| l2tpext Working Group | Q. Sun |
| Internet-Draft | I. Farrer |
| Intended status: Standards Track | Deutsche Telekom AG |
| Expires: September 22, 2016 | B. Liu |
| Huawei Technologies | |
| G. Heron | |
| Cisco Systems | |
| March 21, 2016 |
A YANG Data Model for Keyed IPv6 Tunnels
draft-ietf-l2tpext-keyed-v6-tunnel-yang-01
This document defines a YANG data model for the configuration and management of Keyed IPv6 tunnels. The data model includes both configuration and state data. Due to the stateless nature of keyed IPv6 tunnels, a model for NETCONF notifications is not necessary.
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].
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 http://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 22, 2016.
Copyright (c) 2016 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 (http://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.
Keyed IPv6 Tunnels [I-D.ietf-l2tpext-keyed-ipv6-tunnel] defines a mechanism for transporting L2 Ethernet frames over IPv6 using L2TPv3 tunnel encapsulation with a mandatory 64-bit cookie. It is a static layer 2 tunnelling mechanism that leverages IPv6's vast number of IP addresses to uniquely identify each tunnel, instead of using the L2TPv3 Session ID as the differentiator (as defined in [RFC3931]). The layer 2 circuit is mapped to an IPv6 address on the network side so typically, there is one session per-tunnel.
Since the L2TPv3 control plane is not used by Keyed IPv6 tunnels, the parameters for building a Keyed IPv6 tunnel need to be pre-configured on the two tunnel endpoint devices. NETCONF [RFC6241]/YANG [RFC6020] provide mechanisms for such configuration. This document defines a YANG data model for the configuration and management of Keyed IPv6 Tunnels.
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].
The following terms are defined in [RFC6241] and are not redefined here:
The following terms are defined in [RFC6020] and are not redefined here:
A simplified graphical representation of the data model is provided in this document. The meaning of the symbols in these diagrams is as follows:
The YANG model comprises of two modules, one for configuration and one for state. To correctly identify a tunnel and create the mapping between the L2 circuit and the IPv6 address, the tuple of source interface, local IPv6 address and remote IPv6 address MUST be unique. Because Session ID is not mandatory for a Keyed IPv6 tunnel to function, Session ID related parameters are optional in the model. Cookies MUST be 64-bit long according to the Section 3 of [I-D.ietf-l2tpext-keyed-ipv6-tunnel]. The requirement for 64-bit cookie constrains interoperability with existing RFC3931 implementations to those configured with a 64-bit cookie.
The data model also includes read-only counters so that statistics for sent and received octets and packets, received packets with errors, and packets that could not be sent due to errors can be read.
This model defines three features for OAM parameters. Those features enable devices to perform related OAM operations on the tunnel if related functions are supported.
This section describes the tree diagram for the Keyed IPv6 Tunnel YANG model:
module: ietf-keyed-v6-tunnel
+--rw tunnelConfigurations
| +--rw tunnelConfiguration* [tunnelName]
| | +--rw tunnelName string
| | +--rw srcInterface if:interface-ref
| | +--rw localIPv6 inet:ipv6-address
| | +--rw remoteIPv6 inet:ipv6-address
| | +--rw localSessionId? uint32
| | +--rw remoteSessionId? uint32
| | +--rw localCookies
| | | +--rw localCookie* [cookieName]
| | | +--rw cookieName string
| | | +--rw cookieValue uint64
| | +--rw remoteCookie uint64
| | +--rw retainFCS? empty
| | +--rw enable-vccv!
| | | +--rw enable-bfd? empty
| | +--rw enable-bfd? empty
| +--rw disable-pmtu? empty
| +--rw enable-fragmentation!
| | +--rw fragment-mru? uint16
| +--rw enable-sequencing empty
+--ro tunnelStates
+--ro tunnelState* [tunnelName]
+--ro tunnelName string
+--ro sentPacket? yang:zero-based-counter64
+--ro sentByte? yang:zero-based-counter64
+--ro rcvdPacket? yang:zero-based-counter64
+--ro rcvdByte? yang:zero-based-counter64
+--ro droppedPacket? yang:zero-based-counter64
+--ro droppedByte? yang:zero-based-counter64
+--ro fragmentCounter? yang:zero-based-counter64
Figure 1: Keyed IPv6 Tunnel Tree
The data model defines a configuration container and a state container.
