INTERNET DRAFT Editors:
Expires September 2000 M. Borella
3Com Corp.
J. Lo
NEC USA
Contributors:
D. Grabelsky
3Com Corp.
G. Montenegro
Sun Microsystems
March 2000
Realm Specific IP: Framework
<draft-ietf-nat-rsip-framework-04.txt>
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
This document examines the general framework of Realm Specific IP
(RSIP). RSIP is intended as a alternative to NAT in which the end-to-
end integrity of packets is maintained. We focus on implementation
issues, deployment scenarios, and interaction with other layer-three
protocols.
1. Introduction
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Network Address Translation (NAT) has become a popular mechanism of
enabling the separation of addressing spaces. A NAT router must
examine and change the network layer, and possibly the transport
layer, header of each packet crossing the addressing domains that the
NAT router is connecting. This causes the mechanism of NAT to violate
the end-to-end nature of the Internet connectivity, and disrupts
protocols requiring or enforcing end-to-end integrity of packets.
While NAT does not require a host to be aware of its presence, it
requires the presence of a proxy module, the application layer
gateway (ALG), within the NAT router for each application that embeds
addressing information, IP address or port content, within the packet
payload (e.g., FTP). RSIP (Realm Specific IP) provides an alternative
to remedy these limitations.
RSIP is based on the concept of granting a host from one addressing
realm a presence in another addressing realm by allowing it to use
resources (e.g., addresses and other routing parameters) from the
second addressing realm. An RSIP gateway replaces the NAT router, and
RSIP-aware hosts on the private network are referred to as RSIP
hosts. RSIP requires ability of the RSIP gateway to grant such
resources to RSIP hosts. ALGs are not required on the RSIP gateway
for communications between an RSIP host and a host on a different
addressing realm.
It is important to note that RSIP is not a replacement for IPv6. We
fully advocate the adoption and deployment of IPv6. RSIP has been
designed to restore some of the end-to-end transparency that NAT has
taken away from the Internet, and it may smooth the IPv6 transition
process.
1.1. Document Scope
This document provides a framework for RSIP by focusing on three
particular areas:
- Implementation issues that are not specific to the RSIP protocol
defined in [RSIP-PROTO].
- Likely initial deployment scenarios.
- Interaction with other layer-three protocols.
The interaction sections will be at an overview level. Detailed
modifications that would need to be made to RSIP and/or the
interacting protocol are left for separate documents to discuss in
detail.
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Beyond the scope of this document is discussion of RSIP in large,
multiple-gateway networks, or in environments where RSIP state
would need to be distributed and maintained across multiple
redundant entities.
Discussion of RSIP solutions that do not use some form of tunnel
between the RSIP host and RSIP gateway are also not considered in
this document.
1.2. Terminology
Private Realm
A routing realm that uses private IP addresses from the ranges
(10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) specified in
[RFC1918], or addresses that are non-routable from the
Internet.
Public Realm
A routing realm with unique network addresses assigned by the
Internet Assigned Number Authority (IANA) or an equivalent
address registry.
RSIP Host
A host within an addressing realm that uses RSIP to acquire
addressing parameters from another addressing realm via an RSIP
gateway.
RSIP Gateway
A router situated on the boundary between two addressing realms
and owns one or more IP addresses. An RSIP gateway is
responsible for parameter management and assignment from one
realm to RSIP hosts in the other realm. An RSIP gateway may act
as a normal NAT router for hosts within the a realm that are
not RSIP enabled.
RSIP Client
An application program that performs the client portion of the
RSIP client/server protocol. An RSIP client application MUST
exist on all RSIP hosts, and MAY exist on RSIP gateways.
RSIP Server
An application program that performs the server portion of the
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RSIP client/server protocol. An RSIP server application MUST
exist on all RSIP gateways.
RSA-IP: Realm Specific Address IP
An RSIP method in which each RSIP host is allocated a unique IP
address from the public realm.
RSAP-IP: Realm Specific Address and Port IP
An RSIP method in which each RSIP host is allocated an IP
address (possibly shared with other RSIP hosts) and some number
of per-address unique ports from the public realm.
RSIP-enabled Mobile Node (RMN)
A host that uses RSIP for connectivity to the public network,
and also uses Mobile IP for roaming support.
RSIP Home Network (RHN)
A network on which a number of hosts use RSIP to share one or
more public IP addresses.
RSIP Home Agent (RHA)
A router, running an RSIP gateway, that manages Mobile IP
connectivity for RSIP-enabled mobile nodes belonging to an RSIP
home network.
RSIP Foreign Network (RFN)
A network which can support RSIP-enabled mobile nodes as they
roam.
RSIP Foreign Agent (RFA)
A router that manages Mobile IP connectivity for roaming RSIP-
enabled mobile nodes. This router may or may not use RSIP on
its local network.
Demultiplexing Fields
Any set of packet header or payload fields that an RSIP gateway
uses to route an incoming packet to an RSIP host.
All other terminology found in this document is consistent with
that of [RFC2663].
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1.3. Specification of Requirements
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this documents are to be interpreted as described in [RFC2119].
2. Architecture
In a typical scenario where RSIP is deployed, there are some number
of hosts within one addressing realm connected to another addressing
realm by an RSIP gateway. This model is diagrammatically represented
as follows:
RSIP Host RSIP Gateway Host
Xa Na Nb Yb
[X]------( Addr sp. A )----[N]-----( Addr sp. B )-------[Y]
( Network ) ( Network )
Hosts X and Y belong to different addressing realms A and B,
respectively, and N is an RSIP gateway (which may also perform NAT
functions). N has two interfaces: Na on address space A, and Nb on
address space B. N may have a pool of addresses in address space B
which it can assign to or lend to X and other hosts in address space
A. These addresses are not shown above, but they can be denoted as
Nb1, Nb2, Nb3 and so on.
As is often the case, the hosts within address space A are likely to
use private addresses while the RSIP gateway is multi-homed with one
or more private addresses from address space A in addition to its
public addresses from address space B. Thus, we typically refer to
the realm in which the RSIP host resides as "private" and the realm
from which the RSIP host borrow addressing parameters as the "public"
realm. However, these realms may both be public or private - our
notation is for convenience.
Host X, wishing to establish an end-to-end connection to a network
entity Y situated within address space B, first negotiates and
obtains assignment of the resources (e.g., addresses and other
routing parameters of address space B) from the RSIP gateway. Upon
assignment of these parameters, the RSIP gateway creates a mapping,
referred as a "bind", of X's addressing information and the assigned
resources. This binding enables the RSIP gateway to correctly de-
multiplex and forward inbound traffic generated by Y for X. If
permitted by the RSIP gateway, X may create multiple such bindings on
the same RSIP gateway, or across several RSIP gateways. A lease time
SHOULD be associated with each bind.
