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Internet Draft Shai Herzog
Expiration: Oct. 1997 IPHighway
File: draft-ietf-rsvp-policy-oops-01.txt
Dimitrios Pendarakis
Raju Rajan
Roch Guerin
IBM T.J. Watson Research Center
Open Outsourcing Policy Service (OOPS) for RSVP
07/30/97
Status of Memo
This document is an Internet-Draft. 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."
To learn the current status of any Internet-Draft, please check the
"1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net
(Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
Rim).
Abstract
This document describes a protocol for exchanging policy information
and decisions between an RSVP-capable router (client) and a policy
server. The OOPS protocol supports a wide range of router
configurations and RSVP implementations, and is compatible with the
RSVP Extensions for Policy Control [Ext].
Shai Herzog et al. Expiration: Oct. 1997 [Page 1]
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1. Overview Reservation protocols function by discriminating between
users by providing some users with better service at the expense of
others. The utility of reservation protocols is sharply degraded in
the absence of mechanisms for restricting access to higher service
categories and enforcing network and bandwidth usage criteria. In
this document, we refer to such mechanisms as "policy control". This
term is quite broad; it ranges from simple access control to
sophisticated accounting and debiting mechanisms.
The policy control component may reside fully within the router (as
an add-on module to RSVP). However, it is often advantageous for
routers to outsource some of their policy decision making to external
entities. Open Outsourcing Policy Service (OOPS) is a protocol for
exchanging policy information and decisions between Local Policy
Modules (LPMs) located within RSVP-capable routers and one or more
external policy servers. OOPS is an open protocol in a sense that it
does not define or depend on particular policies; instead, it
provides a framework for adding, modifying and experimenting with new
policies in a modular, plug-n-play fashion. Moreover, the OOPS
protocol supports both partial and complete delegation of policy
control.
The OOPS protocol was designed to be compatible with the RSVP
Extensions for Policy Control [Ext], both in the format of RSVP
objects, as well as the set of supported services.
The basic features of OOPS are as follows:
Asymmetry between client and server
Adding policy support to RSVP may require substantial
modifications to platforms (e.g., routers) which may not have
the required implementation flexibility and/or processing power.
OOPS assumes that the server is more sophisticated than the
client, in terms of processing power and support for diverse
policies.
Support for a wide range of client implementation
The OOPS protocol supports a wide range of client
implementations. At one end of the spectrum, a "dumb" client
may delegate total responsibility to the server for all policy
decisions without even maintaining cached states. At the other
end, smart clients can perform most policy processing locally
and only address the server for a small number of sub-policy
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elements and only when things change (otherwise, cache can be
used).
Support for different policy interfaces
The OOPS protocol allows clients and servers to negotiate the
nature and sophistication of their interaction. For instance,
responses from the server to the client may be restricted to
allow the server to merely accept, deny or remain neutral on
reservation requests, while a more sophisticated implementation
may allow the server to respond with preemption priorities or
other characteristics of the reservation. The negotiation
handshake is simple, and may always fall back onto the lowest
level of interaction that must always be supported.
Minimal knowledge of RSVP's processing rules.
The server must be aware of the format of several RSVP objects
and basic RSVP message types. However, it is not required to
understand RSVP's processing rules (e.g., different reservation
styles). Moreover, OOPS functionality is not tied to that of
RSVP, and OOPS may be extended to be used by other, non-RSVP,
connection setup protocols.
Asynchronicity
Both client and server may asynchronously generate queries or
requests.
TCP for reliable communications
TCP is used as a reliable communication protocol between client
and server.
1.1 Glossary
Policy
Comprehensive set of rules for controlling some aspects of
the network.
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Sub-policies
Modular building blocks out of which comprehensive policies
are compiled.
POLICY_DESC
Data representation of policy information (e.g., POLICY_DATA
objects in RSVP).
Sub-policy element
Data representation of sub-policy information, as
encapsulated in POLICY_DESC objects.
1.2 Representative OOPS Scenarios
Figure 1 depicts some representative scenarios for policy control
along an RSVP path, as envisioned in OOPS. Nodes A, B and C
belong to one administrative domain AD-1 (advised by policy server
PS-1), while D and E belong to AD-2 and AD-3, respectively.
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AD-1 AD-2 AD-3
_______________/\___________ __/\__ __/\__
{ } { } { }
+------+ +------+ +------+ +------+ +------+
+----+ | A | | B | | C | | D | | E | +----+
| S1 |--| RSVP |---| RSVP |---| RSVP |---| RSVP |---| RSVP |--| R1 |
+----+ +------+ +------+ +------+ +------+ +------+ +----+
| LPM | | LPM | | LPM | | LPM |
+------+ +------+ +------+ +------+
\ / |
\ / +------+
\ / |Policy|
\ / |Server|
\ / | PS-2 |
\ / +------+
+------+
|Policy|
|Server|
| PS-1 |
+------+
Figure 1: Policy Control along an RSVP path
Policy objects are carried in RSVP messages along the path
consisting of four typical node types:
(1) Policy incapable nodes: Node B. (2) Self-sufficient policy
node: Node D does not need to outsource policy tasks to external
servers since its LPM satisfies its entire policy needs. (3)
"Dumb" policy nodes: Node E is an unsophisticated node that lacks
processing power, code support or caching capabilities, and needs
to rely on PS-2 for every policy processing operation. In this
case, the volume of traffic and delay requirements make it
imperative to connect Node E to PS-2 a direct link or a LAN. (4)
"Smart" policy nodes: Nodes A and C include sophisticated LPMs,
in that these nodes can process some sub-policy elements, and have
the capacity to cache responses from PS-1. In this case, the
contact between the clients and server would be limited to
occasional updates, and PS-1 could be located somewhere in AD-1.
Consider the case where the receiver R1 sends a Resv message
upstream toward sender S1. Assuming that the reservation is
successful, the conceptual flow of policy objects is:
R1 -- E -- ELPM -- PS-2 -- ELPM -- E -- D -- DLPM -- D -- C -- CLPM
-- PS-1 -- CLPM -- C -- B -- A -- ALPM -- PS-1 -- ALPM -- A -- S1.
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Of course, other OOPS messages may be exchanged between policy
servers and nodes before authorizing the reservation at individual
nodes.
