| NETCONF Working Group | K. Watsen |
| Internet-Draft | Watsen Networks |
| Intended status: Standards Track | M. Scharf |
| Expires: September 9, 2020 | Hochschule Esslingen |
| March 8, 2020 |
YANG Groupings for TCP Clients and TCP Servers
draft-ietf-netconf-tcp-client-server-04
This document defines three YANG modules: the first defines a grouping for configuring a generic TCP client, the second defines a grouping for configuring a generic TCP server, and the third defines a grouping common to the TCP clients and TCP servers.
This draft contains many placeholder values that need to be replaced with finalized values at the time of publication. This note summarizes all of the substitutions that are needed. No other RFC Editor instructions are specified elsewhere in this document.
Artwork in this document contains placeholder values for the date of publication of this draft. Please apply the following replacement:
The following Appendix section is to be removed prior to publication:
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 September 9, 2020.
Copyright (c) 2020 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.
This document defines three YANG 1.1 [RFC7950] modules: the first defines a grouping for configuring a generic TCP client, the second defines a grouping for configuring a generic TCP server, and the third defines a grouping common to the TCP clients and TCP servers.
It is intended that these groupings will be used either standalone, for TCP-based protocols, as part of a stack of protocol-specific configuration models. For instance, these groupings could help define the configuration module for SSH, TLS, or HTTP based applications.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
This document defines a common "grouping" statement for basic TCP connection parameters that matter to applications. In some TCP stacks, such parameters can also directly be set by an application using system calls, such as the socket API. The base YANG model in this document focuses on modeling TCP keep-alives. This base model can be extended as needed.
Network stacks may include "keep-alives" in their TCP implementations, although this practice is not universally accepted. If keep-alives are included, [RFC1122] [RFC793bis] mandates that the application MUST be able to turn them on or off for each TCP connection, and that they MUST default to off.
Keep-alive mechanisms exist in many protocols. Depending on the protocol stack, TCP keep-alives may only be one out of several alternatives. Which mechanism to use depends on the use case and application requirements. If keep-alives are needed by an application, it is RECOMMENDED that the aliveness check happens at the highest protocol layer possible that is meaningful to the application, in order to maximize the depth of the aliveness check.
[[TODO: Further guidance on keep-alives is provided in draft-xyz-tsvwg-... ]]
A TCP keep-alive mechanism should only be invoked in server applications that might otherwise hang indefinitely and consume resources unnecessarily if a client crashes or aborts a connection during a network failure [RFC1122]. TCP keep-alives may consume significant resources both in the network and in endpoints (e.g., battery power). In addition, frequent keep-alives risk network congestion. The higher the frequency of keep-alives, the higher the overhead.
Given the cost of keep-alives, parameters have to be configured carefully:
This section provides a tree diagram [RFC8340] for the "ietf-tcp-common" module.
module: ietf-tcp-common
grouping tcp-common-grouping
+-- keepalives! {keepalives-supported}?
+-- idle-time uint16
+-- max-probes uint16
+-- probe-interval uint16
grouping tcp-connection-grouping
+-- keepalives! {keepalives-supported}?
+-- idle-time uint16
+-- max-probes uint16
+-- probe-interval uint16
This section presents an example showing the tcp-common-grouping populated with some data.
<tcp-common xmlns="urn:ietf:params:xml:ns:yang:ietf-tcp-common">
<keepalives>
<idle-time>15</idle-time>
<max-probes>3</max-probes>
<probe-interval>30</probe-interval>
</keepalives>
</tcp-common>
The ietf-tcp-common YANG module references [RFC6991].
<CODE BEGINS> file "ietf-tcp-common@2020-03-08.yang"
module ietf-tcp-common {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-tcp-common";
prefix tcpcmn;
organization
"IETF NETCONF (Network Configuration) Working Group and the
IETF TCP Maintenance and Minor Extensions (TCPM) Working Group";
contact
"WG Web: <http://datatracker.ietf.org/wg/netconf/>
<http://datatracker.ietf.org/wg/tcpm/>
WG List: <mailto:netconf@ietf.org>
<mailto:tcpm@ietf.org>
Authors: Kent Watsen <mailto:kent+ietf@watsen.net>
Michael Scharf
<mailto:michael.scharf@hs-esslingen.de>";
description
"This module defines reusable groupings for TCP commons that
can be used as a basis for specific TCP common instances.
