Internet DRAFT - draft-hares-i2rs-isis-compare-yang
draft-hares-i2rs-isis-compare-yang
I2RS working group S. Hares
Internet-Draft L. Wang
Intended status: Standards Track Huawei
Expires: May 14, 2015 November 10, 2014
Comparison Between 2 ISIS Yang Drafts
draft-hares-i2rs-isis-compare-yang-00
Abstract
This document contains a comparison of two ISIS yang models: draft-
litkowski-isis-yang-isis-cfg-01 and draft-wang-i2rs-isis-dm. The
yang model in draft-litkowski-isis-yang-isis-cfg-01 is model focused
on configuration. The yang model in d raft-wang-i2rs-isis-dm-00 is
focused on the status and ephemeral state changes needed for IGP use
cases specified for I2RS interface by the I2RS WG. The conclusion of
comparison is that there little overlap except the definitions of
common ospf structures. The draft-wang-i2rs-isis-dm-00 is necessary
to fulfil a majority of the requirement drawn from the IGP use cases
in the I2RS use cases.
Status of This Memo
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This Internet-Draft will expire on May 14, 2015.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 3
3. Comparison of draft-litkowski-isis-yang-isis-cfg-01 with
draft-wang-ospf-dm-00 . . . . . . . . . . . . . . . . . . . . 3
4. Major differences in yang structures . . . . . . . . . . . . 4
5. Unique features for I2RS IGP Requirements . . . . . . . . . . 5
5.1. mt-rib . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.2. nbr-list . . . . . . . . . . . . . . . . . . . . . . . . 6
5.3. state information for route change and neighbor change . 7
6. Merge Suggestions . . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Informative References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
The Interface to the Routing System (I2RS) provides read and write
access to the information and state within the routing process within
routing elements. The I2RS client interacts with one or more I2RS
agents to collect information from network routing systems. The
processing of collecting information at the I2RS agent may require
the I2RS Agent to filter certain information, group pieces of
information, or perform actions on the I2rs collected information
based on specific I2rs policies.
This draft is a comparison of the following two ISIS yang models:
[I-D.litkowski-isis-yang-isis-cfg], and [I-D.wang-i2rs-isis-dm]. The
comparison provides an overview of the differences, overlaps, and
unique features of each yang model. The analysis also evaluates
whether both models or a single model is necessary to satisfy the
requirements for the IGP use cases found in the
[I-D.ietf-i2rs-usecase-reqs-summary]. Additional explanatory
information on the [I-D.wang-i2rs-isis-dm] is available in the
[I-D.wu-i2rs-isis-info-model].
Please note the IGP use cases have been determined to be out of
charter (OC) by the I2RS chairs.
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The rest of this draft is the details so those who desire "sounds
bytes" level reading may stop reading now.
2. Definitions and Acronyms
BGP - Border Gateway Protocol version 4
CLI: Command Line Interface
IGP: Interior Gateway Protocol
ISIS: Intermediate System to Intermediate System Routing Protocol
(IGP)
I2RS: Interface to (2) Routing system.
Information Model: An abstract model of a conceptual domain,
independent of a specific implementations or data representation
INSTANCE: Routing Code often has the ability to spin up multiple
copies of itself into virtual machines. Each Routing code
instance or each protocol instance is denoted as Foo_INSTANCE in
the text below.
NETCONF: The Network Configuration Protocol
RESTCONF: The RESTCONF Protocol
3. Comparison of draft-litkowski-isis-yang-isis-cfg-01 with draft-wang-
ospf-dm-00
[I-D.litkowski-isis-yang-isis-cfg] was released on June 27, 2014.
The [I-D.litkowski-isis-yang-isis-cfg] has the following parts:
o configuration,
o operational status information per protocol instance,
o RPC operations (clear adjacency, clear isis-database), and
o notifications events (read-only).
The configuration portion of [I-D.litkowski-isis-yang-isis-cfg] has a
different structure than [I-D.wang-i2rs-isis-dm] with the key
difference being how the isis-mt structure is defined. The
[I-D.litkowski-isis-yang-isis-cfg] document has the following
sections: isis protocol (section 2.1), multi-topology parameters
(section 2.2), per isis-level configuration (2.3), and per interface
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parameters (2.4). The draft [I-D.wang-i2rs-isis-dm] closely mirrors
one variant of the internal structure of the ISIS protocol that
contains multi-topology having configuration definitions for:
protocol (isis), multi-topology support (isis-mt, mt-route), per isis
level (isis-level), lsdb (isis-lsdb), and per interface (isis-
interface). The [I-D.litkowski-isis-yang-isis-cfg] variant of
configuration uses a boolean value (isis-multi-topology-cfg)to
determine if a family is supported in the isis-mt configuration
support.
