IRTF E. Lear
Internet Draft Name Space Research Group
Category: Informational
April 2002
Expires: October 25, 2002
draft-irtf-nsrg-report-03.txt
What's In A Name:
Thoughts from the NSRG
Status of this Memo
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
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progress."
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Abstract
Over the last few years, the character of end to end connectivity
has changed dramatically. A research group in the IRTF has been
chartered to review these changes, and make recommendations on
whether or not remediation within the protocol stack is necessary.
This document discusses the outcome of those discussions. The key
question we will consider is this: does the stack need an
additional level of naming above layer 3 but below the application
layer? While we do not conclude an answer at this point, we flush
out the question a bit more, talk about existing work, and discuss
additional questions, such as the structure and use of such names.
Although this document has a single author, the ideas
described are those of many people both within and outside of the
IRTF (see the References and Acknowledgements sections for more
details).
1 Introduction
The Internet has gone through several metamorphoses, and how one
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gets around on the Internet has changed over time. Even though the
IP packet has remained largely unchanged, the routing of that
packet has changed considerably. For many years, addressing of end
points was a somewhat trivial matter. One could name end points,
the computers intended to send and receive communications, either
by IP address or by the mnemonic pointing to that address- a domain
name. The difference between name and address seemed unimportant.
However, with the advent of PPP[PPP] and DHCP[DHCP], private
network address space and network address translators (NAT), the
addressing model on the Internet has become one of transients. One
borrows an address from place to place, or from time to time, when
one needs to assert a location in the network topology.[BCP5,NAT]
In addition, a single IP address can now be shared by multiple
servers to represent a single logical end point. The converse is
also true- a single server can represent multiple logical end
points, and not even have to use multiple addresses.[HTTP11]
We are not the first to point out the differences between names,
addresses, and routes. That was done as early as 1978 in
IEN-119[Shoch]. The argument has been sharpened and carried forth
in a number of discussions, including [Saltzer92] and [Saltzer84].
However, we are now faced with some logical outcomes earlier
authors may well have predicted.
Today we ask the question: given the changing nature of end points
on the network, is something more than IP addresses and DNS needed
to resolve end points? What functionality would that something
bring to the table?
1.1 How Endpoints Communicate Today
While attempting not to burden the reader with a long review of how
IP works, we must consider the process of communication between end
points on the Internet in order to address the question we pose.
We consider three forms of communication:
Unicast Connection Oriented
A good example is classic TCP. In order for two ends to establish
a connection, one end resolves the address of the other, usually by
DNS lookup, and then the two exchange SYNs and ACKs, thereby
exchanging state.[TCP] A TCP connection may last for a brief
fraction of a second, or it may last for days.
We also consider connection oriented UDP services, such as SIP or
H.323. Again, state is exchanged, this time in an application
specific way.
Multicast
Unicast communications are by-and-large connection-oriented,
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meaning that there is an explicit beginning, middle, and end of a
two way communication, involving multiple exchanges. Because
multicast is a one-to-many method of communication it is for the
most part connectionless, albeit not necessarily stateless. When a
host is to receive a multicast it declares its interest in the
communication via IGMP [MCAST] and the routing system then arranges
for that host to receive messages to a particular address.
Although most of our discussions will focus on unicast, we are
mindful of the impact any changes made may have on multicast.
Anycast
Finally, a form of communication that has of late become useful:
anycast. An anycast request is served the "nearest" computer
participating in that anycast service, for some value of "near".
Examples of anycast mechanisms include use of multiple DNS servers
answering on a single IP address. Modern anycast service requires
that either the requests consist of a single packet exchange or
that those endpoints sharing the name or address closely coordinate
so as not to break routing or other semantics.
1.1.1 Security Considerations
In this document we address the notion of identity, which is a key
component of security, and key to privacy. Thus, while we entitle
a section "Security Considerations", we do not limit those
considerations to the bounds of this section.
Communications today are secured through one of several means. For
strongest protocol security, the communication is encrypted and the
ends are identified with verifiable public keys. Several systems
are available today to do this, including SSH[SSH], the IPSEC
mechanisms of ESP[ESP] and IKE[IKE], TLS[TLS], and PGP[PGP].
