SparkyChick's Guide To IP Networking 1.1

Nice to see all the information in one place. Often feel the IT geeks want to keep it all to themselves and its not rocket science :-)

An excellent summary which I have just discovered. I have some detailed comments which I pass on to you for consideration. I am a network architect by profession.

Token Ring section

Collisions on traditional Ethernet are partially avoided because the sender "listens" to the network and only sends when it sees no data. Each data block starts with a preamble. Collisions occur due to the time it takes data packets to traverse the network (rule of thumb speed of light (c) = 1 nanosecond for foot, pulse travel at about 0.6 c). This limits the size of a network segment to 500 metres so that network collisions can be detected before any real data is sent. If a collision is detected both senders back off for a randomised time before trying again. A second collision causes the randomised time to double. This works very well until the average traffic approaches around 60% to 80% of the theoretical rate (depending on the segment size and hence the propagation delay). After this threshold the throughput drops dramatically to extent that the network is unusable.

Token Ring avoids this cliff edge and performance degrades smoothly.

A Switched Ethernet network still has this theoretical issue but the collisions occur on the back-plane of the Switch which typically are a few centimetres long and run at multi-gigabit speeds. These are never noticeable on modern high speed switches.


Cat 5 (5e, 6 etc. cabling) - splitting cat5/6 into two circuits

This only works at 100 Mbps. One pair is used for transmit and another pair is used for receive. The other two pairs are not used.

Most home network switches now support 1 Gbps and this requires all four pairs which are each used in full duplex. Each pair carries signals at 250 Mbps, which is 2.5 time the data rate of 100 Mbps networks, and are aggregated to give 1000 Mbs data rate.

You could also add that Cat 5 cables are only designed to operate over 90 metres infrastructure cabling between network devices. The specification states 100 metres but this allows for patch cords and drop cables from floor/wall boxes to devices. It will sometimes work over longer distances but reliability falls (I have seen 125 metres sort of work but the performance was noticeably degraded.

Brilliant. Thanks SparkyChick. A lot of info in there!

Concise & very understandable for anybody wanting to get a hold of IP networking- great effort!

Well done - good stuff! THANKS

Excellent piece of work SparkyChick.

There is a typo in the table on page 8 - you have the subnet mask in as 255.255.255.255 on line 2.

A superb resource - thanks SC!