Networks

INDEX

• What IS a Network?
  
• How Do Networks Work?
  
• Network Structure
  
• Network Personalities
  
  • Peer-to-Peer Networks
  • Server based Networks
  • Client/Server Networks
• Servers
  
• Network Operating Systems
  • Microsoft Networking (WFW, Win95/98)
  • Artisoft LANtastic
  • OS/2 Peer
  • Windows NT/2000 Server
  • Novell NetWare
  • Linux/SAMBA
  • OS/2 Warp Server
  • Unix (Solaris, etc.)
  • AS/400
  • SNA
• Topologies
  • Star, Bus, Ring
• Protocols
  • Physical Protocols: - Ethernet, Token Ring, Arcnet
    
  • Logical Protocols: - TCP/IP, IPX/SPX, NetBIOS, NetBEUI, SMB
• Wire and Cable - Getting Physical

• Back - to Design

What IS a Network?

• A network is a system by which a computer called a "server" can offer its resources (hard disks, directories, CD-ROMs, modems,etc.) for use by other computers as if they were their own resources.
  
• A network is a means by which people working at different computers can be working with, and updating, the exact same data files simultaneously. That way no one is working with obsolete versions of the data.
  
• A network is a system by which data can be moved from one computer to another.
  
• A network is a communications system, hosting electronic mail, Internet access, and even voice telephone communications.
  
• A network is a method by which security and company policies can be enforced across the diverse computers scattered about the business.

How do Networks Work?

Circuit Switched Networks

POTS (Plain Old Telephone Service) is a switched network. When you make a call from one phone to another, switches make an actual connection between the two phones. That connection is dedicated to traffic between those two "nodes" until you hang up.

Today, the #9 crossbar is gone from the telephone system, and the telephone switches are all actually big Unix based computers.

The connection between a dumb terminal and a computer is a "switched" network (even if the only "switch" is plugging and unplugging cables). This includes terminals connected through a modem and computers acting as terminals (terminal emulation) over a modem connection or serial cable.

Packet Switched Networks

A packet network works like the postal system. Information to be transmitted is cut into pages of convenient size. Each page is numbered, put in an envelope (packet) and the envelope is addressed (both destination and return address). It is then dumped into the network to find its way to its destination. At the destination, the pages are reassembled in numbered order. If any page is lost or damaged, it will be re-sent.

Obviously, to participate in a packet network, each "node" (workstation, server, router) must have an "address". Most familiar today is the "IP address" in the form 168.44.210.98. The real address is the "MAC" (Media Access Controller) address hard coded into the device by its manufacturer (say, 0000C0037DF8 for an individual Ethernet card). The IP address is an alias for the MAC address in the same way a url (www.aaxnet.com) is an alias for an IP address.

When you connect to your ISP (Internet Service Provider) through a modem, you establish a switched connection to the ISP, but it's actually carrying packets through a protocol called PPP (Point to Point Protocol) or (rarely now) SLIP (Serial Line Protocol).

Packet networks are somewhat more expensive to build, but tremendously cheaper to operate than circuit switched networks. Packet networks are now even being used for voice (VOIP (Voice Over IP)).

How it Works

Network "client" software running within each workstation includes a module called a redirector. The redirector intercepts data traffic which would normally go to a disk drive, printer, modem or other device attached to the computer and redirects it over the network to "resources" of similar type offered by some other computer.

In this way, a Windows computer which physically has only a "C:" hard disk, can be told it also has an "F:" hard disk. Any traffic intended for drive F: is actually intercepted by the redirector and redirected over the network to the hard disk of another computer. To the user and his software, it looks as though the F: drive is attached to his own workstation. The same works for printers and modems.

More "network aware" software doesn't need the "F:" alias, but can ask for a network resource by name. For instance, on a NetBIOS network it could ask for \\RHINO\CustData instead of F:. This might be a hard disk or directory server RHINO is offering on the network under the name CustData. Perhaps, for instance, it's actually RHINO's D: drive. Much software just isn't this smart, and it's also easier to tell users about their "F: drive" than it is to tell them about \\RHINO\CustData, but the resource name is more reliable.

