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IRTF                                                        E. Lear
Internet Draft                            Name Space Research Group
Category: Informational
July 2002
Expires: December 30, 2002


                    draft-irtf-nsrg-report-06.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
   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

   Over the last few years, the character of Internet 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 some 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).  However, others within the NSRG hold views that differ
   from those presented in this document.

1  Introduction


Lear                  draft-irtf-nsrg-report-06.txt            [Page 1]


   The Internet has gone through several metamorphoses, and how one
   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] to ease address
   management, private network address space and network address
   translators (NAT), the overall 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.  In short, today the function of
   IP addresses is overloaded to serve the function of a location in
   the network, an interface, a host name, and a portion of that which
   identifies a TCP connection.

   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

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   specific way.

   Multicast

   Unicast communications are by-and-large connection-oriented,
   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.

   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

Lear                  draft-irtf-nsrg-report-06.txt            [Page 3]


   indicated in the IP destination address.  Until a few years ago,
   this would not have been an unreasonable assumption.  Today
   there are exceptions, particularly transparent web proxies and
   firewalls.

   With some of the currently contemplated changes, the risk of a
   transport connection being hijacked changes.  Instead of having to
   intercept every packet, an attacker may only need to forge a
   rebinding message to one end or the other of a connection.

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.
   The perils of NAT have been well documented by others. [TRANSP,
   INAT,NATCOMP]

   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).

   One of the largest changes in the character of Internet usage
   involves the resources we access and how we access them.  Whereas
   in the past we intended to access a particular host with a
   particular IP address, today we are likely more interested in
   accessing a service, such as a news service, or a banking service,
   and we are less interested in the host upon which the service sits.
   An industry has built up around the notion these so-called content
   delivery or overlay networks.  The IP address of the web server
   matters only in as much as it will serve the necessary web pages.
   In particular with secure services, what matters most to the user
   is that a particular trusted company has verifiably provided the
   service.

   This brings us to our question: would a new name space enable new
   functionality or return to us old capabilities in the face of NAT,
   DHCP, PPP, and other forms of borrowed IP addresses without
   compromising security?

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.

Lear                  draft-irtf-nsrg-report-06.txt            [Page 4]


   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 (or later).  As
   a result, however, the unique identification of an end point and
   the universal ability to reach it 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
   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.

   In summary, the Internet has exploded in size, NATs are now widely
   present, and the use of mechanisms such as PPP and DHCP are widely
   deployed.   In addition, services are now as much or more of
   interest than are individual hosts.  Given all of these changes, is
   it possible to add a new name space that will make connectivity
   more stable and allow us to establish some new operating
   assumptions, such as the ones that these complications broke?

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 destination
   options.  An end system uses its home address to create transport
   connections and communicate with the other end, one or more

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   correspondent nodes.  IPV4 mobile hosts are tunneled through a home
   agent and optionally a foreign 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 foreign agent
   is likely to be near the mobile host, the home agent is unlikely to
   be near anybody.

     _______                      ________
    |       |Care-of Address     |        | foreign 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

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   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.

   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 three 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).

   Finally, because SCTP does not have a home agent, SCTP does not
   handle what some would argue is a corner case, when two nodes
   change their location at the same time.

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.

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             ______________________________________
            |                                      |
            |            Application               |
            |______________________________________|
            |                                      |
            |             Transport                |
            |______________________________________|  The Host Stack
            |                                      |
            |         HIP or ESP w/ HI as SPI      |
            |______________________________________|
            |                                      |
            |             IP Header                |
            |______________________________________|


                   Figure 2: Host Identity

   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.

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   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?

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

Lear                  draft-irtf-nsrg-report-06.txt            [Page 9]


   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.  Where a NAT or a web cache translates from one name
   space to another, MIDCOM enables end points to identify that
   translation.

   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 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

Lear                  draft-irtf-nsrg-report-06.txt            [Page 10]


   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
   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 with 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 operating assumption no longer holds,
   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 or
   the process on one side of an end-to-end communication.  That
   participant may move, and may be represented by multiple hosts.

   When two devices represent a single end point they must share state
   in order to keep the other end from becoming confused (to say the
   very least).  When doing so, such stacks may indeed consist of
   multiple processes on each end.  One view is that such processes
   can theoretically be named independently of the Internet layer,
   allowing for sessions to migrate at the behest of applications.
   However, it is not possible to standardize migration independent of
   applications, who retain state in all manner of places, from
   configuration files to memory.  Additional names of such processes
   serve only to identify those who are authorized somehow to
   represent the end point, and do not themselves alleviate effort
   required to ensure application consistency.

   Such an addition may be useful enough to identify mobile nodes,
   devices behind NATs, and participants of a content delivery or

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   overlay network.

   We use the word "sessions" above, a mechanism that the current IP
   stack does not formally provide.  If we were to have a session
   layer in the classic sense it might sit above the transport layer,
   and a session could consist of more than a single transport
   connection.  If we view the session at below the transport layer,
   then transport connections can be bound to an identifier of some
   form other than that of the IP address, and transport connections
   could persist across IP address changes.  It is unlikely, however,
   that anything that the transport layer binds to would entirely
   obviate the need for sessions above the transport layer.

   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 now 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
   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

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   incur any additional protocol engineering, at least initially.  By
   representing stack names in this way 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
   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

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   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 therefore (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.

   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

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   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.

            __________________   ________________________
           |                  | |                        |
           |   _______________| |____________________    |
           |  /_______________| |___________________ /|  |
           | |       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


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   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 largely 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).

   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

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   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 or Questions

   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.  What is its lifetime?
   4.  Where does it live in the stack?
   5.  How is it used on the end points?
   6.  What administrative infrastructure is needed to support it?
   7.  If we add an additional layer would it make the address list in
       SCTP unnecessary?
   8.  What additional security benefits would a new naming scheme
       offer?
   9.  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
   possibility of a HIP working group within the IETF.  Although this
   work might occur within the IETF, it should be noted that there is

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   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 Holdrege, 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.

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

Lear                  draft-irtf-nsrg-report-06.txt            [Page 18]


   Internets", BCP-5 (RFC 1918), 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-12.txt, January, 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,
   February, 2000.

   [INAT] Hain, T., "Architectural Implications of NAT", RFC 2993,
   November, 2000.

   [NATCOMP] Holdrege, M., Srisuresh, P., "Protocol Complications
   with the IP Network Address Translator", RFC 3027, January, 2001.

   [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",

Lear                  draft-irtf-nsrg-report-06.txt            [Page 19]


   Work in Progress, draft-ietf-mobileip-ipv6-18.txt, June, 2002.

   [ADDIP] Stewart, et. al., "SCTP Extensions for Dynamic
   Reconfiguration of IP Addresses", Work in Progress,
   draft-ietf-tsvwg-addip-sctp-05.txt, May, 2002.

   [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-01.txt, July, 2002.

   [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

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
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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
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10.  Full Copyright Statement

   Copyright (C) The Internet Society (2002).  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
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   However, this document itself may not be modified in any way, such

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   as by removing the copyright notice or references to the Internet
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   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
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11.  Expiration Date

   This memo is filed as <draft-irtf-nsrg-report-06.txt>, and expires
   December 30, 2002.


































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