The functioning of the policy module at a policy aware router is
presented through the following conceptual diagram.
+---------+ +----------+
| RSVP | | Policy |
| Module | | Server |
+---------+ OOPS | |
| LPM |---------| |
+- - - - -+ +----------+
|PSM| |PSM| |PSM| |PSM|
|___| |___| |___| |___|
Figure 2: Local Policy Modules and Policy Server communications
The policy server and the local policy module provide support for
a number of sub-policy elements, each embodied by a policy sub-
module (PSM). The policy object forwarded by RSVP may contain a
number of elements, each identified by a number, and hence
destined to the sub-module that enforces that sub-policy element's
number. For instance, some of these sub-objects may deal with
authentication, others with security, accounting and so on. The
LPM is aware of the sub-modules it is capable of processing
locally; After the handshake comes to know the set of sub-policies
that are supported by the server. Processing of policy sub-objects
can be split between the LPM and the policy server, and responses
may be merged back before returning a unified response to RSVP.
2. OOPS Protocol: Basic Features
OOPS is a transaction protocol, in which most communication is in the
form of queries from the client followed by responses from the
server. However, a small portion of the communication may also
consist of queries originating from the server, or of unidirectional
notifications from one entity to another. In this context, it is
important that messages be distinguished by a unique association, so
that responses may identify the query to which they correspond.
This section discusses four fundamental concepts of the OOPS
protocol: (a) query/response mechanism, (b) flexible division of
labor between client and server, and (c) consistent management of
client, server and RSVP state.
2.1 Query/Response mechanism
Each OOPS message is uniquely identified by a sequence number;
Both client and server begin communication with Mseq = 0 (the
handshake message), and number consecutive messages in increasing
order. These sequence numbers do not imply the order of execution;
while the server receives messages in-order, it is free to execute
them in any reasonable order.
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These sequence numbers are mainly used by the Error-Notification
operation as a means to identify the message that is associated
with the reported error. [Note 2]
2.1.1 Associating Queries and Responses
Queries and responses carry a Q_ASSOC object which relates
newly received responses to their original query operations.
The contents of this object is client-specific and therefore
opaque to the server; it is set by the client for each query
and is echoed back as-is by the server. The client must store
enough information in the Q_ASSOC object to enable its own
unique identification of the original query.
2.2 Division of Labor between Client and Server
The OOPS protocol allows for a flexible division of
responsibilities between server and client. First, the client must
be able to decide how to distribute the processing and second, it
must be able to merge the distributed responses into one unified
result.
2.2.1 Distributed Processing
Processing of sub-policies (sub-policy elements within
POLICY_DESC objects) can be performed by the server, the
client, or by both. The decision on which sub-policies are to
be handled locally and which are to be sent to the server is
always made by the client based on information exchanged during
the connection establishment handshake (see Section 3.1).
The client may remove sub-policy elements which are not to be
processed by the server. In this case, the client is solely
responsible for checking the integrity of the incoming policy
object; [Note 3]
_________________________
[Note 1] Execution order is implementation and policy specific; any
order that does not violate the policy specific requirements is assumed
to be reasonable.
[Note 2] Senders must be informed about the receiver's failure to
process their messages. This is especially critical given that OOPS
relies on TCP's reliability and lacks additional reliability mechanisms.
[Note 3] If any portion of the POLICY_DESC object is modified, the
digest integrity verification at the server is bound to fail.
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the client must also set the OP-Code header flag to inform the
server to that fact.
During connection establishment, the server may request to have
oversight over the clients local decisions; in this case, the
client should forward incoming policy objects in their
entirety, and consult the server for all RSVP flows, regardless
of whether they include POLICY_DATA objects. This oversight is
transparent to the client and is therefore post factum. [Note
4]
OOPS does not impose limitations on the number of servers
connected to the client; when appropriate, the client could
divide the work along policy lines between several servers, and
be responsible for combining their results. In the rest of this
document we describe the protocol for a single server-client
pair.
2.2.2 Unification of Distributed Responses
Division of labor between client and server is only possible to
the extent that the client has the capability to unify or merge
results; the client must be able to merge the results of
queries arriving from servers with its own local results, to
produce a single unified response to the underlying protocol
(e.g., RSVP).
Results unification is straight-forward for outgoing
POLICY_DESC object; since sub-policy elements are independent,
their unification is performed by concatenating all local and
server elements and packing them in POLICY_DESC objects. [Note
5]
Unification is more complex for status queries, since the
various responses must truly be merged to produce a single
status result. OOPS defines one basic (default) status
response interface (object and unification rules).
_________________________
[Note 4] The client should not wait for an oversight decision; if the
server overrides a local decision, it may notify the client sometime
later, even after the local client authorized the RSVP operation.
[Note 5] An oversight sub-policy element would override the locally
generated element, if the two are of the same type.
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However, given that OOPS is an extensible framework, it allows
the the client and server to negotiate a more sophisticated
interface (see Section 3.1). Additional response interfaces
could be described in separate documents which should define
the response object format and unification rules. [Note 6]
2.2.3 Default Status Response
The default status response object is of the C-Type 1. C-Type
1 objects may contain two values: a policy admission decision
(PAD) and a preemption priority value (PP). It is reasonable
to assume that some clients would not be able to utilize the
flow preemption priority information; such clients are free to
ignore this value and assume that all flows are created equal.
(have priority 0).
PADs may have one of three values: ACCEPT, SNUB, and VETO.
ACCEPT authorizes the query, SNUB signifies neutrality (neither
accept nor reject). A VETO from the server or LPM has a
stronger semantics than a snub, since it has the power to
forcefully reject a flow regardless of any accept decisions
made by the other.
The rules for unification of PAD values A and B are straight-
forward:
+----------------------+---------------------+
| A+B | IF... |
+----------------------+---------------------+
| SNUB | A=SNUB and B=SNUB |
| VETO | A=VETO or B=VETO |
| ACCEPT (+PP value) | Otherwise |
+----------------------+---------------------+
A unified result of ACCEPT provides approval for the status
query; both SNUB and VETO signal the rejection of the query.
Note that a client and/or server should complete their policy
processing even if a veto was cast by some policy. [Note 7]
_________________________
[Note 6] A separate template document and a list of more sophisticated
responses should be prepared.
