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rfc:rfc1077

Network Working Group Gigabit Working Group Request for Comments: 1077 B. Leiner, Editor

                                                         November 1988
            Critical Issues in High Bandwidth Networking

Status of this Memo

 This memo presents the results of a working group on High Bandwidth
 Networking.  This RFC is for your information and you are encouraged
 to comment on the issues presented.  Distribution of this memo is
 unlimited.

ABSTRACT

 At the request of Maj. Mark Pullen and Maj. Brian Boesch of DARPA, an
 ad-hoc working group was assembled to develop a set of
 recommendations on the research required to achieve a ubiquitous
 high-bandwidth network as discussed in the FCCSET recommendations for
 Phase III.
 This report outlines a set of research topics aimed at providing the
 technology base for an interconnected set of networks that can
 provide highbandwidth capabilities.  The suggested research focus
 draws upon ongoing research and augments it with basic and applied
 components.  The major activities are the development and
 demonstration of a gigabit backbone network, the development and
 demonstration of an interconnected set of networks with gigabit
 throughput and appropriate management techniques, and the development
 and demonstration of the required overall architecture that allows
 users to gain access to such high bandwidth.

Gigabit Working Group [Page 1] RFC 1077 November 1988

 1.  Introduction and Summary
 1.1.  Background
 The computer communications world is evolving toward both high-
 bandwidth capability and high-bandwidth requirements.  The recent
 workshop conducted under the auspices of the FCCSET Committee on High
 Performance Computing [1] identified a number of areas where
 extremely high-bandwidth networking is required to support the
 scientific research community.  These areas range from remote
 graphical visualization of supercomputer results through the movement
 of high rate sensor data from space to the ground-based scientific
 investigator.  Similar requirements exist for other applications,
 such as military command and control (C2) where there is a need to
 quickly access and act on data obtained from real-time sensors.  The
 workshop identified requirements for switched high-bandwidth service
 in excess of 300 Mbit/s to a single user, and the need to support
 service in the range of a Mbit/s on a low-duty-cycle basis to
 millions of researchers.  When added to the needs of the military and
 commercial users, the aggregate requirement for communications
 service adds up to many billions of bits per second.  The results of
 this workshop were incorporated into a report by the FCCSET [2].
 Fortunately, technology is also moving rapidly.  Even today, the
 installed base of fiber optics communications allows us to consider
 aggregate bandwidths in the range of Gbit/s and beyond to limited
 geographical regions.  Estimates arrived at in the workshop lead one
 to believe that there will be available raw bandwidth approaching
 terabits per second.
 The critical question to be addressed is how this raw bandwidth can
 be used to satisfy the requirements identified in the workshop: 1)
 provide bandwidth on the order of several Gbit/s to individual users,
 and 2) provide modest bandwidth on the order of several Mbit/s to a
 large number of users in a cost-effective manner through the
 aggregation of their traffic.
 Through its research funding, the Defense Advanced Research Projects
 Agency (DARPA) has played a central role in the development of
 packet-oriented communications, which has been of tremendous benefit
 to the U.S. military in terms of survivability and interoperability.
 DARPA-funded research has resulted in the ARPANET, the first packet-
 switched network; the SATNET, MATNET and Wideband Network, which
 demonstrated the efficient utilization of shared-access satellite
 channels for communications between geographically diverse sites;

Gigabit Working Group [Page 2] RFC 1077 November 1988

 packet radio networks for mobile tactical environments; the Internet
 and TCP/IP protocols for interconnection and interoperability between
 heterogeneous networks and computer systems; the development of
 electronic mail; and many advances in the areas of network security,
 privacy, authentication and access control for distributed computing
 environments.  Recognizing DARPA's past accomplishments and its
 desire to continue to take a leading role in addressing these issues,
 this document provides a recommendation for research topics in
 gigabit networking.  It is meant to be an organized compendium of the
 critical research issues to be addressed in developing the technology
 base needed for such a high bandwidth ubiquitous network.
 1.2.  Ongoing Activities
 The OSTP report referred to above recommended a three-phase approach
 to achieving the required high-bandwidth networking for the
 scientific and research community.  Some of this work is now well
 underway.  An ad-hoc committee, the Federal Research Internet
 Coordinating Committee (FRICC) is coordinating the interconnection of
 the current wide area networking systems in the government; notably
 those of DARPA, Department of Energy (DoE), National Science
 Foundation (NSF), National Aeronautics and Space Administration
 (NASA), and the Department of Health and Human Services (HHS).  In
 accordance with Phases I and II of the OSTP report, this activity
 will provide for an interconnected set of networks to support
 research and other scholarly pursuits, and provide a basis for future
 networking for this community.  The networking is being upgraded
 through shared increased bandwidth (current plans are to share a 45
 Mbit/s backbone) and coordinated interconnection with the rest of the
 world.  In particular, the FRICC is working with the European
 networking community under the auspices of another ad-hoc group, the
 Coordinating Committee for Intercontinental Research Networks
 (CCIRN), to establish effective US-Europe networking.
 However, as the OSTP recommendations note, the required bandwidth for
 the future is well beyond currently planned public, private, and
 government networks.  Achieving the required gigabit networking
 capabilities will require a strong research activity.  There is
 considerable ongoing research in relevant areas that can be drawn
 upon; particularly in the areas of high-bandwidth communication
 links, high-speed computer switching, and high-bandwidth local area
 networks.  Appendix A provides some pointers to current research
 efforts.

Gigabit Working Group [Page 3] RFC 1077 November 1988

 1.3.  Document Overview
 This report outlines a set of research topics aimed at providing the
 technology base for an interconnected set of networks that can
 provide the required high-bandwidth capabilities discussed above.
 The suggested research focus draws upon ongoing research and augments
 it with basic and applied components.  The major activities are the
 development and demonstration of a Gigabit Backbone network (GB) [3],
 the development and demonstration of an interconnected set of
 networks with gigabit throughput and appropriate management
 techniques, and the development and demonstration of the required
 overall architecture that allows users to gain access to such high
 bandwidth.  Section 2 discusses functional and performance goals
 along with the anticipated benefits to the ultimate users of such a
 system.  Section 3 provides the discussion of the critical research
 issues needed to achieve these goals.  It is organized into the major
 areas of technology that need to be addressed: general architectural
 issues, high-bandwidth switching, high-bandwidth host interfaces,
 network management algorithms, and network services.  The discussion
 in some cases contains examples of ongoing relevant research or
 potential approaches.  These examples are intended to clarify the
 issues and not to propose that particular approach.  A discussion of
 the relationship of the suggested research to other ongoing
 activities and optimal methods for pursuing this research is provided
 in Section 4.
 2.  Functional and Performance Goals
 In this section, we provide an assessment of the types of services a
 GN (four or five orders of magnitude faster than the current
 networks) should provide to its users.  In instances where we felt
 there would be a significant impact on performance, we have provided
 an estimate of the amount of bandwidth needed and delay allowable to
 provide these services.
 2.1.  Networking Application Support
 It is envisioned that the GN will be capable of supporting all of the
 following types of networking applications.

Gigabit Working Group [Page 4] RFC 1077 November 1988

 Currently Provided Packet Services
    It is important that the network provide the users with the
    equivalent of services that are already available in packet-
    switched networks, such as interactive data exchange, mail
    service, file transfer, on-line access to remote computing
    resources, etc., and allow them to expand to other more advanced
    services to meet their needs as they become available.
 Multi-Media Mail
    This capability will allow users to take advantage of different
    media types (e.g., graphics, images, voice, and video as well as
    text and computer data) in the transfer of messages, thereby
    increasing the effectiveness of message exchange.
 Multi-Media Conferencing
    Such conferencing requires the exchange of large amounts of
    information in short periods of time.  Hence the requirement for
    high bandwidth at low delay.  We estimate that the bandwidth would
    range from 1.5 to 100 Mbit/s, with an end-to-end delay of no more
    than a few hundred msec.
 Computer-Generated Real-time Graphics
    Visualizing computer results in the modern world of supercomputers
    requires large amounts of real time graphics.  This in turn will
    require about 1.5 Mbit/s of bandwidth and no more than several
    hundred msec.  delay.
 High-Speed Transaction Processing
    One of the most important reasons for having an ultra-high-speed
    network is to take advantage of supercomputing capability.  There
    are several scenarios in which this capability could be utilized.
    For example, there could be instances where a non-supercomputer
    may require a supercomputer to perform some processing and provide
    some intermediate results that will be used to perform still
    further processing, or the exchange may be between several
    supercomputers operating in tandem and periodically exchanging
    results, such as in a battle management, war gaming, or process
    control applications.  In such cases, extremely short response
    times are necessary to accomplish as many as hundreds of
    interactions in real time.  This requires very high bandwidth, on
    the order of 100 Mbit/s, and minimum delay, on the order of
    hundreds of msec.

Gigabit Working Group [Page 5] RFC 1077 November 1988

 Wide-Area Distributed Data/Knowledge Base Management Systems
    Computer-stored data, information, and knowledge is distributed
    around the country for a variety of reasons.  The ability to
    perform complex queries, updates, and report generation as though
    many large databases are one system would be extremely powerful,
    yet requires low-delay, high-bandwidth communication for
    interactive use.  The Corporation for National Research
    Initiatives (NRI) has promoted the notion of a National Knowledge
    base with these characteristics.  In particular, an attractive
    approach is to cache views at the user sites, or close by to allow
    efficient repeated queries and multi-relation processing for
    relations on different nodes.  However, with caching, a processing
    activity may incur a miss in the midst of a query or update,
    causing it to be delayed by the time required to retrieve the
    missing relation or portion of relation.  To minimize the overhead
    for cache directories, both at the server and client sites, the
    unit of caching should be large---say a megabyte or more.  In
    addition, to maintain consistency at the caching client sites,
    server sites need to multicast invalidations and/or updates.
    Communication requirements are further increased by replication of
    the data.  The critical parameter is latency for cache misses and
    consistency operations.  Taking the distance between sites to be
    on average 1/4 the diameter of the country, a one Gbit/s data rate
    is required to reduce the transmission time to be roughly the same
    as the propagation delay, namely around 8 milliseconds for this
    size of unit.  Note that this application is supporting far more
    sophisticated queries and updates than normally associated with
    transaction processing, thus requiring larger amount of data to be
    transferred.
 2.2.  Types of Traffic and Communications Modes
 Different types of traffic may impose different constraints in terms
 of throughput, delay, delay dispersion, reliability and sequenced
 delivery.  Table 1 summarizes some of the main characteristics of
 several different types of traffic.