The absence of a name space that uniquely named a host created
problems in the design of ESP/AH (so-called "IPsec"). ESP/AH
really want to bind security associations to a hostname distinct
from either DNS or IP address, because both the DNS entry and the
IP address can change when in fact the security association could
remain valid. This could occur in the case where a PC moves from
one point in a topology to another. In the absence of a persistent
name in the Internet Architecture, IP addresses are used for the
binding of Security Associations. This is an architectural
shortcoming, not a feature. Among other advantages, a real unique
name space would mean that ESP/AH did not care about the
presence/absence of NAT devices.
At a different level, there is an expectation that the routing
system guides a packet toward the destination end point, as
indicated in the IP destination address. Until a few years ago,
this would not have been an unreasonable assumption. Today
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there are exceptions, particularly transparent web proxies and
firewalls.
With some of the currently contemplated changes, the risk of
hijacking a connection changes from that of a continuous intercept
to the potential of a redirection through some form of spoofed
rebinding.
1.2 How Things Have Changed
As mentioned earlier, the nature of communications has changed.
When one transfers a web page to one's system it is quite likely
that the remote address and TCP port, as it appears to the web
server, will not bear much relation to what the client browsing
host stated. Furthermore, without great difficulty the client
cannot determine the address it is in fact using when speaking to a
server. And indeed it itself cannot become a server because
another end has no way to address it. This is the essence of NAT.
All the perils of NAT have been well documented by
others.[TRANSP,INAT]
In addition, computers are far more mobile than they were just a
few years ago. When one moves from one location to another, one's
address changes to reflect one's change in topology. Because TCP
bases its transport connection state on IP addresses, any
connections to the old address are lost (but see below).
This brings us to our question: what if we provide a new name space
at the layers above the internet layer? Would it be possible to do
that which cannot be done with NAT? What impact would this have on
mobility and server farms?
1.3 Stresses
The most important change the Internet has undergone is spectacular
growth. The result of the growth has been shortages in address
space and routing resources.
As the growth of the Internet exploded so did address space
utilization. A combination of measures, including the introduction
of private address space, NATs, and a tightening of policy by
addressing registries reduced the risk of the Internet running out
of allocatable addresses until the 2010 time frame. As a result,
however, the unique identification of an end point was lost.
At the same time, Internet routing tables exploded in size. To
reduce routing tables routes, classless routing [BGP4] was
developed and deployed to aggregate routes on bit boundaries,
rather than on old classful boundaries. Next, the IANA
discontinued its policy of allocating addresses directly to end
users and instead allocated them hierarchically to providers,
requiring providers to show sufficient allocation and utilization
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to justify further assignments. This retarded for a time the
explosion in routing, but did not eliminate growth. While work
continues in this area, it is important to understand that as of
this writing the aggregation of routes through CIDR is the most
efficient way to route Internet traffic, given its current design
goals.
There is a natural conflict between the above two policies. If one
allocates addresses in small chunks, more routing entries will
result. Periodically providers will renumber to get larger blocks,
at the inconvenience of all of their customers.
2 Related Work
There exists a large body of work on name spaces and their
bindings. The work we discuss below primarily relates to the
binding of stacks to IP addresses, with an eye toward mobility or
transience. The first mechanism is Mobile-IP.
2.1 Mobile-IP
Mobile-IP addresses the problem of having a stable end point
identifier on mobile hosts. As hosts move through the topology
they update a home agent which acts as an ever-present anchor.
Mobile-IP provides a different solution depending on whether one is
using IPv4 or IPv6.[MobileIP,MobileIPv6]. In IPv4, Mobile-IP is a
tunneling mechanism. In IPv6, mobile hosts make use of end host
options. An end system uses its home address to create transport
connections and communicate with the other end, one or more
correspondent nodes. IPV4 mobile hosts are tunneled through a home
agent and optionally a remote agent, so that the end system's
address space is found in the routing system without additional
global routing overhead. In IPv4 the home agent is separate from
the other end of a transport connection, and packets take a
triangular route. In IPv6, support of mobility is required, and
the likely non-mobile host, the correspondent node, is aware that
the other end is mobile. Therefore, once the mobile host and
remote host establish communications they can "short circuit" to
remove the home agent. This is key because while the remote agent
is likely to be near the mobile host, the home agent is unlikely to
be near anybody.
