Network Working Group                                         E. Britton
Request for Comments: 1678                                       J. Tavs
Category: Informational                                              IBM
                                                             August 1994


             IPng Requirements of Large Corporate Networks

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   This document was submitted to the IETF IPng area in response to RFC
   1550.  Publication of this document does not imply acceptance by the
   IPng area of any ideas expressed within.  Comments should be
   submitted to the big-internet@munnari.oz.au mailing list.  This draft
   summarizes some of the requirements of large corporate networks for
   the next generation of the Internet protcol suite.

Executive Overview

   As more and more corporations are using TCP/IP for their mission-
   critical applications, they are bringing additional requirements,
   summarized below, the satisfaction of which would make TCP/IP even
   more appealing to businesses.  Since these are requirements rather
   than solutions, we include capabilities that might be provided in
   protocol layers other than the one that IPv4 occupies; i.e., these
   items might lie outside the scope typically envisioned for IPng, but
   we'll refer to them as IPng requirements nonetheless.  When we
   mention potential solutions, it is not to suggest that they are the
   best approach, but merely to clarify the requirement.

   Among business users the major requirements we see for IPng are:

      -- smooth migration from, and coexistence with, IPv4;
      -- predictable levels of service for predictable costs;
      -- security; and
      -- accommodation of multiple protocols suites.

   We also mention several more specific requirements.

   IPng must have a viable strategy for migration from, and coexistence
   with, IPv4.  IPv4 and IPng must coexist well, because they will need
   to do so for several years.  To encourage IPv4 users to upgrade to

   IPng, IPng must offer compelling advantages and an easy migration
   path.

   Corporate networks must meet promised levels of service while
   controlling costs through efficient use of resources.  The IETF
   should consider both technical solutions (such as service classes and
   priorities) and administrative ones (such as accounting) to promote
   economy.

   Many businesses will not connect to a network until they are
   confident that it will not significantly threaten the
   confidentiality, integrity, or availability of their data.

   Corporations tend to use multiple protocols.  Numerous forces stymie
   the desire to settle on just one protocol for a large corporation:
   diverse installed bases, skills, technical factors, and the general
   trend toward corporate decentralization.  The IETF needs a strategy
   for heterogeneity flexible enough to accommodate the principal
   multiprotocol techniques, including multiprotocol transport,
   tunneling, and link sharing.

   Some of these requirements might be satisfied by more extensive
   deployment of existing Internet architectures (e.g., Generic Security
   Service and IPv4 type of service).  The current Internet protocols
   could be enhanced to satisfy most of the remaining requirements of
   commercial users while retaining IPv4.  Nevertheless, some
   corporations will be scared away from TCP/IP by the publicity about
   the address space until the IETF sets a direction for its expansion.

Migration and Coexistence

   As the use of IPv4 continues to grow, the day may come when no more
   IPv4 network addresses will be left, and no additional networks will
   be able to connect to the Internet.  Classless Inter-Domain Routing
   (CIDR, RFC 1519) and careful gleaning of the address space will
   postpone that cutoff for several years.  The hundreds of millions of
   people on networks that do get IPv4 addresses won't be affected
   directly by the exhaustion of the address space, but they will miss
   the opportunity to communicate with those less lucky.

   Because the Internet is too large for all its users to cutover to
   IPng quickly, IPng must coexist well with IPv4.  Furthermore, IPv4
   users won't upgrade to IPng without a compelling reason.  Access to
   new services will not be a strong motivation, since new services will
   want to support both the IPng users and the IPv4 users.  Only
   services that cannot exist on IPv4 will be willing to use IPng
   exclusively.  Moreover, if IPng requires more resources (e.g.,
   storage, memory, or administrative complexity) than IPv4, users will

   not install IPng unless it has clear benefits over IPv4.  Indeed, the
   millions of users of low-end systems (DOS, sub-notebooks) might not
   ever be able to use IPng if it takes more memory.  Thus there will be
   a long period of coexistence between IPng and IPv4, so the
   coexistence needs to be quite painless, and not based on any
   assumption that IPv4 use will diminish quickly.

Service Level Agreements

   If a corporation depends on its network for applications that are
   critical to its business (such as airlines do for reservations, and
   brokerages do for stock and bond trades), then the corporation
   insists that the network provide the needed service level for a
   predictable cost, so they can allow for it in their budget ahead of
   time.  A service level agreement (SLA) is a contract between
   network's provider and users that defines the service level which a
   user will see and the cost associated with that level of service.
   Measurements in an SLA may include response times (average and
   maximum), availability percentages, number of active sessions,
   throughput rates, etc..  Businesses need to be able to predict and
   guarantee the service levels and costs (routing capacity, link
   bandwidth, etc.) for their traffic patterns on a TCP/IP network.