Gigabit Working Group [Page 6] RFC 1077 November 1988

              Table 1: Communication Traffic Requirements
 +------------------------+-------------+-------------+-------------+
 |                        |             |             | Error-free  |
 | Traffic                | Delay       | Throughput  | Sequenced   |
 | Type                   | Requirement | Requirement | Delivery    |
 +------------------------+-------------+-------------+-------------+
 | Interactive Simulation | Low         |Moderate-High| No          |
 +------------------------+-------------+-------------+-------------+
 | Network Monitoring     | Moderate    | Low         | No          |
 +------------------------+-------------+-------------+-------------+
 | Virtual Terminal       | Low         | Low         | Yes         |
 +------------------------+-------------+-------------+-------------+
 | Bulk Transfer          | High        | High        | Yes         |
 +------------------------+-------------+-------------+-------------+
 | Message                | Moderate    | Moderate    | Yes         |
 +------------------------+-------------+-------------+-------------+
 | Voice                  |Low, constant| Moderate    | No          |
 +------------------------+-------------+-------------+-------------+
 | Video                  |Low, constant| High        | No          |
 +------------------------+-------------+-------------+-------------+
 | Facsimile              | Moderate    | High        | No          |
 +------------------------+-------------+-------------+-------------+
 | Image Transfer         | Variable    | High        | No          |
 +------------------------+-------------+-------------+-------------+
 | Distributed Computing  | Low         | Variable    | Yes         |
 +------------------------+-------------+-------------+-------------+
 | Network Control        | Moderate    | Low         | Yes         |
 +------------------------+-------------+-------------+-------------+
 The topology among users can be of three types: point-to-point (one-
 to-one connectivity), multicast (one sender and multiple receivers),
 and conferencing (multiple senders and multiple receivers).  There
 are three types of transfers that can take place among users.  They
 are connection-oriented network service, connectionless network
 service, and stream or synchronous traffic.  Connection and
 connectionless services are asynchronous.  A connection-oriented
 service assumes and provides for relationships among the multiple
 packets sent over the connection (e.g., to a common destination)
 while connectionless service assumes each packet is a complete and
 separate entity unto itself.  For stream or synchronous service a
 reservation scheme is used to set up and guarantee a constant and
 steady amount of bandwidth between any two subscribers.

Gigabit Working Group [Page 7] RFC 1077 November 1988

 2.3.  Network Backbone
 The GB needs to be of high bandwidth to support a large population of
 users, and additionally to provide high-speed connectivity among
 certain subscribers who may need such capability (e.g., between two
 supercomputers).  These users may access the GN from local area
 networks (LANs) directly connected to the backbone or via high-speed
 intermediate regional networks.  The backbone must also minimize
 end-to-end delay to support highly interactive high-speed
 (supercomputer) activities.
 It is important that the LANs that will be connected to the GN be
 permitted data rates independent of the data rates of the GB.  LAN
 speeds should be allowed to change without affecting the GB, and the
 GB speeds should be allowed to change without affecting the LANs.  In
 this way, development of the technology for LANs and the GB can
 proceed independently.
 Access rate requirements to the GB and the GN will vary depending on
 user requirements and local environments.  The users may require
 access rates ranging from multi-kbit/s in the case of terminals or
 personal computers connected by modems up to multi-Mbit/s and beyond
 for powerful workstations up to the Gbit/s range for high-speed
 computing and data resources.
 2.4.  Directory Services
 Directory services similar to those found in CCITT X.500/ISO DIS 9594
 need to be provided.  These include mapping user names to electronic
 mail addresses, distribution lists, support for authorization
 checking, access control, and public key encryption schemes,
 multimedia mail capabilities, and the ability to keep track of mobile
 users (those who move from place to place and host computer to host
 computer).  The directory services may also list facilities available
 to users via the network.  Some examples are databases,
 supercomputing or other special-purpose applications, and on-line
 help or telephone hotlines.
 The services provided by X.500 may require some extension for GN.
 For example, there is no provision for multilevel security, and the
 approach taken to authentication must be studied to ensure that it
 meets the requirements of GN and its user community.

Gigabit Working Group [Page 8] RFC 1077 November 1988

 2.5.  Network Management and Routing
 The objective of network management is to ensure that the network
 functions smoothly and efficiently, and consists of the following:
 accounting, security, performance monitoring, fault isolation and
 configuration control.
 Accounting ensures that users are properly billed for the services
 that the network provides.  Accounting enforces a tariff; a tariff
 expresses a usage policy.  The network need only keep track of those
 items addressed by the tariff, such as allocated bandwidth, number of
 packets sent, number of ports used, etc.  Another type of accounting
 may need to be supported by the network to support resource sharing,
 namely accounting analogous to telephone "900" numbers.  This
 accounting performed by the network on behalf of resource providers
 and consumers is a pragmatic solution to the problem of getting the
 users and consumers into a financial relationship with each other
 which has stymied previous attempts to achieve widespread use of
 specialized resources.
 Performance monitoring is needed so that the managers can tell how
 the network is performing and take the necessary actions to keep its
 performance at a level that will provide users with satisfactory
 service.  Fault isolation using technical control mechanisms is
 needed for network maintenance.  Configuration management allows the
 network to function efficiently.
 Several new types of routing will be required by GN.  In addition to
 true type-of-service, needed to support diverse distributed
 applications, real-time applications, interactive applications, and
 bulk data transfer, there will be need for traffic controls to
 enforce various routing policies.  For example, policy may dictate
 that traffic from certain users, applications,  or hosts may not be
 permitted to traverse certain segments of the network.
 Alternatively, traffic controls may be used to promote fairness; that
 is, to make sure that busy link or network segment isn't dominated by
 a particular source or destination.  The ability of applications to
 reserve network bandwidth in advance of its use, and the use of
 strategies such as soft connections, will also require development of
 new routing algorithms.
 2.6.  Network Security Requirements
 Security is a critical factor within the GN and one of those features
 that are difficult to provide.  It is envisioned that both

Gigabit Working Group [Page 9] RFC 1077 November 1988

 unclassified and classified traffic will utilize the GN, so
 protection mechanisms must be an integral part of the network access
 strategy.  Features such as authentication, integrity,
 confidentiality, access control, and nonrepudiation are essential to
 provide trusted and secure communication services for network users.
 A subscriber must have assurance that the person or system he is
 exchanging information with is indeed who he says he is.
 Authentication provides this assurance by verifying that the claimed
 source of a query request, control command, response, etc., is the
 actual source.  Integrity assures that the subscriber's information
 (such as requests, commands, data, responses, etc.) is not changed,
 intentionally or unintentionally, while in transit or by replays of
 earlier traffic.  Unauthorized users (e.g., intruders or network
 viruses) would be denied use of GN assets through access control
 mechanisms which verify that the authenticated source is authorized
 to receive the requested information or to initiate the specified
 command.  In addition, nonrepudiation services can be offered to
 assure a third party that the transmitted information has not been
 altered.  And finally, confidentiality will ensure that the contents
 of a message are not divulged to unauthorized individuals.
 Subscribers can decide, based upon their own security needs and
 particular activities, which of these services are necessary at a
 given time.
 3.  Critical Research Issues
 In the section above, we discussed the goals of a research program in
 gigabit networking; namely to provide the technology base for a
 network that will allow gigabit service to be provided in an
 effective way.  In this section, we discuss those issues which we
 feel are critical to address in a research program to achieve such
 goals.
 3.1.  General Architectural Issues
 In the last generation of networks, it was assumed that bandwidth was
 the scarce resource and the design of the switch was dictated by the
 need to manage and allocate the bandwidth effectively.  The most
 basic change in the next generation network is that the speeds of the
 trunks are rising faster than the speeds of the switching elements.
 This change in the balance of speeds has manifested itself in several
 ways.  In most current designs for local area networks, where

Gigabit Working Group [Page 10] RFC 1077 November 1988

 bandwidth is not expensive, the design decision was to trade off
 effective use of the bandwidth for a simplified switching technique.
 In particular, networks such as Ethernet use broadcast as the normal
 distribution method, which essentially eliminates the need for a
 switching element.
 As we look at still higher speed networks, and in particular networks
 in which the bandwidth is still the expensive component, we must
 design new options for switching which will permit effective use of
 bandwidth without the switch itself becoming the bottleneck.
 The central thrust of new research must thus be to explore new
 network architectures that are consistent with these very different
 speed assumptions.
 The development of computer communications has been tremendously
 distorted by the characteristics of wide-area networking: normally
 high cost, low speed, high error rate, large delay.  The time is ripe
 for a revolution in thinking, technology, and approaches, analogous
 to the revolution caused by VCR technology over 8 and 16 mm. film
 technology.
 Fiber optics is clearly the enabling technology for high-speed
 transmission, in fact, so much so that there is an expectation that
 the switching elements will now hold down the data rates.  Both
 conventional circuit switching and packet switching have significant
 problems at higher data rates.  For instance, circuit switching
 requires increasing delays for FTDM synchronization to handle skew.
 In the case of packet switching, traditional approaches require too
 much processing per packet to handle the tremendous data flow.  The
 problem for both switching regimes is the "intelligence" in the
 switches, which in turn requires electronics technology.
 Besides intelligence, another problem for wide-area networks is
 storage, both because it ties us to electronics (for the foreseeable
 future) and because it produces instabilities in a large-scale
 system.  (See, for instance, the work by Van Jacobson on self-
 organizing phenomena for self-destruction in the Internet.)
 Techniques are required to eliminate dependence on storage, such as
 cut-through routing.
 Overall, high-speed WANs are the greatest agents of change, the
 greatest catalyst both commercially and militarily, and the area ripe
 for revolution.  Judging by the attributes of current high-speed
 network research prototypes, WANs of the future will be photonic,
 multi-gigabit networks with enormous throughput, low delay, and low
 error rate.

