INTERNET DRAFT Editors:
Expires June 2000 M. Borella
3Com Corp.
J. Lo
NEC USA
Contributors:
D. Grabelsky
3Com Corp.
G. Montenegro
Sun Microsystems
December 1999
Realm Specific IP: Framework
<draft-ietf-nat-rsip-framework-03.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 server/gateway replaces the NAT
router, and RSIP-aware hosts on the private network are referred to
as RSIP clients. RSIP requires ability of the RSIP server to grant
such resources to RSIP clients. ALGs are not required on the RSIP
server for communications between an RSIP client 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 client and RSIP server 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 Server
A router situated on the boundary between two addressing realms
and owns one or more IP addresses. An RSIP server is
responsible for parameter management and assignment from one
realm to RSIP clients in the other realm. An RSIP server may
act as a normal NAT router for hosts within the a realm that
are not RSIP enabled.
RSIP Client
A host within an addressing realm that uses RSIP to acquire
addressing parameters from another addressing realm via an RSIP
server.
RSA-IP: Realm Specific Address IP
An RSIP method in which each RSIP client 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 client is allocated an IP
address (possibly shared with other RSIP clients) and some
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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 server, 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 server
uses to route an incoming packet to an RSIP client.
All other terminology found in this document is consistent with
that of [RFC2663].
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 server. This model is diagrammatically represented
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as follows:
RSIP Client RSIP Server 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 server (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 server 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 client resides as "private" and the realm
from which the RSIP client 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 server. Upon
assignment of these parameters, the RSIP server creates a mapping,
referred as a "bind", of X's addressing information and the assigned
resources. This binding enables the RSIP server to correctly de-
multiplex and forward inbound traffic generated by Y for X. If
permitted by the RSIP server, X may create multiple such bindings on
the same RSIP server, or across several RSIP servers. A lease time
SHOULD be associated with each bind.
Using the public parameters assigned by the RSIP server, RSIP clients
tunnel data packets across address space A to the RSIP server. The
RSIP server 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 server maintains a mapping of the assigned
public parameters as demultiplexing fields for uniquely mapping them
to RSIP client private addresses. When a packet from the public
realm arrives at the RSIP server and it matches a given set of
demultiplexing fields, then the RSIP server will tunnel it to the
appropriate RSIP client. The tunnel headers of outbound packets from
X to Y, given that X has been assigned Nb, are as follows:
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+---------+---------+---------+
| X -> Na | Nb -> Y | payload |
+---------+---------+---------+
There are two basic flavors of RSIP: RSA-IP and RSAP-IP. RSIP
clients and servers MAY support RSA-IP, RSAP-IP, or both.
When using RSA-IP, an RSIP server maintains a pool of IP addresses to
be leased by RSIP clients. Upon client request, the RSIP server
allocates an IP address to the client. Once an address is allocated
to a particular client, only that client may use the address until
the address is returned to the pool. Clients MAY NOT use addresses
that have not been specifically assigned to them. The clients may
use any TCP/UDP port in combination with their assigned address.
Clients may also run server applications at any port and these
applications will be available to the public network without
assistance from the RSIP server. A client MAY lease more than one
address from the same or different RSIP servers. The demultiplexing
fields of an RSA-IP session MUST include the IP address leased to the
client.
When using RSAP-IP, an RSIP server maintains a pool of IP addresses
as well as pools of port numbers per address. RSIP clients lease an
IP address and one or more ports to use with it. Once an address /
port tuple has been allocated to a particular client, only that
client may use the tuple until it is returned to the pool(s). Clients
MAY NOT use address / port combinations that have not been
specifically assigned to them. Clients may run server applications
bound to an allocated tuple, but their applications will not be
available to the public network unless the RSIP server has agreed to
route all traffic destined to the tuple to the client. A client MAY
lease more than one tuple from the same or different RSIP servers.
The demultiplexing fields of an RSAP-IP session MUST include the
tuple(s) leased to the client.
3. Implementation Considerations
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 client, 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
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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. Client and Server Requirements
An RSIP client must be able to maintain one or more virtual
interfaces for the IP address(es) that it leases from an RSIP
server. The client must also support tunneling and be able to
serve as an end-point for one or more tunnels to RSIP servers. An
RSIP client MUST NOT respond to ARPs for a public realm address
that it leases.
An RSIP client supporting RSAP-IP MUST be able to maintain a set
of one or more ports assigned by an RSIP server from which choose
ephemeral source ports. If the client's pool does not have any
free ports and the client 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 server is a multi-homed host that routes packets between
two or more realms. Often, an RSIP server 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
clients. The RSIP server 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 server must reassemble all
incoming packet fragments from the public network in order to be
able to route and tunnel them to the proper client. As is
necessary for all fragment reassembly, an RSIP server must timeout
fragments that are never fully reassembled.
