Aligning an 80GHZ link at a mile and other licensed backhauls

Recently we had a teaching moment for a couple of folks who had not had much experience with aligning higher frequency antennas with very tight beamwidths.  This particular day we were aligning 2 foot Siklu 80GHZ antennas.

One of the questions we often get asked is how do you align these? These questions are usually asked by someone who is familiar with aligning 5ghz antennas with a 10 or 20 degree beam which you can eyeball and has tried a microwave shot. They find out it is much harder.  The higher you go in frequency the tighter and smaller the beam is.  Distance also affects how far off you can be.  Think of it as a laser pointer.  If you have ever taken a laser pointer out at night and shone it a long distance you will notice even the slightest movement will cause it to jump inches, even feet.  Keep laser pointer analogy in mind for this next section.

In order to understand alignment, we need to understand lobes on an antenna. An antenna is just a device that focuses radiation in a direction.  In a licensed microwave setup, these antennas focus the radiation in a tighter “beam”.  Let’s go back to our laser pointer analogy.  Some laser pointers project a smaller dot at 10 feet than others.  Same for antennas.   The diagram below shows what is called the main lobe and the side lobe.

The way to get the best signal is to get both dishes locked on to the main lobe. Sounds easy right? With higher frequencies, you are talking about millimeter waves. This means the main lobe may only be 3mm wide, about the size of this text on a laptop screen.  Now imagine trying to keep that 3mm beam in the center of a paper plate at a mile.  On top of that, the difference between the main lobe and locking onto a side lobe could be the difference of 1-2mm. A slight wind can move a dish 2mm.

To give you a real-world example. A 2ft 23 GHz antenna having 3 dB beamwidth of 1.6 degrees. Allowing for a path length of about 2.5 miles (this is licensed 23GHZ) the actual beamwidth at the receiving antenna is around 370 ft and is, therefore, likely to be greater than the height of the tower. If the antenna’s out of horizontal by even a couple of degrees to start, the antennas will miss by around 460 ft and not be able to “see” each other. This can be amplified as frequency and distance increase.

This is all fine and dandy, but what about the practical world? How do I align the thing?
It all starts with the FCC path coordination paperwork you will receive on your licensed link. There is a wealth of information in here.  It tells you all of the following:
-Your mounting height (this is typically already known)
-Your heading (more on this in a bit)
-The antenna angle downtilt or uptilt (very important)
-The expected signal target

Armed with this information you will have all of the information you need to align the link.  From this point, the philosophical side of things kicks in.  Some tower climbers are good with using a compass to get their exact bearings.  Others have high dollar tools to do it all via GPS such as microwave path alignment from Sunsight.

What everyone doing alignment should have in their toolkit are the following:
-A small magnetic bubble Level. We want to make sure we start with a level mount.  We would be fighting an uphill battle if the pipe or standoff we are mounting to is not level.

-An angle Finder is very helpful for determining the antenna down or uptilt per the path calculation.

Obviously, the above tools are just one of many examples.  There are more expensive ones and bare bones ones.  Tools are only as good as the person using them.

-Ratcheting wrenches for the left and right and up and down adjustments.
Having ratcheting wrenches makes fine-tuning a very easy process.  You will see why later.

-A good hands-free communication method.  Depending on the tower FM communications may or may not work.  Cell phones may or may not work. Being able to talk to the crew on the other end is crucial.  And yes, to make this smooth you want a crew on the other end.

Aligning backhauls, especially microwave, is a skilled trade.  With any skilled trade, you will get all kinds of tips and tricks of the trade.  Some you may use, others you may not.  Ask any Carpenter, Drywaller, or Mason and they will tell you little tips and tricks. They probably all are great and will work, but you may only use some of them.  I am going to tell you mine. You may find others you like better.

We always start with a google earth plot of the path. I call this Phase 1.  The goal of phase 1 is to get the radios talking.  We make sure the line is exactly on the two points, not just approximate.  If the backhaul it on the left side of the tower, we draw the line to/from the left side of the tower.  We then pick 2-3 landmarks along the path as we can.  We start with something close to the tower the climber should be able to see.