Gigabit Working Group [Page 11] RFC 1077 November 1988

 A zero-based budgeting approach is required to develop the new high-
 speed internetwork architecture.  That is, the time is ripe to
 significantly rethink the Internet, building on experience with this
 system.  Issues of concern are manageability, understanding
 evolvability and support for the new communication requirements,
 including remote procedure call, real-time, security and fault-
 tolerance.
 The GN must be able to deal with two sources of high-bandwidth
 requirements.  There will be some end devices (computers) connected
 more or less directly to the GN because of their individual
 requirements for high bandwidth (e.g., supercomputers needing to
 drive remote high-bandwidth graphics devices).  In addition, the
 aggregate traffic due to large numbers of moderate rate users
 (estimates are roughly up to a million potential users needing up to
 1 Mbit/s at any given time) results in a high-bandwidth requirement
 in total on the GN.  The statistics of such traffic are different and
 there are different possible technical approaches for dealing with
 them.  Thus, an architectural approach for dealing with both must be
 developed.
 Overall, the next-generation architecture has to be, first and
 foremost, a management architecture.  The directions in link speeds,
 processor speeds and memory solve the performance problems for many
 communication situations so well that manageability becomes the
 predominant concern.  (In fact, fast communication makes large
 systems more prone to performance, reliability, and security
 problems.)  In many ways, the management system of the internetwork
 is the ultimate distributed system.  The solution to this tough
 problem may well require the best talents from the communications,
 operating systems and distributed systems communities, perhaps even
 drawing on database and parallelism research.
 3.1.1.  High-Speed Internet using High-Speed Networks
 The GN will need to take advantage of a multitude of different and
 heterogeneous networks, all of high speed.  In addition to networks
 based on the technology of the GB, there will be high-speed LANs.  A
 key issue in the development of the GN will be the development of a
 strategy for interconnecting such networks to provide gigabit service
 on an end to end basis.  This will involve techniques for switching,
 interfacing, and management (as discussed in the sections below)
 coupled with an architecture that allows the GN to take full
 advantage of the performance of the various high-speed networks.

Gigabit Working Group [Page 12] RFC 1077 November 1988

 3.1.2.  Network Organization
 The GN will need an architecture that supports the need to manage the
 system as well as obtain high performance.  We note that almost all
 human-engineered systems are hierarchically structured from the
 standpoint of control, monitoring, and information flow.  A
 hierarchical design may be the key to manageability in the next-
 generation architecture.
 One approach is to use a general three-level structure, corresponding
 to interadministrational, intraadministrational, and cluster
 networks.  The first level interconnects communication facilities of
 truly separate administrations where there is significant separation
 of security, accounting, and goals.  The second level interconnects
 subadministrations which exist for management convenience in large
 organizations.  For example, a research group within a university may
 function as a subadministration.  The cluster level consists of
 networks configured to provides maximal performance among hosts which
 are in frequent communication, such as a set of diskless workstations
 and their common file server.  These hosts are typically, but not
 necessarily, geographically collocated.  For example, two remote
 networks may be tightly coupled by a fiber optic link that bridges
 between the two physical networks, making them function as one.
 Research along these lines should study the interorganizational
 characteristics of communications, such as those being investigated
 by the IAB Task Force on Autonomous Networks.  Based on current
 results, we expect that such work would clearly demonstrate that
 considerable communication takes place between particular
 subadministrations in different administrations; communication
 patterns are not strictly hierarchical.  For example, there might be
 intense direct communication between the experimental physics
 departments of two independent universities, or between the computer
 support group of one company and the operating system development
 group of another.  In addition, (sub)administrations may well also
 require divisions into public information and private information.
 3.1.3.  Fault-Tolerant System
 Although the GN will be developed as part of an experimental research
 program, it will also serve as part of the infrastructure for
 researchers who are experimenting with applications which will use
 such a network.  The GN must have reasonably high availability to
 support these research activities.  In addition to facilitate the
 transfer of this technology to future operational military and

Gigabit Working Group [Page 13] RFC 1077 November 1988

 commercial users, it will need to be designed to become highly
 reliable.  This can be accomplished through diversity of transmission
 paths, the development of fault-tolerant switches, use of a
 distributed control structure with self-correcting algorithms, and
 the protection of network control traffic.  The architecture of a GN
 should support and allow for all of these things.
 3.1.4.  Functional Division of Control Between Network Elements
 Current protocol architectures use the layered model of functional
 decomposition first developed in the early work on ARPANET protocols.
 The concept of layering has been a powerful concept which has allowed
 dramatic variation in network technologies without requiring the
 complete reimplementation of applications.  The concept of layering
 has had a first-order impact on the development of international
 standards for data communication---witness the ISO "Reference Model
 for Open Systems Interconnection."
 Unfortunately, however, the powerful concept of layering has been
 paired, both in the DoD Internet work and the ISO work, with an
 extremely weak concept of the interface between layers.  The
 interface designs are all organized around the idea of commands and
 responses plus an error indicator.  For example, the TCP service
 interface provides the user with commands to set up or close a TCP
 connection and commands to send and receive datagrams.  The user may
 well "know" whether they are using a file transfer service or a
 character-at-a- time virtual terminal, but can't tell the TCP.  The
 underlying network may "know" that failures have reduced the path to
 the user's destination to a single 9.6 kbit/s link, but it also can't
 tell the TCP implementation.
 All of the information that an analyst would consider crucial in
 diagnosing system performance is carefully hidden from adjacent
 layers.  One "solution" often discussed (but rarely implemented) is
 to condense all of this information into a few bits of "Type of
 Service" or "Quality of Service" request flowing in one direction
 only---from application to network.  It seems likely that this
 approach cannot succeed, both because it applies too much compression
 to the knowledge available and because it does not provide two-way
 flow.
 We believe it to be likely that the next-generation network will
 require a much richer interface between every pair of adjacent layers
 if adequate performance is to be achieved.  Research is needed into
 the conceptual mechanisms, both indicators and controls, that can be
 implemented at these interfaces and that, when used, will result in

Gigabit Working Group [Page 14] RFC 1077 November 1988

 better performance.  If real differences in performance can be
 observed, then the implementors of every layer will have a strong
 incentive to make use of the mechanisms.
 We can observe the first glimmers of this sort of coordination
 between layers in current work.  For example, in the ISO work there
 are 5 classes of transport protocol which are supposed to provide a
 range of possible matches between application needs and network
 capabilities.  Unfortunately, it is the case today that the class of
 transport protocol is chosen statically, by the implementer, rather
 than dynamically.  The DARPA Wideband net offers a choice of stream
 or datagram service, but typically a given host uses all one or all
 the other---again, a static rather than a dynamic choice.  The
 research that we believe is needed, therefore, is not how to provide
 alternatives, but how to provide them and choose among them on a
 dynamic, real-time basis.
 3.1.5.  Different Switch Technologies
 One approach to high-performance networking is to design a technology
 that is expected to work as a stand-alone demonstration, without
 addressing the need for interconnection to other networks.  Such an
 experiment may be very valuable for rapid exploration of the design
 space.  However, our experience with the Internet project suggests
 that a primary research goal should be the development of a network
 architecture that permits the interconnection of a number of
 different switching technologies.
 The Internet project was successful to a large extent because it
 could incorporate a number of new and preexisting network
 technologies: various local area networks, store and forward
 switching networks, broadcast satellite nets, packet radio networks,
 and so on.  In this way, it decoupled the use of the protocols from a
 particular technology base.  In fact, the technology base evolved
 rapidly, but the Internet protocols themselves provided a stability
 that led to their success.
 The next-generation architecture must similarly deal with a diverse
 and evolving technology base.  We see "fast-packet" switching now
 being developed (for example in B-ISDN); we see photonic switching
 and wavelength division multiplexing as more advanced technologies.
 We must divorce our architecture from dependence on any one of these.
 At the host interface, we must divorce the multiplexing of the medium
 from the form of data that the host sees.  Today the packet is used
 both as multiplexing and interface element.  In the future, the host

Gigabit Working Group [Page 15] RFC 1077 November 1988

 may see the network as a message-passing system, or as memory.  At
 the same time, the network may use classic packets, wavelength
 division, or space division switching.
 A number of basic functions must be rethought to provide an
 architecture that is not dependent on the underlying switching model.
 For example, our transport protocols assume that data will be lost in
 units of a packet.  If part of a packet is lost, we discard the whole
 thing.  And if several packets are systematically lost in sequence,
 we may not recover effectively.  There must be a host-level unit of
 error recovery that is independent of the network.  This sort of
 abstraction must be applied to all the aspects of service
 specification: error recovery, flow control, addressing, and so on.
 3.1.6.  Network Operations, Monitoring, and Control
 There is a hierarchy of progressively more effective and
 sophisticated techniques for network management that applies
 regardless of network bandwidth and application considerations:
    1.  Reactive problem management
    2.  Reactive resource management
    3.  Proactive problem management
    4.  Proactive resource management.
 Today's network management strategies are primarily reactive rather
 than proactive:  Problem management is initiated in response to user
 complaints about service outages; resource allocation decisions are
 made when users complain about deterioration of quality of service.
 Today's network management systems are stuck at step 1 or perhaps
 step 2 of the hierarchy.
 Future network management systems will provide proactive problem
 management---problem diagnosis and restoral of service before users
 become aware that there was a problem; and proactive resource
 management---dynamic allocation of network bandwidth and switching
 resources to ensure that an acceptable level of service is
 continuously maintained.
 The GN management system should be expected to provide proactive
 problem and resource management capabilities.  It will have to do so
 while contending with three important changes in the managed network
 environment:

Gigabit Working Group [Page 16] RFC 1077 November 1988

    1.  More complicated devices under management
    2.  More diverse types of devices
    3.  More variety of application protocols.
 Performance under these conditions will require that we seriously
 re-think how a network management system handles the expected high
 volumes of raw management-related data.  It will become especially
 important for the system to provide thresholding, filtering, and
 alerting mechanisms that can save the human operator from drowning in
 data, while still permitting access to details when diagnostic or
 fault isolation modes are invoked.
 The presence of expert assistant capabilities for early fault
 detection, diagnosis, and problem resolution will be mandatory.
 These capabilities are highly desirable today, but they will be
 essential to contend with the complexity and diversity of devices and
 applications in the Gigabit Network.
 In addition to its role in dealing with complexity, automation
 provides the only hope of controlling and reducing the high costs of
 daily management and operation of a GN.
 Proactive resource management in GNs must be better understood and
 practiced, initially as an effort requiring human intervention and
 direction.  Once this is achieved, it too must become automated to a
 high degree in the GN.
 3.1.7.  Naming and Addressing Strategies
 Current networks, both voice (telephone) and data, use addressing
 structures which closely tie the address to the physical location on
 the network.  That is, the address identifies a physical access
 point, rather than the higher-level entity (computer, process, human)
 attached to that access point.  In future networks, this physical
 aspect of addressing must be removed.
 Consider, for example, finding the desired party in the telephone
 network of today.  For a person not at his listed number, finding the
 number of the correct telephone may require preliminary calls, in
 which advice is given to the person placing the call.  This works
 well when a human is placing the call, since humans are well equipped
 to cope with arbitrary conversations.  But if a computer is placing
 the call, the process of obtaining the correct address will have to
 be incorporated in the architecture as a core service of the network.