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_______ ________
| |Care-of Address | | remote agent optionally
|Mobile |--------------------| Remote | forwards packets to mobile
| Host | | Agent | host
|_______| |________|
::Home Address |
:: | home agent encapsulates and passes
:: | packets to the remote agent or
:: ___|____ directly to the mobile node
:: | |
:: | Home |
:: | Agent |\ remote host sends packets
:: |________| \ to home agent
:: \
\\ \
\\ \
\\ \_____________
\\ tunneled transport connection | |
=====================================|Correspondent|
| Node |
|_____________|
Figure 1: Mobile-IPv4
In effect, Mobile-IP turns the mobile node's IP address into a host
identifier, where the "care of" address is the host's current
location. The way Mobile-IP succeeds is that it uses tunneling
within the topology to represent an address at one location when it
is in fact at another. However, a route to the mobile node's
address itself must be available within the topology at all times.
In an IPv4 world this would be untenable because of constraints on
both the addressing system. With IPv6, the addressing pressures
are off, and so each host can have a unique end address. However,
problems remain with the routing system. In addition, there is a
class of devices for which there may be no "home", such as devices
in airplanes, mobile homes, or constant travelers. Additionally,
there is a desire within some of the mobility community to have
"micromobility" mechanisms that enable faster movement than
envisioned by Mobile-IP. The Routing Research Group (rrg) is
currently investigating this area.
Most importantly, mobile devices can't withstand the loss of the
home agent, even if they are still online somewhere. With the home
agent offline, no incoming connections can get to them, and
long-lived communications cannot be re-established. If the
rendezvous point location/identity wasn't overloaded on the home
address (which is, of necessity, a place in the network, and might
go offline, not a distributed database), it might be possible to
work around that for those entities that cared about that failure
mode.
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2.2 Stream Control Transport Protocol (SCTP)
Many of the problems raised have to do with the use of layer 3
information at higher layers, such as the pseudo-header in TCP.
A protocol that is considered an alternative to TCP has certain
potential benefits in the area of names and addresses. TCP
transport connection end points are named by IP addresses, and
there are precisely two end point addresses, one for each end.
SCTP allows for multiple transport addresses per end, nominally for
redundancy of applications that require high availability.
However, it is possible to move a transport connection as a host
moves from one location to another, or as its address changes due
to renumbering (for whatever purpose). Work has progressed within
the IETF to introduce a new capability to SCTP, that allows
connection end points to change the set of IP addresses used for a
transport connection.[ADDIP]
There are two limitations to this idea. For one, it only affects
those hosts that use SCTP, and so long as there exist other
transports that are considered more appropriate for specific tasks,
solving an Internet naming problem within SCTP will be susceptible
to the charge that the solution is not sufficiently general.
The second problem is that as contemplated in the draft the risk of
an attacker hijacking a connection is elevated. This same
problem exists within MobileIP, and may similarly be mitigated by
purpose built keys (see below).
2.3 Host Identity Payload
Host Identity Payload (HIP) is a new approach to the problem of
naming end points. It inserts an additional "name" between layer 3
and layer 4, thus becoming layer 3.5.[HIP-ARCH] The goal is to
decouple the transport layer from the Internet layer, so that
changes in the Internet layer do not impact the transport, and the
benefit is shared by all mechanisms atop transports that use HIP.
______________________________________
| |
| Application |
|______________________________________|
| |
| Transport |
|______________________________________| The Host Stack
| |
| HIP or ESP w/ HI as SPI |
|______________________________________|
| |
| IP Header |
|______________________________________|
Figure 2: Host Identity
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HIP itself relies on a cryptographic host identity (HI) that is
represented in a Host Identity Tag (HIT) of various forms. One is
a hash of the public key host identity, another is an
administratively assigned value coupled with a smaller hash of the
public key host identity. Host identities can be public or
anonymous, the difference being whether or not they are published
in a directory.
Whereas today one binds the transport to an IP address, HIP
proposes that the transport binds to a host identity tag (HIT).
DNS is used to determine the HI and HIT, or to validate via reverse
lookup an HIT. Further, DNS continues to be used to get an
Internet address.
Whether one should want to decouple the transport layer from the
Internet layer is a controversial question. After all, that
coupling has for many years provided the barest bones of the
security of knowing that the packets that make up the transport
connection are being guided through the network by routing
tables in Internet routers that are owned by people and
organizations whose intent is to get one's packets from source to
destination. If we divorce the transport from the Internet layer,
we introduce another way for an attacker to potentially hijack
connections. HIP attempts to address this through the use of
public key verification.
Additionally, HIP raises an issue regarding other uses for
aggregation of IP addresses. Today, they are not only aggregated
for purposes of reduced routing, but also for reduced
administration. A typical access list used on the Internet will
have some sort of a mask, indicating that a group of hosts from the
same subnet may access some resource. Because the value of a HIT
is a hash in part, only the administratively assigned value can be
aggregated, introducing an allocation limitation and authorization
concerns.