In our photo above we have picked out two reference points close to the tower the climber can see.  The first is the clump of trees on the climbers left.  The path passes “just to the right” of the edge of the end of the trees.  The second reference is the intersection of the county roads about 2-3 miles out.  Our path should be just to the right of those.  That point of reference is more of a sanity check. More than anything. The climber at the other end has a similar printout.   I have found communication during this process works best if both climbers and someone logged to at least one radio on the ground with a laptop are on a conference bridge.  Many radios have lights, tones, or multimeter outputs to indicate signal.  Some modern radios only have web-interfaces and apps.  Hold a phone while trying to align can be cumbersome.  This is where the guy on the ground can take some load off what the climbers are doing.

Regardless of the mechanics of the radio, the goal of Phase 1 is to establish a radio link, no matter how bad it is. Now, here is where the real meat and potatoes of backhaul alignment come into play.  This is a very deliberate and calculated process.  Your goal at the end of the entire alignment process is to end up with the following diagram

What many folks don’t realize is it is possible to establish a signal on a side lobe. So how do you know if you are on a side lobe? Here is how we start phase 2. This is what I call fine-tuning. Real original huh? Depending on good, or lucky you were during phase 1 you may have a long way to go or a short way to go to meet target.  Remember that in your paperwork we talked about earlier?  One side and one side only starts moving their fine adjustment on their antenna to the left and right and up and down.  This is typically called sweeping.  The key thing to note here is you need to find the very edges of the radio signal, not just the lobe you happen to be on.

Let’s take a real-world example to explain how sweeping affects main and side lobes.  At the start of this article, we mentioned an 80ghz link.  With our phase 1 rough alignment, we were able to get linked at a -86.  The target was a -32.   The first side to start alignment started sweeping to the right, signal started going from a -86 down to a -72 rather quickly. This was using very small turns of the adjustment.  The ratcheting wrench was only clicking 1-2 times for each 2-3 db of signal change. Once it reached a -72 it started climbing back up.   The climber then kept going to the right to find the edge of the signal, not just the lobe we were on.  The signal started getting worse until we were back into the upper 80’s.

Now, the climber brings the alignment back to the left, and stops at the -72 and makes a mental note of where that is in relationship to the overall placement of the dish, etc.  Some mounts have distinct notches, some guys use markers, others just remember.  Now the climber continues on to the left and the -72 gets worse and goes back down to the -86 and continues to get worse.  So the climber, at least for now, has found the sweet spot for the left and right alignment.  The climber also knows this will probably change, but has found it for now.   Climber repeats the same procedure for the up and down. Due to the anglefinder, the climbers have with them they feel pretty confident they are fairly close with the up and down so they do not adjust the up and down travel as much as the procedure goes on.

Next, the other side does the same procedure the first side did. They do the left to right and get the signal down to a -62. Essentially, what the climbers are trying to do is find the center, which will contain the strongest signal, by sweeping past the other signals.  Keep in mind there may be only millimeters separating these other lobes.  Due to physics, and the shape of the signal, the first lobe is actually stronger than the edges of the main beam.

Say what? The first lobe is stronger than the edges of the main beam? Yes, but not stronger than the main beam.  Let’s go back to our installers. They have each had a go around at alignment and are only at a -62.  On a 5ghz backhaul that would be respectable, depending on your noise floor. But we are 30db away from our target of -32. Some climbers, incorrectly I might add, try to do a shortcut by scanning in an x pattern instead of x and y-axis separately. This makes it easier to lock onto a side lobe.

80ghz backhaul

So now our first climber goes back to making the left and right adjustments.   At this point, the installer finds something odd.  He has gotten the signal down to a -55, but that’s the best he can do. Even a small turn jumps the signal up    Then our installer remembers the above statement.  The first lobe is always stronger than the edges of the main beam.  He gets the signal back down to a -55 and turns the alignment over to the other side.

Here is a very important thing to note.  Both of our installers have now “gotten a feel” for the few turns needed to adjust the signal on these dishes.  To them compared to 5ghz dishes, these are very tiny and almost insignificant movements. But they sure make a difference in signal.  Now our installer at tower B has his second alignment session.  As he is making adjustments the signal is not changing.  He is moving his wrench for what seems like forever and the signal is barely moving, Any other time their signal would have been a -90 or dropped.  What has happened here? The main lobe of one side has locked onto the first lobe because it is always stronger.  Since the main lobe is bigger it seems like it takes forever to make any change.  If we had a guy on the laptop he was probably also probably seeing very mismatched data rates.  One side was probably much higher than the other by a large margin.

Then boom, all of a sudden the signal goes from a -55 to a -42.  A 17 db jump!   We can now tell we are on the main lobe.  If the laptop person looks at the data rates now they should be more balanced.