Gigabit Working Group [Page 17] RFC 1077 November 1988

 Since it is reasonable to expect mobile hosts, hosts that are
 connected to multiple networks, and replicated hosts, the issue of
 mapping to the physical address must be properly resolved.
 To permit the network to maintain the dynamic mapping to current
 physical address, it is necessary that high-level entities have a
 name (or logical address) that identifies them independently of
 location.  The name is maintained by the network, and mapped to the
 current physical location as a core network service.  For example,
 mobile hosts, hosts that are connected to multiple networks, and
 replicated hosts would have static names whose mapping to physical
 addresses (many-to-one, in some cases) would change with time.
 Hosts are not the only entities whose physical location varies.
 Users' electronic mail addresses change.  Within distributed systems,
 processes and files migrate from host to host.  In a computing
 environment where robustness and survivability are important, entire
 applications may move about, or they may be redundant.
 The needed function must be considered in the context of the mobility
 and address resolution rates if all addresses in a global data
 network were of this sort.  The distributed network directory
 discussed elsewhere in this report should be designed to provide the
 necessary flexibility, and responsiveness.  The nature and
 administration of names must also be considered.
 Names that are arbitrary or unwieldy would be barely better than the
 addresses used now.  The name space should be designed so that it can
 easily be partitioned among the agencies that will assign names.  The
 structure of names should facilitate, rather than hinder, the mapping
 function.  For example, it would be hard to optimize the mapping
 function if names were flat and unstructured.
 3.2.  High-Speed Switching
 The term "high-speed switching" refers to changing the switching at a
 high rate, rather than switching high-speed links, because the latter
 is not difficult at low speeds.  (Consider, for example, manual
 switching of fiber connections).  The switching regime chosen for the
 network determines various aspects of its performance, its charging
 policies, and even its effective capabilities.  As an example of the
 latter, it is difficult to expect a circuit-switched network to
 provide strong multicast support.
 A major area of debate lies in the choice between packet switching
 and circuit switching.  This is a key research issue for the GN,

Gigabit Working Group [Page 18] RFC 1077 November 1988

 considering also the possibility of there being combinations of the
 two approaches that are feasible.
 3.2.1.  Unit of Management vs. Multiplexing
 With very high data rates, either the unit of management and
 switching must be larger or the speed of the processor elements for
 management and switching must be faster.  For example, at a gigabit,
 a 576 byte packet takes roughly 5 microseconds to be received so a
 packet switch must act extremely fast to avoid being the dominant
 delay in packet times.  Moreover, the storage time for the packet in
 a conventional store and forward implementation also becomes a
 significant component of the delay.  Thus, for packet switching to
 remain attractive in this environment, it appears necessary to
 increase the size of packets (or switch on packet groups), do so-
 called virtual cut-through and use high-speed routing techniques,
 such as high-speed route caches and source routing.
 Alternatively, for circuit switching to be attractive, it must
 provide very fast circuit setup and tear-down to support the bursty
 nature of most computer communication.  This problem is rendered
 difficult (and perhaps impossible for certain traffic loads) because
 the delay across the country is so large relative to the data rate.
 That is, even with techniques such as so-called fast select,
 bandwidth is reserved by the circuit along the path for almost twice
 the propagation time before being used.
 With gigabit circuit switching, because it is not feasible to
 physically switch channels, the low-level switching is likely doing
 FTDM on micro-packets, as is currently done in telephony.  Performing
 FTDM at gigabit data rates is a challenging research problem if the
 skew introduced by wide-area communication is to be handled with
 reasonable overhead for spacing of this micro-packets.  Given the
 lead and resources of the telephone companies, this area of
 investigation should, if pursued, be pursued cooperatively.
 3.2.2.  Bandwidth Reservation Algorithms
 Some applications, such as real-time video, require sustained high
 data rate streams over a significant period of time, such as minutes
 if not hours.  Intuitively, it is appealing for such applications to
 pre-allocate the bandwidth they require to minimize the switching
 load on the network and guarantee that the required bandwidth is
 available.  Research is required to determine the merits of bandwidth

Gigabit Working Group [Page 19] RFC 1077 November 1988

 reservation, particular in conjunction with the different switching
 technologies.  There is some concern to raise that bandwidth
 reservation may require excessive intelligence in the network,
 reducing the performance and reliability of the network.  In
 addition, bandwidth reservation opens a new option for denial of
 service by an intruder or malicious user.  Thus, investigations in
 this area need to proceed in concert with work on switching
 technologies and capabilities and security and reliability
 requirements.
 3.2.3.  Multicast Capabilities
 It is now widely accepted that multicast should be provided as a
 user-level service, as described in RFC 1054 for IP, for example.
 However, further research is required to determine the best way to
 support this facility at the network layer and lower.  It is fairly
 clear that the GN will be built from point-to-point fiber links that
 do not provide multicast/broadcast for free.  At the most
 conservative extreme, one could provide no support and require that
 each host or gateway simulate multicast by sending multiple,
 individually addressed packets.  However, there are significant
 advantages to providing very low level multicast support (besides the
 obvious performance advantages).  For example, multicast routing in a
 flooding form provides the most fault-tolerant, lowest-delay form of
 delivery which, if reserved for very high priority messages, provides
 a good emergency facility for high-stress network applications.
 Multicast may also be useful as an approach to defeat traffic
 analysis.
 Another key issue arises with the distinction between so-called open
 group multicast and closed group multicast.  In the former, any host
 can multicast to the group, whereas in the latter, only members of
 the group can multicast to it.  The latter is easier to support and
 adequate for conferencing, for example.  However, for more client-
 server structured applications, such as using file/database server,
 computation servers, etc. as groups, open multicast is required.
 Research is needed to address both forms of multicast.  In addition,
 security issues arise in controlling the membership of multicast
 groups.  This issue should be addressed in concert with work on
 secure forms of routing in general.

Gigabit Working Group [Page 20] RFC 1077 November 1988

 3.2.4.  Gateway Technologies
 With the wide-area interconnection of local networks by the GN,
 gateways are expected to become a significant performance bottleneck
 unless significant advances are made in gateway performance.  In
 addition, many network management concerns suggest putting more
 functionality (such as access control) in the gateways, further
 increasing their load and the need for greater capacity.  This would
 then raise the issue of the trade-off between general-purpose
 hardware and special-purpose hardware.
 On the general-purpose side, it may be feasible to use a general-
 purpose multiprocessor based on high-end microprocessors (perhaps as
 exotic as the GaAs MIPS) in conjunction with a high-speed block
 transfer bus, as proposed as part of the FutureBus standard (which is
 extendible to higher speeds than currently commercially planned) and
 intelligent high-speed network adaptors.  This would also allow the
 direct use of hardware, operating systems, and software tools
 developed as part of other DARPA programs, such as Strategic
 Computing.  It also appears to make this gateway software more
 portable to commercial machines as they become available in this
 performance range.
 The specialized hardware approach is based on the assumption that
 general-purpose hardware, particularly the interconnection bus,
 cannot be fast enough to support the level of performance required.
 The expected emphasis is on various interconnection network
 techniques.  These approaches appear to require greater expense, less
 commercial availability and more specialized software.  They need to
 be critically evaluated with respect to the general-purpose gateway
 hardware approach, especially if the latter is using multiple buses
 for fault-tolerance as well as capacity extension (in the absence of
 failure).
 The same general-purpose vs. special-purpose contention is an issue
 with operating system software.  Conventionally, gateways run
 specialized run-time executives that are designed specifically for
 the gateway and gateway functions.  However, the growing
 sophistication of the gateway makes this approach less feasible.  It
 appears important to investigate the feasibility of using a standard
 operating system foundation on the gateways that is known to provide
 the required security and reliability properties (as well as real-
 time performance properties).

Gigabit Working Group [Page 21] RFC 1077 November 1988

 3.2.5.  VLSI and Optronics Implementations
 It appears fairly clear that gigabit communication will use fiber
 optics for at least the near future.  Without major advances in
 optronics to allow effectively for optical computers, communication
 must cross the optical-electronic boundary two or more times.  There
 are significant cost, performance, reliability, and security benefits
 for minimizing the number of such crossings.  (As an example of a
 security benefit, optics is not prone to electronic surveillance or
 jamming while electronics clearly is, so replacing an optic-
 electronic-optic node with a pure optic node eliminates that
 vulnerability point.)
 The benefits of improved technology in optronics is so great that its
 application here is purely another motivation for an already active
 research area (that deserves strong continued support).  Therefore,
 we focus here in the issue of matching current (and near-term
 expected) optronics capabilities with network requirements.
 The first and perhaps greatest area of opportunity is to achieve
 totally (or largely) photonic switches in the network switching
 nodes.  That is, most packets would be switched without crossing the
 optics-electronics boundary at all.  For this to be feasible, the
 switch must use very simple switching logic, require very little
 storage and operate on packets of a significant size.  The source-
 routed packet switches with loopback on blockage of Blazenet
 illustrate the type of techniques that appear required to achieve
 this goal.
 Research is required to investigate the feasibility of optronic
 implementation of switches.  It appears highly likely that networks
 will at some point in the future be totally photonically switched,
 having the impact on networking comparable to the effect of
 integrated circuits on processors and memories.
 A next level of focus is to achieve optical switching in the common
 case in gateways.  One model is a multiprocessor with an optical
 interconnect.  Packets associated with established paths through the
 gateway are optically switched and processed through the
 interconnect.  Other packets are routed to the multiprocessor,
 crossing into the electronics domain.  Research is required to marry
 the networking requirements and technology with optronics technology,
 pushing the state of the art in both areas in the process.
 Given the long-term presence of the optic-electronic boundary,
 improvements in technology in this area are also important.  However,
 it appears that there is already enormous commercial research