In the configuration container, "srcInterface" is used to identify a L2 circuit endpoint. "localIPv6" and "remoteIPv6" respectively hold the local (source) and remote (destination) IPv6 addresses for the tunnel. The tuple of srcInterface and localIPv6 uniquely identify a tunnel endpoint. If a virtual interface is used, the tuple of localIPv6 and remoteIPv6 MUST also be unique. "localCookie" is a list containing two cookies: one is the newly configured cookie, and the other is previously configured. This is used for the purpose of correctly receiving packets while changing cookies.
Nodes are defined for FCS-Retention, VCCV, BFD, VCCV-BFD and fragmentation, so that devices supporting all or some of these features can be configured.
This module imports typedefs from [RFC6991] and [RFC7223].
<CODE BEGINS> file "ietf-keyed-v6-tunnel@2016-03-21.yang"
module ietf-keyed-v6-tunnel {
namespace "urn:ietf:params:xml:ns:yang:ietf-keyed-v6-tunnel";
prefix k6tun;
import ietf-interfaces {
prefix if;
}
import ietf-inet-types {
prefix inet;
}
import ietf-yang-types {
prefix yang;
}
organization "IETF l2tpext Working Group";
contact
"qui.sun@external.telekom.de
ian.farrer@telekom.de
leo.liubing@huawei.com
giheron@cisco.com
";
description
"Keyed IPv6 L2TPv3 Tunnel";
revision 2016-03-21 {
description
"Added sequencing feature";
reference
"draft-ietf-l2tpext-keyed-v6-tunnel-yang-01";
}
revision 2015-07-06 {
description
"General clean-up"
;
reference
"draft-sun-l2tpext-keyed-v6-tunnel-yang-01";
}
revision 2015-03-09 {
description
"Initial version.
";
reference
"draft-sun-l2tpext-keyed-v6-tunnel-yang-00";
}
/*
* features
*/
feature FCS-Retention {
description
"Device supports the retention of frame check sequence (FCS)
as per Section 4.7 of RFC4720";
}
feature VCCV {
description
"Device supports the Pseudowire Virtual Circuit Connectivity
Verification (VCCV) as per RFC5085";
}
feature BFD {
description
"Device supports BFD over the tunnel as per RFC5883";
}
feature VCCV-BFD {
description
"Device supports BFD over VCCV as per RFC5885";
}
feature l2tpv3-fragmentation {
description
"Device supports L2TPv3 fragmentation as per RFC4623";
}
feature l2tpv3-sequencing {
description
"Device supports frame sequencing as per section 4.6.1 of
RFC3931";
}
/*
* typedefs
*/
/*
* groupings
*/
/*
* config parameters
*/
container tunnelConfigurations {
list tunnelConfiguration {
key "tunnelName";
unique "srcInterface remoteIPv6";
unique "localIPv6 remoteIPv6";
leaf tunnelName {
type string;
description "name for this keyed tunnel";
}
leaf srcInterface {
type if:interface-ref;
mandatory true;
description
"Source interface that identifies the L2 circuit
endpoint.";
}
leaf localIPv6 {
type inet:ipv6-address;
mandatory true;
description "IPv6 address for local end of keyed tunnel";
}
leaf remoteIPv6 {
type inet:ipv6-address;
mandatory true;
description "IPv6 address for remote end of keyed tunnel";
}
leaf localSessionId {
type uint32;
default 0xFFFFFFFF;
description
"As the IPv6 address is used to determine the tunnel
and there is a single session per tunnel, the Session ID
can be ignored upon receipt. For compatibility with
other tunnel termination platforms supporting two-stage
resolution (IPv6 address + Session ID), the Session ID
is configured with a random value other than all zeros.
If both ends support one-stage (IPv6 address), then
the Session ID is recommended to be set to all ones.";
}
leaf remoteSessionId {
type uint32;
default 0xFFFFFFFF;
description
"Since IPv6 address is used to determine the tunnel
and there is one session per tunnel, the Session ID
can be ignored upon receipt. For compatibility with
other tunnel termination platforms supporting two-stage
resolution (IPv6 address + Session ID) the Session ID
is configured with a random value other than all zeros.
