Internet DRAFT - draft-zheng-netconf-fragmentation
draft-zheng-netconf-fragmentation
Netconf G. Zheng
Internet-Draft M. Wang
Intended status: Informational Huawei
Expires: December 28, 2018 June 26, 2018
A NETCONF Extension for Data Fragmentation
draft-zheng-netconf-fragmentation-02
Abstract
This document introduces an extension to NETCONF (Network
Configuration) protocol. The extension allows NETCONF to handle
large size data as fragmented RPC messages. Specifically, this
document defines a new <get-block> capability and relevant operations
to handle the fragmentations.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on December 28, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Zheng & Wang Expires December 28, 2018 [Page 1]
Internet-Draft Netconf Fragmentation June 2018
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Concept and Terminology . . . . . . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. Current Large size Handling Methods and Problems . . . . . . 3
3.1. Stream-Oriented Handling . . . . . . . . . . . . . . . . 3
3.2. Requesting a Portion of Data . . . . . . . . . . . . . . 4
3.3. Using tools to extract data respectively . . . . . . . . 4
4. Netconf Fragmentation Mechanism . . . . . . . . . . . . . . . 5
4.1. Fragmentation Requirements . . . . . . . . . . . . . . . 5
4.2. <get-block> extention . . . . . . . . . . . . . . . . . . 5
5. YANG data model . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Normative References . . . . . . . . . . . . . . . . . . . . 8
Appendix A. Appendix A: Examples of the Candidate Solutions . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
NETCONF [RFC6241] is the next generation network management protocol
for configuring devices. It is becoming more and more popular, and
some NMS (Network Management System) only use NETCONF as its
southbound interface. The message procedures of NETCONF are based on
RPC (Remote Procedure Call) interactions. A NETCONF client/server
sends a <rpc> message to the counterpart and then receives a replying
<rpc-reply> message.
In some situations, the <rpc-reply> message might be very large. For
example, when NMS is retrieving a large amount of routes in a core
router or doing a full-synchronizing with a device, the <rpc-reply>
data might exceed Mega-Byte amount. And also in some scenarios, the
client may retrieve a continuous stream of operational data from the
operational datastore [I-D.ietf-netmod-revised-datastores] to perform
network analytics. Then there comes the problem of how to handle the
large size data. This document briefly introduces two typical ways
of current handling on this issue; and analyzes the problems of them.
To fix the problems, in Section 4, this document proposes a method of
extending the NETCONF protocol to allow handling large size data as
fragmented <rpc-reply> messages. The fragmentation is done at the
NETCONF level, so it allows the NETCONF client to terminate the large
size data processing momentarily by protocol interactions; and also
allows the fragmented messages to be instantly parsed piece by piece.
Specifically, the fragmentation is achieved through a newly defined
<get-block> capability and relevant operations.
Zheng & Wang Expires December 28, 2018 [Page 2]
Internet-Draft Netconf Fragmentation June 2018
2. Concept and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2.1. Terminology
DOM: Document Object Model, which is a cross-platform and language-
independent convention for representing and interacting with objects
in HTML, XHTML and XML documents. Objects in the DOM tree may be
addressed and manipulated by using methods on the objects.
SAX: Simple API for XML, which is an event sequential access parser
API developed by the XML-DEV mailing list for XML documents. SAX
provides a mechanism for reading data from an XML document that is an
alternative to that provided by the DOM. Where the DOM operates on
the document as a whole, SAX parsers operate on each piece of the XML
document sequentially.
libxml: a software library for parsing XML documents.
<get-block>: a capability and operation defined in this document to
handle large size
3. Current Large size Handling Methods and Problems
3.1. Stream-Oriented Handling
Stream-Oriented handling mainly includes the following two aspects:
o The server encapsulates the large size replying data in a <rpc-
reply> message and streams it to the client through TCP protocol.
o The client parses the received <rpc-reply> content in a stream-
oriented way. More specifically, the client could utilize SAX to
instantly parse the received content without waiting for the whole
message been transported.
Problems:
o Stream-Oriented method lacks the capability of discontinuing
large size processing in the server. It would cause unnecessary
resource/performance cost in the devices if the NMS has already
got the intended portion or just canceled by the administrators.
Zheng & Wang Expires December 28, 2018 [Page 3]
Internet-Draft Netconf Fragmentation June 2018
o Another problem is the implementation of SAX parsing is more
complex than DOM parsing in the Netconf client. More computing
burden will be taken in Netconf client to support SAX parsing.
