Chassis MIB Proposal.
{3COM/PDD/PeteW}@pdd.3mail.3com.com Fri, 04 December 1992 16:41 UTC
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Date: Fri, 04 Dec 1992 16:33:00 -0800
From: {3COM/PDD/PeteW}@pdd.3mail.3com.com
Subject: Chassis MIB Proposal.
To: chassismib@cs.utk.edu
Message-Id: <921204.083452@3Mail.3Com.COM>
Msg-Date: 1992-12-04
Msg-Time: 16:30
Microsoft Mail v3.0 IPM.Microsoft Mail.Note From: Wilson, Peter To: Heads, Bob Moran, Paul Woodruff, Paul IETF-Chassis MIB Subject: Chassis MIB Proposal. Date: 1992-12-04 16:26 Priority: Message ID: 2C8A5B3D Conversation ID: 2C8A5B3D ------------------------------------------------------------------------------ I tried sending this proposal to the group the week after Washington and again a week later. It doesn't seem to be getting through so this time I've split the thing into two parts. The first is the descriptive text, the second a MIB proposal. The proposal follows on from the ideas I presented at Washington to make the chassis MIB more generic. The most important change is to reduce the relationship table between 3 things, module, entity and segment to a two way relationship between component and entity. I hope you find the suggestions here useful. Pete ---------------------------------------------------------------------------- ------------------------------. Definitions of Managed Objects for a Chassis Containing Multiple Logical Network Devices November 24, 1992 Proposal By: Peter Wilson Peter_Wilson@3Com.com Introduction ============ At the IETF meeting in Washington the definition of a chassis was discussed. It seemed that between those present there was some ambiguity about what we wanted the model to look like. Following on from that discussion it was proposed that the chassis MIB become somewhat more generic. My aims in this proposal are as follows: 1) To produce a more generic MIB. By this I want to get away from the idea that a chassis contains slots, entities and segments. slots and segments are somewhat implementation specific concepts. Segments may not even exist in some network chassis implementations. 2) Reduce the complexity of relationships between parts of the MIB. The current MIB defines a table of relationships between an entity, a slot and a segment. From that model its unclear what relationships could exist and how the configuration can be changed. From the application point of view configuration of the device could be very difficult without having explicit knowledge of each chassis. 3) Produce a MIB that provides good information for a generic chassis management application, even if a particular chassis does not contain knowledge of all the various things contained in that chassis. 4) Make visible the components that make up a physical entity. In the current proposal this information is implicit in the relationship table. One does not know from the MIB what logical components are available on a card. To change a relationship involves destroying that relationship and creating another. There is no continuity between the various operations and one has no way of identifying the component of a module being used in an entity. 5) Move towards SNMPv2 (still a good way to go!) This proposal needs specific MIB definitions to be added (moved from existing proposal) to describe power supplies sensors etc. The Model ========= A chassis is a generic 'container'. It can be any shape and size and can have any position. Examples of things that constitute chassis are the traditional network hub, PABX as well as less common items such as a room, building, campus etc. One chassis can recursively contain other chassis, eg a building could contain some rooms which in turn contain cabinets that contain network hubs. There are two views of a chassis. Firstly the physical view. The physical view considers the chassis to comprise a number of different types of compartment. Each type of compartment is specialised to hold a particular type of item or module. Examples of compartment types would be corridors, rooms, elevator shafts, network card slots and power supply bays. At any instant in time each of these compartments may be occupied or empty. Secondly there is the logical or functional view. In this view the chassis is considered to contain a number of 'entities'. Each entity provides some function. Examples of entities would be company projects and Network Repeaters. An entity is implemented using parts from one or more physical modules. It is necessary to describe the relationship between physical module and logical entity. For the purposes of this relationship a physical module is considered to comprise a number of logical components (resources?). A number of logical components are joined together to construct an entity. To illustrate these concepts consider a company to be the chassis. In this example the physical modules are floors of a building and the logical entities projects. Each floor comprises a number of people which are the components from which project teams are constructed. Each person is specialised for a particular role within a project. Floor Function:Person Project Implemented By (module) (component) (entity) (relationship) -------- ------- -------------- 1 - Marketing:Pete xyz-thing Marketing:Pete Marketing:Jeff Development:Mike Development:Mike Manufacturing:Dave Manufacturing:Alan abc-thing Marketing:Jeff 2 - Marketing:Jane Development:Sharon Development:Sharon Development:Michele Manufacturing:Dave Manufacturing:Alan 3- Development:Michele Marketing:Paul Development:James Analysis of this example provide some interesting relationships that apply equally to a network type device: 1) Each physical entity comprises a number of logical components that can be used in the construction of an entity. 