I need to install a router, bridge, switch, or hub to get more connections or for other, special reasons.  Can I just hook them up?

April 17, 2001

The answer is no.  It is against University policy to allow end-users to attach any type of network infrastructure equipment to the campus network.  This is for the protection of the network and all of the users on it.  Very rarely does Networking grant an exception for a router.  However, bridges, switches and hubs are never allowed.

If you wish to apply for an exception for a router or wish to discuss this information further, please contact Mark Harsen in Networking.

Who says I can't attach my network device to the campus network?

The current operating and funding models have been approved and adopted without exception.  Those giving approval include the Information Technology Council, The Office of Information Technology, Telecommunications Services, Computer Services, and Computer Services Networking.  Connecting such a device to our networks is against Missouri State University policy.  Violating this policy could result in the termination of network services or more severe sanctions being levied against the offender.

Why can't I put my hub, bridge, or switch on a network port?

There is a set of very specific rules on how to build a viable network based on physics.  If anyone violates these rules, severe consequences can occur for all network users, not just the one violating the specifications.  The integrity of the network must be preserved.  Some of the technical and administrative problems are included in the next two sections.

Technical Problems

• Illegal Collisions  -  When data passes through a hub, the device introduces a delay before the data is passed on.  If hubs attached together in such a way that the data from any station to any other station has to go through more than four hubs, the whole network segment becomes non-compliant with design specifications and performs poorly.
  
  Collision detection winds up happening late after Ethernet's physically designed time limit to detect them which causes what are commonly referred to as "illegal collisions".  The whole network suffers and major performance degradation occurs.  Many packets must be retransmitted that should not have to be.  This causes more load on the network which causes more illegal collisions making the problem worse.
  
  
• Lost Data and Retransmissions  -  Our hubs operate in secure mode, meaning that data destined for a specific machine only reaches that machine intact.  To satisfy the Ethernet need to detect collisions, however, the packet is sent to all other ports on the segment in garbled form.  Users hooking up a hub, switch, or certain types of bridges to a network jack run into a problem caused by this security
  
  Let's look at an example where a user hooks up a hub and two workstations, AYE and BEE, to the illegal hub on our network.  AYE transmits, then BEE transmits, AYE gets an answer back, but it is garbled because BEE was the last machine to communicate on the port.  Therefore, AYE looses the response and must eventually retransmit.  BEE receives a response, AYE retransmits, and BEE receives an reply, but loses it because AYE was the last transmitter.  Now BEE must eventually retransmit.
  
  This continuous retransmission causes two major problems.  The two machines on the illegal hub very often get poor response time.  Everyone else on the network segment also suffers because all of the unnecessary retransmissions consume bandwidth.
  
  
• Illegal Switch Depth  -  Switching, to many, appears to eliminate the concerns associated with installing end-user network equipment.  However, switches have what is called a depth parameter which is a timing parameter that determines how many switches can be connected to each other on the same VLAN.  
  
  The results of exceeding the switch depth can vary, but most often result in data loss, retransmissions, or even an infinite loop in the network.  These problems will slow down the network and even cause a segment to crash, thus taking all users down due to packet storms.
  

Administrative Problems

• Troubleshooting  -  Trying to figure out what's wrong with a network full of end-user infrastructure equipment in unknown configurations becomes unwieldy.  Our efforts are two fold here:  1)  We proactively scan for illegal hubs or switches on the network and remove them or disable the offending network jack to protect the network.  2)  We incorporate traditional troubleshooting techniques on the network knowing that illegal equipment isn't causing the problem.
  
  
• Outlet Charges  -  There is a $5 or $10 per month charge levied for all network outlets or jacks.  This money helps pay for many things besides the access hub or switch that supports the given jack.  It helps to pay for the devices and maintenance on those devices that make up the entire network.  The network consists of a lot of common equipment that no one sees or really knows about.  The wide-spread propagation of end-user electronics would destroy the network's funding which is highly subsidized already.  We have been looking for further funding sources.

What about routers.  Can I hook one up anywhere I want?

Routers work on a different level than hubs, switches or bridges.  They must participate in the routing scheme used by Missouri State University and must obtain IP addresses from Networking for local segments or from outside entities for wide area links off of campus.  To date, only one router has ever been approved for use and this was for a special WAN (Wide Area Network) link directly to OCLC for use by the Library.  They needed guaranteed access to OCLC without being subjected to the congestion of the Internet itself.  OCLC required that Missouri State University purchase a router specifically for this purpose.  The library owns and operates the router with consultation from Networking.

We do not approve the use of routers for local campus networks.  Such devices are unnecessary as we can provide all network functions with existing equipment.  The administrative overhead of supporting third entity routes is also prohibitive.  Only very rarely will exceptions be granted to attach routers to our networks.

I'd like to discuss this issue further, who do I contact again?

Please contact Mark Harsen.  He is the Networking Administrator in charge of all of Missouri State University's data and video networks.