| 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
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.
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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.
The rest of this draft is the details so those who desire "sounds bytes" level reading may stop reading now.
[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:
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 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: [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
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.
the remaining difference are the following:
The following are unique features for I2RS IGP requirements: [I-D.wang-i2rs-isis-dm] are described in the sections below.
These I2RS features in
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.
+--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
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 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
+--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
The following are additions that [I-D.wang-i2rs-isis-dm] adds to support route state querying.
[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
This draft includes no request to IANA.
None since this is just an analysis draft
| [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", Internet-Draft draft-ietf-i2rs-architecture-00, August 2013. |
| [I-D.ietf-i2rs-rib-info-model] | Bahadur, N., Folkes, R., Kini, S. and J. Medved, "Routing Information Base Info Model", Internet-Draft draft-ietf-i2rs-rib-info-model-01, October 2013. |
| [I-D.ietf-i2rs-usecase-reqs-summary] | Hares, S. and M. Chen, "Summary of I2RS Use Case Requirements", Internet-Draft draft-ietf-i2rs-usecase-reqs-summary-00, November 2014. |
| [I-D.litkowski-isis-yang-isis-cfg] | Litkowski, S., "Yang Data Model for ISIS protocol", Internet-Draft draft-litkowski-isis-yang-isis-cfg-01, June 2014. |
| [I-D.wang-i2rs-isis-dm] | Wang, L., Hares, S. and N. Wu, "Yang Data model I2RS to IS-IS protocol", Internet-Draft draft-wang-i2rs-isis-dm-00, September 2014. |
| [I-D.wu-i2rs-isis-info-model] | Wu, N., Wang, L. and S. Hares, "Information model for IS-IS protocol", Internet-Draft draft-wu-i2rs-isis-info-model-00, 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. |
| [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. |