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Internet Engineering Task Force M. Hattig
INTERNET DRAFT Intel Corp
June 24, 1999
Home Network Requirements
draft-hattig-homenet-reqts-00.txt
Status of This Memo
This document is a submission by the author for consideration by the
NITS BOF of the Internet Engineering Task Force (IETF). Comments
should be submitted to the nits@merit.edu mailing list.
Distribution of this memo is unlimited.
This document is an Internet-Draft and is in full conformance with
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
Current home networking protocols consist of home automation
protocols, consumer electronics protocols for audio/video systems,
and TCP/IP for data networking. This document focuses on TCP/IP
protocols for home networking. Specifically in this document, home
networking is TCP/IP data networking between devices in a single
home, between devices in separate homes, between devices in the home
and on the Internet, and between devices in the home and on a secure
corporate network. This document provides requirements for this type
of home networking.
The goals of establishing requirements are to develop a common
understanding of TCP/IP home networking within the IETF so that
various IETF Work Groups can define protocols useable in home
networks and to establish best common practices for manufactures of
TCP/IP home network devices. Ultimately, the goal is to have multi-
vendor TCP/IP home network devices that interoperate with minimal
human configuration.
This document includes many of the ideas discussed on Networks In The
Small (NITS) nits@merit.edu list. Draft-guttman-nits-reqts-00.txt
should be read before reading this draft to give the reader the
proper perspective of the current discussion on the nits@merit.edu
list. This home network draft hopes to add to the NITS effort in the
following areas:
1. Provide a strictly home network perspective of NITS to help
evaluate the meaning of SMALL.
2. Promote specific scenarios important to home networks.
3. Provide specific requirements for home networks.
4. Show the diversity of home networks to promote the acceptance of
routers and multiple IP subnets in SMALL networks.
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Table of Contents
1 Introduction.....................................................1
2 Home Network Definition..........................................1
3 Scenarios........................................................1
3.1 Intra-Home Networking...........................................2
3.2 Internet Access Sharing.........................................2
3.3 Telecommuting...................................................2
3.4 Inter-Home Networking...........................................2
3.5 Services from Home..............................................2
3.6 Security........................................................3
4 Requirements.....................................................3
4.1 Scenarios requirements..........................................3
4.2 In-Home Internetworking.........................................4
4.2.1 Bridging.....................................................4
4.2.2 Routing......................................................5
4.2.3 Bridge or route..............................................5
4.2.4 Requirements.................................................6
5 Full Copyright Statement.........................................6
6 Author's Address.................................................6
7 References.......................................................6
1 Introduction
This document defines home networks, states home network scenarios,
and states home network requirements.
2 Home Network Definition
This section provides an anecdotal definition of home networks. An
anecdotal definition spans the gap between the varying definitions
and ideas regarding home networks.
Most people agree that home networks will service a limited number of
humans such as the number of people in a single family. Less clear
are the numbers of devices and services that will exist in the home
network. Services may range from file sharing, to time of day, to a
DNS server. Some project the number of devices may reach several
hundred and the number of services may reach several thousand. Most
agree that home networks will not scale up to tens of thousands of
devices or services. The requirements in this document recognize
these ranges but make no attempts support a specific number of
devices or services.
Another diversity in the home network will be the link-layer
networks. In-the-home link-layer networks will range from low-
bandwidth power-line networks to high-bandwidth IEEE 1394 networks.
To-the-home link-layers range from 9600-baud modems to broadband
cable or ADSL modems.
Hosts such as thermostats, VCRs, and PCs will communicate to each
other within the home. Hosts will communicate outside the home
through a residential gateway. Network devices such as bridges and
routers will connect in-the-home networks using link-layer or network
layer protocols. Gateways will connect higher-layer protocols in the
home.
Note the terms from this section that are commonly used througout
this document are devices, services, in-the-home networks, to-the-
home networks, hosts, residential gateways, and network devices.
3 Scenarios
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The below scenarios start with a description of the actions or user
benefit, then state the basic problems associated with the scenario.
3.1 Intra-Home Networking
Intra-home networking allows user to game, share, and communicate
within the home. In addition, devices can communicate without user
interaction.
Configuration of users profiles, device names, network interfaces,
services, and applications are currently too complex.
3.2 Internet Access Sharing
Internet sharing is multiple users simultaneously sharing Internet
access. That is, individual users may independently access the
Internet to game, share (e.g. file, printer), and communicate (e.g.
email, web browse). Also, a single device may connect to the
Internet, then several devices may be programmed to automatically
perform batch-like activities through shared access to the Internet.