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Using the public parameters assigned by the RSIP gateway, RSIP hosts
tunnel data packets across address space A to the RSIP gateway. The
RSIP gateway acts as the end point of such tunnels, stripping off the
outer headers and routing the inner packets onto the public realm. As
mentioned above, an RSIP gateway maintains a mapping of the assigned
public parameters as demultiplexing fields for uniquely mapping them
to RSIP host private addresses. When a packet from the public realm
arrives at the RSIP gateway and it matches a given set of
demultiplexing fields, then the RSIP gateway will tunnel it to the
appropriate RSIP host. The tunnel headers of outbound packets from X
to Y, given that X has been assigned Nb, are as follows:
+---------+---------+---------+
| X -> Na | Nb -> Y | payload |
+---------+---------+---------+
There are two basic flavors of RSIP: RSA-IP and RSAP-IP. RSIP hosts
and gateways MAY support RSA-IP, RSAP-IP, or both.
When using RSA-IP, an RSIP gateway maintains a pool of IP addresses
to be leased by RSIP hosts. Upon host request, the RSIP gateway
allocates an IP address to the host. Once an address is allocated to
a particular host, only that host may use the address until the
address is returned to the pool. Hosts MAY NOT use addresses that
have not been specifically assigned to them. The hosts may use any
TCP/UDP port in combination with their assigned address. Hosts may
also run gateway applications at any port and these applications will
be available to the public network without assistance from the RSIP
gateway. A host MAY lease more than one address from the same or
different RSIP gateways. The demultiplexing fields of an RSA-IP
session MUST include the IP address leased to the host.
When using RSAP-IP, an RSIP gateway maintains a pool of IP addresses
as well as pools of port numbers per address. RSIP hosts lease an IP
address and one or more ports to use with it. Once an address / port
tuple has been allocated to a particular host, only that host may use
the tuple until it is returned to the pool(s). Hosts MAY NOT use
address / port combinations that have not been specifically assigned
to them. Hosts may run gateway applications bound to an allocated
tuple, but their applications will not be available to the public
network unless the RSIP gateway has agreed to route all traffic
destined to the tuple to the host. A host MAY lease more than one
tuple from the same or different RSIP gateways. The demultiplexing
fields of an RSAP-IP session MUST include the tuple(s) leased to the
host.
3. Implementation Considerations
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RSIP can be accomplished by any one of a wide range of implementation
schemes. For example, it can be built into an existing configuration
protocol such as DHCP or SOCKS, or it can exist as a separate
protocol. This section discusses implementation issues of RSIP in
general, regardless of how the RSIP mechanism is implemented.
Note that on a host, RSIP is associated with a TCP/IP stack
implementation. Modifications to IP tunneling and routing code, as
well as driver interfaces may need to be made to support RSA-IP.
Support for RSAP-IP requires modifications to ephemeral port
selection code as well. If a host has multiple TCP/IP stacks or
TCP/IP stacks and other communication stacks, RSIP will only operate
on the packets / sessions that are associated with the TCP/IP
stack(s) that use RSIP. RSIP is not application specific, and if it
is implemented in a stack, it will operate transparently to all
applications that use the stack.
3.1. Host and Gateway Requirements
An RSIP host must be able to maintain one or more virtual
interfaces for the IP address(es) that it leases from an RSIP
gateway. The host must also support tunneling and be able to
serve as an end-point for one or more tunnels to RSIP gateways.
An RSIP host MUST NOT respond to ARPs for a public realm address
that it leases.
An RSIP host supporting RSAP-IP MUST be able to maintain a set of
one or more ports assigned by an RSIP gateway from which choose
ephemeral source ports. If the host's pool does not have any free
ports and the host needs to open a new communication session with
a public host, it MUST be able to dynamically request one or more
additional ports via its RSIP mechanism.
An RSIP gateway is a multi-homed host that routes packets between
two or more realms. Often, an RSIP gateway is a boundary router
between two or more administrative domains. It must also support
tunneling and be able to serve as an end-point for tunnels to RSIP
hosts. The RSIP gateway MAY be a policy enforcement point, which
in turn may require it to perform firewall and packet filtering
duties in addition to RSIP. The RSIP gateway must reassemble all
incoming packet fragments from the public network in order to be
able to route and tunnel them to the proper host. As is necessary
for all fragment reassembly, an RSIP gateway must timeout
fragments that are never fully reassembled.
An RSIP gateway MAY include NAT functionality so that hosts on the
private network that are not RSIP-enabled can still communicate
with the public network. An RSIP gateway must manage all
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resources that are assigned to RSIP hosts. This management MAY be
done according to local policy.
3.2. Processing of Demultiplexing Fields
Each active RSIP host must have a unique set of demultiplexing
fields assigned to it so that an RSIP gateway can route incoming
packets appropriately. Depending on the type of mapping used by
the RSIP gateway, demultiplexing fields have been defined to be
one or more of the following:
- destination IP address
- IP protocol
- destination TCP or UDP port
- IPSEC SPI present in ESP or AH header (see [RSIP-IPSEC])
- ISAKMP initiator cookie present in an IKE payload (see [RSIP-
IPSEC])
- others
Demultiplexing of incoming traffic can be based on a decision
tree. The process begins with the examination of the IP header of
the incoming packet, and proceeds to subsequent headers and then
the payload.
- In the case where a public IP address is assigned for each host,
a unique public IP address is mapped to each RSIP host.
- If the same IP address is used for more than one RSIP host, then
subsequent headers must have at least one field that will be
assigned a unique value per host so that it is usable as a
demultiplexing field. The IP protocol field SHOULD be used to
determine what in the subsequent headers these demultiplexing
fields ought to be.
- If the subsequent header is TCP or UDP, then destination port
number can be used. However, if the TCP/UDP port number is the
same for more than one RSIP host, the payload section of the
packet must contain a demultiplexing field that is guaranteed to
be different for each RSIP host. Typically this requires
negotiation of said fields between the RSIP host and gateway so
that the RSIP gateway can guarantee that the fields are unique
per-host
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- If the subsequent header is anything other than TCP or UDP,
there must exist other fields within the IP payload usable as
demultiplexing fields. In other words, these fields must be
able to be set such that they are guaranteed to be unique per-
host. Typically this requires negotiation of said fields
between the RSIP host and gateway so that the RSIP gateway can
guarantee that the fields are unique per-host.
It is desirable for all demultiplexing fields to occur in well-
known fixed locations so that an RSIP gateway can mask out and
examine the appropriate fields on incoming packets.
Demultiplexing fields that are encrypted MUST NOT be used for
routing.
3.3. RSIP Protocol Requirements and Recommendations
RSIP gateways and hosts must be able to negotiate IP addresses
when using RSA-IP, IP address / port tuples when using RSAP-IP,
and possibly other demultiplexing fields for use in other modes.
In this section we discuss the requirements and implementation
issues of an RSIP negotiation protocol.
For each required demultiplexing field, an RSIP protocol MUST, at
the very least, allow for:
- RSIP hosts to request assignments of demultiplexing fields
- RSIP gateways to assign demultiplexing fields with an associated
lease time
- RSIP gateways to reclaim assigned demultiplexing fields
Additionally, it is desirable, though not mandatory, for an RSIP
protocol to negotiate an RSIP method (RSA-IP or RSAP-IP) and the
type of tunnel to be used across the private network. The
protocol SHOULD be extensible and facilitate vendor-specific
extensions.
