Tag Archives: network

Aztech Homeplug HL115EP

I’ve been using the Aztech homeplugs for over 3 years now. Started with the HL109EP, used it for some time, and then several months back I upgraded to the HL115EP.

My preference for home networking connectivity is Cat5e UTP cables. However, when I moved into my current apartment in 2008, renovation works was kept to a bare minimal, and so to run new wiring was not an option. The next best thing was to leverage existing cables.

My apartment has 2 levels with the core internet access point in a far end of the apartment. Wireless reach is poor, and I had to extend it. Wireless bridging didn’t give good performance, and would require several Linksys WRT54GL (my old time favorite hacked with DD-WRT) to cover the whole apartment. So, the other alternative was with physical connectivity, which cleverly uses the power lines that reaches to every corner of the apartment.

The Aztech homeplugs were introduced, and worked pretty well. The electric cabling around the house became the core network backbone of my home network.

With the HL109EP, which on the box rates to be 200Mbps, was able to deliver up to 36Mbps with the power points on the lower level, and about 17Mbps on the higher level. The reason was how the electrical connection was done; there’s a big hop from the lower to upper level.

The LAN port on the HL109EP was 100Base-T, which is very common. If you are thinking now, how will 100Base-T give 200Mbps, it’s the common marketing gimmick of adding upstream (100Mbps) and downstream (100Mbps). As my internet connection back then a 10Mbps (ADSL), that was good enough. Anywhere in the apartment I could make use of the full bandwidth of my internet line.

Earlier this year, I upgraded to 50Mbps Fibre. That puts the “core network” to be the bottleneck. The reasonable option was to upgrade. Quite coincidentally, Aztech launched the new HL115EP. On the box it says 500Mbps, and the device has a 1Gbps LAN port. How this has improved is that the device has a built in noise filter. This will effectively improves on the quality of the signal the HL115EP can deliver over the same wires, and therefore achieving higher speed.

The performance of the HL115EP is definitely noticeable. In my case as a 1 to 1 replacement of the HL109EP it gives me double the throughput. At times it can go faster up to 3x but that really depends on how noisy the power lines are.

One thing to note is that the HL115EP does not work with the HL109EP, they will not talk to each other. However, if you have multiples of each, and need 2 discreet networks, that will work just fine. So say if you want to have 2 networks on the same premise that do not talk to each other, you can have one network made up of HL109EP, and another of HL115EP.

I don’t have experience with other competing products and cannot compare. But what I can advise is that keep your Powerline networking gears to be consistent throughout. Don’t attempt to mix and match. I was lucky to be able to upgrade all my HL109EP to HL115EP through an Aztech launch promotion!!

I did say to keep the Powerline equipment consistent; that’s all that really matters. Your internet router, wireless access points, NAS, everything else on the network, does not have to be an Aztech. I have a 2Wire router (provided by my ISP), a DLink Gigabit switch, Linksys WRT54GL, Baffalo WZR-HP-G300NH, Foscam FI8919W, Apple Airport Express connected to various HL115EP and they are working very well.

For those who wonder how I test the network throughput, basically just having a PC/notebook at each end of the HL115EP and run iperf on them.

Anyone in Singapore who is keen to invest in the HL115EP, on tip is Aztech is in every PC show that happens every 3 months in Singapore. You can typically buy a pair for under S$120. Outside the PC show, a pair will cost about S$130 depending on where you shop. Find the brochure of a recent PC show here.

what the hell is speed and duplex?

It’s actually quite amazing that many many many IT professionals out there is actually quite ignorant about some basic network understanding. Perhaps, forgivable if your IT exposure is high up in the application stack… for those who live and breath system administration… and even for those who are network administrators… no excuse at all.

So, what’s this about? This is about fundamental configuration of physical ethernet network connections. Something a vast majority takes for granted. This applies very much to the days of 10/100Mbps networks, which is still very prevalent in current environment, but is slowly going away.

In ethernet, when 2 devices are connected together with a regular UTP cable, they’ll need to communicated at the same speed and mode of transmission. For optimal operations, both ends have got to be operating at the same settings. For speed, there’s a choice of 10Mbps or 100Mbps, and transmission mode is full or half duplex.

If there is speed mismatch, there won’t be any communications at all, and it’s easily corrected. So once you see there’s a link, the speed is definitely a match. However, what’s not obvious at all is that the transmission mode (duplex settings) may not match. And when they don’t match, the result is horrifyingly slow throughput.

So what does full duplex and half duplex mean? It simply means when and how each device is allowed to transmit. In half duplex mode, it means only 1 of the devices is allowed to transmit at any one time. The other just listens. In full duplex mode, both devices are allowed to transmit at the same time. In the very early days of ethernet over UTP, the cores in the wire are shared, such that the transmission cables are shared, as such when more than 1 device transmits, the message on the cable  gets “noisy” and collision occurs.