   IPng should allow control of the cost of networking, a major concern
   for corporations.  Teleprocessing lines are a significant cost in
   corporate networks.  Although the cost per bit-per-second tends to be
   lower on higher-bandwidth links, high-bandwidth links can be hard to
   get, particularly in emerging nations. In many places it is difficult
   to acquire a 64 kpbs line, and T1 service might not exist.
   Furthermore, lead times can be over six months.  Even in the US the
   cost of transcontinental T1 service is high enough to encourage high
   utilization.  Cost-conscious businesses want IPng to allow high
   utilization of teleprocessing links, but without requiring excessive
   processing power to achieve the high utilization.  There has been
   considerable speculation concerning the goodput through congested
   routes when using the Internet's current congestion control
   algorithms; instead, it should be measured in a range of realistic
   cases.  If peak-busy-hour goodput under congestion is near the
   theoretical maximum, publicize the data and move on to other
   requirements.  If not, then the IETF should seek a better standard
   (e.g., they might explore XTP's adaptive rate-based approach and
   other proposals).

   Functions, such as class of service and priority, that let an
   enterprise control use of bandwidth also may help meet service level
   agreements.  On the one hand, it has been said that the absence of
   these inhibits TCP/IP usage in corporate networks, especially when
   predictable interactive response times are required.  On the other

   hand, few vendors have felt motivated to implement TCP's architected
   type-of-service, and priority tends to be handled in a non-standard
   way (e.g., to assure that interactive well-known ports, such as
   Telnet, get faster response times than non-interactive well-known
   ports, such as file transfer).  The IETF should sort out these
   apparently conflicting perspectives.  If the ad hoc techniques can be
   demonstrated to be adequate, then they should be standardized;
   otherwise, effective techniques should be developed and standardized.

   Commercial users often require the options of a higher level of
   service for a higher cost, or a lower level of service for a lower
   cost; e.g., some businesses pay top dollar to assure fast response
   time during business hours, but choose less expensive satellite
   services for data backup during the night.  Pervasive use of IPv4's
   type-of-service markings might satisfy this requirement.

   To discourage waste of bandwidth and other expensive resources,
   corporations want to account for their use.  Direct cost recovery
   would let an entity measure and benchmark its efficiency with minimal
   economic distortion.  Alternatives, such as placing these costs into
   corporate overhead or charging per connection, make sense when the
   administrative cost of implementing usage-based accounting is high
   enough to introduce more economic distortion than the alternatives
   would.  For example, connection-based costs alone may be adequate for
   a resource (such as LAN bandwidth) that is not scarce or expensive,
   but a combination of a connection cost and a usage cost may be more
   appropriate for a more scarce  or expensive resource (such as WAN
   bandwidth).  Balance must be maintained between the overhead of
   accounting and the granularity of cost allocation.

Security

   Many corporations will stick with their private networks until public
   ones can guarantee equivalent confidentiality, integrity, and
   availability.  It is not clear that additional architecture is needed
   to satisfy this requirement;  perhaps more wide spread use of
   existing security technology would suffice.  For example, the
   Internet could encourage wide deployment of Generic Security Service,
   and then solicit feedback on whether additional security requirements
   need to be satisfied.  Note that businesses are so concerned about
   network cost control mechanisms that they want them secured against
   tampering.  IPng should not interfere with firewalls, which many
   corporations consider essential.

Heterogeneity

   Corporate users want the Internet to accommodate multiple protocol
   suites.  Several different protocol suites are growing in use, and
   some older ones will be used for many more years.  Although many
   people wish there were only one protocol in the world, there is
   little agreement on which one it should be.

   Since the marketplace has not settled on one approach to handling
   multiple protocols, IPng should be flexible enough to accommodate a
   variety of technical approaches to achieving heterogeneity.  For
   example, most networking protocols assume they will be the dominate
   protocol that transports all others;  protocol designers should pay
   more attention to making their protocols easily transported by
   others.  IPng needs to be flexible enough to accommodate the major
   multiprotocol trends, including multiprotocol transport networking
   (for an example, see X/OPEN document G306), tunneling (both IP being
   the tunnel and being tunneled), and link sharing (e.g., point-to-
   point protocol and frame relay).  Fair sharing of bandwidth by
   protocols with different congestion control mechanisms is a
   particularly interesting subject.

Flow and Resource Reservation

   Corporate users are becoming more interested in transmitting both
   non-isochronous and isochronous information together across the same
   link.  IPng should coexist effectively with the isochronous protocols
   being developed for the Internet.

