Internet DRAFT - draft-mickles-ngtrans-isp-cases
draft-mickles-ngtrans-isp-cases
INTERNET DRAFT Cleve Mickles
Document: draft-mickles-ngtrans-isp-cases-00.txt AOL Time Warner
Expires: October 2002 July 2002
Transition Scenarios for ISP Networks
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
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The list of current Internet-Drafts can be accessed at
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Abstract
This document describes the different types of Internet Service
Provider (ISP) networks in existence today. It will provide design
and operational considerations in delivering network services to
customers for five specific areas in an effort to better identify
specific issues which may arise during a transition to IPv6.
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Table of Contents
1. Introduction...................................................2
2. Scope of the document..........................................2
3. Transition scenarios...........................................3
3.1 CORE/Backbone Networks ....................................4
3.2 Broadband HFC/Coax........................................4
3.3 Broadband DSL Networks.....................................4
3.4 Narrowband Dialup Networks.................................4
3.5 Ethernet to the Home/Home Networking.......................5
4. Security Considerations........................................6
5. Network Management Considerations..............................7
Acknowledgements..................................................7
References........................................................7
Author's Addresses................................................7
Copyright
(C) The Internet Society (2002). All Rights Reserved.
1. Introduction
This document will describe the basic design of ISP networks today.
It will be used to provide direction on what must be considered to
transition today's networks to IPv6. The main purpose of this
document is to identify, and document the issues that must be
considered before transitioning a network to IPv6.
This document is not meant to determine exactly how the transition
will occur for the various ISP networks. This document will not
describe what is or is not a "Tier 1" or "Tier 2"..."Tier N" ISP.
The document focuses on IP capable network devices and may
reference non-IP related devices for clarification purposes only.
At this point much of this document provides a template for the
scenarios. Content is present only in the Core/Backbone and
Narrowband Dialup sections below.
Comments to this draft may be sent to the primary author.
2. Scope of the document
The scope of this document is to cover the major topics ISPs must
consider in building and running their IP networks. The document
will include sections on Core backbone networks, Broadband DSL
networks, Broadband HFC Cable networks, Narrowband Dialup networks,
and Ethernet to the home networking. The document will also
identify Security and Network Management concerns which in some
cases will be common to all as well some areas that may be unique
to the particular service.
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Although the Optical core is important in today's networks, that
layer is generally transparent to the IP layer except in a few
special cases where ISPs have allowed the IP core to be aware of
the optical layer underneath. Hence, this draft does not include
further optical considerations.
Each scenario will discuss issues related to network topology,
network hardware, routing, policing, security, network management,
configuration and host gear.
3. Transition Scenarios
This section provides the description and design considerations
for the different types of ISP networks in existence today. In
some cases a single ISP may provide services in more than one of
the areas mentioned below.
3.1 Core/Backbone Networks
This section describes the general topologies of and characteristics
of today's CORE networks. Although there are numerous large scale
networks out there today, most employ the same basic set of
principles when designing and building their networks.
In terms of physical equipment, today's backbone networks consist
mainly of high speed routers which are configured in a basic core
and edge configuration. In most configurations, for redundancy,
there are two or more core routers as well as two or more border
routers. The border routers provide any local connectivity and
peering. Generally filtering, routing policy and policing type
functions are done on the border routers. The core routers
provide aggregation of border router traffic as well as aggregation
of long haul circuits to remote sites.
BGP4 is the standard gateway routing protocol. In the core, the
IGP choices are generally OSPF or ISIS. Most networks employ some
type of traffic engineering mechanism to steer traffic around
potentially congestive areas. There are also networks that employ
an over provisioning model to limit packet loss.
In terms of host gear, the CORE networks maintain hosts for
supporting and managing the network, but not necessarily the end
user. The standard set of hosts include DNS servers, mail gateways,
authentication( radius or tacacs), and network management servers.
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3.2 Broadband HFC/Coax Networks
This section describes the infrastructure that exists in today's HFC
cable networks that support cable modem services to the home. Since
many cable providers are regional they generally have used the
backbone ISP networks for transit IP services beyond their region.
3.3 Broadband DSL Networks
This section describes the infrastructure that exists in today's
High Speed DSL Networks. DSL comes in many flavors that are
dependent on the quality of central office facility equipment and
copper plant to the home.
3.4 Narrowband Dialup Networks
This section describes Narrowband dialup networks that the majority
of internet users use today to get online. The scenarios will
include solutions where the dial infrastructure is controlled by
one entity as well as solutions where ISPs lease modems from a
wholesale modem providers.
There are multiple types of dialup services from plain/no frills
access to the Internet, to wholesale dialup networks which can
purchased by an organization wanting to resell internet services,
and then there are the full service dialup providers that provide
a long list of features to the end user.
The infrastructure used in the foundation of these various offerings
is somewhat similar although the deployments vary depending on the
level of service offered. The basic dialup service provider model
that includes modem access to the Internet can be built from a
terminal server (generally a digital modem bank), a Layer 2 switch
and routers. For global reachability the dialup provider must
connect to a backbone provider. The basic design calls for the
terminal server to be attached to a layer 2 switch that would in
turn have connections to a router. For redundancy, a dialup
provider can spread multiple shelves of terminal servers across
individual routers and manually shift traffic if a router becomes
disabled. A more robust redundant solution would be to deploy
pairs of routers and use VRRP functionality to maintain traffic
in the event of a failure of one router.
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Generally smaller dialup ISPs purchase a T1 or greater facility from
a Local Exchange Carrier(LEC) to the facility where modem equipment
is housed. The choice in terms of the number of T1s (or other) is
made dependent on how many simultaneous users are supported in the
ISPs business model. Depending on the coverage area multiple phone
numbers may be provided for the end-user to dial and the LEC may
choose to route all calls to a common termination point or provide
the traffic across multiple T1 facilities. When an end-user dials
an access number, the LEC routes the call to the modem server
location and is generally mapped by the LEC into a T1 facility that
terminates on the modem server. The modem server attempts to
verify the user credentials by querying the authentication server
via an IP interface on the modem server. The modem server is
present on a LAN network segment along with any relevant hosts as
well as the default gateway router. Some services that are common
to all dialup providers include the ability to provide DNS service
either primary or secondary and an authentication server.
The wholesale dial provider builds out the dial network just as the
small dialup provider does. Differences include the ability of the
wholesale provider to hand off aggregated traffic to the
organization purchasing wholesale access or to allow the aggregated
traffic to reach the Internet at large without the purchasing
organization needing major internet access facilities. Each case
has different implications.
3.5 Ethernet to the Home / Home Networking
This section describes the Home Networking arena which is basically
in it's infancy. The home of the future will possibly include a
gateway device that will control access to the home, which will have
numerous IP, enabled devices.
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4. Security Considerations
Security concerns will be described within the context of each
scenario. After the various scenarios are documented, a
summarized section including all of the security considerations
may be provided.
5. Network Management Considerations
Network Management concerns will be described within the context
of each scenario. After the various scenarios are documented, a
summarized section including all of the Network Management
considerations may be provided.
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Acknowledgements
[1] The author would like to thank Margaret Wasserman and Randy
Bush for comments on this initial draft document.
References
[1] None currently
Author's Addresses
Cleveland Mickles
AOL Time Warner IM: MicklesCK
12100 Sunrise Valley Drive. Phone: 703-265-5618
Reston, VA 20191, USA Email: micklesc@aol.net
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