rfc1678.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

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 [e-mail] 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



Britton & Tavs                                                  [Page 1]

RFC 1678     IPng Requirements of Large Corporate Networks   August 1994


   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



Britton & Tavs                                                  [Page 2]

RFC 1678     IPng Requirements of Large Corporate Networks   August 1994


   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



Britton & Tavs                                                  [Page 3]

RFC 1678     IPng Requirements of Large Corporate Networks   August 1994


   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.








Britton & Tavs                                                  [Page 4]