If an RSIP negotiation protocol is implemented at the application
layer, a choice of transport protocol must be made. RSIP hosts
and gateways may communicate via TCP or UDP. TCP support is
required in all RSIP gateways, while UDP support is optional. In
RSIP hosts, TCP, UDP, or both may be supported. However, once an
RSIP host and gateway have begun communicating using either TCP or
UDP, they MAY NOT switch to the other transport protocol. For
RSIP implementations and deployments considered in this document,
TCP is the recommended transport protocol, because TCP is known to
be robust across a wide range of physical media types and traffic
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loads.
It is recommended that all communication between an RSIP host and
gateway be authenticated. Authentication, in the form of a
message hash appended to the end of each RSIP protocol packet, can
serve to authenticate the RSIP host and gateway to one another,
provide message integrity, and (with an anti-replay counter) avoid
replay attacks. In order for authentication to be supported, each
RSIP host and the RSIP gateway must either share a secret key
(distributed, for example, by Kerberos) or have a private/public
key pair. In the latter case, an entity's public key can be
computed over each message and a hash function applied to the
result to form the message hash.
3.4. TCP TIME_WAIT at Public Peers
When a TCP gateway disconnects a socket, it enters the TCP
TIME_WAIT state for a period of time. While it is in this state
it will refuse to accept new connections using the same socket
(i.e., the same source address/port and destination address/port).
Consider the case in which an RSIP host (using RSAP-IP) is leased
an address/port tuple and uses this tuple to contact a public
address/port tuple. Suppose that the host terminates the session
with the public tuple and immediately returns its leased tuple to
the RSIP gateway. If the RSIP gateway immediately allocates this
tuple to another RSIP host (or to the same host), and this second
host uses the tuple to contact the same public tuple while the
socket is still in the TIME_WAIT phase, then the host's connection
may be rejected by the public host. In order to mitigate this
problem, it is recommended that RSIP gateways hold recently
deallocated tuples for at least two minutes, which is the greatest
duration of TIME_WAIT that is commonly implemented [STEV94]. In
situations where port space is scarce, the RSIP gateway MAY choose
to allocate ports in a FIFO fashion from the pool of recently
deallocated ports.
3.5. ICMP Handling
Like NAT, RSIP gateways running RSAP-IP are required to remember
recent ICMP packets for which responses cannot be demultiplexed by
port number (i.e., echo request packets). ICMP request packets
originating on the private network will typically consist of echo
request, timestamp request and address mask request. These
packets and their responses can be identified by the tuple of
source IP address, ICMP identifier, ICMP sequence number, and
destination IP address. An RSIP host sending an ICMP request
packet tunnels it to the RSIP gateway, just as it does TCP and UDP
packets. The RSIP gateway must use this tuple to map incoming
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ICMP responses to the private address of the appropriate RSIP
host. Once it has done so, it will tunnel the ICMP response to
the host. Note that it is possible for two RSIP hosts to use the
same values for the tuples listed above, and thus create an
ambiguity. However, this occurrence is likely to be quite rare,
and is not addressed further in this draft.
Incoming ICMP error response messages can be forwarded to the
appropriate RSIP host by examining the IP header and port numbers
embedding within the packet. In the case of RSA-IP, only the
source IP address is necessary to determine the RSIP host. In the
case of RSAP-IP, the source IP address and source port number is
necessary to determine the RSIP host.
Occasionally, an RSIP host will have to send an ICMP response
(e.g., port unreachable). These responses are tunneled to the
RSIP gateway, as is done for TCP and UDP packets. All ICMP
requests (e.g., echo request) arriving at the RSIP gateway MUST be
processed by the RSIP gateway and MUST NOT be forwarded to an RSIP
host.
3.6. MTU Limitation to Prevent Fragmentation and ID Collision
RSIP hosts MUST limit their MTU so that packets transmitted by an
RSIP gateway are not fragmented. If two or more RSIP hosts on the
same private network transmit outbound packets that get fragmented
to the same public gateway, the public gateway may experience a
reassembly ambiguity if the IP header ID fields of these packets
are identical.
For TCP packets, this is not an issue if path MTU discovery works
properly. For non-TCP packets, an artificially small MTU, such is
required. The setting of this MTU, however, may depend on the
applications being run.
3.7. Gateways on RSAP-IP Hosts
RSAP-IP hosts are limited by the same constraints as NAT with
respect to hosting gateways that use a well-known port. Since
destination port numbers are used as routing information to
uniquely identify an RSAP-IP host, typically no two RSAP-IP hosts
sharing the same public IP address can simultaneously operate
publically-available gateways on the same port. For protocols
that operate on well-known ports, this implies that only one
public gateway per RSAP-IP IP address / port tuple is used
simultaneously. However, more than one gateway per RSAP-IP IP
address / port tuple may be used simultaneously if and only if
there is a demultiplexing field within the payload of all packets
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that will uniquely determine the identity of the RSAP-IP host, and
this field is known by the RSIP gateway.
In order for an RSAP-IP host to operate a publically-available
gateway, the host must inform the RSIP gateway that it wishes to
receive all traffic destined to that port number, per its IP
address. Such a request MUST be denied if the port in question is
already in use by another host.
3.8. Determining Locality of Destinations from an RSIP Host
In general, an RSIP host must know, for a particular IP address,
whether it should address the packet for local delivery on the
private network, or if it has to use an RSIP interface to tunnel
to an RSIP gateway (assuming that it has such an interface
available).
If the RSIP hosts are all on a single subnet, one hop from an RSIP
gateway, then examination of the local network and subnet mask
will provide the appropriate information. However, this is not
always the case.
An alternative that will work in general for statically addressed
private networks is to store a list of the network and subnet
masks of every private subnet at the RSIP gateway. RSIP hosts may
query the gateway with a particular target IP address, or for the
entire list.
If the subnets on the local side of the network are changing more
rapidly than the lifetime of a typical RSIP session, the RSIP host
may have to query the location of every destination that it tries
to communicate with.
If an RSIP host transmits a packet addressed to a public host
without using RSIP, then the RSIP gateway will apply NAT to the
packet (if it supports NAT) or it may discard the packet and
respond with and appropriate ICMP message.
3.9. Implementing RSIP Host Deallocation
An RSIP host MAY free resources that it has determined it no
longer requires. For example, on an RSAP-IP subnet with a limited
number of public IP addresses, port numbers may become scarce.
Thus, if RSIP hosts are able to dynamically deallocate ports that
they no longer need, more hosts can be supported.
However, this functionality may require significant modifications
to a vanilla TCP/IP stack in order to implement properly. The
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RSIP host must be able to determine which TCP or UDP sessions are
using RSIP resources. If those resources are unused for a period
of time, then the RSIP host may deallocate them. When an open
socket's resources are deallocated, it will cause some associated
applications to fail. An analogous case would be TCP and UDP
sessions that must terminate when an interface that they are using
loses connectivity.
On the other hand, this issue can be considered a resource
allocation problem. It is not recommended that a large number
(hundreds) of hosts share the same IP address, for performance
purposes. Even if, say, 100 hosts each are allocated 100 ports,
the total number of ports in use by RSIP would be still less than
one-sixth the total port space for an IP address. If more hosts
or more ports are needed, more IP addresses should be used. Thus,
it is reasonable, that in many cases, RSIP hosts will not have to
deallocate ports for the lifetime of their activity.
