SNA to Client/Server to Switching to a New Era

I have been posting frequently about networking.  Perhaps my posts have been too piecemeal.  This is an attempt to frame my thoughts over a broader period of time; thirty-two years.  When I look back over this time period, I see the rising and falling of four great networking waves. I believe we are at the end of switching era.  A new era is already taking hold despite many people missing the memo.  In this next wave, there will be the creation of many new companies, market share will shift again and like the prior periods, this new era will witness the dismantling of the networking scaffolding erected during the prior era which I call the switching era.

Wave Time Period Foundations
SNA Era 1974-1994 Mainframe, PU_Type 2 Node
Client/Server Era 1981-1995 IBM PC, Novell, Hubs, Bridges, 10BaseT, Routers
Switching Era 1995-2011 GigE, ASICs to MS, Cut-Trough and Store/Forward
New Era 2012-2027 10GE LOMs, VMs, NAS, App Clusters, Optics

Frame 1: SNA Era

In 1980, the industry of computers was dominated by International Business Machines or IBM.  Every major corporation had an IBM mainframe computer worth millions of dollars in their data center.  The data center was typically referred to as the glass house, as it was a restricted facility, with special power, cooling, and glass windows that enabled the mere mortals of the corporation to walk around it, but not gain access.  In 1974, IBM introduced a technology called Systems Network Architecture or SNA.  SNA was one of the first major initiatives at developing networking technology to connect mainframes and mid-size computers using traditional telephony lines supplied by another giant corporation called American Telephony and Telegraph or AT&T.   SNA enabled corporations with IBM computers to extend the reach of those computers to other users at remote locations around the world through a process called networking.  Computers that were networked were able to communicate with other computers as well as allow users to access computers and information at distant locations.

By 1980, IBM was building multi-host (i.e. mainframe) networks with parallel paths, mesh architectures that could support multiple sessions (i.e. users).  What had started as a solution to provide simple point-to-point network connections had begun to evolve towards sophisticated network designs that could route around failures and handle increased traffic loads.  The simple need to connect two remote computers, evolved into what is generally referred to as a network of many computers and many paths.  The importance of SNA was summarized by the well known SNA consultant Anura Guruge (who is a friend and now semi-retired) in January 2004, “SNA’s remarkable twenty year reign over IBM sector networking is now finally and unequivocally at an end.  Most IBM mainframe ‘shops’, though still inescapably reliant on mission-critical SNA applications, are in the process of inexorably moving toward TCP/IP centric networks – in particular those that combine TCP/IP and Internet [ie. Web] technology to create what are now referred to as ‘intranets’ and ‘extranets’. Mainframe resident SNA applications will, nonetheless, continue to play a crucial role in successfully sustaining worldwide commerce well into the next millennium, way past the Year 2000.

The seminal achievement of SNA in the late 1970s to mid 1980s was to make minicomputers viable from an enterprise perspective. Enterprisecomputer networks were completely dependent on the mainframe computers supplied from IBM or one of the minor mainframe suppliers.  SNA was a proprietary solution implemented by IBM, but it was an open source solution.  This enabled the suppliers of mini computers such as DEC, Wang, Prime, Data General, Apollo, and others to use SNA technology to deploy their systems into the network.  Open source meant that competitors as well as providers of non-competitive systems had access to the technical implementation of SNA and thus could use SNA to add their computers to an SNA network.   The mini-computer vendors implemented a PU_Type 2 node capability on their computers, which enabled these machines to seamlessly interact with mainframe computers as well as each other.  This was the genesis of distributed computing.  It was a seminal moment that gave birth to the commercial network within the enterprise market and started the progression towards the client/server network.  This occurrence may not have had the dramatic overtones of Roger Kildall flying his plane while IBM waited in his lobby to license CP/M for the personal computer – but it is significant because networking of computers started with IBM.

Frame 2: Client/Server Era

The client/server architecture is the reason why Cisco Systems exists as a company today.  The general population may think of Cisco in the context of the internet, but Cisco Systems was built by providing corporate America, and most of the industrialized world, with multi-protocol routers and switches that link client/server local area networks with back office mainframe and mid-range computing platforms.  The introduction of the PC created the necessity for the creation of the server – which would drive the development of the client/server network.  Cisco is the company that providing the routers to connect the computer networks of corporateAmerica, but with this accomplishment it achieved a deeper position of strategic importance.  By plan, accident, or both, Cisco’s routers became the control plane for the enterprise network.

