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Broadband is a hot topic in the telecommunications industry nowadays; it is becoming the bread and butter for so many service providers and mobile carriers with the big growth and penetration rates in these technologies in the recent years.  ( Check this report about the EOCD countries). Although it is that important, broadband topics probably are not covered in any certification/education track and the reason might be that there is no “one shop suits all” in this field as in routing and switching technologies. In this post and others my aim is to provide some engineers with a brief but useful information about some of the deployed models today according to my own experience.

First of all let’s set the  scope for this series by starting with a basic question like what is broadband networks as I deal with them?

Technically broadband is any internet connection with higher bandwidth than dial-up connections. Broadband connections can be DSL, cable, satellite or fibre connections. In broadband typically the subscriber has a residential gateway at home/office which might be connected to a MSAN and probably an aggregation network and finally the BNG which will provide the L3 termination point of the connection and is connected to the rest of the service provider network and the Internet.  Many devices are used in broadband networks and cover all the OSI model layers and they typically come from different vendors and they all interact together to provide the service. There is also a decent amount of servers used to provide AAA, billing, Multicast streams, etc services to subscribers. This creates some challenges for engineers working with these networks.

With such number of devices and interactions, I have seen service providers doing a lot of fancy stuff when it comes to service delivery models. Various platforms are used and some providers have fully customized platforms to provide the required flexibility that allows them to design new services anytime, but regardless of the differences, there is always common key points to look for in any network and this is where you can start. I am summing up the story from the networking perspective in the following 5 basic questions, that you might need to ask and answer to make sense of a network you are dealing with. Here they are:

1. Single or Multi-edge topology? In single edge topologies you would find all traffic flows (services) going through the same BNG/BSR, on the other hand in Multi-edge ones you might find that some services are assigned dedicated router, typically this is video services and the dedicated router might be called a VSR or a Video service router.
2. Centralized, distributed model or hybrid? In a distributed model typcially BNGs are distributed in different locations and L3 termination is done as close to the subscriber as possible, however in centralized models you would find that BNGs are collocated in few strategic locations for L3 terminations and subscribers are being aggregated in these locations. Each model has it’s own advantages which I will try to touch from my experience later on also it is good to know that the centralized/distributed model might refer to the service intelligence in which service delivery functions might be centralized on the BNG or distributed on multiple devices along the path and then some protocols are used  for intercommunication between devices like ANCP which I have seen once so far.
3. Traffic Aggregation? This highly depends on the previous two factors and also the next two. It also depends on number of subscribers in each POP, bandwidth requirements and some other considerations and constraints. I have mostly seen aggregation networks with one or more layers of aggregation in big networks.
4. Which Access protocols? PPPOE, DHCP or both? Firstly my experince is that ATM still exists in large old networks but is being migrated or at least not growing anymore. PPPOE and DHCP both are commonly deployed together and each protocol has its own advantages as we will discuss later.
5. Which VLAN model? Customer VLAN (know as C-VLAN) or service VLAN (S-VLAN) or hybrid which combines both models.

Now we will discuss each of these questions in more details in a separate post and There will still be a lot other things you might need to know about a broadband network your are dealing with, as an example if L2TP or whole sale model is used, also QOS models which I am ignoring because they are usually the most complicated and the most customizable to each service provider, I also sometimes find it hard to understand if I didn’t do it myself. But I think the previous five questions is a good starter to dig deeper your design or to get familiar with an existing network.

I  believe in minimalism and what small focused actions can make for a person and small steps is what Juniper learning bytes is all about. Learning bytes is an online learning resource launched last year by Juniper education services organization as a free service.

The nice thing about the learning bytes is that they are focused, short and concise videos that give you a a quick idea about a certain technology, feature or configuration in about 10 minutes  or less and they are created by Juniper’s educational services team right to you.

Here is a good byte, not just because my friend Ayman Aborabh made it but because it’s a good short description of  6PE and how it works. Check it out and explore some of the bytes they offer @ Juniper learning bytes site.

DHCP is vastly growing in service provider networks for broadband subscribers, I had the chance to work lately with a some of these setups. The protocol is really easy to configure for broadband and provide many benefits.  It has lower overhead compared to PPPOE and it is much more suitable for Multicast services.

For those of you who are working with subscriber management, I know sometimes you need to do quick tests to verify new configurations or may be to do some stress or scalability tests. Traffic generators are  more suitable for stress and scalability tests but sometimes I really need some simple tool to play with from my desktop and inspect packets directly.

There are more sophisticated ways to craft packets when needed but this  Linux DHCP client test tool was very handy in doing quick testing, it’s very simple and intuitive to use. It does not offer a complete set of options or operations but it is very useful to test your configuration or to do a simple stress test if your PC can handle it. The limitation I found is that it was not automated, so I had to make my own script to generate MAC addresses and feed it to the tool to issue any number of sessions I like.

I bring up about 16K of DHCP subscribers in about 30min with the script and tool. The script distributes the number of clients on 5 threads to speed up things a bit, but of course this can be optimized in many ways to speed it up, but I will personally keep it simple for everyday use. Feel free to improve this anyway you like but please share the value with the community.