2) A logical component of one type may be substituted for a different component of the same type in a logical entity. eg James may be substituted for Mike but not for Jeff. 3) It is possible that at some time not all components are part of entities. It is however necessary to know all components that exist and the current use or otherwise of those components. Having looked at a generic example consider a practical example of a chassis that contains modules for the token ring and Ethernet. In this example assume that each Ethernet and each Token Ring card contain 4 ports. There currently exist 4 entities in the chassis, two Ethernet repeaters and 2 Token Rings. The chassis contains 4 locations that can contain modules and the configuration is as follows: Slot Number Contains 1 Ethernet Repeater Card 2 802.5 Port Card 3 Ethernet Repeater Card 4 802.5 Port Card The logical configuration of the chassis at a particular time is as follows: Entity Implemented By ------ -------------- Repeater 1 Module 1, Port 1, 2, 3 Module 3, Port 2 Repeater 2 Module 1, Port 4 Module 3, Port 1, 3 Token Ring 1 Module 2, Port 1, 2 Token Ring 2 Module 2, Port 3 Module 4, Port 3 ---------------------------------------- Module 2, Port 4 - Not currently used Module 3, Port 4 - " " " Module 4, Port 1, 2, 4 - " " " Note that a MIB to represent and configure devices such as this must make all components of all cards visible and allow the configuration of those components into entities. Now suppose that an operator needs an additional Ethernet repeater. In order to do this a new Repeater entity is created and some of the repeater ports are assigned to that entity. eg: create Repeater 3 assign Module 3, Port 4 to Repeater 3 -- Currently unassigned assign Module 3, Port 1 to Repeater 3 -- Moved from Repeater 2 >> NOTE >> ==== >> This model does not use the concept of Segment as currently specified >> in the chassis MIB draft. There are a number of reasons for this: >> >> 1) Segment is an implementation specific concept closely allied with >> the idea of a dedicated backplane. A number of chassis implementations >> do not physically have this concept/restriction. >> >> 2) There is no analogous concept to segment in other types of chassis, >> for example a building or company. >> >> 3) The 3 way mapping of module, entity and segment is complex and >> difficult to implement in such a way that all information is >> visible. In this model the three way module/entity/segment relationship >> is replaced with a simpler two way component/entity relationship. >> >> There are a number of ways to achieve the same ends using this model. >> Such implementations are described below: Combining Components into Entities (Network Chassis) ================================== 1. Implicit Assignment ---------------------- This strategy requires the most effort from the chassis agent but provides the best and easiest model for both the application writer and the best abstraction for the user. It is applicable to both chassis that use a hardwired backplane and those that use central or distributed switching services to implement functions. The chassis is required to implement a number of entities. The number and type of entity implemented by a particular chassis depends on the physical capabilities and design of that chassis. For example one chassis may be designed with 3 Ethernet type busses on a backplane. In this chassis it is possible to create 3 repeaters that use components from more than one physical module. The chassis may also be capable of implementing a number of additional repeaters provided only components on the same card are used. Implicit assignment says that the chassis is required to marshal its inherent resources to best meet the requested configuration of the manager. The managers requests are communicated by the creation and destruction of entities and by the assignment of components to entities. In the example of a chassis with 2 Ethernet backplanes the stragtegy of the agent could be as follows: manager agent ----------------------------------------------------------------- create Repeater record repeaters existence assign Mod 1, Port 1 add component to repeater, don't need a to repeater backplane yet! assign Mod 1, Port 2 add component to repeater, don't need a to repeater backplane yet! assign Mod 2, Port 1 Repeater crosses card boundaries so find a spare backplane and assign that to this repeater. Note that if there are no spare backplanes then the assignment is rejected. Note that this approach makes repeater implementation transparent to a user. The model is identical regardless of whether the chassis uses backplanes, has central/distributed switching or any other implementation strategy. 2. Explicit Assignment ---------------------- This is a more manual approach. The effort required in the agent is potentially somewhat less but the savings are really nominal. In this model the manager is responsible for assigning backplanes. A backplane is simply a physical module in the same way that a repeater card is a module. Because it is a module it also has logical components that can be assigned to entities. Now consider the same example of a repeater chassis with 2 backplanes. The example is the same as above: Create a repeater and assign a number of repeater ports to that repeater: manager agent ----------------------------------------------------------------- create Repeater record repeaters existence assign Mod 1, Port 1 add component to repeater, don't need a to repeater backplane yet! assign Mod 1, Port 2 add component to repeater, don't need a to repeater backplane yet! assign Mod 2, Port 1 Request rejected. There is no assigned connection path to allow ports on different cards to be assigned to the same repeater. assign Ether B'plane Repeater can now span cards. 1 to repeater assign Mod 2, Port 1 Request successful. NOTE: Variations on this theme are possible but the idea remains the same. For example one could statically create 2 repeaters that always exist to represent the two backplanes. Ports could be assigned to those repeaters. Additional repeaters could be created but would not be allowed to span cards. In a particular chassis there will also be a number of fixed entities that always exist, although the components assigned to that entity may differ.
- Chassis MIB Proposal. {3COM/PDD/PeteW}