[Note 7] A wide range of sub-policies may not care about the final
status results and should be activated regardless. For instance: a
policy that logs all policy queries.
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An ACCEPT response is accompanied by a PP value between 0..255.
Lower values describe higher priorities (priority 1 is the
highest). The value 0 is reserved for "N/A"; this value is
used when preemption priority is not applicable.
The unification of PP values A and B attempts to provide the
highest priority (lowest value) which is supported by an ACCEPT
decision. The value 0 has no effect on the unified priority:
+----------------------+---------------------+
| A+B | IF... |
+----------------------+---------------------+
| MIN(A,B) | A!=0 and B!=0 |
| A | B=0 |
| B | A=0 |
| 0 (n/a) | A=0 and B=0 |
+----------------------+---------------------+
2.3 State Management
In order for policy objects contained in RSVP messages to be
processed quickly and correctly, it is often required that the
results of past policy decisions be cached and maintained at the
LPM or the policy server. During normal operations, the state
maintained in the client and in the server must remain consistent,
and must timeout at roughly the identical times in RSVP, the
client, and the server.
The most straightforward method for state maintenance is for the
LPM and the policy server to use the same soft-state mechanism as
the RSVP capable router. Unfortunately, this soft-state approach
has undesirable scaling properties since it requires the client to
contact the server on each refresh period (regardless of state
changes).
An alternative approach is to allow both client and server to use
hard-state mechanisms that could limit the client-server
communication to state updates only. To support the hard-state
mode, the client must be able to distinguish between repeats
(refreshes) and updates; it must also be able to translate the
soft-state that is provided by RSVP into the hard-state exchanged
with the server.
Thus, we envision one end of the spectrum where a "dumb" client
would use a soft-state approach and simply pass all policy objects
to the server relying on it for all policy processing. The rate
of queries and lack of caching at the client implies the need for
a dedicated, close-by server (PS-2, in our example). As we move
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towards the other extreme, clients become smarter, split the work
between themselves and the server, utilize caching capabilities.
Such clients could take advantage of the benefits of hard-state
management, and initiate queries only on actual state updates.
OOPS supports soft and hard state mechanisms seamlessly, as
described in this section. The client determines its desired type
of state management, and communicates it on an object-by-object
basis. A single client can use soft-state for some information,
and hard state for others. Furthermore, the OOPS protocol allows
clients to modify their caching strategies on the fly (without
having to renegotiate with the server). While the protocol does
not impose strategy limitations, a client implementation could
restrict itself to a more modest and simple combination of soft
and hard state.
There are two types of state information that is stored at the
client: (a) client state information that was forwarded to the
server (e.g., policy objects in incoming Path/Resv messages). (b)
server state which is cached at the client (e.g., policy results
computed by the server). The OOPS protocol addresses each of these
types of states separately:
2.3.1 Client State Information Cached at the Server
The client indicates its choice of state management approach by
setting (or resetting) the OOPS_HardState flag in objects sent
to the server. When the client chooses soft-state management,
policy state for that specific object ages and expires at the
server according to the specified timeout (refresh-period * K).
Therefore, the state cached at the server is kept alive by
constant refreshing (the client must forward ALL incoming RSVP
messages, whether or not they represent refreshes or updates).
On the other hand, when indicating a choice of hard-state
management, the client assumes responsibility for reliably
informing the server on every policy update. In this case, the
state cached at the server would not expire unless explicitly
modified by the client, or when the communication channel to
the client breaks. [Note 8]
The client may refrain from forwarding to the server any
repeat policy objects (which represent no updated information).
The client may switch between hard and soft states on the fly
_________________________
[Note 8] Clearly the channel breaks when either the client or server
become disfunctional or die.
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by modifying the OOPS_HardState flag while forwarding input to
the server.
2.3.2 Server State Information Cached at the Client
The client indicate its state management capabilities by
setting (or resetting) the OOPS_HardState flag in queries sent
to the server. A choice of soft-state indicates that the client
is incapable of caching, and it purges the server responses
after usage (one-time, or disposable results). Clearly, without
caching, the client must issue a new query each time that
responses are needed.
When the server responds to a cached (hard-state) query, it
assumes responsibility to reliably inform the client about any
changes that may occur later with the original response to this
query. The client may rely on cached results as long as there
is no change in RSVP's state (which includes incoming policy
objects), [Note 9]
and the communication channel with the server is intact.
The client may switch between hard and soft states on the fly
by issuing a new query with a modified flag.
2.3.3 State Change Notification
State change notification is done by resending the same type as
the original message but with the modified state instead.
Client notification example (incoming POLICY_DESC objects for
Resv-X):
_________________________
[Note 9] A configurable option may allow the client to use cached
results even when some RSVP state changes. There is a clear trade-off
here between fast and accurate policy processing, however, given that
the server is up, and that authorization was already granted previously
for that RSVP flow, some may find it a reasonable policy approach.
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TYPE DATA
---- ----
CLIENT ==> SERVER: NOTIFY:INPUT RESV-X: PD-1
Time passes; the input POLICY_DESC object associated with
Resv-X changed to PD-2.
CLIENT ==> SERVER: NOTIFY:INPUT RESV-X: PD-2
Server notification example (status query for reservation
Resv-X):
TYPE DATA
---- ----
CLIENT ==> SERVER: QUERY:STATUS Q_ASSOC=ID1, RESV-X
SERVER ==> CLIENT: RESP :STATUS Q_ASSOC=ID1, ACCEPT
Time passes; the status of Resv-X changed to "reject".
SERVER ==> CLIENT: RESP :STATUS Q_ASSOC=ID1, REJECT
2.3.4 State Re-synchronization
Both client and server may re-synchronize their respective
states at any time during the connection. The reset initiator
sends a Bye-Notification with a RESET code, and the receiver
responds with a Bye-Notification with the same code. After
this exchange, all cached state becomes soft, and a new logical
connection is reestablished (beginning with Connection-
Initiation-Query,...). New/hard state gradually replaces
old/soft state as described in Section 2.3.4.
2.4 Error Handling
We distinguish between two types of possible errors; policy errors
and protocol errors.
