Why Startups Fail and Why You Should’ve Too (by Denny K Miu)
Swiss Post on Network Physics

Time to Roll Your Own 802.11n Standard (by Tim O’Neill)

Wireshark_iconSummary of a Conversation with Gerald Combs – Founder of Wireshark and Ethereal


Who is Gerald Combs? – Gerald was a computer science graduate of the University of Missouri-Kansas City, and the creator and lead developer of Ethereal, now Wireshark, which was first released in 1998. Combs worked for Network Integration Services (NIS) until mid-2006 when he moved to a new job at CACE Technologies. Due to trademark issues he was forced to change the name from Ethereal to Wireshark. His goal is to continue to grow Wireshark such that it remains the most wildly used data analyzer in the World.


Tim_oneillEditor Profile - Tim O’Neill is an independent technology consultant. He has over 30 years experience working in the WAN, Analog, ISDN, ATM and LAN test market. Tim has worked with companies like Navtel, Network General, Ganymede and ClearSight Networks and is now helping companies get lab recognition and technology verification. Tim is also the Chief Contributing Editor for LoveMyTool.com, a website designed to help network managers gain access to valuable information and real solution stories from other customers. Tim is a patent holding, published and degreed engineer, who has seen this technology grow from Teletype (current loop) data analysis to today’s 10 Gigabit LAN’s focused on business applications with heavy compliance demands. Tim can be reached at oldcommguy (at) bellsouth (dot) net.


Editor’s Note - It was a real pleasure to spend time with an innovator and a committed technologist like Gerald. Gerald brings to our industry his passion for giving us (network technologist) open source solutions that can help us in our day-to-day management, analysis and troubleshooting needs required of today’s complex networks.

Talking with Gerald is always great. He is an innovator and is dedicated to our industry. He is a leader and a voice to focus our industry toward the global community goals we all must have. If there ever will be peace in this World it will be through information and people like Gerald who help the World get the information it needs.

What makes this article worth reading is that being an open source champion, Gerald does not speak for any corporation and is a unique industry voice who wants interoperability standards for the sake of technology, and not for market shares and profits.


Background - Gerald recently worked on the dissector for IEEE 802.11n to add to Wireshark and his experience with this “standard” got us talking about today’s standards and standards bodies. Gerald said “I was shocked by the lack of requirements in 802.11n. All of the cool stuff that makes 802.11n worthwhile is optional. Is this a standard?”

Once I started reading 802.11n, I was shocked too as I confirmed what Gerald had said. It is all suggestions including the requirement of a base band frequency of 5 MHz, but most of the current “compliant” devices are still running in the 2.4 MHz band. How can there be compliance when there are no real requirements?


Q. How do you meet compliance when everything is an option?

A. You make up your own standard and comply with that!


Why does Gerald care about Standards?

Wireshark (and Ethereal before it) is backed by a world wide community that has helped millions analyze data to solve their network problems and Gerald wants to continue to help grow the diverse support for Wireshark. He, like all developers and manufacturers have a basic need for focused standards and the customers purchasing the next generation equipment need the standards for comparison, access (interoperability) and growth. Without standards there will little support for the technology and interoperability will disappear resulting in the depression of growth in the industry.

More evidence that standards group are having difficulty!

Gerald told me that just a week or so ago there was some controversy surrounding a recent vote in the ISO over the Microsoft Open Office XML (OOXML) format. Almost overnight the call went out to have Microsoft supporters sign up to vote to ratify the MS OOXML format (a competing format, ODF, is already an ISO standard).

This is another example of big business trying to force standards to a business end (money and exclusivity) and not focus on the international best interests (interoperability). Standards should represent the best interests of all users and not special business interests. This story is not over yet as there will be the final vote in February 2008 and MS is only down and not out.

When I was on the T1 committees in the 1980’s working on the ISDN standards, I remember an incident where one group wanted the ability to control the NT1 and NT2 network terminators by a series of special diagnostic packets (digital) and the other incumbent AT&T wanted to use what they had been using for years to loop T1 adaptors, special (analog) tones or signals.

To make sure that AT&T got the standard the way they wanted they sent in many people to vote. Later that night at a reception for all the committee members at a very nice hotel, a physical fight broke out over the anger of losing to this underhanded method. In the end the committees came to a compromise and we had a standard not a group of suggestions.