A computer offering resources for use by other computers is called a "server". A computer using the resources offered by others is called a "client", or "workstation". In many networking systems, a computer can be both a client and server at the same time.

Network Structure

• A LAN is a homogenous entity. Every packet placed on the network is seen by every "node" (server or workstation), but each node processes only the packets addressed to it (except for "sniffers" - network test equipment and hacker tools - which read any packets they please). All nodes on a LAN may be tapped into a single cable (old coax Ethernet) or wired to a central "hub" (10/100BaseT Ethernet, Arcnet).

• A Bridged LAN network is a LAN that got too big and a "bridge" had to be inserted to cut down the traffic. A bridge knows what network addresses are on each side of it, and passes only traffic addressed to the other side, thus "segmenting" the network.

• A Switched LAN (now don't confuse this with the "switched network" described above) has a very fast, multiport bridge called a "switch" or "switching hub". A switched LAN may be so fine grained it has only one node on each port, reducing traffic on each cable as far as it can be reduced.

• A CAN (Campus Area Network) will have at least one "backbone" to which two or more LANs are connected through bridges, switches or routers.

• A Routed Network is one where individual LANs are connected through routers, devices much smarter than bridges or switches. A router knows where stuff is, even if it's several routers away. It keeps this information in a "routing table". It may know several "routes" to the same destination and may be smart enough to figure out which route is fastest.

• A WAN is a network that passes over links not owned by the owner of the network. Generally these links are owned by a telephone company or some other common carier. In a network diagram the common carrier is represented by a cloud (nobody knows what goes on in the cloud, but packets get to the other side (mostly)). The diagram of a WAN is commonly called a "cloud chart".

• The Internet is a huge worldwide WAN consisting of thousands of clouds and millions of routers and servers.

Network Personalities

Peer-to-Peer Networks

In a peer-to-peer network all the computers are roughly equal. All are workstations, but each may offer its resources (hard disks, printers, modems, CD-ROMs) for use by the other computers on the network, thus being a part time server, or peer.

Even today, there are offices where the work is unstructured and peer-to-peer is appropriate for print sharing and general file transfer work. The main problems with peer-to-peer are:

• Difficulty backing up critical data - its scattered all over the place on different hard disks.
• Server tasks take CPU time from workstation jobs, and vice versa.
• General performance can be poor compared to server based.
• Instability - if someone turns off or reboots his/her workstation, it becomes unavailable to its peers.

Artisoft's LANtastic was king of peer-to-peer network software, and can connect DOS, Windows 3.1, Windows95/98, OS/2 and Windows NT workstations as equals. LANtastic, however, has faded because Microsoft set out to destroy it. Peer-to-peer networking capability now comes "free" with Windows95/98, NT and Windows 2000. LANtastic offers better performance, better management, better security, and includes many Internet and communications features, but it isn't "free".

Microsoft networking is based on IBM's antique PCNet (you didn't think Microsoft invented it themselves, did you?), and is pure Microsoft - just "good enough" but "free", so it drives competitors with better products out of business. Win95/98 networking has no security (none), is unstable, frustrating, feature poor, and it's performance sucks - but when you finally can't take it any more, Microsoft has just the solution for your problems - Windows NT/2000 Server! Not at all free, but "compatible".

At the high end, Unix and Linux support both peer-to-peer and server based networking simultaneously (and serial terminals too). The Internet is the world's largest peer-to-peer network. (top)

Server Based Networks

• Stability - the server is never turned off, so it should always be available to all workstations.
• Performance - the server isn't doing anything else, so it can concentrate on serving. Server operating systems usually use file systems much (very, very much) more efficient than the dreadfully slow FAT filesystem of DOS/Windows/Win95/98 infamy.
• Low maintenance - in a small business, the server should require no attention for years at a time - with the notorious exception of Windows NT and 2000 which fragment their disk storage (destroying performance) and crash due to memory leaks (and bad 3rd party software, according to Microsoft). Figure high maintenance for NT, somewhat less for 2000, practically none for Unix, Linux, OS/2 and NetWare.
• Backup - all important files are in one place so can be backed up to tape automatically.
• Security - everything is all in one place that can be locked up, and server operating systems provide good (Windows NT) to better (Windows 2000, Linux, Unix) to excellent (NetWare, OS/2 (third party), some Unix) security features.