2.4.1 Protocol Errors
Protocol errors (e.g., missing or bad parameters) do not reveal
either positive or negative policy decisions and are therefore
neutral (represented as SNUBs). [Note 10]
_________________________
[Note 10] This neutrality allows, when appropriate, other valid sub-
policy elements to support an accept decision.
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It is recommended (although not required) that all local status
processing at the client be completed before querying the
server. This allows the server to immediately commit the
transaction rather than having to wait until the client is
done. (See the Client-Status-Notification Op-Code.)
Some OOPS protocol errors may only affect the OOPS protocol
processing or simply be logged. Other errors may escalate to
become policy errors (e.g., a bad POLICY_DESC is reported as a
policy error).
2.4.2 Policy Errors
Policy errors are reported in a sub-policy element specific
format. These elements are encapsulated in POLICY_DESC objects
and are forwarded toward the originator (cause) of the error.
In most cases, a negative Status-Response initiates an
automatic error response (e.g., RSVP ResvErr or PathErr),
however, OOPS allows reporting of other error situations by
scheduling an explicit error message (using the Protocol-
Message-Notification op-code). (See [Ext] for more about the
rules governing error reporting).
Consider a scenario where two receivers R1 and R2 listen to a
multicast transmission from S1. A reservation sent by R1 is
propagated upstream until it reaches node A, where it
encounters a policy rejection.
R1------------+
B--------------A----------- S1
/ \ |
R2------------+ \ |
\ |
PS1 PS2
Figure 3: An Error Reporting Scenario
The following table describes a subset of the relevant
signaling which begins with reservation initiation by R1 and R2
and ends by R1 receiving the appropriate error response.
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From/To Message Comments
________________________________________________________________________________
R1->B Resv [PD1]
R2->B Resv [PD2]
B->PS1 OOPS-Incoming-Policy-Query[PD1,PD2] ;B queries PS1
OOPS-Status-Query?
OOPS-Outgoing-Policy-Query? [Resv]
PS1->B OOPS-Status-Response: ACCEPT
OOPS-Outgoing-Policy-Response[PD3]
B->A Resv [PD3] ;B forwards the Resv to A
A->PS2 OOPS-Incoming-Policy-Query[PD3] ;A queries PS2
OOPS-Status-Query?
PS2->A OOPS-Status-Response: SNUB (reject) ;PS2 reject the reservation
A->PS2 OOPS-Outgoing-Policy-Query? [ResvErr] ;PS2 provides error PD
PS2->A OOPS-Outgoing-Policy-Response [PD1-E]
A->B ResvErr [PD1-E] ;A sends back ResvErr to B
B->PS1 OOPS-Incoming-Policy-Query[PD1-E]
OOPS-Outgoing-Policy-Query? [ResvErr] ;PS1 builds error PD
PS1->B OOPS-Outgoing-Policy-Response[PD1-E'],R1 ; (directed to R1 only)
B->R1 ResvErr [PD1-E'] ;B sends back ResvErr to R1
________________________________________________________________________________
Figure 4: Error Reporting Signaling
All error information is carried in POLICY_DESC objects (as
sub-policy elements). OOPS server may read and modify this
information along the ResvErr path; it may also direct the
error responses only to the relevant branches of the reserved
tree (in this scenario, the error is associated with R1 but not
with R2).
3. Client-Server Connection
The following section describes the fundamentals of client-server
connection: establishment, channel, and termination.
3.1 Connection Establishment
OOPS uses a well known port number (OOPS = 3288) for incoming
connection requests. Usually, the client would attempt to
establish a TCP connection to its preferred policy server,
however, both client and server listen to the OOPS port. [Note 11]
_________________________
[Note 11] New (or recovering) policy servers are allowed to notify
clients on their existence by issuing a TCP connection request to the
client's OOPS port number.
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Regardless of who initiated the TCP connection, once the
connection is in place, the OOPS logical connection establishment
is always initiated by the client and is performed through a two
way handshake.
o Communication Initiation by the Client
The client sends a Connection-Initiation-Query to the server.
This message identifies the client to the server and provides
the basic characteristics of the client as well as a list of
policy responses that are acceptable to the client. This list
is in decreasing order of acceptability, and terminates with
the default element.
o Response by the Server
The server responds with a Connection-Accept-Response to
connect to the client. It may also respond with a
Connection-Reject-Response to refuse and disconnect from the
client.
After connection establishment both the client and server
know the set of sub-policies that the client can send to the
server, which one of them should handle default
(unrecognized) sub-policies, as well as the format of status
responses from server to client. They also establish the
Channel-Hold period which is determined as the minimum
between the two values declared in the handshake messages,
but must be at least 3 seconds.
3.1.1 Reliable Communication
We expect TCP to provide us with reliable, in-order delivery of
packets. Given that TCP is responsible for all the time
critical network operations, reliability errors are assumed to
be virtually nonexistent.
3.1.2 Secure Communications
OOPS relies on standard protocols for security of client-server
communications. An emerging standard protocol IPSEC [IPSEC] is
the mechanism of choice for ensuring either integrity or
secrecy. The use of IPSEC and/or other security protocols is
transparent to OOPS.
3.2 Connection Termination
This section describes the handling of communication breakdown.
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3.2.1 Implicit Termination
The communication channel may be unexpectedly disconnected
because of a misbehaving client or server, network split, or
for other reasons. Both client and server must be able to
detect such channel failures and act accordingly. Consider the
case where OOPS is used for quota enforcement. The server may
approve a reservation while debiting X/min from a local
account. If the OOPS communication channel breaks, it is
critical for the server to detect the break and stop debiting
this account.
The OOPS protocol relies on Keep-Alive messages to provide
application-level communication-channel verification. [Note 12]
Implicitly, the communications channel is assumed to be
disconnected after it has been idle (no message was received on
it) for more than a Channel-Hold period (see Section 3.1).
Keep-Alive messages are sent by both client and server as
needed [Note 13]
to ensure the liveness of the connection (to prevent a
Channel-Hold timeout). Keep-Alive messages are not
acknowledged.
3.2.2 Explicit Termination
The client (or server) may terminate the connection by sending
a Bye-Notification, and wait until either it receives an echoed
Bye-Notification or the Channel-Hold period had passed. In
between, it should ignore incoming messages (and not reset the
Channel-Hold timer).