The second of [I-D.litkowski-isis-yang-isis-cfg] contains the read-
only operational state information (isis-state) for adjacencies, spf
events, lsp events, LSDB database, and system-id host name mappings.
The same state is included in [I-D.wang-i2rs-isis-dm]. The isis-lsp-
database in [I-D.litkowski-isis-yang-isis-cfg] contains a description
of the lsp, but not in accordance with the mt-extensions to the ISIS
protocol since it omits the mpls-te information and multi-topology
(mt) information. This information is found in
[I-D.wang-i2rs-isis-dm].
The third section of [I-D.litkowski-isis-yang-isis-cfg] contains:
o an RPC to clear a isis-adjacency within a protocol instance for a
particular set of interfaces and levels.
o an RPC to clear the isis lsdb data base at a particular isis level
The [I-D.wang-i2rs-isis-dm] does have a read/write variable for
adjacencies and for lsdbs so the config and I2RS methods operate to
do the same function. The I2RS Agent must be aware of the
possibility for an isis-adjacency and isis lsdb to be cleared via the
configuration module.
The fourth section on notifications examines provides a notification
based on adjacency up/down. The I2RS notification process will
specify a section of the yang module and a use notifications to
updated the information.
4. Major differences in yang structures
the remaining difference are the following:
o The nodes of [I-D.wang-i2rs-isis-dm] are mostly read/write. This
includes the isis lsp-database and the isis-neighbor lists. In
[I-D.litkowski-isis-yang-isis-cfg] status nodes are only readable.
o [I-D.wang-i2rs-isis-dm] contains the isis mt-rib which
[I-D.litkowski-isis-yang-isis-cfg] lacks.
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5. Unique features for I2RS IGP Requirements
The following are unique features for I2RS IGP requirements:
o mt-ipv4-rib and mt-ipv6-rib - which is used for transient loop
avoidance.
o nbr-list - to aid fast route convergence in the event of the loss
of a neighbor
o route state information for subscribing for notification of route
changes and neighbor changes
These I2RS features in [I-D.wang-i2rs-isis-dm] are described in the
sections below.
5.1. mt-rib
Link-state protocols may need to re-converge when the network
topology changes. During this phase packet loss and transient loops
are frequently observed since inconsistent RIBs exist, even the
reachability of the destinations is not compromised after the
topology change. [IGP-REQ-02] in [I-D.ietf-i2rs-usecase-reqs-
summary] suggests that the there should be rapid cycle of querying
and configuration change. Monitoring via the mechanisms in [IGP-REQ-
04] and [IGP-REQ-05], [IGP-REQ-06], [IGP-REQ-07], and [IGP-REQ-08] in
[I-D.ietf-i2rs-usecase-reqs-summary] may aid in detecting the
condition.
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+--rw mt-ipv4-rib* [ipv4-prefix]
| +--rw ipv4-prefix inet:ipv4-prefix
| +--rw nexthop-list* [nexthop]
| | +--rw nexthop inet:ipv4-prefix
| +--rw back-nexthop? inet:ipv4-prefix
| +--rw ipv4-isis-route-para
| +--rw metric? uint32
| +--ro type? enumeration
| +--ro route-current-state? route-state-def
| +--ro route-previous-state? route-state-def
| +--rw lsp-id? isis-lsp-id-def
| +--ro route-chg-reason? enumeration
+--rw mt-ipv6-rib* [ipv6-prefix]
| +--rw ipv6-prefix inet:ipv6-prefix
| +--rw nexthop-list* [nexthop]
| | +--rw nexthop inet:ipv6-prefix
| +--rw back-nexthop? inet:ipv4-prefix
| +--rw ipv6-isis-route-para
| +--rw metric? uint32
| +--ro type? enumeration
| +--ro route-current-state? route-state-def
| +--ro route-previous-state? route-state-def
| +--rw lsp-id? isis-lsp-id-def
| +--ro route-chg-reason? Enumeration
Figure 1: draft-i2rs-wang-isis-dm-00 mt-ipv4-rib and mt-ipv6-rib structures
5.2. nbr-list
The isis yang structure nbr-list supports fast convergence during
loss of an ospf neighbor.
IGP Hello packet is used to discover and maintain adjacencies among
different IS-IS nodes. Without the deployment of fast detection
techniques, one node has to wait for several seconds before it
realizes the adjacency has been broken. This kind of issue can cause
one device is cut off from its network causing a complete loss of
connectivity. No matter planned or accidentally this outage causes
traffic to be blackholed before damage can be controlled. [IGP-REQ-
01] and [IGP-REQ-02] plus the monitoring requirements in [IGP-REQ-04]
and [IGP-REQ-05], [IGP-REQ-06], [IGP-REQ-07], and [IGP-REQ-08] in [I-
D.ietf-i2rs-usecase-reqs-summary] may aid in detecting the condition.