Imagine, that if at one end, device A is told to communicate at half duplex, and at the other end, device B thinks full duplex is in operation. So, when A is sending out signal to B, and B needs to send something back to A, B thinks it’s ok and sends out the message. A is not expecting anything from B at all, and so is unable to handle the traffic from B. As a result collision occurs. A will keep resending it’s data thinking that it never reached B, and in the end, a whole lot of miscommunication occurs. This causes what appears to be very very slow throughput.

In this day and age, I would say all cat 5 UTP cables and devices are full duplex capable. Also, there is a 5th setting called “Autodetect”. It’s this “autodetect” setting which introduces a lot convenience as well as headache. Personally, I love “autodetect” and advocate the use of it. But by those who don’t understand it, avoids it at all cost. In fact, some IT shops will default to move away from “autodetect” at all costs.

So, why are some network people so afraid of “autodetect”? More often than not, they’ve had bad experience with poor performances due to duplex mismatch. There is some history to this…. when autodetect first showed up, there was interoperability issues between different vendors. Naturally, for that reason, it’s fair to set a standard to avoid “autodetect” as a default setting. But this is something one will observe maybe 15-20 years ago.

Soon after, the IEEE stepped in to resolve this by standardizing how “autodetect” should work. It’s a good thing, but the standardization is quite peculiar. Here’s why….

Autodetect is great with speed negotiation, if there’s no cabling issue, both devices will negotiate at the highest possible speed. Usually no issues here. Even if one end is put to a manual setting on speed, the other end on auto will still get it right.

Then, here comes the fun part… if one end is set manually on the duplex, the end which is on auto will default to half duplex. Yes, half, not full. I never understood what the reason is. But you can see that if someone sets one end to full duplex, the other end on auto will always talk in half duplex. As a result, we have a duplx mismatch, and performance will be bad.

So, if no one takes care to understand why performance tanks when network settings don’t match at both ends, you’ll get an environment without a standard. You’ll see some ports are set to autonegotiate, and some are set to manual… and some do have mismatch and some don’t.

My take is that, if you’ve got fairly recent equipment, just leave everything on default to be on “autonegotiate”. If you’ve got flaky performance, it’s more likely due to bad cabling, and have that fixed. If you are using manual or static type settings, cable issues are less likely to surface, and it’s not obvious that there may be cabling issue at all.

XBMC on XBOX not playing MP4 files – solved!!

I’ve been using XMBC on the XBOX for several months now… (yes it’s kinda late) but hey, it still rocks!!

Then recently, I moved the XBOX to the living room and for some reason the MP4 files would not play anymore. Everything else worked fine… but not MP4. I spent over a month troubleshooting it, re-installing XMBC, etc.. nothing worked. All I knew was that these files would play, when the XBOX was in my study & in the bedroom.

Finally, I was shown the light, by someone a lot less techy than me… my wife. I lamented to her about the unexplainable problem I was having with the XBOX. Then she asked… “is it because of the TV?” That literally lit up the bulb in my head and it lit up the path to the solution.

So, how does the TV have anything to do with the XBOX? What ever the XBOX should not be dependent on the TV. So, up front, that theory should have gone out the window… but not exactly. It was due to the TV, or rather… the xbox is connected to the TV using component cables. Everywhere else was using regular RCA. So… what’s the difference?

The difference was 1080i. Because the XBOX was using component cables, I had it configured to go up to 1080i. So, I turned of all hi-def resolutions (480p, 720p & 1080i) and tried. The movie played flawlessly. It was just that simple!! Further testing confirmed that MP4 would play in 480p and 720p… but not 1080i. That’s good enough… since my MP4 were all standard def anyway.

So, the month long troubleshooting, network testing, performance tuning, all went no where. It was simply just the XBOX settings for the TV.

Definitely learnt a new lesson about checking on the basics… even if it’s seemingly unrelated.

All thanks to my dear wife, Winny =)

PPTP over cellular network with iPhone 3GS

ever since I upgraded my iPhone to OS3.0, I’ve been having trouble trying to get PPTP VPN to work. Never had the time to seriously look at it until now.

My VPN end point is a Linksys WRT54GL running with DD-WRT. I know that PPTP service works there as I can connect with my notebook, even with my 3G dongle.

Initial findings pointed towards the support for encryption on the DD-WRT implementation, and it has to be forced to “none” on the iPhone. Even that didn’t work.

With the release of OS 3.1, I started to tether my notebook to the iPhone, and through that, the PPTP will fail. That stumped me! Initially I thought could be due to the NAT implementation to enable tethering.

With trial and errors, I found out that over a WIFI connection, PPTP connection will work. Did I forget to mention that CISCO based IPSEC VPN to my office network works nicely over cellular and WIFI? That really baffled me. So, there’s something that’s in place that only works for IPSEC over cellular.