In the early days of the PC industry, computer hard drives and storage space were expensive.  It was technically easier and financially superior to network PCs in the same way mainframe computers and terminals were networked.  The server would act as a host (i.e. mainframe) and users (i.e. personal computers) would access applications and data on the server over the network.  To create the local area network (i.e. LAN) of PCs and servers, networking technologies such as Ethernet, Token-Ring, and AppleTalk was deployed.  Ethernet was developed at Xerox’s Palo Alto Research Center (PARC).  Token-Ring was developed and introduced by IBM.  For much of the late 1980s and into the early 1990s, Token-Ring and Ethernet were the competing technologies for the deployment of LANs.  Today, Ethernet is the most widely deployed LAN technology and will soon dominate the Wide Area Network (WAN).

The development of applications to reside on servers by companies such as Novell enabled the desktop computer to access a central computer (i.e. server) that housed data and applications.  To create a LAN, companies needed to provide connectivity from each desktop computer to the location of the client/server.  The architecture for networking a client/server network came from the heritage of the SNA network.  IBM deployed mainframe computers in a central location (i.e. glass house) and linked them to remote terminals (i.e. personal computers).  The client/server LAN deployed servers in a central location, called a data center or wiring closet, and networked each personal computer to the server using Ethernet or Token-Ring.  Suddenly, there was a market beyond the desktop computer and it began to spawn many new companies.  In the early to mid-1980s the first networking companies began to emerge.  The first explosive growth market for networking companies was not for routers or bridges – it was for hubs.  Hubs were bridging platforms that enabled corporations to rewire their office facilities and provide to each desktop computer access to central locations where the servers resided.  The mass introduction of the PC into corporateAmericabegan in the early to mid 1980s.  At the time, LANs were new.  Buildings had to be wired to support the personal computer and products installed to provide connectivity.  The two dominant companies to emerge in this market segment were Cabletron and Synoptics.  The second tier players were Ungermann-Bass, Chipcom, Bytex, 3Com, DEC, and a host of minor players.  The wiring of corporateAmericawas the first great networking market to find its roots directly linked to the PC.

Frame 3: Switching Era

The switching era finds its roots in a company called Kalpana, full duplex ethernet and the development of gigabit ethernet.  In 1990, Kalpana introduced an ethernet networking device that used cut through switching technology to quickly parse the header of the ethernet packet to complete a fast processing decision.  Soon store and forward ASICs would equal cut-through switching speed.  ASICs would evolve to what we know today as the merchant silicon phase with networking vendors buying chips from Broadcom or Intel.

The era was dominated by M&A in the early years: Cresendo, Kalpana,Grand Junction, Synernetics, Xedia, Xylan, and Prominet are a few examples of M&A deals.  Synoptics and Wellfleet merged and Cabletron broke up.  Cisco acquired IBM’s networking division in 1999 and thirteen years later I expect IBM to be active in building a new networking division as they have a start with XIV and BNT.

I inserted a few charts to highlight the switching era.  The first is just a collection of network diagrams taken from various presentations, web sites and the internet archive from 1991 to 2011.  My conclusion is a slow rate of change.  I also inserted three diagrams that show various startups in during the switching era by technology.  I have not updated since Dec 2007

Frame 4: New Era

In my opinion we have reached the end of the 15-20 year cycle called switching.  There are many reasons for me to make this conclusion: 10G LOM, Virtualization, Big Data, 100G, NAS, etc.  These technology drivers are the engines behind the need to scrap the old approaches.  We have reached a point of Moore’s Law Exhaustion.  The new era of networking is going to be built on a different frame work of application, compute, storage an network assumptions.  As with prior eras, the compute element is a driver.  The network must become extensible in the same way compute, applications and storage are evolving.  Ridged network structures that scale vertically become passé.  The network becomes a dynamic and extensible resource.  That is the future and each week I meet more people searching for this type of network and it is emerging from the data center.


* It is all about the network stupid, because it is all about compute. *

** Comments are always welcome in the comments section or in private. ** 

3 thoughts on “SNA to Client/Server to Switching to a New Era

  1. Pingback: PE-Buyout, Technology Companies and Vertical Integration « SIWDT

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