Campus Data Networking Architecture:
A Process As Well As a Product

QUESTnet '96
Townsville, Queensland, Australia
July 3, 1996

Noam H. Arzt, Ph.D.


Setting the Stage


Process

Network Architecture Task Force


Methodology

Definition:
Technical architecture is a blueprint for making technology choices, more a process than a product


Network Needs

Definitions:

Full discussion...


Assumptions

Definition: Assumptions help bound the set of possible architectures

Examples:

TCP/IP TCP/IP will continue to be the enterprise-wide networking protocol. OSI protocol is not, and will not, become significant.
"Killer Apps" "Killer Apps" (perhaps desktop video-conferencing?) will change network usage patterns in ways we cannot predict.

Full discussion...


Alternatives

Network Architecture Template

Three Basic Architectures

Three basic architectural alternatives have been defined, and they fall along a continuum from least aggressive to most aggressive with respect to the reliability, performance, and functionality they enable. These three basic alternatives represent a migration path that can be followed one to the other if Penn chooses. As markets and products develop, Penn may end up skipping one or more alternatives in the "pipeline," or implementing other variations that develop as time goes on.

Common elements include the following:

Alternative A: Pervasive Ethernet Switches/Selective 100 Mb

Alternative A is the closest to PennNet's current condition. It preserves our current investment in the technology and operations of a central routing core, installs ethernet switches in all buildings, continues EIA/TIA 568 as the wiring standard, but only increases speeds within and between buildings to greater than 10 Mb/sec on a case by case basis.

Major features include:

Alternative B: Fully Switched Core

Alternative B presents a transition point between Alternative A and Alternative C. The only changes are in the central routing core ("Inter-building backbone"). Rather than a collapsed backbone of routers, the central hub now uses an ATM switch coupled to a "super router" to route between the subnets. A series of smaller routing switches, still located in a central core, start to share a distributed routing load. While management and operations continue to benefit from a single, consolidated location for this equipment, Penn moves one step closer to being able to distribute its routing load to multiple locations when necessary. The nature of the routers and switches at the center are now changing substantially, both in terms of cost and the relative functionality of each object (switching versus routing).

Since ATM switching is now a feature, some direct ATM connections are made possible into the production network either to support advanced projects now in production or servers that require the added bandwidth.

Alternative C: Pervasive ATM

Alternative C represents where the Task Force believes Penn should be in 3-5 years. This is mostly dependent on the necessary investment level, but even more important on the development of products and standards in the marketplace to make deployment of or migration to this alternative possible.

Major features include:

Three Additional Variations

Three additional architectural alternatives recognize that the marketplace may not develop in the directions we expect, and/or Penn may need to improve the performance of PennNet in advance of the availability of components to build Alternative C.

Alternative A': Pervasive 100+ Mb Backbone

In most respects this alternative is identical to Alternative A, except that in this case there is the need for all buildings to be connected to the campus backbone using a 100+ Mb/sec technology. To accommodate this bandwidth to every building, the campus backbone needs to change: the collapsed backbone is now interconnected via ATM switch to increase capacity at the core. Subnets are connected to central routers via shared or dedicated connections using 100+ Mb/sec technology.

Alternative AB': Distributed Routing with 100+ Mb Backbone

If the availability of the products needed to implement Alternative C becomes more distant, this alternative may provide some necessary solutions. It provides for a regionalized campus with several clusters of buildings connected together via 100+ Mb/sec technology, and fully distributed routing to each building.

Major features include:

Alternative B': Selective ATM

This alternative allows the campus to migrate more slowly to ATM for inter-building connections.

Major features include:

Network Alternatives Strengths and Weaknesses
Alternative "Strength" "Weakness"
Alternative A
  • easy to implement today
  • less expensive compared to other alternatives
  • perpetuates use of today's technologies
  • Alternative B
  • starts down the road to distributed routing
  • may reduce per port costs of central routers and increase overall bandwidth of the routing core
  • significantly newer technologies in the routing core which use proprietary protocols for distributed routing
  • depending on timing, ATM may still be too immature
  • Alternative C
  • probably where we want to be...
  • can't buy it today
  • presumes a lot about market directions
  • Alternative A'
  • will definitely increase bandwidth to buildings today
  • very expensive
  • perpetuates use of today's technologies
  • Alternative AB'
  • will definitely increase bandwidth to buildings today
  • very expensive
  • perpetuates use of today's technologies
  • introduces additional operations issues as routing devices are distributed to each building
  • Alternative B'
  • allows for slower migration to ATM
  • multiple generations of backbone technology difficult (and expensive) to operate and maintain

  • Wrap-up


    Please address comments or questions to Dr. Noam Arzt, arzt@isc.upenn.edu [6/25/96]
    URL: http://www.hln.com/noam/questnet96/arch/arch-full.html