At the opposite side, when a client (or server) receive a Bye-
Notification message, it should echo it, and close the
connection.
_________________________
[Note 12] OOPS implementations may utilize system dependent mechanisms
for detecting broken TCP connections, but does not rely on them. This is
especially important since a server may be in a dysfunctional state
while its TCP connection is still open and viable.
[Note 13] When the intermediate period in between two OOPS messages
approaches the Channel-Hold time.
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3.2.3 Post Termination
Soft-state has an inherent cleanup mechanism; when the channel
disconnects, the soft-state begins to age until it eventually
expires (using the same mechanism and refresh-period * K used
by RSVP).
In contrast, hard-state is assumed to be valid unless
explicitly modified. However, when the channel disconnects such
an explicit notification is not possible. Clearly, purging all
state immediately upon disconnection is not an acceptable
approach since should cause disruption of service and would not
allow enough time to contact an alternate server. OOPS uses
the following simple rule:
When the communication channel disconnects, all hard state
associated with it is assumed to be soft-state that had been
refreshed recently.
3.2.4 Switching to An Alternative Server
We assume that as part of their local configuration, clients
obtain a list of policy servers and site specific selection
criteria. This list can be the basis for server switching
decisions.
A switch to an alternate server may be triggered by a voluntary
disconnection (i.e., Bye-Notification) or an unexpected break
in the communication channel. During normal operations, the
client may wish to switch to an alternate server (for any
reason). The client is advised to first connect to the new
server before sending a Bye-Notification to the original one.
If the communication channel unexpectedly disconnects, the
client should quickly attempt to connect to an alternate
server.
In both cases, after the connection to a new server [Note 14]
is established, the aging cached state from the old server
would be gradually replaced by responses from the new server.
[Note 15]
_________________________
[Note 14] The term "new server" may be the same as the "previous
server"; it may happen that the connection encounters a problem and the
client chooses to disconnected and re-established the connection.
[Note 15] The client could speed-up replacement of cached state by
sending copies of cached input to the server and issuing repeated
queries, on connection establishment (instead of waiting until objects
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As general guidelines, state replacement from a new server
should not cause a disruption of service that would not
otherwise occur (if a new server was not found). [Note 16]
After switching to an alternate server, the client may
periodically poll its old (preferred) server by attempting a
TCP connection to its OOPS port. Similarly, a new (or recovered
server) may notify clients about its liveness by attempting to
connect to their OOPS port. In the latter case, clients may
disconnect the TCP connection or respond with a Connection-
Initiation-Query as if the client initiated the connection in
the first place. [Note 17]
%% TOO EARLY: WE SHOULD PUT IT IN THE NEXT VERSION (02)
%% ----------------------------------------------------
%%The client may choose to use both the main and the alternate
servers
%%in tandem. In this case, the client would send inputs and
updates to
%%both servers, but will make status and outgoing-policy
queries only
%%to the main server. Given that both servers have the same
state image,
%%a switch between them could be fast without causing
disruption of
%%service.
4. OOPS Message Format
OOPS messages serve as a wrapper that may include one or more Op-
Codes; the message wrapper allows common operation (e.g., MD5
integrity, HOP_DESCs, protocol version, etc.) to be performed and
verified in one-shot. All OOPS messages are composed of the following
fields:
_________________________
arrive from RSVP).
[Note 16] Practically, this means that as long as there is no change in
RSVP messages, the client is advised to choose between cached and new
results in favor of authorizing the request.
[Note 17] Future version of this document may include the use of
multicast to advertise the liveness of servers.
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+---------------+---------------+---------------+---------------+
| Ver | #Op-Codes | Flags | ////// |
+---------------+---------------+---------------+---------------+
| Message Length |
+---------------+---------------+---------------+---------------+
| Message Sequence Number |
+---------------+---------------+---------------+---------------+
| OOPS_MSG_AUTH (Optional) |
+---------------+---------------+---------------+---------------+
| List of Op-Codes... |
+---------------+---------------+---------------+---------------+
Version: 8 bits
Protocol version number. The current version is 1.
Flags: 8 bits
0x01 H_Integrity_Checked POLICY_DESC Integrity already checked by client
0x02 H_Hops_Checked Prev/Next HOPs already checked by client
#Op-Codes: 8 bits
Number of Op-Codes included in this message.
Message Length: 32 bits
The total length of this OOPS message in bytes.
Message Sequence Number: 32 bits
The sequence number of the message being sent.
OOPS_MSG_AUTH (optional): variable length
This Message Authenticator provides integrity verification based
on a shared-keyed message digest. The message digest is
calculated over the entire OOPS message.
There is only one object format currently defined is identical
to the RSVP INTEGRITY object (defined in [Bak96]).
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List of OOPS operation codes (Op-Codes): variable length
Described in the following section.
4.1 OOPS Operation Codes (Op-Codes)
Each OOPS message may contain multiple OOPS operations each
encapsulating a different query, response or notification. For
example, multiple Incoming-Policy-Queries might be followed by a
Status-Query operation in the same message.
Individual OOPS Op-Codes have the following header:
+---------------+---------------+---------------+---------------+
| Operation Code| Op. Subtype | Flags | ////// |
+---------------+---------------+---------------+---------------+
| Length (bytes) |
+---------------+---------------+---------------+---------------+
| Refresh Period |
+---------------+---------------+---------------+---------------+
The operation header has the following fields:
operation Code: 8 bits
The type of OOPS operation.
Operation Subtype: 8 bits
This field can be used to indicate an attribute of the Op-
Code, such as its version; currently it is always set to 1.
Flags: 8 bits
0x01 OOPS_HardState: Hard State (soft-state if not set (0) )
0x02 OOPS_Shared : Resv shared among sources as filter specs
0x02 OOPS_FullList : Last in the set of status queries.
Length: 32 bits
Contains the total operation length in bytes (including
header).
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Refresh Period
The refresh-period associates with this object (e.g., RSVP's
refresh period).
The remainder of this section describes the set of operations that
may appear in OOPS messages and their object format. OOPS does
not bind itself to a particular protocol (i.e., RSVP) and is built
around objects that may belong to different (other) protocols. The
current draft is based on the assumption that RSVP would be one
(the first) of these protocols and thus, the draft provides the
appropriate RSVP objects format.