Finally, I came across some forum postings that lead me to the solution. There are many other people with similar issues in Canada and USA, and for some, they are able to tweak their APN on the phone to a different one and it worked for them. Of course they needed to be on different data subscription etc… for that to work.

I’m in Singapore, and my cellular provider is SingTel. I whipped out my iPhone 3GS and compared it’s APN settings to my 3G dongle for my notebook. Wallah! they are different, even though they are both with SingTel. I swapped in the new APN settings on to the iPhone, and PPTP started to work.

So, for all those in Singapore and on SingTel with similar needs and issues, the solution is to change the APN from “e-ideas” to “internet”. And here’s SingTel’s official instructions. BTW, these instructions are generic for all data devices.

For everyone else, what I realize from this is that some services/ports are controlled by the service provider. So, just by changing the APN won’t work if you don’t have access to the relevant APN.

If you need some guide on how to set your APN on your iPhone, the official Apple guide is found here.

*update 2009 Oct 09* after changing the APN, the “tethering” feature disappears. But if I reset the “Cellular Network” settings, “tethering” comes back. Got to figure out how to enable both.

free way to manage IP addresses

if you’ve ever setup a network and handled IP address allocation, more often than not, you may try to remember the network addressing in your head.

C’mon, how many people out there really document what you do. Techies are well known to not document what we do. Just about very often, we’ll end up forgetting what we have done before. When ever we have to revisit the environment, we’ll need to dig deep into our memory, hoping we can recall our work.

Face it, even I have learnt the lesson of not documenting. Age is catching up and memory is not as good as it used to be. Now, the very least I’ll document the important stuffs.

So, how’s this related to IP address management? I see it simply as documentation of IP address usage. If you do document your IP addresses, I’d guess you’ll probably be using an excel spreadsheet. Heck, a lot of people I know uses excel spreadsheets to track IP address allocations.

Such a document is critical to keep up to date, and you’ll need good team discipline to keep the information current. All you need is just one, yes one, slack in the updates and hell can potentially break loose.

So, here I have stumbled upon a nice tool released by Solarwinds. My network engineer once told me that Solarwind products are very powerful and useful to manage large networks. I never had the chance to experience it, but I’ve played a little with this niftly little free tool they have, the “IP Address Tracker”.

This free version runs standalone, and capable of scanning the given subnet for all IPs which are online at the time. If SNMP is enabled, it will also tryto automatically pick up some details regarding each device. You can also flag each IP manually to categorize them, in addtion you can certainly put down little comments for every address. It will also keep track on the current latency of the IP, the last known date and time it was reacheable.

The user interface is pretty straighforward, and I like it. I use it personally to help me document the few home networks I’m helping to up-keep for my family.

Now, it gets even better, this tool has a paid version which can integrate into the Solarwinds suite of tools. I haven’t seen how it works, but some features I’ve read include running the app as a service, so it can do a realtime tracking of used IP addresses. In addition, it will provide a web interface, meaning a team of network engineers can potentially use it at the same time. That’s my favorite bit, real-time automated documentation and tracking of IP addresses being used.

This tool can certainly save time and effort for network engineers.

With all these said, this tool is only for those networks which allows (I assume) ICMP pings. Otherwise, excel will be your best friend.

Best Home Router?

For a techie like myself, I tend to prefer devices which are less of an all-in-one design. These devices though reduces the clutter you may have, but makes the situation more restrictive when you want or need an upgrade. You’ll end up having to either find a new device which has all the functions, or you’ll need to start to break them up.

This is especially true for my home broadband connection. I don’t like to use an all-in-one modem/router/wifi device. Although I don’t have a choice to use one provided by my ISP,  as I need it for the VOIP function it provides, but I still use another router to perform the routing function.

So, I have a 2wire 2700HGV-2, it’s a VOIP/WIFI/DSL Modem/Router rolled into one. I only use it for the VOIP and DSS Modem function. For Router, I use a Linksys WRT54GL (with a 3rd party firmware hack).

Don’t trust my 2700HGV-2 to do everything, as it ends up hanging every other day. With this combination, my overall setup runs more stable. And on top of that, I have a great router that does a lot more.

How about giving you a day by day chart on your internet usage volume, a realtime chart on your network & internet traffic, or the ability to create more SSID for your home WIFI network, for those times when a friend visits, needs to have internet access on his iPhone, but you want to only grant him “guest” access? These are features of commercial routers which are at the cheapest, several hundred dollars.

The Linksys WRT54GL costs under S$88 and DD-WRT (the 3rd party firmware) is free! [donation to the developer is available if you like the firmware]

You just need to download and re-flash the firmware and you’ve upgraded your S$88 router to be capable of features found in a US$399 router!

I’ve been using DD-WRT for a few years now, and I totally like the stability and what it can do for me. In fact, one of my main reasons that I encourage my friends to use it is to setup bridged wireless networks.

My next upgrade to my router will definitely a router capable of running DD-WRT, and provides good wireless N performance.