On the other hand, there is the old computer science saying, any
problem can be fixed by an additional layer of indirection
(arguably what we're talking about). It should be possible to
administratively aggregate on groupings that are made at higher
layers.
An alternative approach would be to aggregate based on DNS names,
rather than HI values. See [HIP-ARCH] for more details.
A key concern with HIP is whether or not it will work in a mobile
world. If the DNS is involved, or if any directory is involved,
will caching semantics eventually limit scalability, or are there
mobility mechanisms that can be employed make use of directories
feasible?
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2.4 Purpose Built Keys
Purpose built keys (PBKs) are temporary end point identifiers that
are used to validate a given endpoint during a communication. PBKs
are similar to HIP.[PBK] Rather than attempting to build an
infrastructure to validate the end points, however, PBK's sole
purpose is to ensure that two hosts that originate a communication
may continue that communication with the knowledge that when
finished each end point will be the same end point it was at the
start. Thus, even if one's address changes for whatever reason it
is still possible to validate oneself to the other side of the
communication.
PBKs take the form of ad hoc public / private key pairs. When a
node wishes to validate itself to another node it signs a piece of
data with its private key that is validated by the other end with
the public key. The public key itself becomes an end point
identifier.
PBKs make no claim as to who the parties actually are. They make
no use of public key infrastructures. PBKs are themselves
ephemeral for the duration of a communication.
2.5 RSIP and MIDCOM
Two related efforts have been made to stitch together name spaces
that conflict. One is RSIP, which allows for the temporary
allocation of address space in one "realm" by a host in another
realm, not unlike the way an address is gotten via DHCP. The
benefit of RSIP is that it allows the end point to know what
address it is assigned, so that it may pass such information along
in the data path, if necessary. The problem with RSIP is that host
routing decisions within the stack are very complex. The host
makes decisions based on destination address (a process that a fair
amount of configuration, and lacked certainty as it was based on
potentially non-unique IP addresses). Because RSIP borrows public
addresses it must relinquish them as quickly as possible, or the
point of NAT is negated. In order to make better use of the scarce
public resource, RSIP implementations would need to route not just
on destination address, but on application information as well.
For example, internal hosts would probably not need external
addresses merely to browse the web.
MIDCOM is a similar approach. However, rather than tunneling
traffic, an agreement between an end point and its agent and a
"middle box" such as a NAT or a firewall is made so that the end
point understands what transformation will be made by the middle
box. Thus, where a NAT or a web cache translates from one name
space to another, MIDCOM enables end points to identify that
translation.
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MIDCOM is contemplated for use by specific applications, and thus
avoids the stack problems associated with RSIP. However, neither
MIDCOM nor RSIP resolve how to discover such middle boxes. Nor do
they provide a unique way for a host behind a NAT to identify
itself in an enduring way. Finally, they both run into problems
when multiple NATs are introduced in a path.
2.6 GSE or "8+8"
One proposal attempts to ease the conflict between the desire of
end systems to have a fixed name for themselves, and the needs of
the routing systems for address assignments which minimize the
overhead of routing calculations. The clash between these two
desires produces either the inconvenience (for the end systems) of
renumbering, or routing inefficiency and potentially poor address
space utilization as well; the latter caused by the difficulty of
renumbering to allows effective use of address space.
Known as 8+8 or GSE, it would have split the IPv6 address into two
parts: a routing system portion that would be assigned and managed
by service providers that would change based on routing system
requirements, and a locally managed portion that would be assigned
and managed by terminal autonomous systems.[GSE] While each portion
is globally unique, there are in effect two addresses, one to get a
packet to an autonomous system and another to get to the host.
Further, end hosts might not be aware, at least initially, of their
routing portions. It was thus envisioned that the renumbering of
the routing portion could be done as a matter of signaling, with
little administrative involvement from the end point. Another goal
of GSE was to eliminate additional routing overhead caused by
multihomed end systems, whose information must today be carried
throughout the routing system. By allowing end enterprises to have
multiple global parts for purposes of multihoming, the terminal
ASes would become what are today's last-hop ISPs. There are a
number of challenges that GSE would have to overcome. For one, how
does one glue together the provider portion of an address with the
more local part, and how would one accomplish the task securely?
Would doing so eliminate the need or interest in adding other
additional name spaces?
