Internet DRAFT - draft-hares-i2rs-ospf-compare-yang
draft-hares-i2rs-ospf-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 OSPF Yang Drafts
draft-hares-i2rs-ospf-compare-yang-00
Abstract
This document contains a comparison of two OSPF yang models: draft-
yeung-netmod-ospf-02 and draft-wang-i2rs-ospf-dm. The yang model in
draft-yeung-netmod-ospf-02 is model focused on configuration. The
yang model in draft-wang-i2rs-ospf-dm-00 is focused on the status and
ephemeral state changes needed for the I2RS interface. The
conclusion of comparison is that there little overlap except the
definitions of common ospf structures. The draft-wang-i2rs-ospf-
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-yeung-netmod-ospf-01 with draft-wang-
ospf-dm-00 . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Comparison of draft-yeung-netmod-ospf-02 with draft-wang-
ospf-dm-00 . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Differences between the drafts . . . . . . . . . . . . . . . 4
6. Unique features for I2RS IGP Requirements . . . . . . . . . . 4
6.1. mt-rib . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.2. nbr-list . . . . . . . . . . . . . . . . . . . . . . . . 5
6.3. router-number . . . . . . . . . . . . . . . . . . . . . . 6
6.4. route-info-list . . . . . . . . . . . . . . . . . . . . . 7
6.5. ospf route status information . . . . . . . . . . . . . . 7
7. Merge Suggestions . . . . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. 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 OSPF yang models:
[I-D.yeung-netmod-ospf], and [I-D.wang-i2rs-ospf-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-ospf-dm] is available in the
[I-D.wu-i2rs-ospf-info-model].
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At this time the I2RS chairs have determined that the IGP use cases
found in the [I-D.ietf-i2rs-usecase-reqs-summary] are out of scope.
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
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-yeung-netmod-ospf-01 with draft-wang-ospf-dm-00
The draft-yeung-netmod-ospf-01 has substantial differences with
[I-D.wang-i2rs-ospf-dm]. However, these differences are most mostly
configuration, in which the configurations utilize different views:
ospf-view (protocol), ospf-area-view, and ospf-interface-view.
[I-D.wang-i2rs-ospf-dm] has a similar structure for the following
group and type definitions: ospf ,ospf-area, ospf interface and TE
information. In the draft [I-D.wang-i2rs-ospf-dm] this information
is just for the definitions in order to attach the necessary status
status. The draft [I-D.wang-i2rs-ospf-dm] does not provide any
configuration. The real-time status information provided by
[I-D.wang-i2rs-ospf-dm] includes: ospf-mt, ospf-rib, ospf-neighbor,
ospf-lsa-database, ospf state, and ospf status and state information
which is not included in draft-yeung-netmod-ospf-01.
The difference to these two documents is appropriate for the
configuration versus I2RS split.
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4. Comparison of draft-yeung-netmod-ospf-02 with draft-wang-ospf-dm-00
[I-D.yeung-netmod-ospf] was released on October 14, 2014. This draft
more closely aligns with [I-D.wang-i2rs-ospf-dm].
[I-D.yeung-netmod-ospf] adds ospf-mt, ospf lsa database, ospf-TE,
and ospf status and state information which was included in
[I-D.wang-i2rs-ospf-dm]. The [I-D.yeung-netmod-ospf] has the
following three parts:
o configuration with the multi-topology view (write/read)
o protocol state and ospf-lsa-database (read only)
o notification on events (read-only)
Parts 2 and 3 of [I-D.yeung-netmod-ospf] to and provide more
comprehensive support for status information. The authors of
[I-D.wang-i2rs-ospf-dm] support these additions since this draft
brings the definitions of OSPF config and OSPF I2RS closer.
5. Differences between the drafts
the remaining difference are the following:
o The nodes of [I-D.wang-i2rs-ospf-dm] are mostly read/write. This
includes the ospf-ls-database and the ospf-neighbor. In
[I-D.yeung-netmod-ospf] nodes are only readable.
o [I-D.wang-i2rs-ospf-dm] contains the ospf-rib which
[I-D.yeung-netmod-ospf] does not have.
o [I-D.wang-i2rs-ospf-dm] has special nodes for I2RS OSPF use cases
which draft-yeung-netmod-ospf-02 do not have. These nodes are:
router-number and route-info-list.
6. Unique features for I2RS IGP Requirements
The following are unique features for I2RS IGP requirements:
o mt-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 router-number - which is used for router number monitoring
o route-info-list - which is used for router-ID conflict recovery
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o route state information for subscribing for notification of route
changes and neighbor changes
These I2RS features in [I-D.wang-i2rs-ospf-dm] are described in the
sections below.