   The Internet protocols should take advantage of services that may be
   offered by an underlying fast packet switching service. Constant-
   bit-rate and variable-bit-rate services typically require
   specification of, and conformance to, traffic descriptors and
   specification of quality-of-service objectives from applications or
   users.  The Internet's isochronous protocols should provide
   mechanisms to take advantage of multimedia services that will be
   offered by fast packet switching networks, and must ensure that
   quality-of-service guarantees are preserved all the way up the
   protocol stacks to the applications.  Protocols using available-bit-
   rate services may achieve better bandwidth utilization if they react
   to congestion messages from a fast packet switching network, and if
   they consider consequences of cell discard (e.g., if one cell of an
   IP datagram is discarded, it would be a waste to continue forwarding
   the rest of the cells in that datagram; also, selective retransmit
   should be revisited in this context).

   When the Internet protocol suite allows mixing of non-isochronous and
   isochronous traffic on one medium, it should provide mechanisms to

   discourage inappropriate reservation of resources; e.g., a Telnet
   connection probably doesn't need to reserve 45Mbps.  Accounting,
   class-of-service, and well-known-port distinctions are possible ways
   to satisfy that requirement.

Mobile Hosts

   Wireless technology opens up opportunities for new TCP/IP
   applications that are specific to mobile hosts.  In addition to
   coordinating with organizations developing wireless standards, the
   IETF also should encourage the specification of new TCP/IP
   applications enabled by wireless, such as connectionless messaging.

   IPng should deal well with the characteristics (delay, error rates4,
   etc.) peculiar to wireless.

Topological flexibility

   Today a TCP/IP host moved to a different subnet needs a new IP
   address.  Such moves and changes can become a significant
   administrative cost.  Moreover, mobile hosts require flexible
   topology.  Note how the wireless world is trying to defeat the subnet
   model of addressing either by proxy or by IPaddress servers.  Perhaps
   IPng needs an addressing model more flexible than subnetting, both to
   reduce the administrative burden and to facilitate roaming users.

   The need to eliminate single points of failure drives the business
   requirement for multi-tail attachment of hosts to networks.
   Corporate users complain that TCP/IP can non-disruptively switch a
   connection from a broken route to a working one only if the new route
   leads to the same adapter on the end system.

Configuration, Administration and Operation

   Businesses would like dynamic but secure updating of Domain Name
   Servers, both to ease moves and changes and to facilitate cutover to
   backup hosts.  In this vein, secure and dynamic interaction between
   DNS and Dynamic Host Configuration Protocol (DHCP, RFC 1541) is
   required.  The IETF should encourage wide deployment of DHCP, and
   then solicit feedback on whether additional configuration
   requirements need to be satisfied.

Policy-Based Routing

   Policy-based routing is a more a solution than a requirement.
   Businesses rarely require a general purpose policy architecture,
   although they do state requirements that policy-based routing could
   satisfy.  For example, corporations do not want to carry for free the

   transit traffic of other enterprises, and they may not want their
   sensitive data to flow through links controlled by certain other
   enterprises.  Policy-based routing is one possible way to satisfy
   those requirements, but there seems to be a concern that general
   purpose policy-based routing may have high administrative cost and
   low routing performance.

Scaling

   If IPng satisfies the scaling requirement of the Internet, then it
   satisfies it for corporate networks a fortiori.

Conclusions

   Enhancements to the Internet protocol suite, together with wider
   deployment of some of its existing architectures, could satisfy these
   requirement of commercial customers while retaining IPv4.  Expansion
   of the address space eventually will be necessary to allow continued
   Internet growth, but in RFC 1518 Tony Li and Yakov Rehkter have shown
   that from a technical perspective the addressing issue of IPng is not
   an immediate concern.

   Nevertheless, the TCP/IP community should establish a direction for
   enlargement of the address space, because unfounded publicity about
   the address space is scaring away potential TCP/IP users.  If the
   IETF does not provide direction on how its address space will grow,
   then people may use non-standard, and probably incompatible,
   approaches.

Security Considerations

   The IETF should encourage wide deployment of GSS API, and then
   solicit feedback on whether additional security requirements need to
   be satisfied.  Businesses are so concerned about network cost control
   mechanisms that they want them secured against tampering.  IPng
   should not interfer with firewalls, which many corporations consider
   essential.  See other comments on Security throughout this memo.

Authors' Addresses

   Edward Britton
   IBM Corp.
   E69/503
   P.O.Box 12195
   Research Triangle Park, NC 27709

   Phone: (919) 254-6037
   EMail: brittone@vnet.ibm.com


   John Tavs
   IBM Corp.
   E69/503
   P.O.Box 12195
   Research Triangle Park, NC 27709

   Phone: (919) 245-7610
   EMail: tavs@vnet.ibm.com