We both remember when a standard was agreed upon by representative industry technologist and finally published, it was a standard to be measured by and build your equipment to, not a bunch of suggestions, maybes and if you want, comments.

Today’s lack of real requirements is now allowing (or forcing) companies to developing their own standards as we have seen already in the VoIP market.

What does it mean to have 801.11n Compliance?

To be able to say that “One Comply” with a standard there must be some items in the standard that are “Must Do”. Gerald points out that in the 802.11n “Standard”, there is not even one “Must Do” so where is the “Standard”.

(I have a short brief on 802.11n at the end of this article.)

As a result, while 802.11n is not in final release (which is scheduled for March 2009), several manufactures are already building proprietary versions today with over 70 products marketed as meeting “Standard Compliance”. You are seeing pre-n, draft-n and MIMO products already but one must ask “Comply to ‘What’ Standard”?

What we must do?

Gerald said that if he had his way there would be at least 2 “Must Do” requirements –

- Dual Band a must – 802.11n’s wide channels clobber the popular 1-6-11 channel allocation in the 2.4 GHz band.

- Efficiency improvements – 802.11n specifies (but does not require) Block Acks, aggregated MPDUs, aggregated MSDUs, and other features. No more 1 ack per frame in the style of Xmodem.

He also pointed out that some parts of the specification (particularly Greenfield) aren’t widely implemented, if at all.

Gerald’s goals are attainable but we all must mandate that the standards organizations develop real standards with rigid requirements for compliance!


Editor's Note - Gerald, thank you for your valuable time you spent with me discussing some of the problems you have been facing as you develop a broader support base for Wireshark. You have pointed out that we all MUST be involved and help drive standards for the good of the technology and not necessarily just for business reasons. You have reminded us that Standards organization must retake their global goals and focus on the global needs as technical reflections of the best of what our technology must be in the future.

Thank you for all your efforts to help us in our daily network support with Wireshark.


A Short Technical Brief on 802.11n

802.11n builds on the 802.11 group of standards. The 802.11 standard now has up to 802.11y additions, most not released but in process. 802.11n discussion started in January 2004 and is scheduled to be finalized by March 2009. The focus of .11n is to add MIMO (multiple inputs, multiple outputs) pronounced “my mo”, and to significantly increase throughput and reliability.

MIMO has 3 categories Precoding, Diverse Coding and Spatial Multiplexing. The 802.11n is really focused on the Spatial Multiplexing scheme which is a transmission method allowing for the use of many antennas and each one will carry an individually and separately encoded data signals. These signals are referred to as Streams and the design is to take a high rate of data and break it down into a slower stream which is encoded for each antenna.

Each antenna is in the same frequency range and reuses the space of transmission or space dimension more than one time for each antenna. It is like having 6 ears listening to 6 different conversations and than making it into one fast conversation. Each Stream is received by the receiver antennas and decoded than multiplexed back together into the original faster data stream.

The goal of 802.11n is to eventually replace a, b and g modes but the Enhanced Wireless Consortium (EWC) is supporting 3 interoperability modes –

a) Legacy (only 802.11a, and b/g)
b) Mixed (802.11a, b/g, and n)
c) 802.11n only (Greenfield development*) - maximum performance based only on MIMO and nAntennas

* Greenfield is a development term that means all new work not based on any previous works. In the 802.11 world it means replacing the current modes of a, b and g completely.

802.11n goal is a 54 Mbps data rate in the same and moves the base transmission frequency into the 5 Mhz band.

Definitions of the 3 main methods of aggregation techniques to help increase wireless LAN speed.

Block Ack (802.1e) – This is where multiple acknowledgement frames are aggregated into one frame for acknowledgement. There are 2 types of Block Ack’s – Delayed or Immediate.

A-MPDU – Aggregated Mac Protocol Data Unit – This is a method of aggregating multiple MAC layer headers and payloads in a single transmission.

A-MSDU – Aggregated MAC Service Data Unit – This method aggregates multiple MAC payloads that share the same MAC header, e.g. a TCP or RTP stream.


Continue reading other Editorial posts by Tim O'Neill »

Comments