Copyright (c) 2019 IETF Trust and the persons identified
as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with
or without modification, is permitted pursuant to, and
subject to the license terms contained in, the Simplified
BSD License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC
itself for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
are to be interpreted as described in BCP 14 (RFC 2119)
(RFC 8174) when, and only when, they appear in all
capitals, as shown here.";
revision 2020-03-08 {
description
"Initial version";
reference
"RFC XXXX: YANG Groupings for TCP Clients and TCP Servers";
}
// Features
feature keepalives-supported {
description
"Indicates that keepalives are supported.";
}
// Groupings
grouping tcp-common-grouping {
description
"A reusable grouping for configuring TCP parameters common
to TCP connections as well as the operating system as a
whole.";
container keepalives {
if-feature "keepalives-supported";
presence "Indicates that keepalives are enabled.";
description
"Configures the keep-alive policy, to proactively test the
aliveness of the TCP peer. An unresponsive TCP peer is
dropped after approximately (idle-time + max-probes
* probe-interval) seconds.";
leaf idle-time {
type uint16 {
range "1..max";
}
units "seconds";
mandatory true;
description
"Sets the amount of time after which if no data has been
received from the TCP peer, a TCP-level probe message
will be sent to test the aliveness of the TCP peer.
Two hours (7200 seconds) is safe value, per RFC 1122.";
reference
"RFC 1122:
Requirements for Internet Hosts -- Communication Layers";
}
leaf max-probes {
type uint16 {
range "1..max";
}
mandatory true;
description
"Sets the maximum number of sequential keep-alive probes
that can fail to obtain a response from the TCP peer
before assuming the TCP peer is no longer alive.";
}
leaf probe-interval {
type uint16 {
range "1..max";
}
units "seconds";
mandatory true;
description
"Sets the time interval between failed probes. The interval
SHOULD be significantly longer than one second in order to
avoid harm on a congested link.";
}
} // container keepalives
} // grouping tcp-common-grouping
grouping tcp-connection-grouping {
description
"A reusable grouping for configuring TCP parameters common
to TCP connections.";
uses tcp-common-grouping;
}
/*
The following is for a future bis...
This comment is here now so as support discussion with TCPM.
This comment will be removed before publication.
Should future system-level parameters be defined as a
grouping or a container?
grouping tcp-system-grouping {
description
"A reusable grouping for configuring TCP parameters common
to the operating system as a whole.";
// currently just a placeholder
}
*/
}
<CODE ENDS>
This section provides a tree diagram [RFC8340] for the "ietf-tcp-client" module.
module: ietf-tcp-client
grouping tcp-client-grouping
+-- remote-address inet:host
+-- remote-port? inet:port-number
+-- local-address? inet:ip-address {local-binding-supported}?
+-- local-port? inet:port-number {local-binding-supported}?
+-- keepalives! {keepalives-supported}?
+-- idle-time uint16
+-- max-probes uint16
+-- probe-interval uint16
This section presents an example showing the tcp-client-grouping populated with some data.
<tcp-client xmlns="urn:ietf:params:xml:ns:yang:ietf-tcp-client">
<remote-address>www.example.com</remote-address>
<remote-port>443</remote-port>
<local-address>0.0.0.0</local-address>
<local-port>0</local-port>
<keepalives>
<idle-time>15</idle-time>
<max-probes>3</max-probes>
<probe-interval>30</probe-interval>
</keepalives>
</tcp-client>
The ietf-tcp-client YANG module references [RFC6991].
<CODE BEGINS> file "ietf-tcp-client@2020-03-08.yang"
module ietf-tcp-client {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-tcp-client";
prefix tcpc;
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-tcp-common {
prefix tcpcmn;
reference
"RFC XXXX: YANG Groupings for TCP Clients and TCP Servers";
}
organization
"IETF NETCONF (Network Configuration) Working Group and the
IETF TCP Maintenance and Minor Extensions (TCPM) Working Group";
contact
"WG Web: <http://datatracker.ietf.org/wg/netconf/>
<http://datatracker.ietf.org/wg/tcpm/>
WG List: <mailto:netconf@ietf.org>
<mailto:tcpm@ietf.org>
Authors: Kent Watsen <mailto:kent+ietf@watsen.net>
Michael Scharf
<mailto:michael.scharf@hs-esslingen.de>";
description
"This module defines reusable groupings for TCP clients that
can be used as a basis for specific TCP client instances.