An RSIP server MAY include NAT functionality so that clients on
the private network that are not RSIP-enabled can still
communicate with the public network. An RSIP server must manage
all resources that are assigned to RSIP clients. This management
MAY be done according to local policy.
3.2. Processing of Demultiplexing Fields
Each active RSIP client must have a unique set of demultiplexing
fields assigned to it so that an RSIP server can route incoming
packets appropriately. Depending on the type of mapping used by
the RSIP server, demultiplexing fields have been defined to be one
or more of the following:
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- 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
client, a unique public IP address is mapped to each RSIP
client.
- If the same IP address is used for more than one RSIP client,
then subsequent headers must have at least one field that will
be assigned a unique value per client 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 client, the payload section of the
packet must contain a demultiplexing field that is guaranteed to
be different for each RSIP client. Typically this requires
negotiation of said fields between the RSIP client and server so
that the RSIP server can guarantee that the fields are unique
per-client
- 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-
client. Typically this requires negotiation of said fields
between the RSIP client and server so that the RSIP server can
guarantee that the fields are unique per-client.
It is desirable for all demultiplexing fields to occur in well-
known fixed locations so that an RSIP server can mask out and
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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 servers and clients 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 clients to request assignments of demultiplexing fields
- RSIP servers to assign demultiplexing fields with an associated
lease time
- RSIP servers 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 clients
and servers may communicate via TCP or UDP. TCP support is
required in all RSIP servers, while UDP support is optional. In
RSIP clients, TCP, UDP, or both may be supported. However, once
an RSIP client and server 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 loads.
It is recommended that all communication between an RSIP client
and server 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 client and server to one another,
provide message integrity, and (with an anti-replay counter) avoid
replay attacks. In order for authentication to be supported, each
RSIP client and the RSIP server must either share a secret key
(distributed, for example, by Kerberos) or have a private/public
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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 server 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 client (using RSAP-IP) is
leased an address/port tuple and uses this tuple to contact a
public address/port tuple. Suppose that the client terminates the
session with the public tuple and immediately returns its leased
tuple to the RSIP server. If the RSIP server immediately
allocates this tuple to another RSIP client (or to the same
client), and this second client uses the tuple to contact the same
public tuple while the socket is still in the TIME_WAIT phase,
then the client's connection may be rejected by the public host.
In order to mitigate this problem, it is recommended that RSIP
servers 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 server MAY choose to allocate ports in a FIFO fashion
from the pool of recently deallocated ports.
3.5. ICMP Handling
Like NAT, RSIP servers 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 client sending an ICMP request
packet tunnels it to the RSIP server, just as it does TCP and UDP
packets. The RSIP server must use this tuple to map incoming ICMP
responses to the private address of the appropriate RSIP client.
Once it has done so, it will tunnel the ICMP response to the
client. Note that it is possible for two RSIP clients 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 client by examining the IP header and port
numbers embedding within the packet. In the case of RSA-IP, only
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the source IP address is necessary to determine the RSIP client.
In the case of RSAP-IP, the source IP address and source port
number is necessary to determine the RSIP client.
Occasionally, an RSIP client will have to send an ICMP response
(e.g., port unreachable). These responses are tunneled to the
RSIP server, as is done for TCP and UDP packets. All ICMP
requests (e.g., echo request) arriving at the RSIP server MUST be
processed by the RSIP server and MUST NOT be forwarded to an RSIP
client.
3.6. MTU Limitation to Prevent Fragmentation and ID Collision
RSIP clients MUST limit their MTU so that packets transmitted by
an RSIP server are not fragmented. If two or more RSIP clients on
the same private network transmit outbound packets that get
fragmented to the same public server, the public server 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 UDP packets, an artificially small MTU, such as 512
bytes, is required.
3.7. Servers on RSAP-IP Clients
RSAP-IP clients are limited by the same constraints as NAT with
respect to hosting servers that use a well-known port. Since
destination port numbers are used as routing information to
uniquely identify an RSAP-IP client, typically no two RSAP-IP
clients sharing the same public IP address can simultaneously
operate publically-available servers on the same port. For
protocols that operate on well-known ports, this implies that only
one public server per RSAP-IP IP address / port tuple is used
simultaneously. However, more than one server 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
that will uniquely determine the identity of the RSAP-IP client,
and this field is known by the RSIP server.
In order for an RSAP-IP client to operate a publically-available
server, the client must inform the RSIP server 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 client.
3.8. Determining Locality of Destinations from an RSIP Client
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In general, an RSIP client 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 server (assuming that it has such an interface
available).
If the RSIP clients are all on a single subnet, one hop from an
RSIP server, 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 server. RSIP clients
may query the server 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
client may have to query the location of every destination that it
tries to communicate with.