If all devices in the home have globally addressable IPv4 or IPv6
addresses this scenario generates few unique requirements. However,
Internet Service Providers (ISP) generally do not use IPv6. Each
additional globally unique IPv4 address from an ISP - if the ISP
provides multiple IPv4 addresses - generally cost an additional
monthly fee. A few users may pay extra for a second IPv4 address, but
as the number of devices in the home increase, either the consumer
will not purchase enough IPv4 addresses or the ISP will not have
enough addresses for all devices in all the subscribers' homes. The
reality is that many devices in the home will share a limited number
of globally unique IPv4 addresses.
3.3 Telecommuting
Single user telecommutes to a corporate net via a virtual private
network (VPN).
This communication must be secure when traversing the Internet and
possibly when traversing the in-the-home links. The host in the home
must communicate through the residential gateway and through the
firewall of the corporate LAN.
In addition, the host (e.g. laptop PC) will likely be brought home
from the office. When operating on the corporate LAN at the office,
the host likely depends on DHCP, DNS, file servers, mail servers,
etc. These services may be either different or non-existent in the
home network; therefore, the host must adapt from the corporate
environment to the home environment.
3.4 Inter-Home Networking
Single user games, shares, and communicates to another home via VPN.
This communication may need to be secure when traversing the
Internet. The host in a home must communicate through the local
residential gateway, then through the residential gateway of the
other home.
3.5 Services from Home
Allow in-home servers to be accessed from the Internet. An example is
a WEB server that provides all the Web pages that all family members
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wish to publish to the Internet. Another example is a VCR service
where someone can program the VCR in the home from the office.
The server needs to be accessible from the Internet. The server may
have a globally unique IPv4 address or the residential gateway may
act as some type of proxy to forward information to the server over
the home network.
In addition, a service may be discoverable from the Internet. If
the residential gateway is acting as a proxy, the residential
gateway must first discover the server, then expose the service to
the Internet.
3.6 Security
Security in some form or another is necessary for all the above
scenarios. The descriptions of telecommuting and VPN access to
another home describe the security for those scenarios. That leaves
three other scenarios to consider: intra-home networking, Internet
access sharing, and services from the home.
Users, devices, services, protocols, and applications need controlled
access to and from various users, devices, services, protocols, and
applications. This may affect the design of user profiles, devices,
services, protocols, and applications.
4 Requirements
The first sub-section below provides requirements necessary to
satisfy the scenarios. Subsequent subsections provide specific
requirements related to specific topics. The descriptions of the
scenarios provide the motivation for those requirements. The
motivate for specific topics is provided with those sections.
Currently the only specific topic is in-home internetworking.
The common thread to all home network requirements is that minimal
human effort should be exerted to configure, maintain, and use the
network.
4.1 Scenarios requirements
Here are the requirements for the scenarios listed in section 3.0.
Some requirements may apply to more than one scenario, but in most
cases are not duplicated.
Intra-home networking:
1. Auto configuration of network interface
2. Auto resolution of host name to IP address
3. Auto configuration of services
4. Auto configuration of applications
5. Auto discovery of services
6. Auto discovery of applications
7. Easy configuration of user, device, service, protocol, and
application access
8. Users, devices, services, protocols, and applications have
controlled access to and from any combination of users, devices,
services, protocols, or applications
9. Communication among hosts on different link-layer networks (see
section 4.2)
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Shared Access to the Internet:
1. Allow hosts in the home to simultaneously access the Internet
using a limited number globally unique IPv4 addresses
2. Forward requests (e.g. DNS resolution, DHCP request) to outside
the home when the request cannot be satisfied within the home-
network (this is really just Internet access, not shared Internet
access)
Telecommuting:
1. Host must coordinate with the residential gateway or rely on the
residential gateway to communicate with firewall of the corporate
LAN to access the corporate network
2. Host must be easily adapt from operating on the corporate LAN to
operating on the home network
Inter-Home Networking:
1. Host must with the residential gateway or solely rely on the
residential gateway to communicate with residential gateway of the
other home.
Services from the Home:
1. Allow access from the Internet to a home server
Security
1. Users, devices, services, protocols, and applications have
controlled access to and from users profiles, devices, services,
protocols, or applications
2. Residential gateway is configurable to allow certain protocols in
and out of home network
3. Encrypt to protect data when necessary
4.2 In-Home Internetworking
With the diversity of in-the-home link-layer protocols, it is obvious
that internetworking in some form is required to allow hosts on
different links to communicate. Internetworking requires solving the
problems of link-layer specific address spaces, link-layer specific
max packet sizes, and link-layer specific bandwidths. Internetworking
can be accomplished through bridging or routing.
4.2.1 Bridging
Bridging is internetworking based on link-layer (layer 2) protocols.