Copyright (c) 2019 IETF Trust and the persons identified
as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with
or without modification, is permitted pursuant to, and
subject to the license terms contained in, the Simplified
BSD License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC
itself for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
are to be interpreted as described in BCP 14 (RFC 2119)
(RFC 8174) when, and only when, they appear in all
capitals, as shown here.";
revision 2020-03-08 {
description
"Initial version";
reference
"RFC XXXX: YANG Groupings for TCP Clients and TCP Servers";
}
// Features
feature local-binding-supported {
description
"Indicates that the server supports configuring local
bindings (i.e., the local address and local port) for
TCP clients.";
}
feature tcp-client-keepalives {
description
"Per socket TCP keepalive parameters are configurable for
TCP clients on the server implementing this feature.";
}
// Groupings
grouping tcp-client-grouping {
description
"A reusable grouping for configuring a TCP client.
Note that this grouping uses fairly typical descendent
node names such that a stack of 'uses' statements will
have name conflicts. It is intended that the consuming
data model will resolve the issue (e.g., by wrapping
the 'uses' statement in a container called
'tcp-client-parameters'). This model purposely does
not do this itself so as to provide maximum flexibility
to consuming models.";
leaf remote-address {
type inet:host;
mandatory true;
description
"The IP address or hostname of the remote peer to
establish a connection with. If a domain name is
configured, then the DNS resolution should happen on
each connection attempt. If the DNS resolution
results in multiple IP addresses, the IP addresses
are tried according to local preference order until
a connection has been established or until all IP
addresses have failed.";
}
leaf remote-port {
type inet:port-number;
default "0";
description
"The IP port number for the remote peer to establish a
connection with. An invalid default value (0) is used
(instead of 'mandatory true') so that as application
level data model may 'refine' it with an application
specific default port number value.";
}
leaf local-address {
if-feature "local-binding-supported";
type inet:ip-address;
description
"The local IP address/interface (VRF?) to bind to for when
connecting to the remote peer. INADDR_ANY ('0.0.0.0') or
INADDR6_ANY ('0:0:0:0:0:0:0:0' a.k.a. '::') MAY be used to
explicitly indicate the implicit default, that the server
can bind to any IPv4 or IPv6 addresses, respectively.";
}
leaf local-port {
if-feature "local-binding-supported";
type inet:port-number;
default "0";
description
"The local IP port number to bind to for when connecting
to the remote peer. The port number '0', which is the
default value, indicates that any available local port
number may be used.";
}
uses tcpcmn:tcp-connection-grouping {
augment "keepalives" {
if-feature "tcp-client-keepalives";
description
"Add an if-feature statement so that implementations
can choose to support TCP client keepalives.";
}
}
}
}
<CODE ENDS>
This section provides a tree diagram [RFC8340] for the "ietf-tcp-server" module.
module: ietf-tcp-server
grouping tcp-server-grouping
+-- local-address inet:ip-address
+-- local-port? inet:port-number
+-- keepalives! {keepalives-supported}?
+-- idle-time uint16
+-- max-probes uint16
+-- probe-interval uint16
This section presents an example showing the tcp-server-grouping populated with some data.
<tcp-server xmlns="urn:ietf:params:xml:ns:yang:ietf-tcp-server">
<local-address>10.20.30.40</local-address>
<local-port>7777</local-port>
<keepalives>
<idle-time>15</idle-time>
<max-probes>3</max-probes>
<probe-interval>30</probe-interval>
</keepalives>
</tcp-server>
The ietf-tcp-server YANG module references [RFC6991].