3.2. Requesting a Portion of Data
The clients actively limit the search range of the data so that the
servers only need to reply with a part of the large size data. Thus
the clients could control the replies in a reasonable size. One
example is that the clients get a list of the content, and provide a
start offset and a max-count, to get a portion at a time.
Problems:
o This method has an implication that the client needs to know the
list/index of the intended large size data in advance before it
starting the search request. It can't fit the scenarios of real-
time on-demand data retrieving. And there is no standard to
specify the list/index format in a uniform way. Thus it is only
suitable for private implementation, thus multi-vendor interaction
is not supported.
o More important, it is just an indirect way to solve the problem.
It could not fit the scenarios where the client just needs the
whole large size data in the server.
3.3. Using tools to extract data respectively
There are some tools/functions which can handle the iteration. For
example, the XPATH's position() function can help to do this work.
The following examples show some instances:
<filter type="xpath" select="/interfaces/interface[position() >= 0 and position() < 25]" />
<filter type="xpath" select="/interfaces/interface[position() >= 25 and position() < 50]" />
Problems:
o Xpath function just can meet the "xpath filter" case, which
cannot cover the "subtree filter" case.
o Different encoding format request different tools, and there is
no standard to process the received data in a uniform way. Thus
it is only suitable for private implementation, thus multi-vendor
interaction is not supported.
Zheng & Wang Expires December 28, 2018 [Page 4]
Internet-Draft Netconf Fragmentation June 2018
4. Netconf Fragmentation Mechanism
4.1. Fragmentation Requirements
this document proposes an RPC fragmentation mechanism to handle the
large size data. Two essential requirements of the fragmentation
are:
o It needs to allow the NETCONF client to terminate the large size
data processing momentarily by protocol interactions. In the
proposed mechanisms in this draft, when the NETCONF server replies
the client an <rpc-reply> fragmentation, it will wait the response
from the client that whether it needs to send the next
fragmentation. So if the initiator has got the intended portion,
it could terminate the large size process immediately.
o It needs to allow the NETCONF client to instantly parse the
fragmentations piece by piece through the more widely supported
DOM parsing. So in this document, it specifies that each <rpc-
reply> fragmentation MUST be in a complete XML form.
4.2. <get-block> extention
o Function
The devices can only use <get-block> operation when the Get-block
capability was announced.
The <get-block> fragmentation rules are:
A. There should be a Max-Size for fragmentation. [Ope
Question]Should there be a clear specification of the size? E.g.
64K bytes.
B. When the message reaches the Max-Size, it is sent to the
client and the next message could be created in advance.
C. Different records from one same table could be put into
different <rpc-reply> messages
D. All of the fields in one record MUST be put into one <rpc-
reply> message.
E. XML syntax MUST be complete in each fragmented message, so
that each fragmentation could be parsed individually.
F. If the record(s) of the child node(s)/table(s) and the parent
node(s)/table(s) are replied in different fragmentations, the
Zheng & Wang Expires December 28, 2018 [Page 5]
Internet-Draft Netconf Fragmentation June 2018
child node/table fragmentations MUST include the path and index
information of all the ancestor node(s)/table(s) in a hierarchical
mode.
o Parameters
<discard-fragmentation>: in <get-block> operation, if the <discard-
fragmentation> parameter is conveyed, it means the operation is
terminated. Then it doesn't need to reply the remaining
fragmentations.
o Successful Operation Reply
A <rpc-reply> message conveying a <data> element indicates the
operation is successful. If there exists a next fragment, then an
set-id attribute MUST be included in the <rpc-reply> messge. The
attribute set-id is used to identify different fragment sets.
o Exception Handling
After the NETCONF server replies a fragment, if there is no
corresponding Get-block request from the client in a reasonable
period (the time valued to be specified in the future), then the
server release the offset of the replying data and cannot use <get-
block> operation anymore, and the remaining data needs to be replied.
Please refer to Appendix A.1 for an example.
5. YANG data model
<CODE BEGINS> file "ietf-netconf-fragmentation@2018-06-20.yang"
module ietf-netconf-fragmentation {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-fragmentation";
prefix fgm;
import ietf-datastores{
prefix ds;
}
import ietf-yang-types {
prefix yang;
}
import ietf-netconf {
prefix nc;
}
Zheng & Wang Expires December 28, 2018 [Page 6]
Internet-Draft Netconf Fragmentation June 2018
organization
"IETF NETCONF Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Guangying Zheng
<zhengguangying@huawei.com>
Author: Zitao Wang
<wangzitao@huawei.com>";
description
"This document introduces an extension to NETCONF (Network Configuration) protocol.