If an RSIP client transmits a packet addressed to a public host
without using RSIP, then the RSIP server 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 Client Deallocation
An RSIP client 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 clients are able to dynamically deallocate ports
that they no longer need, more clients can be supported.
However, this functionality may require significant modifications
to a vanilla TCP/IP stack in order to implement properly. The
RSIP client 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 client 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
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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 clients will not have
to deallocate ports for the lifetime of their activity.
Since RSIP demultiplexing fields are leased to clients, 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 server) and for lookups of public hosts, (2)
private DNS services for use only on the private network, and (3)
dynamic DNS services for RSIP clients.
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
clients 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
clients should be allowed to update their A records but not PTR
records, while RSIP servers can update both. In order for the
RSIP server to update DNS records on behalf on an RSIP client, the
client must provide the server with its FQDN.
Note that when using RSA-IP, the interaction with DNS is
completely analogous to that of DHCP because the RSIP client
"owns" an IP address for a period of time. In the case of RSAP-
IP, the claim that an RSIP client has to an address is only with
respect to the port(s) that it has leased along with an address.
Thus, two or more RSIP clients' FQDNs may map to the same IP
address. However, a public client 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 Servers
When an RSIP client initializes, it requires (among other things)
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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 server. This information can be statically configured
or dynamically assigned.
In the dynamic case, the client's private address is typically
supplied by DHCP. A DHCP option has been proposed to provide the
IP address of an RSIP server in DHCPOFFER messages (the Next
Server option) [DHC-NS]. Thus, the client's startup procedure
would be as follows: (1) perform DHCP, (2) if the Next Server
option is present in the DHCPOFFER, record the IP address therein
as the RSIP server.
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 server. This RSIP
server may control only one, or perhaps several, public IP
addresses. The RSIP server may also perform firewall
functions, as well as routing inbound traffic to particular
destination ports on to a small number of dedicated servers on
the private network.
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 server's resources. In
particular, many of these devices may be thin clients or so-
called "network appliances" and therefore not require access to
the public Internet frequently. The RSIP server 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
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to a small number of dedicated servers on the private network.
It is likely that only one gateway to the public network will
be present and that this gateway's RSIP server 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 server's resources. The
RSIP server 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 servers on the private
network. It is likely that only one gateway to the public
network will be present and that this gateway's RSIP server
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 servers 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 server's
resources. The RSIP server 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 servers
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 server 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
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 server for a short period of time. At
most several hundred hosts will share the server's resources.
The RSIP server 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 servers on the private
network. It is likely that only one gateway to the public
network will be present and that this gateway's RSIP server
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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 servers as
well as cascading of RSIP servers 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.
+-----------+
| |
| RSIP |
| server +---- 10.0.0.0/8
| B |
| |
+-----+-----+
|
| 10.0.1.0/24
+-----------+ | (149.112.240.0/25)
| | |
149.112.240.0/24| RSIP +--+
----------------+ server |
| A +--+
| | |
+-----------+ | 10.0.2.0/24
| (149.112.240.128/25)
|
+-----+-----+
| |
| RSIP |
| server +---- 10.0.0.0/8
| C |
| |
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+-----------+
RSIP-server A is in charge of the IP addresses of subnet
149.112.240.0/24. It distributes these addresses to RSIP-
clients and RSIP-servers. In the given configuration, it
distributes addresses 149.112.240.0 - 149.112.240.127 to RSIP-
server B, and addresses 149.112.240.128 - 149.112.240.254 to
RSIP-server 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-
server A. Also, the subnets between RSIP-server A and RSIP-
servers B and C will use private addresses.
Due to the tree-like fashion in which addresses will be
cascaded, we will refer to RSIP-servers A as the 'parent' of
RSIP-servers B and C, and RSIP-servers B and C as 'children' of
RSIP-servers A. An arbitrary number of levels of children may
exist under a parent RSIP- server.
A parent RSIP-server will not necessarily be aware that the
address(es) and port blocks that it distributes to a child
RSIP- server will be further distributed. Thus, the RSIP-
clients MUST tunnel their outgoing packets to the nearest RSIP-
server. This server will then verify that the sending host has
used the proper address and port block, and then tunnel the
packet on to its parent RSIP-server.
For example, in the context of the diagram above, host
10.0.0.1, behind RSIP-server 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-server C. RSIP-server C strips
off the outer IP header. After verifying that the source
public IP address and source port number is valid, RSIP-server
C will tunnel the packets over the 10.0.2.0/8 subnet to RSIP-
server A. RSIP-server A strips off the outer IP header. After
verifying that the source public IP address and source port
number is valid, RSIP-server A transmits the packet on the
public network.
While it may be more efficient in terms of computation to have
a RSIP-client tunnel directly to the overall parent of an RSIP-
server tree, this would introduce significant state and
administrative difficulties.