Client/Server Networks

CS networks were the darling of the industry a few year ago, and if you weren't deploying Client/Server, you just weren't "with the program". Unfortunately, the way Client/Server was deployed resulted in absolutely stunning administration costs (see Failure on a Grand Scale for details), and it is now commonly considered dead.

A new generation of Client/Server is being quietly deployed. The most advanced version is IBM's WSOD (WorkSpace On Demand) but it is being deployed mainly by banks, airlines and other highly critical businesses, because no one else wants to admit to running OS/2 when "Windows NT is clearly the future". WSOD eliminates client administration problems, making Client/Server not only practical, but economical.

The other new version of Client/Server is the Java/NC (Network Computer) environment. Because this environment didn't take over the world in 90 days, the computer magazines have all declared Java/NC dead, but it is being successfully deployed by corporations at an accelerating rate and will soon be working its way down into small business. (top)

Servers

The proliferation of Servers: In the past, a modest sized business would have one server, a larger business one at each branch or campus building. Now even modest sized companies have swarms of servers scattered all to Hell and back. This is caused by the growing popularity of Microsoft's Windows NT as server operating system of choice. Its poor performance and instability mean companies must have (and Microsoft strongly recommends) a separate physical server for each significant server process. This has become a major administration and security headache.

Among enterprises that have gone the Windows NT route, there is now a counter movement to consolidate most server processes on a big honk'n high performance Sun Enterprise or IBM AS/400 server, or even an IBM 360 (the dinosaurs are back, "stronger then ever!"). These machines do not do Windows. (top)

NOS - Network Operating Systems

With the exception of NetWare, the server and client parts of the NOS are distinct processes running under a general operating system such as Unix or Windows NT. A single computer may host both server and client parts and may simultaneously act as a server and as a workstation. This configuration is referred to as a peer.

Here are the common NOS, listed roughly in order of overall power. .

• Microsoft Networking (WFW, Win95/98)
  
• Artisoft LANtastic
  
• OS/2 Peer
  
• Windows NT/2000 Server
  
• Novell NetWare
  
• Linux/SAMBA
  
• OS/2 Warp Server
  
• Unix (Solaris, etc.)
  
• AS/400
  
• SNA

Microsoft Networking

Microsoft Networking is Microsoft's interpretation of IBM's old PC-Net network (you didn't think Microsoft actually "innovated", did you?). It is variously known as a NetBIOS, NetBEUI (Enhance User Interface) or SMB (Server Message Block) network.

Microsoft's Windows95/98 Networking is prone to many ailments, such as suddenly forgetting where other computers are. It has NO security, and, in fact, compromises the security of any other network it is attached to. Management and performance tuning features are almost non-existent.

Microsoft Networking Supports peers: DOS (client only), Windows 3.1x, Windows95/98,Windows NT, OS/2 (reluctantly).

AAx Recommendation: Think real hard about putting in a Linux/SAMBA server to get some stability. (NOS)

Artisoft's LANtastic

LANtastic provides a good degree of security, stability and management features. The Windows95/98 version has, however, been wounded by Microsoft's insistence Artisoft go through their services (limiting how much better LANtastic can be). Every time Windows is updated Microsoft will break LANtastic (as they did with Windows98), and you will have to update to the latest version of LANtastic to get a fix.

Lantastic Supports peers/workstations: DOS, Windows 3.1x, OS/2, Windows95/98, and Windows NT. If you have a situation where a DOS machine must act as a server, you have few other options. Microsoft Networking can't do that.

AAx recommendation: before Windows95 we enthusiastically endorsed LANtastic, but, because Microsoft deliberately sabotaged it, we have had to temper that enthusiasm. If you already have LANtastic, stick with it until you're ready for a server based network. (NOS)

OS/2 Peer

OS/2 peer networking is compatible with Windows NT Server and Windows workstations running Microsoft Networking. Microsoft has tried to make Microsoft Networking incompatible, but they have only created a few annoyances - it is IBM's network, after all, and they are limited by what they can do without breaking their own stuff.

