Circuit Redundancy Groups

[tardoe]

NetBox version

v2.11.12

Feature type

New functionality

Proposed functionality

This proposal adds a new model for defining the relationship between circuits to track a designed redundancy between them.

A Circuit Redundancy Group (CRG) should contain two or more circuits that provide redundancy to one another. For example, two circuits exist from A to B, when added as members of a CRG, it is then easy to determine the impact of various failure scenarios. Optionally, circuits can be given a priority to indicate their primary, secondary, tertiary etc. status within the group.

Use case

A common use case is for dual circuits between two sites or devices. E.g.:

NYC1 -- DAL1 (provider A)
   |      |
NYC2 -- DAL2 (provider B)

In this case the two circuits linking DAL and NYC sites would be added to the same CRG to indicate they protect each other. One of the most useful example use-cases for this information might be evaluating maintenance notifications. If both circuits have overlapping maintenance events, the user would know to expect an outage. These types of scenarios could be determined well ahead of time given the designed redundancy is documented.

Database changes

An addition of a CRG model and any associated models required to track a many-to-many relationship between CRG and Circuit. It might also be worth considering CRG nesting (similar to how Locations models operate) where redundancy design are more complicated.

External dependencies

None

[tardoe]

Having given this some further thought, we can likely add a field titled "minimum circuits" to the CRG model to indicate the minimum number of circuits required to call the CRG "healthy". This will enable a few use cases such as:

• CRGs with more than two parallel links where more than two are required at any one time.
• Circuits that are related but cannot be modelled with terminations such as back-to-back connected circuits in uncontrolled spaces (e.g. a long-haul circuit and a last-mile circuit that are directly connected without a device in between) that would be considered a single logical circuit. This would have a "minimum circuits" value of 2 in this case - meaning both are required.
• Nesting can be used to group these back-to-back CRGs (as above) with other single-circuits that provide redundancy to on-another.

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[jeremystretch]

After revisiting this, it needs a more detailed implementation proposal. What specifically should this model look like? @tardoe can you provide some more detail?

[tardoe]

@jeremystretch What additional details do you require that's not been specified in the original outline?

I'd expect the CRG model to be similar to the Location model, likely with an added field for "failover type" - this could either be user defined or a pre-defined list, e.g.: "active-passive", "active-active", "at-least-one" etc. etc.

[jeremystretch]

What fields does the proposed CRG model have? Which of those are required? What are its unique constraints and ordering logic?

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[cybarox]

My 2ct on this:

I would like to show an example where CRG could be useful to define which impact an outage could have.

Our branches are dependent on cloud software that have to be always available.
Therefore, we are planning 3 circuits for our sites because of high availability.
We use two ISPs, due to different backbones. Our Main ISP offers an LTE/4G backup option, but this should only be used if our 2 main circuits are down.
If I would transfer our design to CR groups in NetBox, it would look something like this:

                  ________________________
                 [________site-crg________]
                 [ prio = 0               ]
                 [ type = parent          ]
                 [ mode = active-passive  ]
                 [ min_child = 1          ]
                 [ child_type = crg       ]
                 [________________________]
                   /                    \
     _____________/________      ________\_____________
    [_______main-crg_______]    [______backup-crg______]
    [ parent = site-crg    ]    [ parent = site-crg    ]
    [ prio = 1             ]    [ prio = 2             ]
    [ mode = active-active ]    [ mode = passive       ]
    [ min_child = 1        ]    [ min_child = 1        ]
    [ child_type = circuit ]    [ child_type = circuit ]
    [______________________]    [______________________]
      |  __________________       |  __________________
      |-[__circuit1-isp1___]      \-[__circuit3-isp1___]
      [ [ prio = 1         ]        [ prio = null      ]
      | [ type = VDSL      ]        [ type = LTE/4G    ]
      | [ provider = isp1  ]        [ provider = isp1  ]
      | [ crg = main-crg   ]        [ crg = backup-crg ]
      | [__________________]        [__________________]
      |  __________________
      \-[__circuit2-isp2___]
        [ prio = 2         ]
        [ type = VDSL      ]
        [ provider = isp2  ]
        [ crg = main-crg   ]
        [__________________]

I would define a higher-level CRG for the site. In our case, 2 further CRGs are subordinated to this one.
One of the groups combines our two main ciruits. There should minimum 1 circuit be working here.
The other group defines circuits which are defined as backup for the main circuits. (e.g. if the excavator hits the main cable)

We also have custom fields to identify information such as physical location of the circuit handover point, ID of the electrical box, access contacts, etc. Today we fill in these fields for each circuit. It would make more sense to assign these fields to the CRG to maintain them in one place only.

I hope this helps when considering a solution.

[ryanmerolle]

This could be a good candidate for 3.6

[tardoe]

Adding some more thoughts on this while I make time to actually implement it:

• The issue with @cybarox is that you need 3 instances to describe a scenario that you could really do with 1. To lower complexity I would simply create a single CRG with all three circuits. The two main ISPs would have equal weight and the LTE connection with a lower weight. Using those weights you can easily tell if a site is "degraded" based on the weights of all available circuits. You can also offline assess the impact of any set of outages.

• Given a "site" for an enterprise can be treated very differently to a service provider or a campus (e.g. site == building??) I feel that a site-level CRG is probably unnecessary.

I'd like to have a go at implementing this in the coming weeks, time permitting. I feel from an initial, basic cut I can have a better idea of how this model might work.