A RSIP-server 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-server is given a lease time of 3600
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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-client or child RSIP-server.
4.2.2. NAT Behind RSIP
+--------+ +--------+
| NAT w/ | | RSIP |
clients ----+ RSIP +------+ server +----- public network
| client | | |
+--------+ +--------+
In this architecture, an RSIP server is between a NAT box and
the public network. The NAT is also equipped with an RSIP
client. The NAT dynamically requests resources from the RSIP
server as the clients establish sessions to the public network.
The clients are not aware of the RSIP manipulation. This
configuration does not enable the clients 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
+--------+ +--------+
RSIP | RSIP | | |
clients ----+ server +------+ NAT +----- public network
| | | |
+--------+ +--------+
In this architecture, The RSIP clients and server reside behind
a NAT. This configuration does not enable the clients to have
end-to-end transparency and thus the NAT still requires ALGs
and the architecture cannot support IPSEC. The clients 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 |
clients ----+ NAT +------+ server +----- public network
| | | |
+--------+ +--------+
In this architecture, the RSIP clients are separated from the
RSIP server by a NAT. RSIP signaling may be able to pass
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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.
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 client 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 server to uniquely identify and
route packets to an RSIP client. In order to guarantee that RSIP
clients use SPIs that are unique per address, it is necessary for
the RSIP server to allocate unique SPIs to clients 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 client IKE implementations will use source
port 500 as well, but this behavior is not mandatory. If two or
more RSIP clients 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 server will be able to
route incoming IKE packets to the proper client based on initiator
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cookie value. Initiator cookies can be negotiated, like ports and
SPIs. However, since the likelihood of two clients assigned the
same IP address attempting to simultaneously use the same
initiator cookie is very small, the RSIP server can guarantee
cookie uniqueness by dropping IKE packets with a cookie value that
is already in use.
5.2. Mobile IP
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 servers, 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.
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
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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
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 |
+-------------+---------+
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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.
+--------------+-------------+---------+
| 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
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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:
+--------------+--------------+---------+
| 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 server 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.
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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
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 server. In the case of RSAP-IP, the RSIP server can apply
its micro-flow (address/port tuple) knowledge of RSIP
assignments in order to provide different service levels to
different RSIP client. For RSA-IP, the RSIP server will not
necessarily have knowledge of micro-flows, so it must rely on
markings made by the RSIP clients (if any) or apply a default
policy to the packets.
Given most reasonable RSIP deployment scenarios, it is not
likely that supporting differntiated services on the private
network will be absolutely necessary (e.g., the RSIP clients
and server are one hop apart). However, if differentiated
services is to be performed between RSIP clients and servers,
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 server tunnel ingress,
the RSIP server 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
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to the outer header.
For incoming packets arriving at an RSIP client tunnel egress,
behavior with respect to the DSCP is not necessarily important
if the RSIP client 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 client 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 client tunnel ingress,
the client 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 server tunnel egress,
the RSIP server 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.
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 server, while RSVP RESV messages flow in the opposite
direction. Since RSIP uses tunneling between the RSIP client
and server 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 client and server, all intermediate
nodes inclusive of the RSIP server will be treated as a non-
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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
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 client receiver are given QoS
treatment, UDP/IP encapsulation will be rendered in the RSIP
server for all data flows. The tunnel between the RSIP client
and server 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 server implementations that do 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 client to have a temporary presence at
the RSIP server by assuming one of the RSIP server's global
interfaces. As a result, the RSVP PATH messages would be
addressed to the RSIP server. Also, the RSVP SESSION object
within an incoming RSVP PATH would carry the global
destination address, destination port (and protocol) tuples
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that were leased by the RSIP server to the RSIP client. Hence
the realm unaware RSVP daemon running on the RSIP server 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 client is
translated to the true private address of the client. (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 global parameter (plus tunneling) for end-to-end PATH
messages generated by the RSVP daemon towards the RSIP client
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
server 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 clients and servers is dependent on the scope of multicasting
in the RSIP-enabled network, and the roles that the RSIP clients
will play. In this section, we discuss RSIP and multicast
interactions in a number of scenarios.
Note that in all cases, the RSIP server 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 server 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.
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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 server.
Private hosts may join and leave multicast groups by sending
the appropriate IGMP messages to an RSIP server (there may be
IGMP proxy routers between RSIP clients and servers). The RSIP
server 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 a WAN
multicast router. In other words, if one or more private hosts
request to join a multicast group, the RSIP server 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 server 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 server. The RSIP server 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
02 to 03
- Added section on interaction with Integrated and Differentiated
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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 servers
- 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 client and server requirements
- Added RSIP for multi-homed network
- Added deployment scenarios
- Added section on RSAP-IP support for servers
- 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 client and server
- 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 Client 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
The authors would like to thank Pyda Srisuresh, Dan Nessett, Gary
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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.
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