Of course, you have to be running OS/2 workstations to use it.

OS/2 peer supports peers/workstations: OS/2, Windows 3.1x, Windows95/98, Windows NT, and DOS (client only).

AAx recommendation: This is what we use in our office, and we like its trouble free operation (We are also networked to a Linux host where our accounting software lives). (NOS)

Windows NT Server, Windows 2000 Server

An NT/2000 server tends to stabilize Microsoft Networking and provides a reasonable degree of security at the server. Security at the workstations is still between zilch and none. Properly set up, an NT 4.0 server can run for weeks without being rebooted, but that is not as good as NT 3.51, which could run months. Windows 2000 server can run for months.

All in all, Windows NT Server is a decent and capable departmental server, though not outstanding in any way. It provides basic file and print services suitable for a small business, comes with a lot of Internet stuff most people don't use, and is manageable by a version of the familiar Windows95 user interface. The problem is not with What Windows NT is, but in what Microsoft claims it is. It is not a fully scalable, rock stable, enterprise grade operating worthy of betting a corporation on.

Windows 2000 Server and Advanced Server are much more stable than Windows NT 4.0, and can scale to larger networks, but there are some very distinct downsides to Windows 2000, which you will find in our article Adopting Windows 2000.

Window 2000 Datacenter is designed to compete with Unix in large datacenters. It will not be available separately, but pre-installed on certain high-end Intel based servers. It has just been released and has not yet established a track record.

Microsoft has made some of its key software modules to run only on NT/2000 Server. In the case of Microsoft Exchange (email messaging), Microsoft Back Office, Microsoft SQL Server, and Microsoft Internet Information Server (IIS) are some of the other packages that will run only on NT Server. The coming Office 2000 will also be dependent on NT/2000 Server for full function (colaboration features and such). If you choose any of these Microsoft products you have no choice but to run them on NT/2000 Server. Your main file and print server could still be NetWare, Warp Server or Linux, though.

NT Supports clients: DOS (client only) Windows 3.1, Windows95/98, Windows NT, OS/2 (reluctantly).

AAx recommendation: Why? You can get so much more with WarpServer or Linux/SAMBA - unless you have chosen to use Microsoft Back Office, Microsoft SQL Server, Microsoft Exchange or Microsoft IIS (there are better, cheaper alternatives to all of these). (NOS)

Novell NetWare

NetWare is excellent as a high performance file and print server, but is seldom used as an applications server (client/server database server). Novell Directory Services make it highly manageable in large organizations, but are overkill for smaller organizations. NetWare is highly stable and servers have been known to run for years without a reboot. Novell has been having a hard time getting users of older versions to upgrade because they work too well.

NetWare 5.1 has now succeeded the very well received 5.0. It was supposed to come out at the same time as NT 5.0 (Windows 2000), but beat it by more than a year (and has all the features that were promised). Novell is banking heavily on Java to bring it forward and into the application server market.

A very large pool of people familiar with NetWare, including many CNEs (Certified NetWare Engineers) is available. The problem of "paper CNEs" with no experience has largely solved itself - they've either gained experience or moved on to Microsoft.

NetWare Supports clients: DOS, Windows 3.1x, Windows95/98, Windows NT, OS/2, Linux (Caldera).

AAx Recommendation: If you already have or are comfortable with NetWare, stay with it. It is problematical for new installations because Novell has ignored the small business market for so long. Linux/SAMBA is a lot easier to understand and administer. (NOS)

Linux & Linux/SAMBA

Linux can be configured as a workstation, a peer, or a server. It can also be configured as a performance cluster to achieve supercomputer level performance at a ridiculously low price. The U.S Postal service does all its OCR reading and sorting on 900 Linux clusters at centers across the U.S., and all the difficult image rendering for the film Titanic was done on a Linux cluster.

Linux servers can easily be administered remotely with a modem or telnet connection. This is a great cost saver for a small business because no administrative staff is needed on-site, the company's VAR or integrator can do it from his/her office, even from thousands of miles away.