2.7 Universal Resource Names
Universal resource names (URNs) do not provide us a mechanism to
resolve our naming concerns.[URN] Rather, they may provide us the
form of the name to use, and perhaps a framework for resolution.
For instance, an HI may conceivably be represented as a URN. URNs
further the notion of defining a binding and boundaries between the
name of an object and its location.
3. Discussion: Hosts and Stacks
When one's computer moves from one location to another, or when a
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host receives a new address for whatever reason, the computer
itself has largely remained the same, as has the person using it.
The identity of that computer has not changed. That entity may
well be in communication other computers and have access rights to
network resources. Indeed multiple entities may be represented by
a single computer.
Until recently it was generally assumed that a host identified
itself by an IP address or a group of IP addresses. With the
exception of such mechanisms as MX records [ESMTP], one connected
to an IP address, assuming there to be an 1:1 relationship between
IP address and host. This assumption is no longer valid for
reasons previously discussed.
Today, a host may represent multiple entities. This happens when a
service provider hosts many web sites on one server. Similarly, a
single entity may be represented by multiple hosts. Replicated web
servers are just such an example. We refer to these entities as
stacks, instantiations of the TCP/IP model, be they across one or
many hosts. We define a stack or end point as one participant of
an end-to-end communication. That participant may move, and may be
represented by multiple hosts.
Each instance of a stack has a name, a "stack name". At an
architectural level the Name Space Research Group debated the value
of such names, and their associated costs. We see forms of this
name used in numerous places today. As previously mentioned, SSH
uses public/private key pairs to identify end points. An HTTP
cookie anonymously identifies one end of a communication, in such a
manner that both the transport connection and the IP address of the
other end point may change many times.
We thus are left with several questions as to the nature of stack
names.
3.1. What do stack names look like?
Names may be structured or unstructured. If they are structured,
what encoding do they use, and what is their scope? Is the length
of such a name fixed or variable? Are stack names unique across
the Internet? If so, are they guaranteed unique through some sort
of a registry or are they statistically unique? If it is a
registry, is it centralized or distributed, such as DNS?
There is no universal view on many of these questions. For one
thing, many are concerned that any new registry would bring
unwelcome and burdensome administrative costs to connecting to the
Internet, either as a service or a user. One could envision a very
large reverse lookup domain that contains all HIs, leaving little
room for decentralization.
In particular we have seen two problems crop up with centralized
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name spaces. The first problem is that of domain squatting, where
people buy a name simply for its usefulness to others. The second
problem lies with IP addresses, which are allocated and sold by
providers. Those providers may choose to make a "service" out of
making addresses available to customers. When designing a new name
space, one should introduce no artificial scarcity.
As we have seen, one possibility is that stack names could be
represented as MOBILE-IP home addresses. The benefit of this idea
is that one might well derive a large benefit without having to
incur any additional protocol engineering, at least initially. By
representing stack names thusly the architectural distinction
between stack name and location is somewhat muddled. A difficulty
worthy of further debate is whether such incremental approaches
actually help us in the long run. Still, the larger the leap, the
less the likelihood of deployment success.
3.1.1 Uniqueness
This document would not exist were uniqueness not desirable, since
we could live on in with the current state of affairs (and we may
yet). Uniqueness offers certainty that a name represents exactly
one object. DNS A records never were intended to have uniqueness.
and as we've discussed, IP addresses, particularly in a V4
environment, no longer have uniqueness. Uniqueness allows for
people and programs to build operating assumptions the other end of
a communication. TCP was designed with such an assumption. Being
uniquely identified also raises security concerns. What if you
don't want to be uniquely identified by generators of SPAM or by
powerful entities such as governments? Note that we refer to the
uniqueness of the object referenced by the name. An object itself
might have multiple names.
3.1.2 Mapping
This brings into question several related concerns with naming:
what, if any, mapping mechanisms exist? Should stack names map to
IP addresses, to domain names, or for that matter, to anything?
Do domain names, X.509 distinguished names, or other names map to
stack names? Each is a separate question. A name on its own is of
very limited value. The mappings go to how the name will be used.
Is a stack name just something that sits in a transport control
block on a device? In effect purpose built keys could accomplish
that task.
3.1.3 Anonymity
Related to uniqueness and mapping is anonymity. Is it possible or
even desirable to have anonymous names? That is, should my
computer be able to establish a communication to your computer,
such that you can be assured that you are communicating with the
same entity who used a particular name, without actually knowing
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the underlying binding between the name and the object?