Gigabit Working Group [Page 22] RFC 1077 November 1988

 activity in this area, particularly within the telephone companies.
 This is another area in which collaborative investigation appears far
 better than an new independent research effort.
 VLSI technology is an established technology with active research
 support.  The GN effort does not appear to require major new
 initiatives in the VLSI area, yet one should be open to significant
 novel opportunities not identified here.
 3.2.6.  High-Speed Transfer Protocols
 To achieve the desired speeds, it will be necessary to rethink the
 form of protocols.
    1.  The simple idea of a stateless gateway must be replaced by a
        more complex model in which the gateway understands the
        desired function of the end point and applies suitable
        optimizations to the flow.
    2.  If multiplexing is done in the time domain, the elements of
        multiplexing are probably so small that no significant
        processing can be performed on each individually.  They must
        be processed as an aggregate.  This implies that the unit of
        multiplexing is not the same as the unit of processing.
    3.  The interfaces between the structural layers of the
        communication system must change from a simple
        command/response style to a richer system which includes
        indications and controls.
    4.  An approach must be developed that couples the memory
        management in the host and the structure of the transmitted
        data, to allow efficient transfers into host memory.
 The result of rethinking these problems will be a new style of
 communications and protocols, in which there is a much higher degree
 of shared responsibility among the components (hosts, switches,
 gateways).  This may have little resemblance to previous work either
 in the DARPA or commercial communities.
 3.3.  High-Speed Host Interfaces
 As networks get faster, the most significant bottleneck will turn out
 to be the packet processing overhead in the host.  While this does

Gigabit Working Group [Page 23] RFC 1077 November 1988

 not restrict the aggregate rates we can achieve over trunks, it
 prevents delivery of high data rate flows to the host-based
 applications, which will prevent the development of new applications
 needing high bandwidth.  The host bottleneck is thus a serious
 impediment to networked use of supercomputers.
 To build a GN we need to create new ways for hosts and their high
 bandwidth peripherals to connect to networks.  We believe that
 pursuing research in the ways to most effectively isolate host and
 LAN development paths from the GN is the most productive way to
 proceed.  By decoupling the development paths, neither is restricted
 by the momentary performance of capability bottlenecks of the other.
 The best context in which to view this separation is with the notion
 of a network front end (NFE).  The NFE can take the electronic input
 data at many data rates and transform it into gigabit light data
 appropriately packetized to traverse the GN.  The NFE can accept
 inputs from many types of gateways, hosts, host peripherals, and LANS
 and provide arbitration and path set-up facilities as needed.  Most
 importantly, the NFE can perform protocol arbitration to retain
 upward compatibility with the existing Internet protocols while
 enabling those sophisticated network input sources to execute GN
 specific high-throughput protocols.  Of course, this introduces the
 need for research into high-speed NFEs to avoid the NFE becoming a
 bottleneck.
 3.3.1.  VLSI and Optronics Implementations
 In a host interface, unless the host is optical (an unlikely prospect
 in the near-term), the opportunities for optronic support are
 limited.  In fact, with a serial-to-parallel conversion on reception
 stepping the clock rate down by a factor of 32 (assuming a 32-bit
 data path on the host interface), optronic speeds are not required in
 the immediate future.
 One exception may be for encryption.  Current VLSI implementations of
 standard encryption algorithms run in the 10 Mbit/s range.  Optronic
 implementation of these encryption techniques and encryption
 techniques specifically oriented to, or taking advantage of, optronic
 capabilities appears to be an area of some potential (and enormous
 benefit if achieved).
 The potential of targeted VLSI research in this area appears limited
 for similar reasons discussed above with its application in high-
 speed switching.  The major benefits will arise from work that is
 well-motivated by other research (such as high-performance
 parallelism) and by strong commercial interest.  Again, we need to be

Gigabit Working Group [Page 24] RFC 1077 November 1988

 open to imaginative opportunities not foreseen here while keeping
 ourselves from being diverted into low-impact research without
 further insights being put forward.
 3.3.2.  High-Performance Transport Protocols
 Current transport protocols exhibit some severe problems for maximal
 performance, especially for using hardware support.  For example, TCP
 places the checksum in the packet header, forcing the packet to be
 formed and read fully before transmission begins.  ISO TP4 is even
 worse, locating the checksum in a variable portion of the header at
 an indeterminate offset, making hardware implementation extremely
 difficult.
 The current Internet has thrived and grown due to the existence of
 TCP implementations for a wide variety of classes of host computers.
 These various TCP implementations achieve robust interoperability by
 a "least common denominator" approach to features and options.  Some
 applications have arisen in the current Internet, and analogs can be
 envisioned for the GN environment, which need qualities of service
 not generally supported by the ubiquitous generic TCP, and therefore
 special purpose transport protocols have been developed.  Examples
 include special purpose transport protocols such as UDP (user
 datagram protocol), RDP (reliable datagram protocol), LDP
 (loader/debugger protocol), NETBLT (high-speed block transfer
 protocol), NVP (network voice protocol) and PVP (packet video
 protocol).  Efforts are also under way to develop a new generic
 transport protocol VMTP (versatile message transaction protocol)
 which will remedy some of deficiencies of TCP, without the need to
 resort to special purpose protocols for some applications.  Research
 is needed in this area to understand how transport level protocols
 should be constructed for a GN which provide adequate qualities of
 service and ease of implementation.
 A new transport protocol of reasonable success can be expected to
 last for ten years more.  Therefore, a new protocol should not be
 over optimized for current networks and must not ignore the
 functional deficiencies of current protocols.  These deficiencies are
 essential to remedy before it is feasible to deploy even current
 distributed systems technology for military and commercial
 applications.
 Forward Error Correction (FEC) is a useful approach when the
 bandwidth/delay ratio of the physical medium is high, as can be
 expected in transcontinental photonic links.  A degenerate form of
 FEC is to simply transmit multiple copies of the data; this allows

Gigabit Working Group [Page 25] RFC 1077 November 1988

 one to trade bandwidth for delay and reliability, without requiring
 much intelligence.  In fact, it is generally true that reliability,
 bandwidth, and delay are interrelated and an improvement in one
 generally comes at the expense of the others for a given technology.
 Research is required to find appropriate operating points in networks
 using transmission components which offer extremely high bandwidth
 with very good bit-error-rate performance.
 3.3.3.  Network Adaptors
 With the promised speed of networks, the future network adaptor must
 be viewed as a memory interconnect, tying the memory in one host to
 another, at least if the data rate and the low latency made possible
 by the network is to be realized at the host-to-host or process-to-
 process level.  The challenge is too great to be met by just
 implementing protocols in custom VLSI.
 Research is required to investigate the impact of network
 interconnection on a machine architecture and to define and evaluate
 new network adaptor architectures.  Of key importance is integration
 of network adaptor into the operating system so that process-to-
 process communications performance matches that offered by the
 network.  In particular, we conjecture that the transport level will
 be implemented largely, if not entirely, in the network adaptor,
 providing the host with reliable memory-to-memory transfer at memory
 speeds with a minimum of interrupt processing bus overhead and packet
 processing.
 Drawing an analogy to RISC technology again, maximal performance
 requires a well-designed and coordinated protocol, software, and
 hardware (network adaptor) design.  Current standard protocols are
 significantly flawed for hardware compatibility, suggesting a need
 for considerable further research on high-performance protocol
 design.
 3.3.4.  Host Operating System Software
 Conventionally, communication has been an add-on to an operating
 system.  With the GN, the network may well become the fastest
 "peripheral" connected to most nodes.  High-performance process-to-
 process (or application to application) communication will not be
 achieved until the operating system is well designed for fast access
 to and from the network.  For example, incorporating templates of the
 network packet header directly in the process descriptor may allow a

Gigabit Working Group [Page 26] RFC 1077 November 1988

 process to initiate communications with minimal overhead.  Similarly,
 memory mapping can be used to eliminate copies between data arriving
 from the network and it being delivered to the applications.  With a
 GN, an extra copy forced by the operating system may easily double
 the perceived transfer time for a packet between applications.
 Besides matching data transfer mechanisms, operating systems must be
 well-matched in security design to that supported by the host
 interface and network as well.  Otherwise, all but the most trivial
 additional security actions by the operating system in common case
 communication can easily eliminate the performance benefits of the
 GN.  For example, if the host has to do further encryption or
 decryption, the throughput is likely to be at least halved and the
 latency doubled.
 Research effort is required to further refine operating systems for
 the level of performance offered by the GN.  This effort may well be
 best realized with coupling existing efforts in distributed systems
 with the GN activities, as opposed to starting new separate efforts.
 3.4.  Advanced Network Management Algorithms
 An important emphasis for research into network management should be
 on decentralized approaches.  The ratio of propagation delay across
 the country to data rates in a GN appear to be too great to deal
 effectively with resource management centrally when traffic load is
 bursty and unstable (and if it is not, one might argue there is no
 problem).  In addition, important principles of fault containment and
 minimal privilege for reliability and security suggest that a
 centralized management approach is infeasible.  In particular,
 compromising the security of one portion of the network should not
 compromise the security of the whole network.  Similarly, a failure
 or fault should affect at most a local region of the network.
 The challenge is clearly to provide decentralized management
 techniques that lead to good global behavior in the normal case and
 acceptable behavior in expected worst-case failures, traffic
 variations and security intrusions.
 3.4.1.  Control Flow vs. Data Flow
 Network operational communications can be separated into flow of user
 data and flow of management/control data.  However, the user data
 must contain some amount of control data.  One question that needs to

Gigabit Working Group [Page 27] RFC 1077 November 1988

 be explored in light of changes in communications and computing costs
 and performance is the trade-off between these two flows.  An example
 of a potential approach is to use data units which contain predefined
 path indicators.  The switch can perform a simple table look-up which
 maps the path indicator onto the preferred outbound link and
 transmits the packet immediately.  There is a path set-up packet
 which fills in the appropriate tables.  Path set-up occurs before the
 first data packet flows and then, while data is flowing, to improve
 the routes during the lifetime of the connection.  This concept has
 been discussed in the Internet engineering group under the name of
 soft connections.
 We note that separating the data flow from the control flow in the GN
 has security and reliability advantages as well.  We could encrypt
 most of the packet header to provide confidentiality within the GN
 and to limit the ability of intruders to perform traffic analysis.
 And, by separating the control flow, we can encrypt all the control
 exchanges between switches and the host front ends thereby offering
 confidentiality and integrity.  No unauthorized entity will be able
 to alter or examine the control traffic.  By employing a path set-up
 procedure, we can assure that the GN NFE-to-NFE path is functioning
 and also include user-specific requirements in the route.  For
 example, we could request a certain bandwidth allocation and simplify
 the job of the switches in handling flow control.  We could also set
 up backup paths in case the output link will be busy for so many
 microseconds that the packet cannot be stored until the link is
 freed.
 3.4.2.  Resource Management Algorithms
 Most current networks deliver one quality of service.  X.25 networks
 deliver a reliable byte-stream.  Most LANs deliver a best-effort
 unreliable service.  There are few networks today that can support
 multiple types of service, and allocate their resources among them.
 Indeed, for many networks, such as best-effort unreliable service,
 there is little management of resources at all.  The next generation
 of network will require a much more controlled allocation of
 resources.
 There will be a much wider range of desired types of service, with
 current services such as remote procedure call mixing with new
 services such as video streams.  Unless these are separately
 recognized and controlled, there is little reason to believe that
 effective service can be delivered unless the network is very lightly
 loaded.