<CODE BEGINS> file "ietf-tcp-server@2020-03-08.yang"
module ietf-tcp-server {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-tcp-server";
prefix tcps;
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-tcp-common {
prefix tcpcmn;
reference
"RFC XXXX: YANG Groupings for TCP Clients and TCP Servers";
}
organization
"IETF NETCONF (Network Configuration) Working Group and the
IETF TCP Maintenance and Minor Extensions (TCPM) Working Group";
contact
"WG Web: <http://datatracker.ietf.org/wg/netconf/>
<http://datatracker.ietf.org/wg/tcpm/>
WG List: <mailto:netconf@ietf.org>
<mailto:tcpm@ietf.org>
Authors: Kent Watsen <mailto:kent+ietf@watsen.net>
Michael Scharf
<mailto:michael.scharf@hs-esslingen.de>";
description
"This module defines reusable groupings for TCP servers that
can be used as a basis for specific TCP server instances.
Copyright (c) 2019 IETF Trust and the persons identified
as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with
or without modification, is permitted pursuant to, and
subject to the license terms contained in, the Simplified
BSD License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC
itself for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
are to be interpreted as described in BCP 14 (RFC 2119)
(RFC 8174) when, and only when, they appear in all
capitals, as shown here.";
revision 2020-03-08 {
description
"Initial version";
reference
"RFC XXXX: YANG Groupings for TCP Clients and TCP Servers";
}
// Features
feature tcp-server-keepalives {
description
"Per socket TCP keepalive parameters are configurable for
TCP servers on the server implementing this feature.";
}
// Groupings
grouping tcp-server-grouping {
description
"A reusable grouping for configuring a TCP server.
Note that this grouping uses fairly typical descendent
node names such that a stack of 'uses' statements will
have name conflicts. It is intended that the consuming
data model will resolve the issue (e.g., by wrapping
the 'uses' statement in a container called
'tcp-server-parameters'). This model purposely does
not do this itself so as to provide maximum flexibility
to consuming models.";
leaf local-address {
type inet:ip-address;
mandatory true;
description
"The local IP address to listen on for incoming
TCP client connections. INADDR_ANY (0.0.0.0) or
INADDR6_ANY (0:0:0:0:0:0:0:0 a.k.a. ::) MUST be
used when the server is to listen on all IPv4 or
IPv6 addresses, respectively.";
}
leaf local-port {
type inet:port-number;
default "0";
description
"The local port number to listen on for incoming TCP
client connections. An invalid default value (0)
is used (instead of 'mandatory true') so that an
application level data model may 'refine' it with
an application specific default port number value.";
}
uses tcpcmn:tcp-connection-grouping {
augment "keepalives" {
if-feature "tcp-server-keepalives";
description
"Add an if-feature statement so that implementations
can choose to support TCP server keepalives.";
}
}
}
}
<CODE ENDS>
The YANG modules defined in this document are designed to be accessed via YANG based management protocols, such as NETCONF [RFC6241] and RESTCONF [RFC8040]. Both of these protocols have mandatory-to-implement secure transport layers (e.g., SSH, TCP) with mutual authentication.
The NETCONF access control model (NACM) [RFC8341] provides the means to restrict access for particular users to a pre-configured subset of all available protocol operations and content.
Since the modules defined in this document only define groupings, these considerations are primarily for the designers of other modules that use these groupings.
There are a number of data nodes defined in the YANG modules that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability:
Some of the readable data nodes in the YANG modules may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability:
This document does not define any RPC actions and hence this section does not consider the security of RPCs.
This document registers two URIs in the "ns" subregistry of the IETF XML Registry [RFC3688]. Following the format in [RFC3688], the following registrations are requested:
URI: urn:ietf:params:xml:ns:yang:ietf-tcp-client Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-tcp-server Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace.
This document registers two YANG modules in the YANG Module Names registry [RFC6020]. Following the format in [RFC6020], the following registrations are requested:
name: ietf-tcp-common namespace: urn:ietf:params:xml:ns:yang:ietf-tcp-common prefix: tcpcmn reference: RFC XXXX name: ietf-tcp-client namespace: urn:ietf:params:xml:ns:yang:ietf-tcp-client prefix: tcpc reference: RFC XXXX name: ietf-tcp-server namespace: urn:ietf:params:xml:ns:yang:ietf-tcp-server prefix: tcps reference: RFC XXXX
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC6020] | Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010. |
| [RFC6991] | Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013. |
| [RFC7950] | Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016. |
| [RFC8174] | Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017. |
| [RFC8341] | Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018. |
| [RFC3688] | Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004. |
| [RFC6241] | Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011. |
| [RFC8040] | Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017. |
| [RFC8340] | Bjorklund, M. and L. Berger, "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018. |