With bridging, if the address spaces differ on each link-layer, then
a mapping and a set of pseudo-link-addresses must be created for each
address space. Then, on each in-the-home link, a proxy function must
respond for the devices not on the local link and perform the
appropriate address mapping.
If the max packet size differs on each link-layer, either packet
fragmentation or some mechanism to restrict the size of the packets
to the least common size must exist. With either solution, the
solution must be present in all bridge and host interfaces operating
on a link-layer network. When new link-layer protocols are
introduced, either one of the solutions may restrict the new link-
layer protocols or obsolete legacy protocols.
Depending on bandwidth dissimilarity, it may be sufficient to simply
drop packets when one particular link is flooded. Alternately, some
sort of bandwidth management may reduce the number of lost packets.
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4.2.2 Routing
Routing is internetworking based on network-layer (layer 3)
protocols. The Internet Protocol (IP) is the network layer protocol
considered. IP has generic mechanisms for dealing with different
link-layer address spaces and different link-layer packet sizes.
Several TCP/IP solutions exist for managing bandwidth independent of
link-layer protocols.
With IP routing, address resolution protocols (arp) for specific
link-layers translate from the link-layer addresses to IP addresses,
then IP addressing is used as the common address space. This resolves
any differences in any link-layer address spaces.
Either IP fragmentation or a specific link-layer fragmentation
(defined for IP over the specific link-layer) resolves any
differences in link-layer max packet sizes.
4.2.3 Bridge or route
In general bridging is more desirable than routing because routing
requires support for multiple IP subnets and routers. Unfortunately,
in some cases bridging may more difficult than routing.
Consider 10 Mbps Ethernet, HomePNA (Phone Line), and IEEE 1394.
Ethernet uses 48-bit Ethernet addresses, a 1500-byte max packet size,
and 10 Mbps of bandwidth. HomePNA uses 48-bit IEEE allocated Ethernet
addresses, a 1500-byte max packet size, and 1 Mbps bandwidth. IEEE
1394 uses a 64-bit address. There are three 1394 interfaces called
S100, S200, S400. The max packet sizes are 512, 1024, and 2048 bytes.
The bandwidths are 100 Mbps, 200 Mbps, and 400 Mbps.
The address space for 10 Mbps Ethernet and HomePNA is the same; it is
the IEEE allocated 48 bit Ethernet addresses. Max packet sizes for
the two links are identical. In addition, the bandwidths are
reasonably similar. 10 Mbps Ethernet to HomePNA internetworking will
most likely be done through a bridge.
Internetworking between IEEE 1394 and HomePNA is more complex. The
address spaces have a different number of bits and there is no direct
(e.g. bit mask lower 48 bits) mapping between the address spaces. A
proxy would be necessary to generate pseudo-Ethernet addresses,
psuedo-1394 addresses, then translate the pseudo-addresses to actual
addresses. The pseudo-addresses would have to be unique from actual
addresses; this is particularly difficult with 1394 because part of
the 64 bit 1394 address changes dynamically when devices are added
and remove from the 1394 bus.
The link-layer fragmentation scheme defined in xxxx.txt could be
implemented in the bridge to resolve the difference in packet sizes.
End 1394 devices supporting IP/1394 would already implement this link
fragmentation.
A device with a 400 Mbps 1394 interface could easily flood a 1 Mbps
HomePNA link; thus bandwidth management is highly desirable.
This illustrates that internetworking between disparate networks such
as HomePNA and 1394 will most likely be done with a router.
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4.2.4 Requirements
In most cases bridging will be the best internetworking solution. In
some cases - most of which we cannot imagine today - routing will be
the best internetworking solution. This means requirements for
routers should be stated. In addition, multiple IP subnets require
protocols (e.g. auto network configuration) be designed for unique
network portions of IPv4 addresses for each IP subnet, and IPv4
addresses that are routable within a home network.
5 Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
6 Author's Address
Myron Hattig
Intel Corp.
2111 NE 25TH JF3 206
Hillsboro, OR 97124 USA
voice: 503-264-4522
email: myron.hattig@intel.com
7 References
[1] S. Bradner. Key words for use in RFCs to Indicate Requirement
Levels. RFC 2119, March 1997.
[2] E. Guttman, draft-guttman-nits-reqts-00.txt, June 1999 A
work in progress.
[3] R. Troll Automatically Choosing an IP Address in an Ad-Hoc IPv4
Network draft-ietf-dhc-ipv4-autoconfig-04.txt April, 1999. A
work in progress.
[4] P. Johansson, draft-ietf-ip1394-ipv4-15.txt, May 1999 A
work in progress.
[5] IEEE Std 1394-1995, Standard for a High Performance Serial Bus
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