Data Rates on a Mimosa B11 Rates properly aligned but not fine-tuned

At this point, it is just a simple matter of each side making finer and finer adjustments back and forth to get the signal down.  If you think of the above circle/crosshair you are making smaller and smaller adjustments to nudge toward the center of the circle. This is where the ratcheting wrenches help by giving a very measured amount of travel.  This helps with the whole feel of alignment.  Much of it is feel to see how much you can move the adjustment mechanisms to make the numbers move.  Sometimes it may be a single click of the wrench.  Sometimes it may be one or two.  It just depends.  As you get closer and closer to target you are moving the adjustment less and less.

As you get closer and closer to target you need to be thinking about how tightening down the adjustment bolts will affect the alignment.  Even tightening them down snug can affect the signal.  That extra amount movement to tighten them down can move them slightly past their alignment center.  You may need to take into account the amount of travel it takes to tighten down the adjustment bolt into account on smaller dishes.  If it takes a half turn of the bolt to get it tight you may need to stop a half turn and tighten “into” target.  As you tighten it down fully that is where you end up in align.  If you wait until you are in align and then snug it completely down, the force of snugging it down may pull it past and you will end up with a worse signal.

This article sprinkled in some examples from a real-world install, with some theory, with some practical knowledge. Your mileage and experience will vary.  Your experience with 6ghz vs 80ghz will vary as well. Each frequency will have it’s own quirks and tricks.

DHCP Starvation attack

DHCP starvation attacks are designed to deplete all of the addresses within the DHCP scope on a particular segment. Subsequently, a legitimate user is denied an IP address requested via DHCP and thus is not able to access the network.  Yersinia is one such free hacking tool that performs automated DHCP starvation attacks. DHCP starvation may be purely a DoS mechanism or may be used in conjunction with a malicious rogue server attack to redirect traffic to a malicious computer ready to intercept traffic. Imagine a user filling up the dhcp pool and then re-directing users to their own DHCP server.

How do you fix this?
802.11 has several mechanisms built in. DHCP Proxy is one way. Port security is another. If you are running Mikrotik there are some scripts which can alert you to rogue DHCP servers, but that is an after-the-fact kind of thing.

 

Siklu 1200FX Images

WPA is not encrypting your customer traffic

There was a Facebook discussion that popped up tonight about how a WISP answers the question “Is your network secure?” There were many good answers and the notion of WEP vs WPA was brought up.

In today’s society, you need end-to-end encryption for data to be secure. An ISP has no control over where the customer traffic is going. Thus, by default, the ISP has no control over customer traffic being secure.  “But Justin, I run WPA on all my aps and backhauls, so my network is secure.”  Again, think about end-to-end connectivity. Every one of your access points can be encrypted, and every one of your backhauls can be encrypted, but what happens when an attacker breaks into your wiring closet and installs a sniffer on a router or switch port?What most people forget is that WPA key encryption is only going on between the router/ap and the user device.  “But I lock down all my ports.” you say.  Okay, what about your upstream? Who is to say your upstream provider doesn’t have a port mirror running that dumps all your customer traffic somewhere.  “Okay, I will just run encrypted tunnels across my entire network!. Ha! let’s see you tear down that argument!”. Again, what happens when it leaves your network?  The encryption stops at the endpoint, which is the edge of your network.

Another thing everyone hears about is hotspots. Every so often the news runs a fear piece on unsecured hotspots.  This is the same concept.  If you connect to an unsecured hotspot, it is not much different than connecting to a hotspot where the WPA2 key is on a sign behind the cashier at the local coffee shop. The only difference is the “hacker” has an easier time grabbing any unsecured traffic you are sending. Notice I said unsecured.  If you are using SSL to connect to a bank site that session is sent over an encrypted session.  No sniffing going on there.  If you have an encrypted VPN the possibility of traffic being sniffed is next to none. I say next to none because certain types of VPNs are more secure than others. Does that mean the ISP providing the Internet to feed that hotspot is insecure? There is no feasible way for the ISP to provide end to end security of user traffic on the open Internet.

These arguments are why things like SSL and VPNs exist. Google Chrome is now expecting all websites to be SSL enabled to be marked as secure. VPNs can ensure end-to-end security, but only between two points.  Eventually, you will have to leave the safety and venture out into the wild west of the internet.  Things like Intranets exist so users can have access to information but still be protected. Even most of that is over encrypted SSL these days so someone can’t install a sniffer in the basement.