4.1.1 Null-Notification (a.k.a Keep-Alive)
Operation Type = 0, sub-type = 1
<Null-Notification> ::= <Common OOPS header>
This empty or null notification triggers no operation; thus,
can be used as as Keep-Alive signal to test the viability of
the communication channel between client and server (see
Section 3.2.1).
4.1.2 Connection-Initiation-Query
Operation Type = 1, sub-type = 1
<Connection-Initiation-Query> ::= <Common OOPS header>
<CONNECT_DESC>
<CLASS_ID>
<CLIENT_ID>
<RESP_INT>
<COOKIE>
The client sends this query to establish a connection with a
server. This message is sent following the establishment of a
transport connection (TCP).
o CONNECT_DESC
Description of connection parameters.
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o CLASS_ID
The client's class provides an implicit description of the
client's capabilities and requirements; the CLASS_ID is an
index into the class list maintained by the server; it is
used in conjunction with the CLIENT_ID.)
o CLIENT_ID
The network address of the client. From the combination
of CLIENT_ID and CLASS_ID the server can learn about the
set of sub-policies it is required to support for this
particular client; it can also learn which of these sub-
policies are optional and which are mandatory.
o RESP_INT
A list of possible response interfaces.
o COOKIE
4.1.3 Connection-Accept-Response
Operation Type = 2, sub-type = 1
<Connection-Accept-Response> ::= <Common OOPS header>
<CONNECT_DESC>
<PLIST>
<RESP_INT>
<COOKIE>
The server sends this response to accept a client's connection
connection request.
o CONNECT_DESC
o PLIST
Each "From Policy m" and "To Policy m" pair represent a
range of sub-policies that the server is willing to
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support.
o RESP_INT
The chosen (agreed upon) status response interface.
o COOKIE
4.1.4 Connection-Reject-Response
Operation Type = 3, sub-type = 1
<Connection-Reject-Response> ::= <Common OOPS header>
<ERR_DESC>
The server sends this response to reject a client's connection
initiation. It specifies both reason code and text.
4.1.5 Bye-Notification
Operation Type = 4, sub-type = 1
<Bye-Notification> ::= <Common OOPS header>
<BYE_DESC>
[<ERR_DESC>]
This message is used by either client or server to terminate
the OOPS connection.
o BYE_DESC
(Section 3.2.2 includes a description of explicit termination
using Bye-Notification)
4.1.6 Incoming-Policy-Query
Operation Type = 5, sub-type = 1
<Incoming-Policy-Query> ::= <Common OOPS header>
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<Q_ASSOC>
<PROT_MSG_TYPE>
<DST_DESC>
<SRC_DESC list>
<HOP_DESC>
[<ADV_DESC>]
<POLICY_DESC list>
This operation is used to forward POLICY_DESC objects from the
client to the server. Selection between hard and soft state
management is reflected in the OOPS_HardState flag. The other
fields are copied from the PC_InPolicy() function called by
RSVP. (See [Ext]).
4.1.7 Incoming-Policy-Response
Operation Type = 6, sub-type = 1
<Incoming-Policy-Response> ::= <Common OOPS header>
<Q_ASSOC>
<ERR_DESC>
Incoming-Policy-Response is used ONLY to report protocol errors
(e.g., syntax) found with incoming policy objects. (it is not
used in the normal operation of the protocol).
4.1.8 Outgoing-Policy-Query
Operation Type = 7, sub-type = 1
<Outgoing-Policy-Query> ::= <Common OOPS header>
<Q_ASSOC>
<PROT_MSG_TYPE>
<DST_DESC>
<SRC_DESC list>
<HOP_DESC list>
This operation queries the server for a set of outgoing policy
objects for a set of HOP_DESCs. The client can choose between
hard and soft state management through the OOPS_HardState flag.
When hard state is selected, the client caches copies of the
outgoing objects and assumes they remain valid unless
explicitly modified by the server.
4.1.9 Outgoing-Policy-Response
Operation Type = 8, sub-type = 1
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<Outgoing-Policy-Response> ::= <Common OOPS header>
<Q_ASSOC>
{ <HOP_DESC>
<ERR_DESC> or <POLICY_DESC>
} pairs list
The <Query Sequence Number> links the response to the original query.
In the response, the server provides a list of triplets, one
for each outgoing HOP_DESC (For Path messages, only the LIH
part is significant). Each triplet contains a list of policy
objects for that hop and an error description.
The OOPS server can block an outgoing RSVP message by replacing
the outgoing POLICY_DESC list for a particular HOP_DESC with an
<Error-Description> with an appropriate value.
The ability to block outgoing RSVP control messages is
especially useful when policy is enforcement is performed at
border nodes of a network; RSVP control messages that are
allowed through are capable of installing state at internal
nodes without being subject to further policy control.
4.1.10 Status-Query
Operation Type = 9, sub-type = 1
<Status_Query> ::= <Common OOPS header>
<Q_ASSOC>
<PROT_MSG_TYPE>
<DST_DESC>
<SRC_DESC list>
{ <HOP_DESC>
<QOS_DESC>
} triplets list
This operation queries the server for status results of a list
of LIHs. The client can choose between hard and soft state
management through the OOPS_HardState flag. When hard state is
selected, the client caches the status results and assumes they
remain valid unless explicitly modified by the server.
In the upstream direction (e.g., Resv) status may need to be
checked on multiple LIHs (all reservations for a flow). In such
cases, status queries can be perform separately for each LIH,
once for all LIHs, or anything in between. Flag OOPS_FullList
must be set at the last of status query of the series. [Note 18]
_________________________
[Note 18] When sub-policies are interdependent across LIHs (as when the
cost is shared among downstream receivers), flag OOPS_FullList notifies
the server that the list of reserved LIH is complete and that it can
safely compute the status of these reservations.
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4.1.11 Status-Response
Operation Type = 10, sub-type = 1
<Status-Response> ::= <Common OOPS header>
<Q_ASSOC>
{ <HOP_DESC>
<STATUS_DESC>
[<ERR_DESC>]
} triplet list
The <Q_ASSOC> links the response to the original query.