The extension allows NETCONF to handle large size data as fragmented RPC messages.
Specifically, this document defines a new get-block capability and relevant
operations to handle the fragmentations.";
revision 2018-06-20 {
description
"Initial revision.";
reference "draft-zheng-netconf-fragmentation-01";
}
rpc get-block {
description
"Retrieve data from an NMDA datastore.";
input {
leaf source {
type identityref {
base ds:datastore;
}
mandatory true;
description
"Datastore from which to retrieve data.";
}
choice filter-spec {
description
"The content filter specification for this request.";
anydata subtree-filter {
description
"This parameter identifies the portions of the
target datastore to retrieve.";
reference "RFC 6241, Section 6.";
}
Zheng & Wang Expires December 28, 2018 [Page 7]
Internet-Draft Netconf Fragmentation June 2018
leaf xpath-filter {
if-feature nc:xpath;
type yang:xpath1.0;
description
"This parameter contains an XPath expression
identifying the portions of the target
datastore to retrieve.";
}
}
}
}
rpc discard-fragmentation {
description
"Discard the netconf fragmentation, if the discard parameter is conveyed,
it means the operation is terminated.
Then it doesn't need to reply the remaining fragmentations.";
}
}
<CODE ENDS>
6. Security Considerations
TBD.
7. IANA Considerations
TBD.
8. Normative References
[I-D.ietf-netmod-revised-datastores]
Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore
Architecture", draft-ietf-netmod-revised-datastores-10
(work in progress), January 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
Zheng & Wang Expires December 28, 2018 [Page 8]
Internet-Draft Netconf Fragmentation June 2018
Appendix A. Appendix A: Examples of the Candidate Solutions
A.1. <get-block> (RPC Fragmentation) Example:
Example 1: Get the next fragment
<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:NETCONF:base:1.0">
<get-config>
<source>
<running/>
</source>
<filter type="subtree">
<top xmlns="http://example.com/schema/1.2/config">
<users/>
</top>
</filter>
</get-config>
</rpc>
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:NETCONF:base:1.0"
xmlns:hw=http://www.huawei.com/NETCONF/capability/base/1.0
hw:set-id="101">
<data>
<top xmlns="http://example.com/schema/1.2/config">
<users>
<user>
<name>root</name>
<type>superuser</type>
<full-name>Charlie Root</full-name>
<company-info>
<dept>1</dept>
<id>1</id>
</company-info>
</user>
<!-- additional <user> elements appear here... -->
</users>
</top>
</data>
</rpc-reply>
<rpc message-id="102"
xmlns="urn:ietf:params:xml:ns:NETCONF:base:1.0">
<get-block xmlns="http://www.huawei.com/NETCONF/capability/base/1.0"
set-id="101">
</get-block>
</rpc>
Zheng & Wang Expires December 28, 2018 [Page 9]
Internet-Draft Netconf Fragmentation June 2018
<rpc-reply message-id="102"
xmlns="urn:ietf:params:xml:ns:NETCONF:base:1.0"
xmlns:hw=http://www.huawei.com/NETCONF/capability/base/1.0
hw:set-id="101">
<data>
<top xmlns="http://example.com/schema/1.2/config">
<users>
<user>
<name>admin</name>
<type>commonuser</type>
<full-name>Jim Green</full-name>
<company-info>
<dept>9</dept>
<id>90</id>
</company-info>
</user>
<!-- additional <user> elements appear here... -->
</users>
</top>
</data>
</rpc-reply>
Example 2: Abandon the remaining fragments
<rpc message-id="103"
xmlns="urn:ietf:params:xml:ns:NETCONF:base:1.0">
<get-block xmlns=http://www.huawei.com/NETCONF/capability/base/1.0 set-id="1">
<discard-fragmentation/>
</get-block>
</rpc>
<rpc-reply message-id="103"
xmlns="urn:ietf:params:xml:ns:NETCONF:base:1.0">
<ok/>
</rpc-reply>
Authors' Addresses
Guangying Zheng
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: zhengguangying@huawei.com
Zheng & Wang Expires December 28, 2018 [Page 10]
Internet-Draft Netconf Fragmentation June 2018
Michael Wang
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: wangzitao@huawei.com
Zheng & Wang Expires December 28, 2018 [Page 11]