So what is a WISP supposed to say about security? The WISP is no more secure than any other ISP, nor are then any less secure.  The real security comes from the customer. Things like making sure their devices are up-to-date on security patches.  This includes the often forgotten router. Things like secure passwords, paying attention to browser warnings, e-mail awareness, and other things are where the real user security lies. VPN connections to work. Using SSL ports on e-mail. Using SSH and Secure RDP for network admins. Firewalls can help, but they don’t encrypt the traffic. Does all traffic need encrypted? no.

Everything you wanted to know about NTP

Network Time Protocol (NTP) is a service that can be used to synchronize time on network connected devices.   Before we dive into what NTP is, we need to understand why we need accurate time.

The obvious thing is network devices need an accurate clock.  Things like log files with the proper time stamp are important in troubleshooting.  Accurate timing also helps with security prevention measures.  Some attacks use vulnerabilities in time stamps to add in bad payloads or manipulate data. Some companies require accurate time stamps on files and transactions as well for compliance purposes.

So what are these Stratum levels I hear about?
NTP has several levels divided into stratum. All this is the distance from the reference clock source.  A clock which relays UTC (Coordinated Universal Time) that has little to no delay (we are talking nanoseconds) are Stratum-0 servers. These are not used on the network. These are usually atomic and GPS clocks.  A Stratum-0 server is connected to time servers or stratum-1 via GPS or a national time and frequency transmission.  A Stratum 1 device is a very accurate device and is not connected to a Stratum-0 clock over a network.  A Stratum-2 clock receives NTP packets from a Stratum-1 server, a Stratum-3 receives packets from a Stratum-2 server, and so on.  It’s all relative of where the NTP is in relationship to Stratum-1 servers.

Why are there levels?
The further you get away from Stratum-0 the more delay there is.  Things like jitter and network delays affect accuracy.  Most of us network engineers are concerned with milliseconds (ms) of latency.  Time servers are concerned with nanoseconds (ns). Even a server directly connected to a Stratum-0 reference will add 8-10 nanoseconds to UTC time.

My Mikrotik has an NTP server built in? Is that good enough?
This depends on what level of accuracy you want. Do you just need to make sure all of your routers have the same time? then synchronizing with an upstream time server is probably good enough. Having 5000 devices with the same time, AND not having to manually set them or keep them in sync manually is a huge deal.

Do you run a VOIP switch or need to be compliant when it comes to transactions on servers or need to be compliant with various things like Sox compliance you may need a more accurate time source.

What can I do for more accurate time?
Usually, a dedicated appliance is what many networks use.  These are purpose built hardware that receives a signal from GPS. the more accurate you need the time, the more expensive it will become.  Devices that need to be accurate to the nanosecond are usually more expensive than ones accurate to a microsecond.

If you google NTP Appliance you will get a bunch of results.  If you want to setp up from what you are doing currently you can look into these links:

http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html

How to Build a Stratum 1 NTP Server Using A Raspberry Pi

 

Building a Stratum 1 NTP Server with a Raspberry Pi

 

5.8 Cambium Elevated Devices & Max EIRP

Lately, we have had a few clients run into signals becoming worse when they elevated clients to ePMP.   This is not a result of the software being bad, but it enforcing the max EIRP on the units.  This boils down to older devices compliant with original FCC grants which allowed unlimited EIRP.  The Cambium elevate recognizes the latest grant for the devices.  This grant allows for a max of 41 dBM on 5/10/20 mhz channels and 38dBM on 40mhz.

So if you have elevated some older devices from UBNT your signals may have dropped.  This is due to compliance with the latest rules for the device.   As our industry matures, becoming compliant will become more and more important.  On the UBNT units, newer firmware from UBNT also does this.

Cambium has a forum post on this. http://community.cambiumnetworks.com/t5/ePMP-Elevate/5-8-GHz-Elevated-Devices-Maximum-EIRP-in-the-United-States/m-p/73141#M475

We have some tricks of the trade we can do. Contact MTIN for how we can help.

The Importance of cable support in LTE deployments

As the number of WISP LTE deployments increase, there are many things WISPs will need to be mindful of.  One such item is properly supporting antenna cables. LTE systems are more sensitive to cable issues.  In a previous blog post, I talked about pim and low-pim cables.   One of the things that can cause low pim is improperly mated cables.  If cables are not supported they can become loose over time.  Vibration from equipment or even the wind can loosen connections.