3.1.4 Statistical Uniqueness versus Universal Uniqueness
The classic way we have ensured uniqueness of names and addresses
on the Internet has been to have those names and addresses assigned
through a distributed tree-structured database by central
authorities. While this guarantees uniqueness to the level of
competence of those authorities, such delegation introduces
overhead, artificial markets, trademark concerns, and other
problems. One way to avoid a new administrative overhead would be
for individuals to be able to generate statistically unique names.
Statistically unique names can easily be mapped TO, but they are
less easily mapped FROM. This is because it is difficult to
establish trust relationships necessary to make changes to the
mapping. For instance, if a central authority controls the name
space, there must be some sort of authentication and authorization
model in place for the change to be allowed. If such a mechanism
is in place, one has to wonder (a) why the names used for that
infrastructure are not used and thus (b) why statistically unique
names would be of any advantage.
There was a consensus that if we were to introduce a new name space
it should not be mnemonic in nature. DNS exists for that purpose
today, and while others have recently identified a need to revisit
DNS, that was not the purpose of this effort.
3.1.5 Fixed versus variable length names
When the nature of the name is decided one must decide whether the
name should be of fixed length or whether it is variable length.
Traditionally those fields which are found in every packet tend to
be fixed length for performance reasons, as other fields beyond
them are easily indexed. The form the name takes will have some
relevance on this decision. If the name appears along the lines of
an X.509 distinguished name, it must be variable. If the name is
otherwise fixed length and supposed to be universally unique, the
field must allow for large enough numbers to not require a protocol
change anytime soon. Similarly, if the name is statistically
unique, the field must be large enough so that the odds of a
collision are acceptably low so that the protocol needn't change
anytime soon. We leave it to engineers to determine what "anytime
soon" and "acceptably low" are.
A convenient feature of a variable-length name is that it allows
for ease of organizational delegation. If one provides a
hierarchical model such as DNS, one can decentralize authority to
get a new name or to change a name. By the same token, such
structure requires a root authority from which distribution
occurs. So long as the name itself is not a pneumonic, perhaps it
is possible to limit problems such as domain squatting.
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Ultimately, if the name is to be other than statistically unique,
there will be some sort of central root service.
3.2 At what layer are stack names represented?
Where are stack names represented? Are they represented in every
packet, or are they represented in only those packets that the
underlying use requires? The benefit of not requiring stack names
to appear in every packet is some amount of efficiency. However,
the benefit of having them in every packet is that they can be used
by upper layers such as ESP. In addition, end points would be able
to distinguish flows of packets coming from the same host even if
the IP address changes, or if the remote stack migrates to another
piece of hardware. The PBK approach would alert an end point when
one side knows of such a change, but as we have seen, the IP
address one side sees, the other side may not, without a mechanism
such as MIDCOM or RSIP. HIP and ESP solve this problem by putting
an identifier (either the HIT or SPI) in every packet.
______________________________
| ______ ______ |
| /_____ /| /_____ /| |
| | APP |f| | APP |b| |
| |------|o| |------|a| |
| |TRANS |o| |TRANS |r| |
| | PORT |.| | PORT |.| |
| |------|c| |------|c| |
| | IP |o| | IP |o| |
| |______ m| |______ m| |
| | MAC |/ | MAC |/ |
| |______/ |______/ |
| |
| |
|______________________________|
Figure 3: One application: multiple stacks on a single device
If we had a stable Internet layer it might be possible to
represent stack names as IP addresses. Even if a host moved, a
stack name could be represented as a Mobile-IP "home" address. The
PBK proposal suggests that stack names be passed as necessary as
end to end options in IPv6 or simply as options in IPv4.
Lear draft-irtf-nsrg-report-03.txt [Page 14]
__________________ ________________________
| | | |
| _______________| |____________________ |
| /_______________| |___________________ /| |
| | A P P L I| |C A T I O N |f| |
| |----------------| |-------------------|o| |
| | T R A N | | P O R T |o| |
| |----------------| |-------------------|.| |
| | I N T E| |R N E T |c| |
| |----------------| |-------------------|o| |
| | F R A M| | I N G |m| |
| |----------------| |-------------------| / |
| |________________| |___________________|/ |
| | | |
|__________________| |________________________|
Figure 4: Another application: single stack represented by
multiple hosts
If we do not assume a stable Internet layer, then stack names must
appear above it. If we insert a new mechanism between the Internet
and transport layers, all end points that wish to use the mechanism
would need to change.
