Over the last several the years the changes in technology, the onslaught of computer equipment migrating to Building 26, and the changes in how staff currently and in the future do business (i.e., Web-based technologies, large volume data transfers, etc.) have significantly impacted the building's networking throughput. Many users have experienced poor performance and interrupted services caused by a variety of networking problems, ranging from inadequate and faulty cabling and equipment to over-subscribed bandwidth. The Code 630 networking team along with the Center Network Environment (CNE) are currently in the process of redesigning the Building 26 networking infrastructure. It is expected by mid-summer 1998 (barring any unforeseen problems) that the new network will be in place, providing greater bandwidth, flexibility, and scalability and eliminating many of existing networking problems of today.
Currently, Building 26 has two basic networking infrastructures in place, a 10 mb/s shared (with some switched capabilities) Ethernet and a 100 mb/s FDDI ring. Figure 1 below provides a topological view of the existing networking infrastructures. The vertical dashed line delimits Building 26's network from that of the GSFC CNE. The router and the switch are located in the main communications closet in the basement of Building 26 and interface with both the CNE router in Building 1 and the hubs and concentrator in Building 26 via fiber communication links. Each hub is located in a separate communication closet throughout the building and interface with both the building switch and the equipment on users' desktops and other devices (printers, scanners, servers, etc.) throughout the building. The concentrator is located in Room 153 and connects directly to all the servers on the FDDI ring. The E10s and F100s associated with each line represent the 10 mb/s Ethernet and 100 mb/s FDDI communication links, respectively. The Ethernet lines that attach the users at the desktop to the hubs consist of old Category 3 cabling. These lines are only rated to transmit 10 mb/s data rates and are not adequate to handle today's 100 mb/s Ethernet rates. There are also 10 mb/s Ethernet links between the Building 26 router and switch. Although this path is redundant to the communication links connected to the CNE router, it is the preferred path when communicating between the Ethernet and FDDI ring inside the building. This path enables the user to communicate between the Ethernet and FDDI devices without traversing the CNE network.
The Building 26 hubs and switch and the Ethernet card in the CNE router are only 10 mb/s devices. Most of the users reside on the 10 mb/s shared Ethernet (as opposed to the FDDI ring) hubs. This fact implies that many users compete for the same limited bandwidth at various locations on the network. For example, if one device is communicating with another device attached to the same hub, that device competes for the same bandwidth with all users and devices attached to that hub. If a device is communicating with another device attached to a different hub, that device is competing for the bandwidth with the users on its local hub, the Ethernet link from that hub to the switch, the link from the switch to the other hub, and all the devices on the hub shared by the target device. The same scenario holds true for communicating with devices outside the building. On hubs 2 and 3 there are approximately 150 users and devices attached to each, some of which are network intensive, consuming at times a large percentage of the available bandwidth causing slow network response. Since the hubs are relatively old technology by today's standards, they along with the 10 mb/s Ethernet links are the primary source of Building 26's networking problems. In addition, with today's 100 mb/s Ethernet requirements and the 10/100 mb/s Ethernet cards being shipped as the standard in most PCs today, the existing Building 26 Ethernet infrastructure will not satisfy these requirements.
The newly designed network will consist of a combination of switched and shared technologies. This configuration will be easier to maintain and manage, help to eliminate all of the existing network problems, and provide the flexibility and scalability needed for future growth. Although the topological view appears virtually identical to the existing configuration, there are some obvious differences. The Ethernet segments will be upgraded to 10/100 mb/s infrastructure. Figure 2 provides an illustration of the upgraded communication links and equipment. The Ethernet communications links from the CNE router in Building 1 to the switches in the communications closets will all be upgraded to 100 mb/s (E 100) communication lines. Building 26 will be completely recabled with the new 10/100 mb/s Category 5 cabling from the communications closets on each floor to the desktops. The switch in the main communications closet will be upgraded to a 100 mb/s switch, and the hubs in each of the other communications closets will be replaced with 100 mb/s switches. These switches will connect back to the main closet via 100 mb/s communication links as well as connect to a variety of stackable 10 mb/s shared hubs and 10/100 mb/s (E 10/100) switches that connect the users at the desktop. The users will be attached from their desktops to either a shared hub or switch based on their networking requirements and utilization. The switching technology along with the larger communication pipes (100 mb/s links) will enable the network administrators to isolate easily and segment the network intensive users and devices from the average user without significantly impacting the overall network performance. The 10 mb/s communications link between the router and the switch in Building 26's main communications closets will remain as a backup, and the preferred path of communications between the Building 26 Ethernet and FDDI ring will be through the CNE router because of the larger and faster (100 mb/s) communications link.
Erin D. Gardner, firstname.lastname@example.org, (301) 286-0163
Raytheon STX, Code 633, NASA Goddard Space Flight Center
Greenbelt, MD 20771, U.S.A.