Since RSIP demultiplexing fields are leased to hosts, an
appropriately chosen lease time can alleviate some port space
scarcity issues.
3.10. Interaction with DNS
An RSIP-enabled network has three uses for DNS: (1) public DNS
services to map its static public IP addresses (i.e., the public
address of the RSIP gateway) and for lookups of public hosts, (2)
private DNS services for use only on the private network, and (3)
dynamic DNS services for RSIP hosts.
With respect to (1), public DNS information MUST be propagated
onto the private network. With respect to (2), private DNS
information MUST NOT be propagated into the public network.
With respect to (3), an RSIP-enabled network MAY allow for RSIP
hosts with FQDNs to have their A and PTR records updated in the
public DNS. These updates are based on address assignment
facilitated by RSIP, and should be performed in a fashion similar
to DHCP updates to dynamic DNS [DHCP-DNS]. In particular, RSIP
hosts should be allowed to update their A records but not PTR
records, while RSIP gateways can update both. In order for the
RSIP gateway to update DNS records on behalf on an RSIP host, the
host must provide the gateway with its FQDN.
Note that when using RSA-IP, the interaction with DNS is
completely analogous to that of DHCP because the RSIP host "owns"
an IP address for a period of time. In the case of RSAP-IP, the
claim that an RSIP host has to an address is only with respect to
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the port(s) that it has leased along with an address. Thus, two
or more RSIP hosts' FQDNs may map to the same IP address.
However, a public host may expect that all of the applications
running at a particular address are owned by the same logical
host, which would not be the case. It is recommended that RSAP-IP
and dynamic DNS be integrated with some caution, if at all.
3.11. Locating RSIP Gateways
When an RSIP host initializes, it requires (among other things)
two critical pieces of information. One is a local (private) IP
address to use as its own, and the other is the private IP address
of an RSIP gateway. This information can be statically configured
or dynamically assigned.
In the dynamic case, the host's private address is typically
supplied by DHCP. A DHCP option has been proposed to provide the
IP address of an RSIP gateway in DHCPOFFER messages (the Next
Gateway option) [DHC-NS]. Thus, the host's startup procedure
would be as follows: (1) perform DHCP, (2) if the Next Gateway
option is present in the DHCPOFFER, record the IP address therein
as the RSIP gateway.
4. Deployment
When RSIP is deployed in certain scenarios, the network
characteristics of these scenarios will determine the scope of the
RSIP solution, and therefore impact the requirements of RSIP. In
this section, we examine deployment scenarios, and the impact that
RSIP may have on existing networks.
4.1. Possible Deployment Scenarios
In this section we discuss a number of potential RSIP deployment
scenarios. The selection below are not comprehensive and other
scenarios may emerge.
4.1.1. Small / Medium Enterprise
Up to several hundred hosts will reside behind an RSIP-enabled
router. It is likely that there will be only one gateway to the
public network and therefore only one RSIP gateway. This RSIP
gateway may control only one, or perhaps several, public IP
addresses. The RSIP gateway may also perform firewall
functions, as well as routing inbound traffic to particular
destination ports on to a small number of dedicated gateways on
the private network.
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4.1.2. Residential Networks
This category includes both networking within just one
residence, as well as within multiple-dwelling units. At most
several hundred hosts will share the gateway's resources. In
particular, many of these devices may be thin hosts or so-
called "network appliances" and therefore not require access to
the public Internet frequently. The RSIP gateway is likely to
be implemented as part of a residential firewall, and it may be
called upon to route traffic to particular destination ports on
to a small number of dedicated gateways on the private network.
It is likely that only one gateway to the public network will
be present and that this gateway's RSIP gateway will control
only one IP address. Support for secure end-to-end VPN access
to corporate intranets will be important.
4.1.3. Hospitality Networks
A hospitality network is a general type of "hosting" network
that a traveler will use for a short period of time (a few
minutes or a few hours). Examples scenarios include hotels,
conference centers and airports and train stations. At most
several hundred hosts will share the gateway's resources. The
RSIP gateway may be implemented as part of a firewall, and it
will probably not be used to route traffic to particular
destination ports on to dedicated gateways on the private
network. It is likely that only one gateway to the public
network will be present and that this gateway's RSIP gateway
will control only one IP address. Support for secure end-to-
end VPN access to corporate intranets will be important.
4.1.4. Dialup Remote Access
RSIP gateways may be placed in dialup remote access
concentrators in order to multiplex IP addresses across dialup
users. At most several hundred hosts will share the gateway's
resources. The RSIP gateway may or may not be implemented as
part of a firewall, and it will probably not be used to route
traffic to particular destination ports on to dedicated
gateways on the private network. Only one gateway to the public
network will be present (the remote access concentrator itself)
and that this gateway's RSIP gateway will control a small
number of IP addresses. Support for secure end-to-end VPN
access to corporate intranets will be important.
4.1.5. Wireless Remote Access Networks
Wireless remote access will become very prevalent as more PDA
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and IP / cellular devices are deployed. In these scenarios,
hosts may be changing physical location very rapidly -
therefore Mobile IP will play a role. Hosts typically will
register with an RSIP gateway for a short period of time. At
most several hundred hosts will share the gateway's resources.
The RSIP gateway may be implemented as part of a firewall, and
it will probably not be used to route traffic to particular
destination ports on to dedicated gateways on the private
network. It is likely that only one gateway to the public
network will be present and that this gateway's RSIP gateway
will control a small number of IP addresses. Support for
secure end-to-end VPN access to corporate intranets will be
important.
4.2. Cascaded RSIP and NAT
It is possible for RSIP to allow for cascading of RSIP gateways as
well as cascading of RSIP gateways with NAT boxes. For example,
consider an ISP that uses RSIP for address sharing amongst its
customers. It might assign resources (e.g., IP addresses and
ports) to a particular customer. This customer may use RSIP to
further subdivide the port ranges and address(es) amongst
individual end hosts. No matter how many levels of RSIP
assignment exists, RSIP MUST only assign public IP addresses.
Note that some of the architectures discussed below may not be
useful or desirable. The goal of this section is to explore the
interactions between NAT and RSIP as RSIP is incrementally
deployed on systems that already support NAT.
4.2.1. RSIP Behind RSIP
A reference architecture is depicted below.
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+-----------+
| |
| RSIP |
| gateway +---- 10.0.0.0/8
| B |
| |
+-----+-----+
|
| 10.0.1.0/24
+-----------+ | (149.112.240.0/25)
| | |
149.112.240.0/24| RSIP +--+
----------------+ gateway |
| A +--+
| | |
+-----------+ | 10.0.2.0/24
| (149.112.240.128/25)
|
+-----+-----+
| |
| RSIP |
| gateway +---- 10.0.0.0/8
| C |
| |
+-----------+
RSIP-gateway A is in charge of the IP addresses of subnet
149.112.240.0/24. It distributes these addresses to RSIP-hosts
and RSIP-gateways. In the given configuration, it distributes
addresses 149.112.240.0 - 149.112.240.127 to RSIP-gateway B,
and addresses 149.112.240.128 - 149.112.240.254 to RSIP-gateway
C. Note that the subnet broadcast address, 149.112.240.255,
must remain unclaimed, so that broadcast packets can be
distributed to arbitrary hosts behind RSIP-gateway A. Also,
the subnets between RSIP-gateway A and RSIP- gateways B and C
will use private addresses.