In the response, the server provides a list of triplets, each
of which contains an LIH, status, and any applicable error
results. The set of LIHs is an attribute of the results and
not of the query; the server is allowed to respond with a
superset of LIHs specified in the original query, as in the
following example:
SEQ# TYPE DATA
--- ---- ----
Client ==> Server: 150 Query:status Q_ASSOC=ID2, Resv-X, LIH={2}
Server ==> Client: 153 Resp :status Q_ASSOC=ID2, {2,rej}
Two new reservations arrive, carrying new policy data objects:
Client ==> Server: 160 Query:status Q_ASSOC=ID3, Resv-X, LIH={4,7}
Server ==> Client: 169 Resp :status Q_ASSOC=ID3, {2,acc;4,acc;7,rej}
4.1.12 Delete-State-Notification
Operation Type = 11, sub-type = 1
<Delete-State-Notification> ::= <Common OOPS header>
<STATE_OP_DESC>
<DST_DESC>
[<PROT_MSG_TYPE>]
[<SRC_DESC list>]
[<HOP_DESC>]
[<ERR_DESC>]
o STATE_OP_DESC
This object describes the type of requested operation (see
Appendix A).
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This operation informs the sender about an immediate RSVP
teardown of state caused by PATH_TEAR, RESV_TEAR, routes
change, etc. As a result, the server should ignore the
described state as if it was never received from the client.
Despite its name, this operation can be used to switch between
blockaded and non-blockaded state.
The semantics of this operation is described for PC_DelState()
in [Ext].
Error description is used to provide the server with a reason
for the delete (for logging purposes).
4.1.13 Protocol-Message-Notification
Operation Type = 12, sub-type = 1
<Protocol-Message-Notification> ::= <Common OOPS header>
<PROT_MSG_TYPE>
<DST_DESC>
<SRC_DESC list>
<HOP_DESC>
The operation results in the generation of an outgoing protocol
message (e.g., RSVP's Path, Resv). The client should schedule
the requested message to the specified HOP_DESC.
4.1.14 Client-Status-Notification
Operation Type = 13, sub-type = 1
<Client-Status-Notification> ::= <Common OOPS header>
<Q_ASSOC>
<STATUS_DESC>
The Client notifies the server about the status results
computed at the client (that may also include results from
other servers, if policy computation is spread among several
servers).
The overall status of an RSVP flow is computed by merging the
client's status report with the server's. The server should not
commit a transaction (e.g., charge an account) before knowing
its final status. The Client-Status-Results operation can be
sent with the query, if the client computed its status prior to
making the query. It can also be sent later, after the server
sent its response to the status query.
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4.1.15 Error-Notification
Operation Type = 14, sub-type = 1
<Message-Error-Notification> ::= <Common OOPS header>
<Message-Sequence-Number>
<ERR_DESC>
Message-Error-Notification can be used by either client or
server to report errors associated with an entire message (as
opposed to a specific operation). Error-Notification may be
triggered by both syntax or substantive errors (e.g., failure
to verify the integrity of the message).
<Message-Sequence-Number> identified the message that triggered
the error. It uses identical format to the one used by the OOPS
message header.
Message-Error-Notification is not acked.
5. Acknowledgment
This document reflects feedback from Paul Amsden, Fred Baker, Lou
Berger, Bob Braden, Ron Cohen, Deborah Estrin, Steve Jackowski, Tim
O'Malley, Claudio Topolcic, Raj Yavatkar, and many other IPC and RSVP
collaborators,
6. Authors' Address
Shai Herzog Phone: (917) 318-7938
IP"Highway" Email: herzog@iphighway.com
Dimitrios Pendarakis Phone: (914) 784-7536
Email: dimitris@watson.ibm.com
Raju Rajan Phone: (914) 784-7260
Email: raju@watson.ibm.com
Roch Guerin Phone: (914) 784-7038
Email: guerin@watson.ibm.com
IBM T. J. Watson Research Center
P.O. Box 704
Yorktown Heights, NY 10598
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7. References
References
[IPSEC] R. Atkinson, Security Architecture for the Internet Protocol,
"RFC1825", Aug. 1997.
[Bak96] F. Baker. RSVP Cryptographic Authentication "Internet-Draft",
draft-ietf-rsvp-md5-02.txt, 1996.
[RSVPSP] R. Braden, L. Zhang, S. Berson, S. Herzog, and S. Jamin,
Resource ReSerVation Protocol (RSVP) Version 1 Functional
Specification. "Internet-Draft", draft-ietf-RSVPSP-14.[ps,txt],
Nov. 1996.
[Arch] S. Herzog Accounting and Access Control Policies for Resource
Reservation Protocols. "Internet-Draft", draft-ietf-rsvp-policy-
arch-01.[ps,txt], Nov. 1996.
[LPM] S. Herzog Local Policy Modules (LPM): Policy Enforcement for
Resource Reservation Protocols. "Internet-Draft", draft-ietf-rsvp-
policy-lpm-01.[ps,txt], Nov. 1996.
[Ext] S. Herzog RSVP Extensions for Policy Control. "Internet-Draft",
draft-ietf-rsvp-policy-ext-02.[ps,txt], Apr. 1997.
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A Appendix: OOPS Objects
This section describes objects that are used within OOPS OP-Codes. All
objects have a common header:
+---------------+---------------+---------------+---------------+
| Length | Class | C-Type |
+---------------+---------------+---------------+---------------+
Length describes the length of the entire object, in bytes. Class
describes the type of object and C-Type describes the a class sub-type.
o CLASS_ID class
- Class = 1, C-Type = 1
+---------------+---------------+---------------+---------------+
| ASCII String ........ 0 Padded to multiples of 32 bits |
+---------------+---------------+---------------+---------------+
o CLIENT_ID class
- Class = 2, C-Type = 1
A Network Address.