Outfitted with the SAMBA module, a Linux server can act as an SMB (Server Message Block) server. SMB - SAMBA, get it? In other words, workstations can't tell it from a Windows NT Server, except it's faster and doesn't crash. Note, however that Linux cannot host Microosft Server modules (SQL Server, Exchange, SII, Back Office).

Linux supports clients/peers/terminals: any computer supporting TCP/IP networking (basically, everything this side of the Apple II), ASCII terminals, or anything that can emulate an ASCII terminal (Apple II, microwave ovens, digital clocks, coffee makers, etc.).

Linux/SAMBA supports clients: native support for DOS, Windows 3.1x, Windows95/98, Windows NT, OS/2.

AAx recommendation: With major networking companies like Cisco ripping out NT in favor of Linux/SAMBA, with so much of the Internet running on Linux, and with corporate IS departments sneaking it into NT networks so they have something that works, and considering its low cost, we can only give Linux and Linux/SAMBA our highest recommendation as a small business server. (NOS)

OS/2 WarpServer

WarpServer is highly compatible with NT Server networks - they are both based on IBM's PC-Net and further developed cooperatively between IBM and Microsoft (before the split). IBM's version is simply implemented a lot better than Microsoft's version. The new Aurora (v5.0) WarpServer has added features for managing NT Servers, making it a good master server when you must have NT servers (because you have MS SQL Server, MS Back Office, MS Exchange Server or MS Internet Information Server (IIS) - all NT specific).

While OS/2 WarpServer is normally administered using graphic tools, just as NT is, it can easily be administered from afar by modem, either using the graphic interface like NT, or from the command line like Unix. You can use a WarpServer computer as a workstation (peer) but it is not recommended (see disadvantages of peer-to-peer).

When PC magazines first compared WarpServer to NT, they panned Warp Server for not supporting multiple processors. They did, though, have to note that WarpServer on a single processor out performed NT on a multiple processor. Since WarpServer now supports multiple processors, and does so far more effectively than NT, no magazine dares do a comparative review (it would produce the "wrong" answer).

OS/2 WarpServer supports clients: OS/2, DOS, Windows 3.1x, Windows95/98, Windows NT.

AAx recommendation: This is simply one of the best servers money can buy, and we recommend it highly. If you prefer a graphical administration interface rather than Linux/SAMBA's text mode, and still want a server that performs, this is for you. (NOS)

Unix (SCO, Solaris, AIX, BSD, etc.) and Unix/SAMBA

Everything said above in the Linux section applies to Unix except Unix is sold by major corporations (IBM, Compaq, SCO, Sun Microsystems, SGI, Data General, etc.).

As with Linux, a Unix box can run SAMBA so it can look just like an amazingly fast, amazingly stable NT Server

High security versions of Unix are available for special situations.

Note: Caldera, a major Linux vendor, has purchased the Unix assets of SCO, the largest Unix vendor. Caldera will be blending it's Unix and Linux holdings into a single coherent product line running from desktop PC to corporate datacenter.

Unix supports clients/peers/terminals: any computer supporting TCP/IP networking (basically, everything this side of the Apple II), ASCII terminals, or anything that can emulate an ASCII terminal (Apple II, microwave ovens, digital clocks, coffee makers, etc.).

Unix/SAMBA supports clients: native support for DOS, Windows 3.1x, Windows95/98, Windows NT, OS/2.

AAx recommendation: Highly recommended. More expensive than Linux, but you can get well integrated communications and server suites fully backed by a major corporate vendor. (NOS)

AS/400 - for when you really, really care

AS/400 scales with your growth, offering models starting at about $7,000 and going well beyond $700,000 for the enterprise crowd.

If you need the advantages of the AS/400, but really, really need NT Server too, the AS/400 offers plug-in boards that run NT. You can have as many as 14 of these running as 14 NT Servers in a single AS/400 box. Of course, those NT Servers aren't going to be more reliable or any faster than NT Server on any other box, but you can reboot them individually without shutting down the AS/400 side.

A funny story: Microsoft has so conditioned people to the dismal quality of their products, one consultant reports a client who insists on rebooting his AS/400 every morning because, "the PCs act funny if we don't reboot every day, so we'd better do the AS/400 too". Most AS/400s are rebooted only every few years. You can replace hard disks, install applications, even upgrade the operating system without rebooting.