3.2.1 A few words about transport mechanisms
We may not wish to completely divorce the transport layer from the
Internet layer, as currently implemented. The transport mechanisms
today are responsible for congestion control. If one end point
moves it is quite possible that the congestion characteristics of
the links involve will change as well, and it thus might be
desirable for mechanisms such as TCP Slow Start to be invoked. It
is also possible that codecs may no longer be appropriate for the
new path, based on its new characteristics. In as much as mobile
hosts change their locations and bindings with MOBILE-IP today,
this is already an issue.
3.3 Stack names and the routing system
It would seem a certainty that the routing system would want very
little to do with stack names. However, as previously mentioned,
when we break the binding between Internet and transport layers, we
now must take some care to not introduce new security problems,
such that a transport connection cannot be hijacked by another host
that pretends to be authorized on behalf of an end point.
One misguided way to do this would be to enforce that binding in
the routing system by monitoring binding changes. In order for the
routing system to monitor the binding, it realistically must be
done out in the open (i.e., not an encrypted exchange) and the
binding must appear at some standard point, such as an option or at
a predictable point in the packet (e.g., something akin to layer
3.5).
Lear draft-irtf-nsrg-report-03.txt [Page 15]
In other words, one would have gone all the way around from
attempting to break the binding between transport and Internet
layers to re-establishing the binding through the use of some sort
of authorization mechanism to bind stack names and Internet
addresses.
3.4 Is an architectural change needed?
The question of what level in the stack to solve the problem
eventually raises whether or not we contemplate architectural
changes or engineering enhancements. There can be little dispute
that the topic is architectural in nature. For one, there are now
numerous attempts to solve end point identification problems within
the engineering space. We've already mentioned but a few. The
real question is whether the existing architecture can cover the
space. Here there are two lines of thought. The first is that the
use of mobility mechanisms and MOBILE-IP will cover any perceived
need to provide stack names. Assuming that it can be widely and
securely deployed, MOBILE-IP certainly resolves many host mobility
concerns. However, it remains to be seen if it can address other
problems, such as those introduced by content delivery networks.
The other line of thought is that we should make the architectural
distinction between names, addresses, and routes more explicit
since there is otherwise an overloading of operators. Regardless
of whatever tactical benefit one might gain, the sheer
architectural separation should provide value in and of itself over
time. The risk of this argument is that we will have introduced
complexity without having actually solved any specific problem,
initially.
To resolve the differences between the two schools of thought
requires development of the latter idea to the point where it can
be properly defended, or for that matter, attacked.
4 Conclusions
The NSRG was not able to come to unanimity as to whether an
architectural change is needed. In order to answer that question,
as just noted in the previous section, the notion of a stack name
should be further developed.
Specific questions that should be answered are the following:
1. How would a stack name improve the overall functionality of the
Internet?
2. What does a stack name look like?
3. Where does it live in the stack?
4. How is it used on the end points?
5. What administrative infrastructure is needed to support it?
6. If we add an additional layer would it make the address list in
SCTP unnecessary?
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7. What additional security benefits would a new naming scheme
offer?
8. What would the resolution mechanisms be, or what
characteristics of a resolution mechanisms would be required?
Of the many existing efforts in this area, what efforts could such
a name help? For instance, would a stack name provide for a more
natural MIDCOM design?
This document raises more questions than answers. Further studies
will hopefully propose valid answers.
5 Further Studies
Various efforts continue independently. One outgrowth is the HIP
working group within the IETF. Although this work occurs in the
IETF, it should be noted that there is a risk to attempting to
standardize something about which we yet have the full benefit of
having explored in research.
Work on relieving stress between routing and addressing also
continues within the IETF in the MULTI6 and PTOMAIN working groups.
A separate effort proceeds elsewhere in the research community to
address what the Internet should look like ten years from now.
There-in we suspect that stack names will play a considerably
larger role.
It is possible that work will continue within the IRTF. However,
that work should be conducted by smaller teams until mature
proposals can be debated. Questions of "whether additional name
spaces should be introduced" can only be answered in such a manner.
6 Acknowledgments
This document is a description of a review done by the Name Space
Research Group of the Internet Research Task Force. The members of
that group include: J. Noel Chiappa, Scott Bradner, Henning
Schulzrinne, Brian Carpenter, Rob Austien, Karen Sollins, John
Wroclawski, Steve Bellovin, Steve Crocker, Keith Moore, Steve
Deering, Matt Holdredge, Randy Stewart, Leslie Daigle, John
Ioannidis, John Day, Thomas Narten, Bob Moskowitz, Ran Atkinson,
Gabriel Montenegro, and Lixia Xiang.