If both ends support one-stage (IPv6 address), then
the Session ID is recommended to be set to all ones.";
}
container localCookies {
list localCookie {
key "cookieName";
leaf cookieName {
type string;
description "name identifying this cookie";
}
min-elements 2;
max-elements 2;
leaf cookieValue {
type uint64;
mandatory true;
description "value of this cookie";
}
description
"List of local cookies - must contain two entries at
all times to enable lossless cookie rollover";
}
description
"The length of cookie MUST be 64-bit. It MUST be
possible to change the cookie value at any time
in a manner that does not drop any legitimate
tunneled packets - i.e. the receiver
must accept a received cookie matching either
value during a change of cookie value.";
}
leaf remoteCookie {
type uint64;
mandatory true;
description
"The length of cookie MUST be 64-bit. A single
remote cookie is used for sending packets.";
}
leaf retainFCS {
if-feature FCS-Retention;
type empty;
description
"If this parameter is present, the router is configued
to retain FCS. Any such router MUST retain the FCS
for all frames sent over that tunnel.
";
}
container enable-vccv {
if-feature VCCV;
presence "Enable VCCV [RFC5085]";
leaf enable-bfd {
if-feature VCCV-BFD;
type empty;
description "Enable VCCV-BFD [RFC5885].";
}
description "Enable VCCV [RFC5085]";
}
leaf enable-bfd {
if-feature BFD;
type empty;
description
"Enable BFD over the tunnel [RFC5883].";
}
leaf disable-pmtu {
type empty;
description "Disable IPv6 PMTU discovery [RFC1981]";
}
container enable-fragmentation {
if-feature l2tpv3-fragmentation;
presence "Enable L2TPv3 fragmentation [RFC4623]";
leaf fragment-mru {
type uint16;
description "Explicit override for fragmentation MRU";
}
description
"Default is to fragment to PMTU (or 1500 if PMTU is
disabled) minus 52 octets for the encapsulation
overhead";
}
leaf enable-sequencing {
if-feature l2tpv3-sequencing;
type empty;
description
"Enable L2TPv3 sequencing [RFC3931 section 4.6.1]";
}
description
"keyed-v6-tunnel typically supports one l2tpv3 session
per tunnel. The srcInterface and localIPv6 both uniquely
identify a tunnel endpoint. If a virtual interface
is used, the localIPv6 and remoteIPv6 as a pair MUST
also be unique.
";
}
description
"container for list of keyed-v6-tunnel entries";
}
container tunnelStates {
config false;
list tunnelState {
key "tunnelName";
leaf tunnelName {
type string;
description "name of this keyed tunnel";
}
leaf sentPacket {
type yang:zero-based-counter64;
description
"counter for the number of packets sent over tunnel";
}
leaf sentByte {
type yang:zero-based-counter64;
description
"counter for total sent bytes (of inner packets)";
}
leaf rcvdPacket {
type yang:zero-based-counter64;
description
"counter for number of valid packets received from
tunnel";
}
leaf rcvdByte {
type yang:zero-based-counter64;
description
"counter for total received bytes (of inner packets)";
}
leaf droppedPacket {
type yang:zero-based-counter64;
description
"Counter for number of dropped packets matching this
tunnel (e.g. due to invalid received cookie,
insufficient resources to process).";
}
leaf droppedByte {
type yang:zero-based-counter64;
description
"Counter for total dropped bytes (of inner packets)";
}
leaf fragmentCounter {
type yang:zero-based-counter64;
description
"Counter for number of received fragments";
}
description "per-tunnel statistics";
}
description "container for list of tunnel statistics";
}
}
<CODE ENDS>
The YANG module defined in this memo is designed to be accessed via the NETCONF protocol [RFC6241]. The lowest NETCONF layer is the secure transport layer and the mandatory to implement secure transport is SSH [RFC6242]. The NETCONF access control model [RFC6536] provides the means to restrict access for particular NETCONF users to a pre-configured subset of all available NETCONF protocol operations and content.
There are a number of data nodes defined in this YANG module which 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:
/tunnelConfigurations/tunnelConfiguration: Could allow traffic to be redirected, (man-in-the-middle attack) or mis-configured (denial-of-service attack).
Some of the readable data nodes in this YANG module 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:
/tunnelConfigurations/tunnelConfiguration: Could allow an attacker to inject spoofed traffic into the network.
/tunnelStates/tunnelState: Could allow an attacker to get unauthorized access to tunnel usage information.
TBD
The authors would like to thank Haoxing Shen for his valuable comments.
| [RFC3931] | Lau, J., Townsley, M. and I. Goyret, "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", RFC 3931, DOI 10.17487/RFC3931, March 2005. |