Due to the tree-like fashion in which addresses will be
cascaded, we will refer to RSIP-gateways A as the 'parent' of
RSIP-gateways B and C, and RSIP-gateways B and C as 'children'
of RSIP-gateways A. An arbitrary number of levels of children
may exist under a parent RSIP- gateway.
A parent RSIP-gateway will not necessarily be aware that the
address(es) and port blocks that it distributes to a child
RSIP- gateway will be further distributed. Thus, the RSIP-
hosts MUST tunnel their outgoing packets to the nearest RSIP-
gateway. This gateway will then verify that the sending host
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has used the proper address and port block, and then tunnel the
packet on to its parent RSIP-gateway.
For example, in the context of the diagram above, host
10.0.0.1, behind RSIP-gateway C will use its assigned external
IP address (say, 149.112.240.130) and tunnel its packets over
the 10.0.0.0/8 subnet to RSIP-gateway C. RSIP-gateway C strips
off the outer IP header. After verifying that the source
public IP address and source port number is valid, RSIP-gateway
C will tunnel the packets over the 10.0.2.0/8 subnet to RSIP-
gateway A. RSIP-gateway A strips off the outer IP header.
After verifying that the source public IP address and source
port number is valid, RSIP-gateway A transmits the packet on
the public network.
While it may be more efficient in terms of computation to have
a RSIP-host tunnel directly to the overall parent of an RSIP-
gateway tree, this would introduce significant state and
administrative difficulties.
A RSIP-gateway that is a child MUST take into consideration the
parameter assignment constraints that it inherits from its
parent when it assigns parameters to its children. For
example, if a child RSIP-gateway is given a lease time of 3600
seconds on an IP address, it MUST compare the current time to
the lease time and the time that the lease was assigned to
compute the maximum allowable lease time on the address if it
is to assign the address to a RSIP-host or child RSIP-gateway.
4.2.2. NAT Behind RSIP
+--------+ +--------+
| NAT w/ | | RSIP |
hosts ------+ RSIP +------+ gate- +----- public network
| host | | way |
+--------+ +--------+
In this architecture, an RSIP gateway is between a NAT box and
the public network. The NAT is also equipped with an RSIP
host. The NAT dynamically requests resources from the RSIP
gateway as the hosts establish sessions to the public network.
The hosts are not aware of the RSIP manipulation. This
configuration does not enable the hosts to have end-to-end
transparency and thus the NAT still requires ALGs and the
architecture cannot support IPSEC.
4.2.3. RSIP Behind NAT
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+--------+ +--------+
RSIP | RSIP | | |
hosts ------+ gate- +------+ NAT +----- public network
| way | | |
+--------+ +--------+
In this architecture, The RSIP hosts and gateway reside behind
a NAT. This configuration does not enable the hosts to have
end-to-end transparency and thus the NAT still requires ALGs
and the architecture cannot support IPSEC. The hosts may have
transparency if there is another gateway to the public network
besides the NAT box, and this gateway supports cascaded RSIP
behind RSIP.
4.2.4. RSIP Through NAT
+--------+ +--------+
RSIP | | | RSIP |
hosts ------+ NAT +------+ gate- +----- public network
| | | way |
+--------+ +--------+
In this architecture, the RSIP hosts are separated from the
RSIP gateway by a NAT. RSIP signaling may be able to pass
through the NAT if an RSIP ALG is installed. The RSIP data
flow, however, will have its outer IP address translated by the
NAT. The NAT must not translate the port numbers in order for
RSIP to work properly. Therefore, only traditional NAT will
make sense in this context.
5. Interaction with Other Layer-Three Protocols
Since RSIP affects layer-three objects, it has an impact on other
layer three protocols. In this section, we outline the impact of
RSIP on these protocols, and in each case, how RSIP, the protocol, or
both, can be extended to support interaction.
Each of these sections is an overview and not a complete technical
specification. If a full technical specification of how RSIP
interacts with a layer-three protocol is necessary, a separate
document will contain it.
5.1. IPSEC
RSIP is a mechanism for allowing end-to-end IPSEC with sharing of
IP addresses. Full specification of RSIP/IPSEC details are in
[RSIP-IPSEC]. This section provides a brief summary.
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Since IPSEC may encrypt TCP/UDP port numbers, these objects cannot
be used as demultiplexing fields. However, IPSEC inserts an AH or
ESP header following the IP header in all IPSEC-protected packets
(packets that are transmitted on an IPSEC Security Association
(SA)). These headers contain a 32-bit Security Parameter Index
(SPI) field, the value of which is determined by the receiving
side. The SPI field is always in the clear. Thus, during SA
negotiation, an RSIP host can instruct their public peer to use a
particular SPI value. This SPI value, along with the assigned IP
address, can be used by an RSIP gateway to uniquely identify and
route packets to an RSIP host. In order to guarantee that RSIP
hosts use SPIs that are unique per address, it is necessary for
the RSIP gateway to allocate unique SPIs to hosts along with their
address/port tuple.
IPSEC SA negotiation takes place using the Internet Key Exchange
(IKE) protocol. IKE is designated to use port 500 on at least the
destination side. Some host IKE implementations will use source
port 500 as well, but this behavior is not mandatory. If two or
more RSIP hosts are running IKE at source port 500, they MUST use
different initiator cookies (the first eight bytes of the IKE
payload) per assigned IP address. The RSIP gateway will be able
to route incoming IKE packets to the proper host based on
initiator cookie value. Initiator cookies can be negotiated, like
ports and SPIs. However, since the likelihood of two hosts
assigned the same IP address attempting to simultaneously use the
same initiator cookie is very small, the RSIP gateway can
guarantee cookie uniqueness by dropping IKE packets with a cookie
value that is already in use.
5.2. Mobile IP
** NOTE WELL: This section may change significantly in the next
rev **
RSIP can be used as a configuration tool for coarse-grained
mobility (nomadicity). For example, a laptop or handheld device
may use RSIP to temporarily register on a local network. However,
once the host de-registers from this network, or otherwise
terminates its associated with the network, all ongoing
communication between the host and its peers must also terminate.
It is desirable for RSIP to support fine-grained mobility; i.e.,
the ability to move between networks, and register and de-register
with RSIP gateways, without tearing down any communications
sessions. Pragmatically speaking, this means that socket
parameters, such as the host's IP address and port number(s) must
remain the same as it roams.
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Mobile IP [RFC2002] provides the necessary mechanisms for a mobile
host to maintain its sessions and socket parameters while it moves
between its home network and foreign networks. The goal of this
draft is to discuss the architecture, requirements, and
feasibility of integrating RSIP and Mobile IP. In doing so we
expect that the impact on both protocols will be minimal. In
particular, the modifications that we suggest below require minor
messaging changes to both RSIP and Mobile IP.
5.2.1. Mobility Architecture
The general architecture that we will consider is illustrated
below: This architecture is similar to that discussed in
Section 4, but has been annotated specifically for mobility.