+---------------+---------------+---------------+---------------+
| IPv4 Address |
+---------------+---------------+---------------+---------------+
- Class = 2, C-Type = 2
+---------------+---------------+---------------+---------------+
| IPv6 Address |
| |
| |
| |
+---------------+---------------+---------------+---------------+
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From the combination of Client-ID and Class-Indicator the server
can learn about the set of sub-policies it is required to support
for this particular client; it can also learn which of these sub-
policies are optional and which are mandatory.
o RESP_INT class
- Class = 3, C-Type = 1
+---------------+---------------+---------------+---------------+
| Most-Prefered |..... | | |
+---------------+---------------+---------------+---------------+
| | Least-Pref. |...0 Padded to 32 bit multiples|
+---------------+---------------+---------------+---------------+
o COOKIE class
- Class = 4, C-Type = 1
Currently, no values are defined.
o PLIST class
- Class = 5, C-Type = 1
+---------------+---------------+---------------+---------------+
| Number (or pairs) | ////// |
+---------------+---------------+---------------+---------------+
| From Policy 1 | To Policy 1 |
+---------------+---------------+---------------+---------------+
+---------------+---------------+---------------+---------------+
| From Policy n | To Policy n |
+---------------+---------------+---------------+---------------+
Each "From Policy m" and "To Policy m" pair represent a range of
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sub-policies that the server is willing to support.
o ERR_DESC class
- Class = 6, C-Type = 1
+---------------+---------------+---------------+---------------+
| Error-Code | ////// | Reason Code |
+---------------+---------------+---------------+---------------+
| Error ASCII String .... 0 Padded to multiples of 32 bits |
+---------------+---------------+---------------+---------------+
Detailed Error-Code and Reason-Codes would be defined in future
versions of this document.
o Q_ASSOC class
- Class = 7, C-Type = 1
+---------------+---------------+---------------+---------------+
| Client-Specific Semantics |
// (Variable Length) //
| |
+---------------+---------------+---------------+---------------+
The client-specific contents of this object is opaque to the
server; it is set by the client for a query and is echoed by
the server as-is. The client must store enough information
there that will enable it to uniquely identify the original
query when the response arrive. This must at least include a
counter to identify the version of the latest query. [Note 19]
_________________________
[Note 19] A simple association could be the combination of a pointer to
an internal client (router) control-block that describes the query, and
a query version counter.
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o PROT_MSG_TYPE class
- Class = 8, C-Type = 1
+---------------+---------------+---------------+---------------+
| RSVP MSG TYPE |
+---------------+---------------+---------------+---------------+
Values specified in [RSVPSP].
o DST_DESC class
- Class = 9, C-Type = 1
The RSVP SESSION object as defined in [RSVPSP].
o SRC_DESC class
- Class = 10, C-Type = 1
The RSVP FILTER_SPEC object as defined in [RSVPSP].
o HOP_DESC class
- Class = 11, C-Type = 1
The RSVP_HOP object as defined in [RSVPSP].
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o ADV_DESC class
- Class = 12, C-Type = 1
The RSVP ADSPEC object as defined in [RSVPSP].
o QOS_DESC class
- Class = 13, C-Type = 1
The RSVP FLOWDESC object as defined in [RSVPSP].
o POLICY_DESC class
- Class = 14, C-Type = 1
The RSVP POLICY_DATA object as defined in [Ext] and [RSVPSP].
o OOPS_MSG_AUTH class
- Class = 15, C-Type = 1
The RSVP INTEGRITY object as defined in [RSVPSP] and [Bak96].
o STATUS_DESC class
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- Class = 16, C-Type = 1
+---------------+---------------+---------------+---------------+
| Results | Priority | ////// |
+---------------+---------------+---------------+---------------+
Results may have one of the following values:
1 : Accept
2 : Snub
3 : Veto
Priority ranges between 1..255 (see 2.2.3).
o CONNECT_DESC class
- Class = 17, C-Type = 1
This object describes the OOPS connection parameters; in the
Connection-Accept-Response, the refresh-multiplier is an echo
of the value received with the Connection-Initiation-Query.
+---------------+---------------+---------------+---------------+
| Version | Flags | Refresh-Mult. | ////// |
+---------------+---------------+---------------+---------------+
| Max-Msg-Size (in KBytes) | Channel-Hold period (in sec.) |
+---------------+---------------+---------------+---------------+
Ver: 8 bits
Currently, version 1.
Flags:
0x01 OOPS_CONNECT_DefaultC Client handles default sub-policies.
Refresh-Mult.:
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The refresh-period multiplier (e.g., RSVP's K value).
Max-Msg-Size: Upper limit on the length of an OOPS message
Channel-Hold period: Implicit disconnection timeout
o BYE_DESC class
- Class = 18, C-Type = 1
BYE_DESC provides details about the Bye-Notification request.
+---------------+---------------+---------------+---------------+
| Bye-Flags | ////// | BYE_DELAY (seconds) |
+---------------+---------------+---------------+---------------+
Bye-Flags:
0x01 An echo (response) to a received Bye-Notification
The BYE_DELAY could provide both sides with some time delay to
be better prepared to a pending bye. [Note 20]
The delay value is determined by the originator of the bye-
notification, and is echoed in the bye response. The delay
effect should be as if the Bye-Notification was sent BYE_DELAY
seconds later with a delay timer value of 0.
o STATE_OP_DESC class
- Class = 19, C-Type = 1
_________________________
[Note 20] Similar to the delayed shutdown command known in Unix.
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+---------------+---------------+---------------+---------------+
| Op-Type | ////// |
+---------------+---------------+---------------+---------------+
Op-Type values:
1 : Delete State
2 : Block State
3 : Unblock State
B Appendix: Error Codes
This appendix describes an initial list of error codes available in
OOPS, as well as the set of Reason Codes for each error code. (Reason
Code of 0 must be used when Reason Codes are not applicable). This list
should evolve and not be considered conclusive. [Note 21]
o Code = 1, Connection Management
1: Connection Reject: Server does not support client version.
2: Bye: Reset due to routine state re-synchronization
3: Bye: Reset due to connection problems (Bad message formats)
o Code = 2, Protocol problems
1: Syntax: Bad OOPS message
2: Syntax: Bad OOPS Op-Code
3: Syntax: Bad POLICY_DESC format
o Code = 3, Policy Decisions
1: Don't forward: refrain from forwarding an outgoing message.
2: Policy Reject: cancel protocol operation (Reservation, path, etc.)
o Code = 4, State Management
1: Delete State: Reservation Canceled
2: Delete State: route change
3: Delete State: State Timeout
4: Blockade State
5: Unblock State
Shai Herzog et al. Expiration: Oct. 1997 [Page 38]
