Network Working Group Chris Weider, Microsoft
INTERNET DRAFT Andy Herron, Microsoft
Expire in six months Tim Howes, Netscape
February, 1997
LDAP Control Extension for Simple Paged Results Manipulation
draft-ietf-asid-ldapv3-simplepaged-00.txt
1. Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working docu-
ments 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).
2. Abstract
This document describes an LDAPv3 control extension for simple paging of
search results. This control extension allows a client to control the
rate at which an LDAP server returns the results of an LDAP search
operation. This control may be useful when the LDAP client has limited
resources and may not be able to process the entire result set from a
given LDAP query, or when the LDAP client is connected over a low-
bandwidth connection. Other operations on the result set are not defined
in this extension. This extension is not designed to provide more
sophisticated result set management.
The key words "MUST", "SHOULD", and "MAY" used in this document are to
be interpreted as described in [bradner97].
3. The Control
This control is included in the searchRequest and searchResultDone mes-
sages as part of the controls field of the LDAPMessage, as defined in
Section 4.1.12 of [LDAPv3]. The structure of this control is as follows:
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INTERNET DRAFT February 1997
pagedResultsControl ::= SEQUENCE {
controlType 1.2.840.113556.1.4.319,
criticality BOOLEAN DEFAULT FALSE,
controlValue searchControlValue
}
The searchControlValue is an OCTET STRING wrapping the BER-encoded ver-
sion of the following SEQUENCE:
realSearchControlValue ::= SEQUENCE {
size INTEGER (0..maxInt),
-- requested page size from client
-- result set size estimate from server
cookie OCTET STRING
}
4. Client-Server Interaction
An LDAP client application that needs to control the rate at which
results are returned MAY specify on the searchRequest a pagedResultsCon-
trol with size set to the desired page size and cookie set to the zero-
length string. The page size specified MAY be greater than zero and less
than the sizeLimit value specified in the searchRequest.
If the page size is greater than or equal to the sizeLimit value, or
equal to zero, the server should ignore the control as the request can
be satisfied in a single page. If the server does not support this con-
trol, the server MUST return an error of unsupportedCriticalExtension if
the client requested it as critical, otherwise the server SHOULD ignore
the control. The remainder of this section assumes the server does not
ignore the client's pagedResultsControl.
Each time the server returns a set of results to the client when pro-
cessing a search request containing the pagedResultsControl, the server
includes the pagedResultsControl control in the searchResultDone mes-
sage. In the control returned to the client, the size MAY be set to the
server's estimate of the total number of entries in the entire result
set. Servers that cannot provide such an estimate MAY set this size to
zero (0). The cookie MUST be set to an empty value if there are no more
entries to return (i.e., the page of search results returned was the
last), or to an octet string of the server's choosing, used to resume
the search.
The client MUST consider the cookie to be an opaque structure and make
no assumptions about its internal organization or value. When the client
wants to retrieve more entries for the result set, it MUST send to the
server a searchRequest with all values identical to the initial request
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with the exception of the messageID, the cookie, and optionally a modi-
fied pageSize. The cookie MUST be the octet string on the last sear-
chResultDone response returned by the server. Returning cookies from
previous searchResultDone responses besides the last one is undefined,
as the server implementation may restrict cookies from being reused.
The server will then return the next set of results from the whole
result set. This interaction will continue until the client has
retrieved all the results, in which case the cookie in the searchResult-
Done field will be empty, or the client abandons the result. If, for
any reason, the server cannot resume a paged search operation for a
client, then it SHOULD return the appropriate error in a searchResult-
Done entry. If this occurs, both client and server should assume the
paged result set is closed and no longer resumable.
A client may have any number of outstanding search requests pending, any
of which may have used the pagedResultsControl. A server implementation
which requires a limit on the number of outstanding paged search
requests from a given client MAY either return unwillingToPerform when
the client attempts to create a new paged search request, or age out an
older result set. If the server implementation ages out an older paged
search request, it SHOULD return "unwilling to perform" if the client
attempts to resume the paged search that was aged out.
A client may safely assume that all entries that satisfy a given search
query are returned once and only once during the set of paged search
requests/responses necessary to enumerate the entire result set, unless
the result set for that query has changed since the searchRequest start-
ing the request/response sequence was processed. In that case, the
client may receive a given entry multiple times and/or may not receive
all entries matching the given search criteria.
5. Example
The following example illustrates the client-server interaction between
a client doing a search requesting a page size limit of 3. The entire
result set returned by the server contains 5 entries.
Lines beginning with "C:" indicate requests sent from client to server.
Lines beginning with "S:" indicate responses sent from server to client.
Lines beginning with "--" are comments to help explain the example.
-- Client sends a search request asking for paged results
-- with a page size of 3.
C: SearchRequest + pagedResultsControl(3,"")
-- Server responds with three entries plus an indication
-- of 5 total entries in the search result and an opaque
-- cooking to be used by the client when retrieving subsequent
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-- pages.
S: SearchResultEntry
S: SearchResultEntry
S: SearchResultEntry
S: SearchResultDone + pagedResultsControl(5, "opaque")
-- Client sends an identical search request (except for
-- message id), returning the opaque cooking, asking for
-- the next page.
C: SearchRequest + PagedResultsControl(3, "opaque")
-- Server responds with two entries plus an indication
-- that there are no more entries (null cookie).
S: SearchResultEntry
S: SearchResultEntry
S: SearchResultDone + pagedResultsControl(5,"")
6. Security Considerations
Security considerations are not discussed in this document.
7. References
[LDAPv3]
Wahl, M, S. Kille and T. Howes, "Lightweight Directory Access Pro-
tocol (v3)", Internet Draft, February, 1997. Available as draft-
ietf-asid-ldapv3-protocol-04.txt.
[Bradner97]
Bradner, Scott, "Key Words for use in RFCs to Indicate Requirement
Levels", Internet Draft, January, 1997. Available as draft-
bradner-key-words-03.txt.
8. Author's Address
Chris Weider
Microsoft Corp.
1 Microsoft Way
Redmond, WA 98052
USA
cweider@microsoft.com
+1 206 882-8080
Andy Herron
Microsoft Corp.
1 Microsoft Way
Redmond, WA 98052
USA
andyhe@microsoft.com
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+1 206 882-8080
Tim Howes
Netscape Communications Corp.
501 E. Middlefield Road
Mountain View, CA 94043
USA
howes@netscape.com
+1 415 937-2600
Weider, Herron & Howes [Page 5]
