pcap:erf -A 64 -p 1

The maximum buffer memory is 128MB, and this needs to be shared with receiving too. The DAG card is very efficient, and even 1MB of receive buffer is enough to capture 100Mb/s data on two ports (total of 200Mb/s going to the disc). The maximum ERF file size I’ve reliably been able to transmit is 125Mb. There may be tricks to work your way through a larger file, but I haven’t had much luck.

To setup the card to receive on interface 0 and transmit on interface 1, both at 100Mb/s and with the transmitted data to follow the timestamps of the ERF file run:

dagconfig default
dagconfig enablea disableb disablec disabled
dagconfig 100 auto_neg rxtx mem=1:127 relative

To transmit and receive, you will need to console windows.

On the transmit one run

dagflood –f output_file.erf –v –r2

On the receive window do your normal capture, such as:

dagbits -d0 -cv -S2
dagsnap -v -s 15 -o capture_file.erf

It is a good idea to wait until the dagbits command has finished before running the dagflood command. I give the dagsnap and extra 10 seconds or so, I wait until it has started capturing some data and then start dagflood.

Complicated Setup

To capture data on interface 0 at 1000Mb/s, capture on interface 1 at 100Mb/s and transmit on interface 2 at 1000Mb/s the following commands would be used:

dagconfig -d0 relative rxtx mem=1:127 enablea enableb disablec disabled  slen=1600 varlen
dagconfig -1 1000 auto_neg
dagconfig -2 100 auto_neg
dagconfig -3 1000 auto_neg

In the receive window:

dsm_loader -f filter.xml
dagbits -d0 -cv -S2
dagsnap -v -s 15 -o capture_file.erf

In the transmit window:

dagflood –f output_file.erf –v –r2

– Runs for two seconds and clears the buffer

The question "Does anyone know if there are guidelines or industry standard for commissioning substation LAN which focuses on Ethernet switches and possibly routers?"" was asked. My response was:

Yang, RFC2544 has a series of tests for benchmarking the performance of interconnect devices like Ethernet switches. The test protocols in there might be a good start for proving network performance.

Any 61850-based substation FAT or SAT should be for the system, not just for the IEDs.

Without Ethernet you don’t have a substation control/protection system. This testing could be system-level performance-based, making sure the inter-trips and controls work within the required time-frame and reliability. I like component testing, but this is more targeted at type testing or design testing. However, if the substation control functional specification has network performance requirements (latency, throughput etc) then this should be tested at the FAT and SAT too.

IEC 61850-4 has the breakdown of what is done and when. FAT and SAT are described in section 7.3.6 and 7.3.7 respectively.

Hi Yang, thanks for the reminder about Y.1564. I had a nagging feeling there was another test spec out there.

I haven’t seen Y.1564 used in substations, but that doesn’t mean it shouldn’t be considered. I think there is much the power industry can learn from Telecoms.

I think a ping test is a very poor test. Firstly it only tests the IP/Management VLAN and not the others that might be in place. Secondly the performance metrics are coarse (millisec times). A more thorough test would include packet injection and capture to make sure frames are not lost at close to line limits. In addition low priority traffic should be injected (unicast and multicast) while protection timing (if GOOSE used for inter-trips) is conducted. Similarly, responsiveness to controls should be tested with some background traffic.

My philosophy is that I want to take the system to breaking point and figure out the safety margin from there. If you don’t break it you don’t know how close to that point you are.

The question was asked "What is the basic difference between PRP (Parallel Redundancy Protocol) and HSR (High availability Seamless Redundancy)". My response was:

Very simply PRP is a duplicate network of whatever design you have (could be rings, mesh or star), while HSR is a ring network. I've seen PRP used in a star configuration, and I think that is its real strength as it is simple.

HSR is the 'zero delay' alternative to RSTP for rings, but does require the use of Redboxes or devices with native support. Quite a few switch manufacturers have embedded modules that provide HSR or PRP functions, or you can purchase code for FPGAs from a number of vendors and use it directly in your device.

@Rod, perhaps in the utility world duplicate protection is the norm, but this is not the case for distribution and industrial applications.

HSR and PRP have application where network based signalling is used and there is a need to maintain the Ethernet switches. With copper signalling each connection is independent, but with Ethernet a switch will affect multiple connections.

RSTP is ambiguous enough with each vendor having differing parameters and their own tweaks for speed. HSR gives more deterministic performance, and PRP avoids slow recovery times with multiple meshes. A second switch is cheaper than duplicating all the protection, and many vendors are supporting HSR/PRP even in their 'low end' devices.

@Rod, I agree that an engineering design (requirements spec, cost/benefit, failure mode study) should be undertaken for any substation LAN design. Unfortunately this doesn't happen.

For small rings RSTP can work fine, and quite a few vendors have dual port IEDs so switches are not required. The hardware cost to go to HSR is minimal (some FPGA code) since there are already two ports on the device. The 'integrated' switch for ring applications has been around for some time (HiPER Ring, MRP, RSTP) — I don't think HSR/PRP has been driving it. For large rings MRP and HSR have definite speed advantages by knowing the topology is a ring. RSTP is more flexible, but that flexibility slows things down.

BTW, as far as integrating protection into a MU — great idea, shame that one of the large European manufacturers is trying to patent this as their own clever idea.

@Juan, differential protection can work through the exchange of phasors too. 64kb/s channels (C37.94 or G.703) are not really enough for raw values, so IEDs process the samples to get the data rate down to a level that can be transmitted.

I think that “Protection Computers” will ultimately do what you propose. ABB already do this with protection of their SVCs, and a Dutch company has a range of products for distribution based on distributed sampling and central protection (but not using 61850). I forget the name at the moment. The substation of the future will have merging units in the field, a few Ethernet switches and two protection computers to do the thinking. The control room can be replaced with a telephone box sized panel!

The question was asked: "Is is possible to connect different Ethernet switches (Manufacturer / Configuration / Specification) in a ring network ? If yes, then how could be the performance of data transfer?". My response was:

There are a number of international standards that deal with ring topologies. RSTP and MSTP are IEEE standards (802.1D and 802.1Q respectively) that work across vendors. These make a 'virtual break' in the ring that can close when a normally close link opens.

A more reliable (but more complex) alternative is HSR – high-availability seamless redundancy – IEC 62439-3, is vendor independent.

There are vendor specific modifications of standards, such as RuggedCom’s eRSTP that has faster ring repair, or Hirschmann’s HiPER Ring that gives faster ring recovery than RSTP. The Media Redundancy Protocol (MRP), IEC 62439-2, is a derivative of HiPER Ring.

One downside with RSTP is that recovery time increases with the number of devices and especially with the number of meshes. Another is that default parameters may vary between vendors so some tuning is required. RSTP does allow more flexibility in network design than with MRP (which is exclusively for rings).

Performance with HSR and MRP will be deterministic (0 ms for HSR and a defined setting for MRP). RSTP performance will depend on the configured parameters and number of devices, so I would recommend testing of the final design. Software simulation is also a good idea, and something that I don’t see much of in industrial network design.