RMNa RHAa RHAp RFAp RFAb RMNb
RMN]------------[RHA]--------------------[RFA]-------------[RMN]
(RSIP home (public network "p") (RSIP foreign
network "a") network "b")
In this diagram, an RMN roams between an RHN "a" and an RFN
"b". On RHN "a" the RMN uses private address RMNa, and on RFN
"b" the RMN uses private address RMNb. The RHA on the RHN uses
private address RHAa and public address RHAp. The RFA on the
RFN uses private address RFAb and public address RFAp. Note
that the RFN may also act as an RHN for its RMNs, and the RHN
may also act as an RFN for roaming RMNs. In order so that the
RMN can communicate with peers on the public network, the RHA
assigns the RMN address RMNp (not shown). RMNp may be
identical to RHAp.
Note that until standard Mobile IP, the address RMNa is not
guaranteed to be unique. This address is likely to be from the
private space, so when the RMN is on RFN "b", RMNa may collide
with other RMNs in the RFN, or with stationary nodes on the
network. Thus, it is necessary that the RMN be allocated RMNb
when it is on RMN "b". The recommended mechanism to do this
with is DHCP.
We assume that the RHA and RFA will always be on the boundary
between public and private address spaces. Thus RMNs can
always be uniquely identified by the tuple (RMNa, RMNp),
although other identification mechanisms may also be used.
5.2.2. Data Flow
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This section presents the flow of data between the participants
in RSIP / Mobile IP transaction. We ignore both RSIP and
Mobile IP control flow and signaling for now - it is discussed
in the next section.
5.2.2.1. Non-Roaming RMN
When the RMN is not roaming; i.e., it is on the RHN, it
operates just as if it were a stationary node. All data
flows according to [RSIP-PROTO].
5.2.2.2. Roaming RMN
When the RMN is roaming, the typical routing scheme of
Mobile IP is used. In particular, if the RMN is
communicating with a public node (PN) which has address PNp,
the RMN will be known to the PN as RMNp. On the RFN, the RMN
will have a local IP address of RMNb. In the case of RSAP-
IP, the RMN will also be using ports allocated by the RHA.
Packets sent from the RN to the RMN will be addressed
identically to standard Mobile IP operation:
+-------------+---------+
| PNp -> RMNp | payload |
+-------------+---------+
Since the RHA will be advertising a route to RMNp, this
packet will be received by the RHA. The RHA will determine
that the RMN is not on the RHN, and forward the packet to
the RMN's care-of address, RFAp, via an IP-IP tunnel.
+--------------+-------------+---------+
| RHAp -> RFAp | PNp -> RMNp | payload |
+--------------+-------------+---------+
Once the packet arrives at the RFA, it terminates the IP-IP
tunnel from the RHA and initiates a new IP-IP tunnel to the
RMN, as shown below.
+--------------+-------------+---------+
| RFAb -> RMNb | PNp -> RMNp | payload |
+--------------+-------------+---------+
Packets from the RMN are transmitted via the same tunnel
back to the RFA, and then on to the PN.
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+--------------+-------------+---------+
| RMNb -> RFAb | RMNp -> PNp | payload |
+--------------+-------------+---------+
5.2.3. Control Flow
In this section, we illustrate the control flow (signaling)
requirements for RSIP / Mobile IP.
The RMN is always listening for the ICMP Mobile IP Agent
Advertisement messages. Upon receipt of such a message the RMN
determines whether or not it is on the RHN. The RMN may also
transmit Agent Solicitation messages, as per Mobile IP.
When the RMN determines that it has moved from a RHN to a RFN,
or from a RFN to another RFN, it requests a local address
(e.g., RMNb from above) then performs the Mobile IP
registration process. This process includes informing the RHA
of the RMN's new care-of address. Note that the RMN must
identify itself uniquely to the RHA. Since RMNp may be in use
by more than one RMN at a time, the RMN must use either RMNa or
a combination of RMNp and a port number or range of port
numbers (in the case of RSAP-IP) that it has been allocated by
the RHA.
All RSIP messages that would normally flow between the RMN and
the RHA must be forwarded by the RFA. The RMN may request more
resources from or return resources to the RHA. The RMN must
also be prepared to accept DEALLOCATE messages from the RHA
which would force it to discontinue use of certain resources.
Note that if the RMN de-registers from the RHA, it may lose
connectivity entirely.
All RSIP control messages must be tunneled between the RMN and
the RFA, as well as between the RFA and the RHA. The form of
these tunnels is illustrated below.
From RMN to RFA:
+--------------+--------------+---------+
| RMNb -> RFAb | RMNa -> RHAa | payload |
+--------------+--------------+---------+
From RFA to RHA:
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+--------------+--------------+---------+
| RFAp -> RHAp | RMNa -> RHAa | payload |
+--------------+--------------+---------+
From RHA to RFA:
+--------------+--------------+---------+
| RHAp -> RFAp | RHAa -> RMNa | payload |
+--------------+--------------+---------+
From RFA to RMN:
+--------------+--------------+---------+
| RFAb -> RMNb | RHAa -> RMNa | payload |
+--------------+--------------+---------+
Since the RMN has a presence, in the form of an address (RMNb)
on the RFN, it must reply to all ARP messages for RMNb.
However, it MUST NOT respond to ARPs for RMNa or RMNp. The RMN
may communicate with other nodes on the RFN by using RMNb, and
is thus not constrained to use port numbers allocated by the
RHA (in the case of RSAP-IP) when communicating locally.
The RHA must perform all RSIP gateway functions as defined in
[RSIP-PROTO]. The RHA must also perform all home agent Mobile
IP functions as defined in [RFC2002].
The RFA must perform all foreign agent Mobile IP functions as
defined in [RFC2002]. It must also maintain an IP-IP tunnel to
all RMNs so that they can pass control and data flow packets.
5.3. Differentiated and Integrated Services
To attain the capability of providing quality of service between
two communicating hosts in different realms, it is important to
consider the interaction of RSIP with different quality of service
provisioning models and mechanisms. In the section, RSIP
interaction with the integrated service and differentiated service
frameworks is discussed.
5.3.1. Differentiated Services
The differentiated services architecture defined in [RFC2475]
allows networks to support multiple levels of best-effort
service through the use of "markings" of the IP Type-of-Service
(now DS) byte. Each value of the DS byte is termed a
differntiated services code point (DSCP) and represents a
particular per-hop behavior. This behavior may not be the same
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in all administrative domains. No explicit signaling is
necessary to support differentiated services.
For outbound packets from an edge network, DSCP marking is
typically performed and/or enforced on a boundary router. The
marked packet is then forwarded onto the public network. In an
RSIP-enabled network, a natural place for DSCP marking is the
RSIP gateway. In the case of RSAP-IP, the RSIP gateway can
apply its micro-flow (address/port tuple) knowledge of RSIP
assignments in order to provide different service levels to
different RSIP host. For RSA-IP, the RSIP gateway will not
necessarily have knowledge of micro-flows, so it must rely on
markings made by the RSIP hosts (if any) or apply a default
policy to the packets.
