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 other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 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. Mickles, et al. Expires - October 2002 [Page 1] Transition Scenarios for ISP Networks July 2002 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. Mickles, et al. Expires - October 2002 [Page 2] Transition Scenarios for ISP Networks July 2002 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. Mickles, et al. Expires - October 2002 [Page 3] Transition Scenarios for ISP Networks July 2002 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. Mickles, et al. Expires - October 2002 [Page 4] Transition Scenarios for ISP Networks July 2002 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. Mickles, et al. Expires - October 2002 [Page 5] Transition Scenarios for ISP Networks July 2002 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. Mickles, et al. Expires - October 2002 [Page 6] Transition Scenarios for ISP Networks July 2002 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 Mickles, et al. Expires - October 2002 [Page 7]