How do we support cables?
We can take a cue from the cellular industry. The following are some examples of proper cable support.  Thanks to Joshua Powell for these pics.

Where can you get these?
A good place to start are sites like sitepro1 or Tessco has a selection.

So the next time you are planning your LTE deployment think about cable support.

Learning, certifications and the xISP

One of the most asked questions which comes up in the xISP world is “How do I learn this stuff?”.   Depending on who you ask this could be a lengthy answer or a simple one sentence answer.  Before we answer the question, let’s dive into why the answer is complicated.

In many enterprise environments, there is usually pretty standard deployment of networking hardware.  Typically this is from a certain vendor.  There are many factors involved. in why this is.  The first is total Cost of Ownership (TCO).  It almost always costs less to support one product than to support multiples.  Things like staff training are usually a big factor.  If you are running Cisco it’s cheaper to train and keep updated on just Cisco rather than Cisco and another vendor.

Another factor involved is economies of scale.  Buying all your gear from a certain vendor allows you to leverage buying power. Quantity discounts in other words.  You can commit to buying product over time or all at once.

So, to answer this question in simple terms.  If your network runs Mikrotik, go to a Mikrotik training course.  If you run Ubiquiti go to a Ubiquiti training class.

Now that the simple question has been answered, let’s move on to the complicated, and typically the real world answer and scenario.  Many of our xISP clients have gear from several vendors deployed.  They may have several different kinds of Wireless systems, a switch solution, a router solution, and different pieces in-between.  So where does a person start?

We recommend the following path. You can tweak this a little based on your learning style, skill level, and the gear you want to learn.

1.Start with the Cisco Certified Network Associate (CCNA) certification in Routing and Switching (R&S).  There are a ton of ways to study for this certification.   There are Bootcamps (not a huge fan of these for learning), iPhone and Android Apps (again these are more focused on getting the cert), online, books, and even youtube videos. Through the process of studying for this certification, you will learn many things which will carry over to any vendor.  Things like subnetting, differences between broadcast and collision domains, and even some IPV6 in the newest tracks.  During the course of studying you will learn, and then reinforce that through practice tests and such.  Don’t necessarily focus on the goal of passing the test, focus on the content of the material.  I used to work with a guy who went into every test with the goal of passing at 100%.  This meant he had to know the material. CompTIA is a side path to the Cisco CCNA.  For reasons explained later, COMPTIA Network+ doesn’t necessarily work into my plan, especially when it comes to #3. I would recommend COMPTIA if you have never taken a certification test before.

2.Once you have the CCNA under your belt, take a course in a vendor you will be working the most with.  At the end of this article, I am going to add links to some of the popular vendor certifications and then 3rd party folks who teach classes. One of the advantages of a 3rd party teacher is they are able to apply this to your real world needs. If you are running Mikrotik, take a class in that. Let the certification be a by-product of that class.

3.Once you have completed #1 and #2 under your belt go back to Cisco for their Cisco Certifed Design Associate (CCDA). This is a very crucial step those on a learning path overlook.  Think of your networking knowledge as your end goal is to be able to build a house.  Steps one and two have given you general knowledge, you can now use tools, do some basic configuration.  But you can’t build a house without knowing what is involved in designing foundations,  what materials you need to use, how to compact the soil, etc.  Network design is no different. These are not things you can read in a manual on how to use the tool.  They also are not tool specific.   Some of the things in the Cisco CCDA will be specific to Cisco, but overall it is a general learning track.  Just follow my philosophy in relationship to #1. Focus on the material.

Once you have all of this under your belt look into pulling in pieces of other knowledge. Understanding what is going on is a key to your success.  If you understand what goes on with an IP packet, learning tools like Wireshark will be easier.  As you progress let things grow organically from this point.  Adding equipment in from a Vendor? Update your knowledge or press the new vendor for training options.  Branch out into some other areas ,such as security, to add to your overall understanding.

Never stop learning! Visit our online store for links to recommend books and products.

WISP Based Traning Folks.
These companies and individuals provide WISP based training. Some of it is vendor focused. Some are not.  My advice is to ask questions. See if they are a fit for what your goals are.
-Connectivity Engineer
Butch Evans
Dennis Burgess
Rickey Frey
Steve Discher
Baltic Networks

Vendor Certification Pages
Ubiquiti
Mikrotik
Cisco
Juniper
CWNA
CompTIA

If you provide training let me know and I will add you to this list.