All you need to do is to put the tool and script in the same folder and run the script as follows with superuser privileges.

sudo ./dhcptest.py -i eth1.2668 -s 10000
-i is the interface
-s is the number of subscribers you want to randomly create

Download the tool and check documentation on how to use it from the link below and you can download the python script here. Put them in the same directory and you are good to go.

http://sargandh.wordpress.com/2012/02/23/linux-dhcp-client-simulation-tool/

Note: The script does not have much of error handling, so you need to make sure you are using the correct parameters. The tool must be used with root permissions to be able to open promiscuous sockets on your box.

C’est la vie, it has been almost a year since I posted on the blog, a year full of change,  but here I am kicking up again with this simple short post about how scripting could save you time and effort on daily basis.

I know most of you might be using those free or commercially available applications to manage your daily work and they are all great; and I don’t want to convince you of reinventing the wheel but I am  talking here about higher level of control over your very own, tailored to your specific needs tools.

OK, honestly I am combining both myself, I write scripts that interact with other available tools to get me exactly where I want to go. Here are some ways I use scripting everyday:

Managing/Creating configuration: In my daily work I usually need to apply thousands of configuration lines to a router or multiple to build some lab.  There are many simple ways to automate this daunting operation using existing applications.  But it gets harder when I need to write the configuration dynamically or on the fly, for example when I need to create hundreds/thousands of interfaces with some sequence, addresses  or policies to test something.   I usually use scripts to do the job for me.

Try WISB, it is small application that can be used to distribute the same piece of configuration to multiple devices automatically.

Collecting logs: This is another chore in our jobs,  that is sometimes tricky. If troubleshooting problem or debugging how something works in details, mostlyI need to collect logs in a very systematic way or in specific order from multiple devices, and I always miss, if I do manually. Scripts can do a great job in helping you troubleshoot problems while having your lunch. A recent example  was using a script to monitor a small memory leak problem in a production network which would have been very hard to spot manually.

Simulating scenarios: This is another good job for scripts  simulating specific design issues/problems. I use this often in my daily work by combining my own scripts with other available tools I am usually able to come out with a specific scenario to test something. I use this for generating traffic patterns, flapping interfaces, crafting of packets or other application layer services (HTTP, FTP, etc) if needed.

Stress/performance testing:  scripting also is very useful to stress test or measure the performance of  some services or features on your routers or networks. Like for example testing same host (MAC/IP) enforcements, creating large number of connections to some service.

Finally Having Fun:  writing scripts or automating operations is  fun for many, it breaks the boring repetitive tasks by adding some spice and creativity to it. I spend sometime writing/editing/ debugging the script but once I am done; it acts like an employee that keeps working for me for free ( yes I am lazy but not very much) 

So, my general advice to you would be; Go find a powerful Linux box in your network or lab and play with scripts that would save you time and effort in your daily operations and if you can’t write them yourself most probably you will find many ready available on the Internet out there. Also don’t forget about the scripting capabilities offered by the box itself, that’s a very handy tool too.

Happy Networking ..

Networking is constantly being promoted throughout a huge range of industries, and is generally being seen as more valuable than ever before. However, all too often, it can be swept under the carpet. Those of us who work with technical industries can be particularly prone to not making the most of our networking opportunities. However, here’s a quick remind of why it can be so important.

You may encounter a huge number of people within your current profession that it can be worth keeping in touch with. With most work places offering reliable INTERNET access provided by companies at sites like o2.co.uk, online social networks can make networking easier than ever Sites such as Twitter and LinkedIn can provide the perfect way to contact those who you may not have been able to provide with a business card, or other means of contacting you.

Even if the job which you have at the time when you meet them might not seem as if it will require you to have an extensive number of external contacts, it is well worth thinking about the future – no matter how long you plan to stay in your current employment. Building strong business relationships need not be immediately profitable, but it is a good idea to think about the long-term benefits of such contacts.

If you currently work as an employee, then remember that networking with those who work in a different role within a similar field to your own is a good way to create future opportunities for yourself. You might even consider the possibilities of joint ventures and forming future benefits. Sharing you knowledge with others shouldn’t be seen as helping the competition, but can often be an extremely effective way of enhancing your own career.

It’s a beautiful sunny day that puts a big smile on my face and I want to share it with you, so please put a big smile on your face now and before you continue. Your smile will make my day even brighter.

OK, back to our post but keep smiling

If you are reading my blog then you are related to networking one way or another, and if you are related to networking then most probably you write technical documents and this means this is for you.

In our daily lives as network engineers we involve in technical writing activities very often; we write emails, case resolution, tutorials, blog posts, technical documents and reports. We always strive for the best, enhance and polish our technical skills by reading, training or certifications. However we almost forget to develop this very important skill as we develop other skills, writing is a form of communication and sometimes it’s all you have to express your ideas, being technically good does not make you a good technical writer or communicator.

I made some modest effort on this subject which I will be happy to share with you, I made a special report on this subject of technical writing which I hope you find useful and my aim is to bring your attention to this forgotten skill and add one tool to your tools.

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My friends I am trying to add value here by different ways, so point me to the right direction. Please drop me an email or a comment to give me your feedback, all I am asking in return is your feedback and please keep that smile on your face, it makes you look better.

Have a nice Day