Gigabit Working Group [Page 28] RFC 1077 November 1988

 In order to support multiple types of service, two things must
 happen, both a change from current practice.  First, the application
 must describe to the network what type of service is required.
 Second, the network must use this information to make resource
 allocation decisions.  Both of these practices present difficulties.
 Past experience suggests that application code is not prepared to
 know or specify what service it needs.  By custom, operating systems
 provide a virtual world, and the applications in this world are
 unaware of the relation between this and the reality of time and
 space.  Resource requests must be in real terms.  Allocation of
 resources in the network is difficult, because it requires that
 decisions be made in the network, but as network packet throughput
 increases, there is less time for decisions.
 The resolution of this latter conflict is to observe that decisions
 must be made on larger units than the unit of multiplexing such as
 the packet.  This in turn implies that packets must be visible to the
 network as being part of a sequence, as opposed to the pure datagram
 model previously exploited.  As suggested earlier in this report,
 research is required to support this more complex form of switch
 without compromising robustness.
 To permit the application to specify the service it needs, it will be
 necessary to propose some abstraction of service class.  By clever
 design of this abstraction, it should be possible to allow the
 application to describe its needs effectively.  For example, an
 application such as file transfer or mail has two modes of operation;
 bulk data transfer and remote procedure call.  The application may
 not be able to predict when it will be in which mode, but if it just
 describes both of them, the system may be able to adapt by observing
 its current operation.
 Experimentation needs to be done to determine a suitable service
 specification interface.  This experimentation could be done in the
 context of the current protocols, and could thus be undertaken at
 once.
 3.4.3.  Adaptive Protocols
 Network operating conditions can vary quickly and over a wide range.
 This is true of the current Internet, and is likely to affect the GN
 too.  Protocols that can adapt to changing circumstances would
 provide more even and robust service than is currently possible.  For
 example, when error rates increased, a protocol implementation might
 decide to use smaller packets, thus reducing the burden caused by

Gigabit Working Group [Page 29] RFC 1077 November 1988

 retransmissions.
 The environment in which a protocol operates can be described in
 terms of the service it is getting from the next lower layer.  A
 protocol implementation can adapt to changes in that service by
 tuning its internal mechanisms (time-outs, retransmission strategies,
 etc.).  Therefore, to design adaptive protocols, we must understand
 the interaction between protocol layers and the mechanisms used
 within them.  There has been some work done in this area.  For
 example, the SATNET measurement task force has looked at the
 interactions between the protocol used by the SIMP, IP, and TCP.
 What is needed is a more complete characterization of the
 interactions at various layer boundaries, and the development of
 appropriate protocol designs and mechanisms to provide for necessary
 adaptations and renegotiations.
 3.4.4.  Error Recovery Mechanisms
 Being large and complex, GNs will experience a variety of faults such
 as link or nodal failure, excessive buffer overflow due to faulty
 flow and congestion control, and partial failure of switching fabric.
 These failures, which also exist in today's networks, will have a
 stronger effect in GNs where a large amount of data will be "stored"
 in transit and, to expedite the switching, nodes will apply only
 minimal processing to the packets traversing them.  In source
 routing, for example, a link failure may cause the loss of all
 packets sent until the source is notified about the change in
 topology.  The longer is the delay in recovering from failures, the
 higher is the degradation in performance observed by the users.
 To minimize the effects of failures, GNs will need to employ error
 recovery mechanisms whereby the network detects failures and error
 conditions, reconfigures itself to adapt to the new network state,
 and notifies peripheral devices of the new configuration.  Such
 protocols, which have to be developed, will respond quickly, will be
 decentralized or distributed to minimize the possibility of fatal
 failures, and will complement, rather than replicate, the error
 correction mechanisms of the end-to-end protocols, and the two must
 operate in coordinated manner.  To this end, the peripheral devices
 will have to be knowledgeable about the intranet recovery mechanisms
 and interact continuously with them to minimize the effect on the
 connections they manage.

Gigabit Working Group [Page 30] RFC 1077 November 1988

 3.4.5.  Flow Control
 As networks become faster, two related problems arise.  First,
 existing flow control mechanisms such as windows do not work well,
 because the window must be opened to such an extent to achieve
 desired bandwidth that effective flow control cannot be achieved.
 Second, especially for long-haul networks, the larger number of bits
 in transit at one time becomes so large that most computer messages
 will fit into one window.  This means that traditional congestion
 control schemes will cease to work well.
 What is needed is a combination of two approaches, both new.  First,
 for messages that are small (most messages generated by computers
 today will be small, since they will fit into one round-trip time of
 future networks), open-loop controls on flow and congestion are
 needed.  For longer messages (voice or video streams, for example),
 some explicit resource commitment will be required.
 3.4.6.  Latency Control and Real-Time Operations
 Currently, there are several distinct approaches to latency control.
 First, there are some networks which are physically short, more like
 multiprocessor buses.  Applications in these networks are built
 assuming that delays will be short.
 Second, there are networks where the physical length is not
 constrained by the design and may differ by orders of magnitude,
 depending on the scope of the network.  Most general purpose networks
 fall in this category.  In these networks, one of two things happens.
 Either the application takes special steps to deal with variable
 latency, such as echo suppression in voice networks, or these
 applications are not supported.
 For most applications today, the latency in the network is not an
 obvious issue so long as the network is not overloaded (which leads
 to losses and long queues), because the protocol overhead masks the
 variation in the network latency.  This balance will change.  The
 latency due to the speed of light will obviously remain the same, but
 the overhead will drop (of necessity if we are to achieve high
 performance) which will leave speed of light and queueing as the most
 critical sources of delay.
 This conclusion implies that if queueing delay can be controlled, it
 will be possible to build networks with stable and controlled
 latency.  If applications exist that require this class of service,

Gigabit Working Group [Page 31] RFC 1077 November 1988

 it can be supported.  Either the network must be underloaded, so that
 queues do not develop at all, or a specific class of service must be
 supported in which resources are allocated to stabilize the delay.
 If this service is provided, it will still leave the application with
 delays that can vary by several orders of magnitude, depending on the
 physical size of the network.  Research at the application level will
 be required to see how applications can be designed to cope with this
 variation.
 3.4.7.  High-Speed Internetworking and Administrational Domains
 Internetworking recognized that the value of communication services
 increases significantly with wider interconnection but ignored
 management and the role of administrations.  As a consequence we see
 that:
    1.  The Internet is more or less unmanageable, as evidenced by
        performance, reliability, and security problems.
    2.  The Internet is being stressed by administrators that are
        building networks to match their organization rather than the
        geography.  An example is a set of Ethernets at different
        company locations operating as a single Internet network but
        geographically dispersed and connected by satellite or leased
        lines.
 The next generation of internetworking must focus on administration
 and management.  Internetworking must support cohesion within an
 administration and a healthy separation between administrations.  To
 illustrate by analogy, the American and Soviet embassies in Mexico
 City are geographically closer to each other than to their respective
 home countries but further in administrational distance, including
 security, accounting, etc.  The emerging revolution in WANs makes
 this issue that much more critical.  The amount of communication to
 exchange the state of systems is bound to increase enormously.  The
 potential cost of failures and security violations is frightening.
 A promising approach appears to be high-level gateways that guard
 between administrations and require negotiations to set up access
 paths between administrations.  These paths are set up, and labeled
 with agreements on authorization, security, accounting, and possible
 resource limits.  These administrative virtual circuits provide
 transparency to the physical and geographical interconnection, but
 need not support more than datagram packet delivery.  One view is
 that of communication contracts with high-level gateways acting as

Gigabit Working Group [Page 32] RFC 1077 November 1988

 contract monitors at each end.  The key is the focus on controlled
 interadministrational connectivity, not the conventional protocol
 concerns.
 Focus is required on developing an (inter)network management
 architecture and the specifics of high-level gateways.  The
 structures of such gateways will have to take advantage of advances
 in multi-processor architectures to handle the processing load.
 Moreover, a key issue is being able to optimize communication between
 administrations once the contract is in place, but without losing
 control.  Related is the issue of allowing high-speed interconnection
 within a single administration, although geographical dispersed.
 Another issue is fault-tolerance.  High-level gateways contain state
 information whose loss typically disrupts communication.  How does
 one minimize this problem?
 A key goal of these administrational gateways has to be failure
 containment: How to protect against external (to administration)
 problems and how to prevent local problems imposing liability on
 others.  A particular area of concern is the self-organizing problems
 of large-scale systems, observed by Van Jacobson in the Internet.
 Gateways must serve to damp out oscillations and control wide load
 swings.  Rate control appears to be a key area to investigate as a
 basis for buffer management and for congestion control, as well as to
 control offered load.
 Given the speed of new networks, and the sophistication of the
 gateways suggested above, another key area to investigate is the
 provision of high-speed network interface adaptors.
 3.4.8.  Policy-Based Algorithms
 Networks of today generally select routes based on minimizing some
 measure such as delay.  However, in the real world, route selection
 will commonly be constrained at the global level by policy issues,
 such as access rights to resources and accounting and billing for
 usage.
 It is difficult for connectionless protocols such as Internet to deal
 with policy controls, because a lack of state in the gateway implies
 that a separate policy decision must be made for each packet in
 isolation.  As networks get faster, the cost of this processing will
 be intolerable.  One possible approach, discussed above, is to move
 to a more sophisticated model in which there is knowledge in the
 gateways of the ongoing flows.  Alternatively, it may be possible to
 design gateways that simply cache recent policy evaluations and apply