Particular thanks go to Noel Chiappa whose notions and continuing
efforts on end points kicked off the stack name discussion. The
definition of an endpoint is largely taken from Noel's unpublished
draft. Thanks also to Ran Atkinson and Bob Moskowitz whose
comments can be found (in some cases verbatim) in this document.
The idea of GSE or 8+8 was originally developed by Mike O'Dell.
The documents in which GSE is described are not published as RFCs.
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7. Author's Address
Eliot Lear
Cisco Systems, Inc.
170 West Tasman Dr.
San Jose, CA 95134
Phone: +1 408 527 4020
EMail: lear@cisco.com
8. References
[DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March, 1997.
[BCP5] Rekhter, Y. et al, "Address Allocation for Private
Internets", BCP-5, February, 1996.
[NAT] Srisuresh, P., Holdrege, M., "IP Network Address Translator
(NAT) Terminology and Considerations", RFC 2663, August 1999.
[Shoch] Shoch, J., "Inter-Network Naming, Addressing and Routing",
Proceedings of IEEE Compcon, pp 72-97, Fall, 1978.
[GSE] O'Dell, M., "GSE - an alternate addressing architecture for
IPv6", draft-ietf-ipngwg-gseaddr-00.txt, 1997.
[Saltzer92] Saltzer, J., "On The Naming and Binding of Network
Destinations", RFC 1498, September, 1992 (as republished).
[Saltzer84] Saltzer, J, Reed, D., Clark, D., "End-To-End Arguments
in System Design", ACM Transactions on Computer Systems, Vol. 2,
No. 4, November, 1984.
[TCP] Postel, J., "Transmission Control Protocol", RFC 792,
September, 1981.
[MCAST] Deering, S.E., "Host Extensions for IP multicasting",
RFC 1112, August, 1989.
[SSH] Ylonen, T., et. al, "SSH Protocol Architecture", Work in
Progress, draft-ietf-secsh-architecture-09.txt, July, 2001.
[ESP] Kent, S., Atkinson, R., "IP Encapsulating Security Payload
(ESP)", RFC 2406, November, 1998.
[IKE] Harkins, D., Carrel, D., "Internet Key Exchange", RFC 2409,
November 1998.
[TLS] Dierks, T., Allen, C., "The TLS Protocol Version 1.0",
RFC 2246, January, 1999.
[TRANSP] Carpenter, B., "Internet Transparency", RFC 2775,
Lear draft-irtf-nsrg-report-03.txt [Page 18]
February, 2000.
[INAT] Hain, T., "Architectural Implications of NAT", RFC 2993,
November, 2000.
[BGP4] Rekhter, Y., Li, T., "Border Gateway Protocol 4 (BGP-4)",
RFC 1771, March, 1995.
[MobileIP] Perkins, C., "IP Mobility Support", RFC 2002,
October, 1996.
[MobileIPv6] Johnson, P., Perkins, C., "Mobility Support in IPv6",
Work in Progress, draft-ietf-mobileip-ipv6-14.txt, July, 2001.
[ADDIP] Stewart, et. al., "SCTP Extensions for Dynamic
Reconfiguration of IP Addresses", Work in Progress,
draft-ietf-tsvwg-addip-sctp-03.txt, November, 2001.
[HIP-ARCH] Moskowitz, B., "Host Identity Payload Architecture",
Work in Progress, draft-moskowitz-hip-arch-02.txt, February, 2001.
[PBK] Bradner, S., Mankin, A., Schiller, J., "A framework for
Purpose Build Keys (PBK)", Work in Progress,
draft-bradner-pbk-frame-00.txt, February, 2001.
[URN] Sollins, K., "Architectural Principles of Universal Resource
Name Resolution", RFC 2276, January, 1998.
[ESMTP] Klensin, J. (Ed), "Simple Mail Transfer Protocol",
RFC 2821, April, 2001.
9. Intellectual Property Statement
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The IETF invites any interested party to bring to its attention any
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this standard. Please address the information to the IETF
Executive Director.
Lear draft-irtf-nsrg-report-03.txt [Page 19]
10. Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to
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However, this document itself may not be modified in any way, such
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11. Expiration Date
This memo is filed as <draft-irtf-nsrg-report-03.txt>, and expires
October 25, 2002.
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