AS/400 Supports clients: OS/2, DOS, Windows 3.1x, Windows95/98, Windows NT, 5250 class terminals.

AAx recommendation: If you need total security, absolute virus immunity and extreme uptime in a high performance package, what other choice do you have? (NOS)

SNA - System Network Architecture

Topologies

• Star: is now the dominant wiring scheme. A cable runs from each workstation all the way to a backboard where it it is "patched" to a hub or other network device.

• Bus: This topology is being ripped out as fast as it can be ripped. In this scheme workstations are strung along a cable (usually coax) like beads. Break it anywhere and the whole network goes down. Very unreliable and difficult to diagnose because there are so many connectors and possible points of failure.

• Ring: This is like the hated Bus topology except the ends are connected together. Actually, there are usually two cables so adapters can loop back to remake the ring if there is a break. In reality, most rings are virtual, and the actual wiring looks just like a Star pattern (the ring resides in a box and spokes out from there).

Protocols

PHYSICAL PROTOCOLS

• Ethernet - now the dominant network type. It comes in several varieties supporting several cabling styles and transmission rates.
  • 10-Base5 - Thick Ethernet - seldom used today. A large (usually orange) coax cable lies above the ceiling and is tapped into using "vampire taps" to create drops for workstations. Max length: 500-meters. Speed: 10 megabits/second.

  • 10-Base2 - Thin Ethernet - still a lot of it to be ripped out. Thin coax cable runs from workstation to workstation. Max length: 200-meters. Speed: 10 megabits/second.

  • 10-BaseT - UTP (Unshielded Twisted Pair), CAT-3 or better, Star Protocol. This is the current Ethernet for most places. Soon to be replaced with 100-BaseT. Max run to a hub or repeater: 100-meters. Speed: 10 megabits/sec.

  • 100-BaseT - UTP (Unshielded Twisted Pair), CAT-5 or better, Star Protocol. This is the Ethernet being installed now for most new networks. Max run to a hub or repeater: 100-meters. Speed: 100 megabits/sec.

  • Gigabit Ethernet - UTP CAT-5 or better, or Fiber. Star Protocol. Speed: 1,000 megabits/second.

  • 10-Gigibit Ethernet - Fiber. Still in testing and initial deployment phase.

• Token Ring - IBM's answer to Ethernet - theoretically superior but too damned expensive. Originally on IBM Type-3 cable. Now mostly run on UTP. 4-megabit is almost extinct. Most is 16-megabits/sec now, and faster versions are being released.

• Arcnet - supposedly extinct, but still used in industrial control networks where very long cable runs and high immunity from electrical noise outweigh raw speed. Coax in a Star topology with active or passive hubs depending on distance requirements. Once very popular in PC networks when Ethernet was still very expensive. 1600 feet. 2-megabits/sec.
  
  

LOGICAL PROTOCOLS

• TCP/IP - The Internet Protocol. I once attended a seminar (by SCO and Altos) at which we were told TCP/IP was strictly temporary and soon to be replaced by the ISO protocol. Today, ISO exists only in books, where it is used to explain protocols that work. TCP/IP is everywhere and has been adapted to almost every kind of system. TCP/IP is quite good for large, widespread networks, but not so good for smaller LANs.

• IPX/SPX - The Novell NetWare protocol. Fast and efficient for moderate size LANs, but tends to bog down in large widespread networks. A company named WEB "reverse engineered" IPX/SPX and used it for their own network. They were bought by Microsoft and liquidated, their product scrapped, except the IPX/SPX which was incorporated into Microsoft Networking.

• NetBIOS - NetBEUI - SMB - This "stack" of protocols derives from IBM's early PC-NET network. NetBIOS is also used by LANtastic and various other smaller networks. Microsoft adopted NetBIOS as the foundation of Microsoft Networking. It has been extended with NetBEUI (Extended User Interface) and SMB (Server Message Block) layers to make it into a real network. OS/2 Networking also uses these protocols, but it works better. NetBIOS is not routable, so it is usable only in small networks. NetBIOS packets must be encapsulated within TCP/IP or IPX/SPX packets to be routed.