PULLEN@VAX.DARPA.MIL (Mark Pullen) (07/22/88)
The purpose of this message is to provide members of the Arpanet and Internet user communities with a progress report on current changes being made to the Arpanet, as well as some information about their potential impact on network users. As an earlier message to tcp-ip explained, DARPA plans to gradually phase out the Arpanet and replace it with a higher-speed, research-oriented internet (the Defense Research Internet, or DRI). While work on the DRI is progressing, the first phase of Arpanet restructuring has been implemented and is nearly complete. Plans for a second phase are presently being finalized. The goal of these initial phases is a near-term reduction of Arpanet operational costs through the elimination of selected Arpanet PSNs (packet switching nodes) and leased interswitch trunks. What follows is a summary description of the principal actions taken under Phase I restructuring. The most significant aspect of Phase I restructuring is the temporary use of channel streams derived from the DARPA Wideband Satellite Network to maintain adequate cross-country connectivity in the Arpanet while PSNs and leased terrestrial lines comprising existing paths are removed from service (during Phase II restructuring, cross-country trunks will be moved off the Wideband Network and onto 56kb/s lines derived from the terrestrial backbone being implemented for the DRI). Special software has been written for Butterfly Satellite Imps (BSATs), which enables them to accept subnetwork packets from an Arpanet PSN trunk port and encapsulate them in Wideband Network stream messages for transmission to a distant PSN. Three such trunks, terminated at sites where Arpanet and Wideband Network nodes are physically collocated, were established during the first week of May, 1988: BBN to ISI, DCEC to ISI and DCEC to SRI. The intervening weeks have been spent tuning their performance. During the same time period, Phase I disconnect orders have been issued for several of the longest and most expensive leased terrestrial trunks, along with a small number of PSNs. Once these trunk and PSN deletions are complete (this should occur within the next few weeks), only one terrestrial cross-country path will remain in the Arpanet. Trunks comprising the last remaining terrestrial path are currently scheduled to be removed by October 1, 1988. At this point, the Arpanet will rely heavily on the Wideband Network, plus two VSAT satellite trunks, to carry traffic between the east and west coasts of the United States. This will make the quality of Arpanet service more dependent on the Wideband Net. By placing the Wideband Net in this critical role, we may experience significant network congestion if there are Wideband Net outages. In the event such an outage actually occurs, every effort will be made to restore service to normal as soon as possible. The use of the Wideband Net in this capacity is a transitional cost saving measure until more cost effective leased land lines are purchased. They are anticipated to be installed by Dec 1988. DARPA has plans to bring up early versions of the Defense Research Internet using some existing Wideband Net equipment soon afterward. This will produce significant improvement for users in the high load areas (directly supported by this experiment) and indirectly by reducing Arpanet load for all of the other Arpanet users. Please be patient. Change is often a painful process. There will be problems in service during transition, but this effort is necessary to enable future progress. Mark Pullen, DARPA/ISTO -------