Gigabit Working Group [Page 33] RFC 1077 November 1988

 them to successive packets.
 Routing based on policy is particularly difficult because a route
 must be globally consistent to be useful; otherwise it may loop.
 This implies that the every policy decision must be propagated
 globally.  Since there can be expected to be a large number of
 policies, this global passing of information might easily lead to an
 information explosion.
 There are at least two solutions.  One is to restrict the possible
 classes of policy.  Another is to use some form of source route, so
 that the route consistent with some set of policies is computed at
 one point only, and then attached to the packet.  Both of these
 approaches have problems.  A two-pronged research program is needed,
 in which mechanisms are proposed, and at the same time the needed
 policies are defined.
 The same trade-off can be seen for accounting and billing.  A single
 accounting metric, such as "bytes times distance", could be proposed.
 This might be somewhat simple to implement, but would not permit the
 definition of individual billing policies, as is now done in the
 parts of the telephone system.  The current connectionless transport
 architectures such as TCP/IP or the connectionless ISO configuration
 using TP4 do not have good tools for accounting for traffic, or for
 restricting traffic from certain resources.  Building these tools is
 difficult in a connectionless environment, because an accounting or
 control facility must deal with each packet in isolation, which
 implies a significant processing burden as part of packet forwarding.
 This burden is an increasing problem as switches are expected to
 operate faster.
 The lack of these tools is proving a significant problem for network
 design.  Not only are accounting and control needed to support
 management requirements, they are needed as a building block to
 support enforcement of such things as multiple qualities of service,
 as discussed above.
 Network accounting is generally considered to be simply a step that
 leads to billing, and thus is often evaluated in terms of how simple
 or difficult it will be to implement.  Yet an accounting and billing
 procedure is a mechanism for implementing a policy considered to be
 desirable for reasons beyond the scope of accounting per se.  For
 example, a policy might be established either to encourage or
 discourage network use, while fully recovering operational cost.  A
 policy of encouraging use could be implemented by a relatively high
 monthly attachment charge and a relatively low per-packet charge.  A
 policy of discouraging use could be implemented by a low monthly
 charge and a high per-packet charge.

Gigabit Working Group [Page 34] RFC 1077 November 1988

 Network administrators have a relatively small number of variables
 with which to implement policy objectives.  Nevertheless, these
 variables can be combined in a number of innovative ways.  Some of
 the possibilities include:
    1.  Classes of users (e.g., large or small institutions, for-
        profit or non-profit).
    2.  Classes of service.
    3.  Time varying (e.g., peak and off-peak).
    4.  Volume (e.g., volume discounts, or volume surcharges).
    5.  Access charges (e.g., per port, or port * [bandwidth of
        port]).
    6.  Distance (e.g., circuit-miles, airline miles, number of hops).
 Generally, an accounting procedure can be developed to support
 voluntary user cooperation with almost any single policy objective.
 Difficulties most often arise when there are multiple competing
 policy objectives, or when there is no clear policy at all.
 Another aspect of accounting and billing procedures which must be
 carefully considered is the cost of accumulating and processing the
 data on which billing is based.  Of particular concern is collection
 of detailed data on a per-packet basis.  As network circuit data
 rates increase, the number of instructions which must be executed on
 a per-packet basis can become the limiting factor in system
 throughput.  Thus, it may be appropriate to prefer accounting and
 billing policies and procedures which minimize the difficulty of
 collecting data, even if this approach requires a compromise of other
 objectives.  Similarly, node memory required for data collection and
 any network bandwidth required for transmission of the data to
 administrative headquarters are factors which must be traded off
 against the need to process user packets.
 3.4.9.  Priority and Preemption
 The GN should support multiple levels of priority for traffic and the
 preemption of network resources for higher priority use.  Network
 control traffic should be given the highest priority to ensure that
 it is able to pass through the network unimpeded by congestion caused
 by user-level traffic.  There may be additional military uses for
 multiple levels of priority which correspond to rank or level of

Gigabit Working Group [Page 35] RFC 1077 November 1988

 importance of a user or the mission criticality of some particular
 data.
 The use of and existence of priority levels may be different for
 different types of traffic.  For example, datagram traffic may not
 have multiple priority levels.  Because the network's transmission
 speed is so high and traffic bursts may be short, it may not make
 sense to do any processing in the switches to deal with different
 priority levels.  Priority will be more important for flow- (or
 soft-connection-) oriented data or hard connections in terms of
 permitting higher priority connections to be set up ahead of lower
 priority connections.  Preemption will permit requests for high
 priority connections to reclaim network resources currently in use by
 lower priority traffic.
 Networks such as the Wideband Satellite Network, which supports
 datagram and stream traffic, implement four priority levels for
 traffic with the highest reserved for network control functions and
 the other three for user traffic.  The Wideband Network supports
 preemption of lower priority stream allocations by higher priority
 requests.  An important component of the use of priority and
 preemption is the ability to notify users when requests for service
 have been denied, or allocations have been modified or disrupted.
 Such mechanisms have been implemented in the Wideband Network for
 streams and dynamic multicast groups.
 Priority and preemption mechanisms for a GN will have to be
 implemented in an extremely simple way so that they can take effect
 very quickly.  It is likely that they will have to built into the
 hardware of the switch fabric.
 3.5.  User and Network Services
 As discussed in Section 2 above, there will need to be certain
 services provided as part of the network operation to the users
 (people) themselves and to the machines that connect to the network.
 These services, which include such capabilities as white and yellow
 pages (allowing users to determine what the appropriate network
 identification is for other users and for network-available computing
 resources) and distributed fault identification and isolation, are
 needed in current networks and will continue to be required in the
 networks of the future.  The speed of the GN will serve to accentuate
 this requirement, but at the same time will allow for new
 architectures to be put in place for such services.  For example,
 Ethernet speeds in the local environment have allowed for more usable
 services to be provided.

Gigabit Working Group [Page 36] RFC 1077 November 1988

 3.5.1.  Impact of High Bandwidth
 One issue that will need to be addressed is the impact on the user of
 such high-bandwidth capabilities.  Users are already becoming
 saturated by information in the modern information-rich environment.
 (Many of us receive more than 50 electronic mail messages each day,
 each requiring some degree of human attention.) Methods will be
 needed to allow users to cope with this ever-expanding access to
 data, or we will run the risk of users turning back to the relative
 peace and quiet of the isolated office.
 3.5.2.  Distributed Network Directory
 A distributed network directory can support the user-level directory
 services and the lower-level name-to-address mapping services
 described elsewhere in this report.  It can also support distributed
 systems and network management facilities by storing additional
 information about named objects.  For example, the network directory
 might store node configurations or security levels.
 Distributing the directory eases and decentralizes the administrative
 burdens and provides a more robust and survivable implementation.
 One approach toward implementing a distributed network directory
 would be to base it upon the CCITT X.500/ISO DIS 9594 standard.  This
 avoids starting from ground zero and has the advantage of
 facilitating interoperability with other communications networks.
 However, research and development will be required even if this path
 is chosen.
 One area in which research and development are required is in the
 services supplied by the distributed network directory.  The X.500
 standard is very general and powerful, but so far specific provisions
 have been made only for storing information about network users and
 applications.  As mentioned elsewhere, multilevel security is not
 addressed by X.500, and the approach taken toward authentication must
 be carefully considered in view of DoD requirements.  Also, X.500
 assumes that administration of the directory will be done locally and
 without the need for standardization; this may not be true of GN or
 the larger national research network.
 The model and algorithms used by a distributed network directory
 constitute a second area of research.  The model specified by X.500
 must be extended into a framework that provides the necessary
 flexibility in terms of services, responsiveness, data management

Gigabit Working Group [Page 37] RFC 1077 November 1988

 policies, and protocol layer utilization.  Furthermore, the internal
 algorithms and mechanisms of X.500 must be extended in a number of
 areas; for example, to support redundancy of the X.500 database,
 internal consistency checking, fuller sharing of information about
 the distribution of data, and defined access-control mechanisms.
 4.  Avenues of Approach
 Ongoing research and commercial activities provide an opportunity for
 more rapidly attacking some of the above research issues.  At the
 same time, there needs to be attention paid to the overall technical
 approach used to allow multiple potential solutions to be explored
 and allow issues to be attacked in parallel.
 4.1.  Small Prototype vs. Nationwide Network
 The central question is how far to jump, and how far can the current
 approaches get.  That is, how far will connectionless network service
 get us, how far will packet switching get us, and how far do we want
 to go.  If our goal is a Gbit/s net, then that is what we should
 build.  Building a 100 Mbit/s network to achieve a GN is analogous to
 climbing a tree to get to the moon.  It may get you closer, but it
 will never get you there.
 There are currently some network designs which can serve as the basis
 for a GN prototype.  The next step is some work by experts in
 photonics and possibly high-speed electronics to explore ease of
 implementation.  Developing a prototype 3-5 node network at a Gbit/s
 data rate is realistic at this point and would demonstrate wide-area
 (40 km or more) Gbit/s networking.
 DARPA should consider installing a Gbit/s cross-country set of
 connected links analogous to the NSF backbone in 2 years.  A Gbit/s
 link between the east and west coasts would open up a whole new
 generation of (C3I), distributed computing, and parallel computing
 research possibilities and would reestablish DARPA as the premier
 network research funding agency in the country.  This will require
 getting "dark" fiber from one or more of the common carriers and some
 collaboration with these organizations on repeaters, etc.  With this
 collaboration, the time to a commercial network in the Gbit/s range
 would be substantially reduced, and the resulting nationwide GN would
 give the United States an enormous technical and economic advantage
 over countries without it.

