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Linux Rate-Limiting of an ADSL Link

After great pain I’ve got tc working on some Linux routers. The difficulty with limiting an ADSL link is that the ADSL modem has significant buffers and the link between the Linux machine and the modem is significantly faster than the ADSL upstream channel. This means that the transmission speed needs to be artificially limited, [...]

Redundancy in Network Infrastructure

It’s generally accepted that certain things need redundancy. RAID is generally regarded as essential for every server except for the corner case of compute clusters where a few nodes can go offline without affecting the results (EG the Google servers). Having redundant network cables with some sort of failover system between big switches is regarded [...]

Fixing the Correct Network Bottleneck

The latest news in the Australian IT industry is the new National Broadband Network (NBN) plan [1]. It will involve rolling out Fiber To The Home for 90% of the population, the plan is that it will cost the government $43,000,000,000 making it the biggest government project. Kevin Rudd used Twitter to say “Just announced [...]

Bridging and Redundancy

I’ve been working on a redundant wireless network for a client. The network has two sites that have pairs of links (primary and backup) which have dedicated wireless hardware (not 802.11 and some proprietary controller in the device – it’s not an interface for a Linux box).

When I first started work the devices were [...]

Gmail and Anti-Spam

I have just received an email with a question about SE Linux that was re-sent due to the first attempt being blocked by my anti-spam measures. I use the rfc-ignorant.org DNSBL services to stop some of the spam that is sent to me.

The purpose of rfc-ignorant.org is to list systems that are run by [...]

The National Cost of Slow Internet Access

Australia has slow Internet access when compared to other first-world countries. The costs of hosting servers are larger and the cost of residential access is greater with smaller limits. I read news reports with people in other countries complaining about having their home net connection restricted after they transfer 300G in one month, I have [...]

Jabber

I’ve just been setting up jabber.

I followed the advice from System Monitoring on setting up ejabberd [1]. I had previously tried the default jabber server but couldn’t get it working. The ejabberd is written in Erlang [2] which has it’s own daemon that it launches. It seems that Erlang is designed for concurrent and [...]

RPC and SE Linux

One ongoing problem with TCP networking is the combination of RPC services and port based services on the same host. If you have an RPC service that uses a port less than 1024 then typically it will start at 1023 and try lower ports until it finds one that works. A problem that I have [...]

Switches and Cables

I’ve just read an amusing series of blog posts about bad wiring [1]. I’ve seen my share of wiring horror in the past. There are some easy ways of minimising wiring problems which seem to never get implemented.

The first thing to do is to have switches near computers. Having 48 port switches in a [...]

New Net Connections

On Thursday my new InterNode ADSL2+ service was connected [1]. I needed to get a connection with a larger download cap and a better upload speed because one of my clients wants me to transfer some significant amounts of data as well as hosting some Xen DomU’s for him. Strangely InterNode couldn’t offer a regular [...]