6.1. mt-rib
Link-state protocols may need to reconverge 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.
| +--rw mt-rib
| | +--rw route* [prefix]
| | +--rw prefix inet:ipv4-prefix
| | +--rw nexthop-list
| | | +--rw nexthop* [ospf-nexthop]
| | | +--rw ospf-nexthop inet:ipv4-prefix
| | +--rw back-nexthop? inet:ipv4-prefix
| | +--rw metric? uint32
| | +--rw type? ospf-route-type-def
| | +--rw route-state-info
| | +--rw metric? uint32
| | +--rw route-current-state? ospf-route-state-def
| | +--rw route-previous-state? ospf-route-state-def
| | +--rw route-chg-reason? route-chg-reason-def
| | +--rw lsid? inet:ip-address
| | +--rw lsa-type? lsa-type-def
| | +--rw advertiser? inet:ip-address
Figure 1: draft-i2rs-wang-ospf-dm-00 mt-rib structure
6.2. nbr-list
The ospf 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 ospf nodes. Without the deployment of fast detection
techniques, one node has to wait for several seconds before it
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realized the adjacency had broken. This kind of issue can cause one
device is cut off from its network and lose connectivity completely.
No matter planned or accidentally it may cause traffic blackhole
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 I2RS and IGP information model 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 suggest this as a
beginning step, but there are additional steps to support fast-
convergence when neighbor's change.
| | +--rw nbr-list
| | +--rw nbr* [router-id]
| | +--rw router-id inet:ip-address
| | +--rw interface-index? uint64
| | +--rw interface-name? string
| | +--rw nbr-status? nbr-status-def
| | +--rw nbr-previous-status? nbr-status-def
| | +--rw nbr-down-reason? nbr-down-reason-def
| | +--rw nbr-address? inet:ipv4-address
| | +--rw ip-address? inet:ipv4-address
Figure 2 draft-i2rs-wang-ospf-dm-00 ospf-nbr-list structure
6.3. router-number
Customers complain regarding the limits on the number of routers
routers should be deployed in one area. The answer for this question
is not clear in vendor's guide since the product specification
provide limits that guarantee operations. For operations people
looking to see the real limits, the field engineers use words like
"usually", "roughly" or "most of the time". As the consequence, the
customers may simply deploy all routers in one OSPF area, and deal
with the scaling issues after the network grows.
With the help of OSPF information model and I2RS interfaces, it is
possible to give such deployment warnings when the limits will be hit
in the real-time manner. Based on the statistics of router number
and system resource consuming, plus the ratio relationship between
them, one notification or warning can be sent to I2RS Client. From
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there decision can be made to expand safely or have to shrink for
precaution.
+--rw area-list
| +--rw area* [area-id]
| +--rw area-id uint16
| +--rw router-number? uint32
Figure 3 draft-i2rs-wang-bgp-dm-00 router-id
6.4. route-info-list
It is become more common that networks have router-ID conflict in
networks both intra and inter area, especially after different area
have merged. It is time-consuming and troublesome to detect the
places where this trouble happened. The frequently used solution is
to rename one of the conflicted router-ID to a new one then reboot
the involved OSPF instance to force all adjacencies to rebuild and
re-synchronize the LSDB.
It MAY be possible to alleviate this issue with the help of OSPF
information model and programmatic I2RS interfaces. With the help of
the router-info-list, this conflict can be detected automatically.
When one substantial conflict is on the horizon, no need to wait for
mutual re-origination happened, ID conflict can be found in router-
info-list with help of their coordinate information, no matter the
conflict routers come from the same area or not. What is more,
through I2RS interfaces and Agent, it is possible to rewrite one of
the conflicted router-ID into a new one then reboot the routing-
protocol.
+--rw route-info-list* [route-info-index]
| +--rw route-info-index uint32
| +--rw router-id inet:ipv4-address
| +--rw ip-address-list* [ip-address]
| | +--rw ip-address inet:ipv4-address
Figure 4 - OSPF route information
6.5. ospf route status information
The following yang top-level diagram shows additional status for each
ospf route:
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| +--rw mt-rib
| | +--rw route-state-info
| | +--rw metric? uint32
| | +--rw route-current-state? ospf-route-state-def
| | +--rw route-previous-state? ospf-route-state-def
| | +--rw route-chg-reason? route-chg-reason-def
| | +--rw nbr-list
| | +--rw nbr* [router-id]
| | +--rw router-id inet:ip-address
| | +--rw interface-index? uint64
| | +--rw interface-name? string
| | +--rw nbr-status? nbr-status-def
| | +--rw nbr-previous-status? nbr-status-def
| | +--rw nbr-down-reason? nbr-down-reason-def
Figure 5 ospf route and neighbor additions.
7. Merge Suggestions
[I-D.yeung-netmod-ospf] and [I-D.wang-i2rs-ospf-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
8. IANA Considerations
This draft includes no request to IANA.
9. Security Considerations
None since this is just an analysis draft
10. 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.
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[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.wang-i2rs-ospf-dm]
Wang, L., Hares, S., and N. Wu, "Yang Data model for I2RS
interface to the OSPF protocol", draft-wang-i2rs-ospf-
dm-00 (work in progress), September 2014.
[I-D.wu-i2rs-ospf-info-model]
Wu, N., Wang, L., and S. Hares, "I2RS Information Model
for OSPF protocol", draft-wu-i2rs-ospf-info-model-00 (work
in progress), September 2014.
[I-D.yeung-netmod-ospf]
Yeung, D., Qu, Y., Zhang, J., Bogdanovic, D., and K.
Sreenivasa, "Yang Data Model for OSPF Protocol", draft-
yeung-netmod-ospf-02 (work in progress), October 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.
[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
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Lixing Wang
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 10095
China
Email: wanglixing@huawei.com
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