Gigabit Working Group [Page 38] RFC 1077 November 1988

 Demonstrating a high-bandwidth WAN is not enough, however.  As one
 can see from the many research issues identified above, it will be
 necessary to pursue via study and experiment the issues involved in
 interconnecting high-bandwidth networks into a high-bandwidth
 internet.  These experiments can be done through use of a new
 generation of internet, even if it requires starting at lower speeds
 (e.g., T1 through 100 Mbit/s).  Appropriate care must be given,
 however, to assure that the capabilities that are demonstrated are
 applicable to the higher bandwidths (Gbit/s) as they emerge.
 4.2.  Need for Parallel Efforts/Approaches
 Parallel efforts will therefore be required for two major reasons.
 First is the need to pursue alternative approaches (e.g., different
 strategies for high-bandwidth switching, different addressing
 techniques, etc).  This is the case for most research programs, but
 it is made more difficult here by the costs of prototyping.  Thus, it
 is necessary that appropriate review take place in the decisions as
 to which efforts are supported through prototyping.
 In addition, it will be necessary to pursue the different aspects of
 the program in parallel.  It will not be possible to wait until the
 high-bandwidth network is available before starting on prototyping
 the high-bandwidth internet.  Thus, a phased and evolutionary
 approach will be needed.
 4.3.  Collaboration with Common Carriers
 Computer communication networks in the United States today
 practically ignore the STN (the Switched Telephone Network), except
 for buying raw bandwidth through it.  However, advances in network
 performance are based on improvements in the underlying communication
 media, including satellite communication, fiber optics, and photonic
 switching.
 In the past we used "their" transmission under "our" switching.  An
 alternative approach is to utilize the common-carrier switching
 capabilities as an integral part of the networking architecture.  We
 must take an objective scientific and economic look and reevaluate
 this question.
 Another place for cooperation with the common carriers is in the area
 of network addressing.  Their addressing scheme ("numbering plan")
 has a few advantages such as proven service to 300 million users [4].

Gigabit Working Group [Page 39] RFC 1077 November 1988

 On the other hand, the common carriers have far fewer administrative
 domains (area codes) than the current plethora of locally
 administered local area networks in the internet system.
 It is likely that future networks will eventually be managed and
 operated by commercial communications providers.  A way to maximize
 technology transfer from the research discussed here to the
 marketplace is to involve the potential carriers from the start.
 However, it is not clear that the goals of commercial communications
 providers, who have typically been most interested in meeting the
 needs of 90+ percent of the user base, will be compatible with the
 goals of the research described here.  Thus, while we recommend that
 the research program involve an appropriate amalgam of academia and
 industry, paying particular attention to involvement of the potential
 system developers and operators, we also caution that the specific
 and unique goals of the DARPA program must be retained.
 4.4.  Technology Transfer
 As we said above, it is our belief that future networks will
 ultimately be managed and operated by commercial communications
 providers.  (Note that this may not be the common carriers as we know
 them today, but may be value-added networks using common carrier
 facilities.) The way to assure technology transfer, in our belief, is
 to involve the potential system developers from the start.  We
 therefore believe that the research program would benefit from an
 appropriate amalgam of university and industry, with provision for
 close involvement of the potential system developers and operators.
 4.5.  Standards
 The Internet program was a tremendous success in influencing national
 and international standards.  While there were changes to the
 protocols, the underlying technology and approaches used by CCITT and
 ISO in the standardization of packet-switched networks clearly had
 its roots in the DARPA internet.  Nevertheless, this has had some
 negative impact on the research program, as the evolution of the
 standards led to pressure to adopt them in the research environment.
 Thus, it appears that there is a "catch-22" here.  It is desirable
 for the technology base developed in the research program to have
 maximal impact on the standards activities.  This is expedited by
 doing the research in the context of the standards environment.
 However, standards by their very nature will always lag behind the

Gigabit Working Group [Page 40] RFC 1077 November 1988

 research environment.
 The only reasonable approach, therefore, appears to be an occasional
 "checkpointing" of the research environment, where the required
 conversions take place to allow a new plateau of standards to be used
 for future evolution and research.  A good example is conducting
 future research in mail using X.400 and X.500 where possible.
 5.  Conclusions
 We hope that this document has provided a useful compendium of those
 research issues critical to achieving the FCCSET phase III
 recommendations.  These problems interact in a complex way.  If the
 only goal of a new network architecture was high speed, reasonable
 solutions would not be difficult to propose.  But if one must achieve
 higher speeds while supporting multiple services, and at the same
 time support the establishment of these services across
 administrative boundaries, so that policy concerns (e.g., access
 control) must be enforced, the interactions become complex.

Gigabit Working Group [Page 41] RFC 1077 November 1988

                               APPENDIX

A. Current R and D Activities

 In this appendix, we provide pointers to some ongoing activities in
 the research and development community of which the group was aware
 relevant to the goal of achieving the GN.  In some cases, a short
 abstract is provided of the research.  Neither the order of the
 listing (which is random) nor the amount of detail provided is meant
 to indicate in any way the significance of the activity.  We hope
 that this set of pointers will be useful to anyone who chooses to
 pursue the research issues discussed in this report.
    1.  Grumman (at Bethpage) is working on a three-year DARPA
        contract, started in January 1988 to develop a 1.6 Gbit/s LAN,
        for use on a plane or ship, or as a "building block".  It is
        really raw transport capacity running on two fibers in a
        token-ring like mode.  First milestone (after one year?) is to
        be a 100 Mbit/s demonstration.
    2.  BBN Laboratories, as part of its current three-year DARPA
        Network-Oriented Systems contract, has proposed design
        concepts for a 10-100 Gbit/s wide area network.  Work under
        this effort will include wavelength division multiplexing,
        photonic switching, self-routing packets, and protocol design.
    3.  Cheriton (Stanford) research on Blazenet, a high-bandwidth
        network using photonic switching.
    4.  Acampora (Bell Labs) research on the use of wavelength
        division multiplexing for building a shared optical network.
    5.  Yeh is reserching a VLSI approach to building high-bandwidth
        parallel processing packet switch.
    6.  Bell Labs is working on a Metropolitan Area Network called
        "Manhattan Street Net."  This work, under Dr. Maxemchuck, is
        similar to Blazenet.  It is in the prototype stage for a small
        number of street intersections; ultimately it is meant to be
        city-wide.  Like Blazenet, is uses photonic switching 2 x 2
        lithium niobate block switches.
    7.  Ultra Network Technologies is a Silicon Valley company which
        has a (prototype) Gbit/s fiber link which connects backplanes.
        This is based on the ISO-TP4 transport protocol.
    8.  Jonathan Turner, Washington University, is working on a
        Batcher-Banyan Multicast Net, based on the "SONET" concept,

Gigabit Working Group [Page 42] RFC 1077 November 1988

        which provides 150 Mbit/s per pipe.
    9.  David Sincowskie, Bellcore, is working with Batcher-Banyan
        design and has working 32x32 switches.
    10. Stratacom has a commercial product which is really a T1 voice
        switch implemented internally by a packet switch, where the
        packet is 192 bits (T1 frame).  This switch can pass 10,000
        packets per second.
    11. Stanford NAB provides 30-50 Mbit/s throughput on 100 Mbit/s
        connection using Versatile Message Transaction Protocol (VMTP)
        [see RFC 1045]
    12. The December issue of IEEE Journal on Selected Areas in
        Communications, provides much detail concerning interconnects.
    13. Ultranet Technology has a 480 Mbit/s connection using modified
        ISO TP4.
    14. At MIT, Dave Clark has an architecture proposal of interest.
    15. At CMU, the work of Eric Cooper is relevant.
    16. At Protocol Engines, Inc., Greg Chesson is working on an XTP-
        based system.
    17. Larry Landweber at Wisconsin University is doing relevant
        work.
    18. Honeywell is doing relevant work for NASA.
    19. Kung at CMU is working on a system called "Nectar" based on a
        STARLAN on fiber connecting dissimilar processors.
    20. Burroughs (now Unisys) has some relevant work within the IEEE
        802.6 committee.
    21. Bellcore work in "Switched Multimedia Datanet Service" (SMDS)
        is relevant (see paper supplied by Dave Clark).
    22. FDDI-2, a scheme for making TDMA channel allocations at 200
        Mbit/s.
    23. NRI, Kahn-Farber Proposal to NSF, is a paper design for high-
        bandwidth network.
    24. Barry Goldstein work, IBM-Yorktown.

Gigabit Working Group [Page 43] RFC 1077 November 1988

    25. Bell Labs S-Net, 1280 Mbit/s prototype.
    26. Fiber-LAN owned by Bell South and SECOR, a pre-prototype 575
        Mbit/s Metro Area Net.
    27. Bellcore chip implementation of FASTNET (1.2 Gbit/s).
    28. Scientific Computer Systems, San Diego, 1.4 Gbit/s prototype.
    29. BBN Monarch Switch, Space Division pre-prototype, chips being
        fabricated, 64 Mbit/s per path.
    30. Proteon, 80 Mbit/s token ring.
    31. Toronto University, 150 Mbit/s "tree"--- really a LAN.
    32. NSC Hyperchannel II, reputedly available at 250 Mbit/s.
    33. Tobagi at Stanford working on EXPRESSNET; not commercially
        available.
    34. Columbia MAGNET-- 150 Mbit/s.
    35. Versatile Message Transaction Protocol (VMTP).
    36. ST integrated with IP.
    37. XTP (Chesson).
    38. Stanford Transport Gateway.
    39. X.25/X.75.
    40. Work of the Internet Activities Board.

Gigabit Working Group [Page 44] RFC 1077 November 1988

B. Gigabit Working Group Members

Member Affiliation

Gordon Bell Ardent Computers Steve Blumenthal BBN Laboratories Vint Cerf Corporation for National Research Initiatives David Cheriton Stanford University David Clark Massachusetts Institute of Technology Barry Leiner (Chairman) Research Institute for Advanced Computer Science Robert Lyons Defense Communication Agency Richard Metzger Rome Air Development Center David Mills University of Delaware Kevin Mills National Bureau of Standards Chris Perry MITRE Jon Postel USC Information Sciences Institute Nachum Shacham SRI International Fouad Tobagi Stanford University

Gigabit Working Group [Page 45] RFC 1077 November 1988

End Notes

   [1] Workshop on Computer Networks, 17-19 February 1987, San Diego,
       CA.
   [2] "A Report to the Congress on Computer Networks to Support
       Research in the United States: A Study of Critical Problems and
       Future Options", White House Office of Scientific and Technical
       Policy (OSTP), November 1987.
   [3] We distinguish in the report between development of a backbone
       network providing gigabit capacity, the GB, and an
       interconnected set of high-speed networks providing high-
       bandwidth service to the user, the Gigabit Network (GN).
   [4] Incidentally, they already manage to serve 150 million
       subscribers in an 11-digit address-space (about 1:600 ratio).
       We have a 9.6-digit address-space and are running into troubles
       with much less than 100,000 users (less than 1:30,000 ratio).

Gigabit Working Group [Page 46]

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