When differentiated services is to be performed between RSIP
hosts and gateways, it must be done over the tunnel between
these entities. Differentiated services over a tunnel is
considered in detail in [DS-TUNN], the key points that need to
be addressed here are the behaviors of tunnel ingress and
egress for both incoming and going packets.
For incoming packets arriving at an RSIP gateway tunnel
ingress, the RSIP gateway may either copy the DSCP from the
inner header to the outer header, leave the inner header DSCP
untouched, but place a different DSCP in the outer header, or
change the inner header DSCP while applying either the same or
a different DSCP to the outer header.
For incoming packets arriving at an RSIP host tunnel egress,
behavior with respect to the DSCP is not necessarily important
if the RSIP host not only terminates the tunnel, but consumes
the packet as well. If this is not the case, as per some
cascaded RSIP scenarios, the RSIP host must apply local policy
to determine whether to leave the inner header DSCP as is,
overwrite it with the outer header DSCP, or overwrite it with a
different value.
For outgoing packets arriving at an RSIP host tunnel ingress,
the host may either copy the DSCP from the inner header to the
outer header, leave the inner header DSCP untouched, but place
a different DSCP in the outer header, or change the inner
header DSCP while applying either the same or a different DSCP
to the outer header.
For outgoing packets arriving at an RSIP gateway tunnel egress,
the RSIP gateway must apply local policy to determine whether
to leave the inner header DSCP as is, overwrite it with the
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outer header DSCP, or overwrite it with a different value.
It is reasonable to assume that in most cases, the diffserv
policy applicable on a site will be the same for RSIP and non-
RSIP hosts. For this reason, a likely policy is that the DSCP
will always be copied between the outer and inner headers in
all of the above cases. However, implementations should allow
for the more general case.
5.3.2. Integrated Services
The integrated services model as defined by [RFC2205] requires
signalling using RSVP to setup a resource reservation in
intermediate nodes between the communicating endpoints. In the
most common scenario in which RSIP is deployed, receivers
located within the private realm initiate communication
sessions with senders located within the public realm. In this
section, we discuss the interaction of RSIP architecture and
RSVP in such a scenario. The less common case of having senders
within the private realm and receivers within the public realm
is not discussed although concepts mentioned here may be
applicable.
With senders in the public realm, RSVP PATH messages flow
downstream from sender to receiver, inbound with respect to the
RSIP gateway, while RSVP RESV messages flow in the opposite
direction. Since RSIP uses tunneling between the RSIP host and
gateway within the private realm, how the RSVP messages are
handled within the RSIP tunnel depends on situations elaborated
in [RSVP-Tunnel].
Following the terminology of [RSVP-Tunnel], if Type 1 tunnels
exist between the RSIP host and gateway, all intermediate nodes
inclusive of the RSIP gateway will be treated as a non-RSVP
aware cloud without QoS reserved on these nodes. The tunnel
will be viewed as a single (logical) link on the path between
the source and destination. End-to-end RSVP messages will be
forwarded through the tunnel encapsulated in the same way as
normal IP packets. We see this as the most common and
applicable deployment scenario.
However, should Type 2 or 3 tunnels be deployed between the
tunneling endpoints , end-to-end RSVP session has to be
statically mapped (Type 2) or dynamically mapped (Type 3) into
the tunnel sessions. While the end-to-end RSVP messages will be
forwarded through the tunnel encapsulated in the same way as
normal IP packets, a tunnel session is established between the
tunnel endpoints to ensure QoS reservation within the tunnel
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for the end-to-end session. Data traffic needing special QoS
assurance will be encapsulated in a UDP/IP header while normal
traffic will be encapsulated using the normal IP-IP
encapsulation. In the type 2 deployment scenario where all data
traffic flowing to the RSIP host receiver are given QoS
treatment, UDP/IP encapsulation will be rendered in the RSIP
gateway for all data flows. The tunnel between the RSIP host
and gateway could be seen as a "hard pipe". Traffic exceeding
the QoS guarantee of the "hard pipe" would fall back to the
best effort IP-IP tunneling.
In the type 2 deployment scenario where data traffic could be
selectively channeled into the UDP/IP or normal IP-IP tunnel,
or for type 3 deployment where end-to-end sessions could be
dynamically mapped into tunnel sessions, integration with the
RSIP model could be complicated and tricky. (Note that these
are the cases where the tunnel link could be seen as a
expandable soft pipe). Two main issues are worth considering.
- For RSIP gateway implementations that does encapsulation of
the incoming stream before passing to the IP layer for
forwarding, the RSVP daemon has to be explicitly signaled
upon reception of incoming RSVP PATH messages. The RSIP
implementation has to recognize RSVP PATH messages and pass
them to the RSVP daemon instead of doing the default
tunneling. Handling of other RSVP messages would be as
described in [RSVP-Tunnel].
- RSIP enables an RSIP host to have a temporary presence at the
RSIP gateway by assuming one of the RSIP gateway's global
interfaces. As a result, the RSVP PATH messages would be
addressed to the RSIP gateway. Also, the RSVP SESSION object
within an incoming RSVP PATH would carry the global
destination address, destination port (and protocol) tuples
that were leased by the RSIP gateway to the RSIP host. Hence
the realm unaware RSVP daemon running on the RSIP gateway has
to be presented with a translated version of the RSVP
messages. Other approaches are possible, for example making
the RSVP daemon realm aware.
A simple mechanism would be to have the RSIP module handle the
necessary RSVP message translation. For an incoming RSVP
signalling flow, the RSIP module does a packet translation of
the IP header and RSVP SESSION object before handling the
packet over to RSVP. The global address leased to the host is
translated to the true private address of the host. (Note that
this mechanism works with both RSA-IP and RSAP-IP). The RSIP
module also has to do an opposite translation from private to
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global parameter (plus tunneling) for end-to-end PATH messages
generated by the RSVP daemon towards the RSIP host receiver. A
translation on the SESSION object also has to be done for RSVP
outbound control messages. Once the RSVP daemon gets the
message, it maps them to an appropriate tunnel sessions.
Encapsulation of the inbound data traffic needing QoS treatment
would be done using UDP-IP encapsulation designated by the
tunnel session. For this reason, the RSIP module has to be
aware of the UDP-IP encapsulation to use for a particular end-
to-end session. Classification and scheduling of the QoS
guaranteed end-to-end flow on the output interface of the RSIP
gateway would be based on the UDP/IP encapsulation. Mapping
between the tunnel session and end-to-end session could
continue to use the mechanisms proposed in [RSVP-Tunnel].
Although [RSVP-Tunnel] proposes a number of approaches for this
purpose, we propose using the SESSION_ASSOC object introduced
because of its simplicity.
5.4. IP Multicast
The amount of specific RSIP/multicast support that is required in
RSIP hosts and gateways is dependent on the scope of multicasting
in the RSIP-enabled network, and the roles that the RSIP hosts
will play. In this section, we discuss RSIP and multicast
interactions in a number of scenarios.
Note that in all cases, the RSIP gateway MUST be multicast aware
because it is on an administrative boundary between two domains
that will not be sharing their all of their routing information.
The RSIP gateway MUST NOT allow private IP addresses to be
propagated on the public network as part of any multicast message
or as part of a routing table.