Under the scenario of where I2RS and IGP information model are
deployed, it is RECOMMENDED that the adjacency data of the other end
side can be removed simultaneously or LSP can be updated directly by
I2RS Agent when IS-IS is disabled or detached on one side. The
configuration of [IGP-REQ-02] can aid in configuring. The authors
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suggest this as a beginning step, but there are additional steps to
support fast-convergence when an ISIS neighbor changes.
| +--rw l1-nbr-list* [l1nbr-system-id]
| | +--rw l1nbr-system-id isis-system-id-def
| | +--rw snpa? uint32
| | +--ro nbr-status? nbr-status-def
| | +--ro nbr-down-reason? nbr-down-reason-def
| | +--ro nbr-type? nbr-type-def
| +--rw l2-nbr-list* [l2nbr-system-id]
| | +--rw l2nbr-system-id isis-system-id-def
| | +--rw snpa? uint32
| | +--ro nbr-status? nbr-status-def
| | +--ro nbr-down-reason? nbr-down-reason-def
| | +--ro nbr-type? nbr-type-def
Figure 2 draft-i2rs-wang-isis-dm-00 l1-nbr-list and l2-nbr-list structures
5.3. state information for route change and neighbor change
The following are additions that [I-D.wang-i2rs-isis-dm] adds to
support route state querying.
+--rw mt-ipv4-rib* [ipv4-prefix]
+--rw ipv4-prefix
+--rw next-hop-list*
| +--rw next-hop inet:ipv4-prefix
+--rw back-nexthop? inet:ipv4-prefix
+--rw ipv4-isis-route-para
| +--rw metric ?
| +--rw type?
| +--ro route-current-state? route-state-def
| +--ro route-previous-state? route-state-def
| +--rw lsp-id? isis-lsp-id-def
| +--ro route-chg-reason? enumeration
figure 3 draft i2rs-wang-isis-dm-00 route status information
6. Merge Suggestions
[I-D.litkowski-isis-yang-isis-cfg] and [I-D.wang-i2rs-isis-dm] cover
two separate areas: configuration and ephemeral state. These two
drafts need to align the definitional part of the drafts (groupings,
typedefs, etc.)to allow implementations to choose configuration or
configuration plus I2RS
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7. IANA Considerations
This draft includes no request to IANA.
8. Security Considerations
None since this is just an analysis draft
9. Informative References
[I-D.ietf-i2rs-architecture]
Atlas, A., Halpern, J., Hares, S., Ward, D., and T.
Nadeau, "An Architecture for the Interface to the Routing
System", draft-ietf-i2rs-architecture-05 (work in
progress), July 2014.
[I-D.ietf-i2rs-rib-info-model]
Bahadur, N., Folkes, R., Kini, S., and J. Medved, "Routing
Information Base Info Model", draft-ietf-i2rs-rib-info-
model-03 (work in progress), May 2014.
[I-D.ietf-i2rs-usecase-reqs-summary]
Hares, S. and M. Chen, "Summary of I2RS Use Case
Requirements", draft-ietf-i2rs-usecase-reqs-summary-00
(work in progress), November 2014.
[I-D.litkowski-isis-yang-isis-cfg]
Litkowski, S., "Yang Data Model for ISIS protocol", draft-
litkowski-isis-yang-isis-cfg-01 (work in progress), June
2014.
[I-D.wang-i2rs-isis-dm]
Wang, L., Hares, S., and N. Wu, "Yang Data model I2RS to
IS-IS protocol", draft-wang-i2rs-isis-dm-00 (work in
progress), September 2014.
[I-D.wu-i2rs-isis-info-model]
Wu, N., Wang, L., and S. Hares, "Information model for IS-
IS protocol", draft-wu-i2rs-isis-info-model-00 (work in
progress), September 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3060] Moore, B., Ellesson, E., Strassner, J., and A. Westerinen,
"Policy Core Information Model -- Version 1
Specification", RFC 3060, February 2001.
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[RFC3460] Moore, B., "Policy Core Information Model (PCIM)
Extensions", RFC 3460, January 2003.
[RFC3644] Snir, Y., Ramberg, Y., Strassner, J., Cohen, R., and B.
Moore, "Policy Quality of Service (QoS) Information
Model", RFC 3644, November 2003.
Authors' Addresses
Susan Hares
Huawei
7453 Hickory Hill
Saline, MI 48176
USA
Email: shares@ndzh.com
Lixing Wang
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 10095
China
Email: wanglixing@huawei.com
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