5.4.1. Receiving-Only Private Hosts, No Multicast Routing on
Private Network
In this scenario, private hosts will not source multicast
traffic, but they may join multicast groups as recipients. In
the private network, there are no multicast-aware routers,
except for the RSIP gateway.
Private hosts may join and leave multicast groups by sending
the appropriate IGMP messages to an RSIP gateway (there may be
IGMP proxy routers between RSIP hosts and gateways). The RSIP
gateway will coalesce these requests and perform the
appropriate actions, whether they be to perform a multicast WAN
routing protocol, such as PIM, or to proxy the IGMP messages to
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a WAN multicast router. In other words, if one or more private
hosts request to join a multicast group, the RSIP gateway MUST
join in their stead, using one of its own public IP addresses.
Note that private hosts do not need to acquire demultiplexing
fields and use RSIP to receive multicasts. They may receive
all multicasts using their private addresses, and by private
address is how the RSIP gateway will keep track of their group
membership.
5.4.2. Sending and Receiving Private Hosts, No Multicast Routing
on Private Network
This scenarios operates identically to the previous scenario,
except that when a private host becomes a multicast source, it
MUST use RSIP and acquire a public IP address (note that it
will still receive on its private address). A private host
sending a multicast will use a public source address and tunnel
the packets to the RSIP gateway. The RSIP gateway will then
perform typical RSIP functionality, and route the resulting
packets onto the public network, as well as back to the private
network, if there are any listeners on the private network.
If there is more than one sender on the private network, then,
to the public network it will seem as if all of these senders
share the same IP address. If a downstream multicasting
protocol identifies sources based on IP address alone and not
port numbers, then it is possible that these protocols will not
be able to distinguish between the senders.
6. Changelog
03 to 04
- Terminology change. An "RSIP client" now refers to the application
that performs RSIP client duties -- i.e., running the client
side of the RSIP protocol. The physical device on which the RSIP
client runs is now called the "RSIP host". An "RSIP server" now
refers to the application that performs RSIP server duties --
i.e., running the server side of the RSIP protocol. The physical
device on which the RSIP server runs is now called the "RSIP
gateway".
- Noted that limiting the MTU size for non-TCP-using applications
is application dependent.
- Modified diffserv section to note that most site will probably
copy the DSCP between headers, but implementations should be
flexible.
- Noted that the Mobile IP section will change soon.
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02 to 03
- Added section on interaction with Integrated and Differentiated
Services
- Added section on document scope.
- Reorganized draft into three main areas: implementation, deployment,
and interaction with other protocols.
- Added section on protocol requirements and recommendations, which
replaces several old sections with much more concise verbiage, and
now contains a discussion of authentication.
- Added section on interaction with DNS
- Added section on locating RSIP gateways
- Added overview of RSIP/IPSEC
- Added overview of integration with diffserv
- Added section on interaction with multicast
01 to 02:
- Added section on Mobile IP integration
- Added to section on cascaded RSIP
- Added section on host and gateway requirements
- Added RSIP for multi-homed network
- Added deployment scenarios
- Added section on RSAP-IP support for gateways
- Added section on MTU limitations
- Elaborated on discussion in the Architecture section
- Elaborated on discussion under demultiplexing fields
- Elaborated on discussion on Negotiation Protocol
- Clarified section on tunneling between the host and gateway
- Editorial changes
00 to 01:
- Synched up terminology with the latest NAT terminology draft.
- Changed all instances of "global" to "public"
- Modified section on "Architecture"
- Added discussion of demultiplexing parameters tree to the
"Negotiation and assignment of demultiplexing fields" section
- Added discussion of subnet list query in "Determining Locality of
Destination" section
- Added "RSIP Host Deallocation" discussion section
- Added more explanation in "Tunnel Use and Establishment" section
7. Security Considerations
RSIP, in and of itself, does not provide security. It may provide
the illusion of security or privacy by hiding a private address
space, but security can only be ensured by the proper use of security
protocols and cryptographic techniques.
8. Acknowledgements
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The authors would like to thank Pyda Srisuresh, Dan Nessett, Gary
Jaszewski, Ajay Bakre, Cyndi Jung, and Rick Cobb for their input.
The IETF NAT working group as a whole has been extremely helpful in
the ongoing development of RSIP.
9. References
[DHC-NS] J. Privat and M. Borella, "DHCP Next Server Option," <draft-
xxxx-nextserver-00.txt>, to be submitted, Dec. 1999.
[DHCP-DNS] M. Stapp and Y. Rekhter, "Interaction Between DHCP and
DNS," <draft-ietf-dhc-dhcp-dns-11.txt>, work in progress, Oct.
1999.
[DS-TUNN] D. Black, "Differentiated Services and Tunnels," <draft-
black-diffserv-tunnels-00.txt>, work in progress, Oct. 1999.
[RSIP-IPSEC] G. Montenegro and M. Borella, "RSIP Support for End-to-
end IPSEC," <draft-ietf-nat-rsip-ipsec-01.txt>, work in progress,
Oct. 1999.
[RSIP-PROTO] M. Borella, D. Grabelsky, J. Lo and K. Taniguchi,
"Realm Specific IP: Protocol Specification," <draft-ietf-nat-rsip-
protocol-04.txt>, work in progress, Nov. 1999.
[RSVP-Tunnel] A. Terzis, J. Krawczyk, J. Wroclawski, L. Zhang, "RSVP
Operation Over IP Tunnels," <draft-ietf-rsvp-tunnel-04.txt>, work-
in-progress, Nov. 1999
[RFC1918] Y. Rekhter, B. Moskowitz, D. Karrenberg, G. J. de Groot,
and E. Lear, "Address Allocation for Private Internets," RFC 1918,
Feb. 1996.
[RFC2002] C. Perkins, "IP Mobility Support," RFC 2002, Oct. 1996.
[RFC2119] S. Bradner, "Key words for use in RFCs to indicate
requirement levels," RFC 2119, Mar. 1997.
[RFC2663] P. Srisuresh and Matt Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations," RFC 2663, Aug.
1999.
[RFC2205] R. Braden, L. Zhang, S. Berson, S. Herzog, S. Jamin,
"Resource Reservation Protocol (RSVP)," RFC 2205, Sep. 1997
[RFC2475] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, W.
Weiss, "An Architecture for Differentiated Services," RFC 2475,
Dec. 1998
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10. Authors' Addresses
Michael Borella
3Com Corp.
1800 W. Central Rd.
Mount Prospect IL 60056
(847) 342-6093
mike_borella@3com.com
Jeffrey Lo
NEC USA
C&C Research Labs.
110 Rio Robles
San Jose, CA 95134
(408) 943-3033
jlo@ccrl.sj.nec.com
David Grabelsky
3Com Corp.
1800 W. Central Rd.
Mount Prospect IL 60056
(847) 222-2483
david_grabelsky@3com.com
Gabriel E. Montenegro
Sun Microsystems, Inc.
15 Network Circle
Menlo Park CA 94025
650 786 6288
gab@sun.com
11. Copyright Statement
Copyright (c) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
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The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Borella et. al. Expires September 2000 [Page 33]
