computer science

Passport Carrier Release

Passport Carrier Release is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Passport Carrier Release rather than just read about it. In short: Passport Carrier Release (PCR) is a version of the Passport Switch (now Multiservice Switch) software designed to run in telecommunications carrier environments. It was formerly developed by Nortel.

Key takeaways

Passport Carrier Release belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Passport Carrier Release to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Passport Carrier Release from memory before moving on to harder problems.

Reference excerpt

Passport Carrier Release (PCR) is a version of the Passport Switch (now Multiservice Switch) software designed to run in telecommunications carrier environments. It was formerly developed by Nortel. After the sale in 2009 of most Nortel's assets, the passport SW is still used in several products of Alcatel-Lucent, Ericsson and Kapsch. The passport products are now part of Ericsson's PPX products under IP Networking. The Ericsson PPX products can be found at the following link.

Technologies Internally, PCR is largely built up of custom applications on top of a VxWorks kernel. A benefit of the software is that it is completely modular and can load components to Passport control processors (CPs) and function processors (FPs) on an as-needed basis. FPs (also known as line cards) each run their own instance of the Operating System, and as such can be rebooted without the need to take the entire switch out of service, for example due to a software failure. As well, as would be expected, entire cards can be replaced while the system is hot, thus minimizing downtime due to hardware failure.

OAM and provisioning PCR consists of a custom OAM interface that is highly object oriented. This reflects the modular nature of the operating system. The core component when provisioning IP networks is the Virtual Router (however, a Passport switch can act in more than IP environments). Interfaces are provisioned as "application" objects, which are then in turn connected to Protocol Ports on a Virtual Router. It is best to consider the environment in which provisioning occurs to be object oriented, in the sense that the behaviour of the router is defined based on which objects are instantiated and how they are related. Note that there is a change in this paradigm noticeable in recent releases of PCR -- MPLS, for example, now resides on an object called simply a Router with built-in IP features. This provisioning approach is more similar to that of Cisco or Juniper Networks.

Drawbacks Unfortunately, at this time the OAM interface is unable to select which components are to be loaded on the fly. For example, if Multi-link Point-to-Point Protocol (PPP) is a required feature, before this feature can be used the CP and the FP hosting the MLPPP interface must have the mlppp feature loaded. As well, the vast array of objects available to an operator can be daunting, especially for an individual starting out with Nortel Passport switches for the first time. As well, built in documentation leaves much to be desired (thus not helping the first-time operator), and tab completion features are non-existent (though some objects and parameters have shorthand names, for example the Virtual Router component can simply be known as a Vr).

Versioning PCR releases are assigned a release code, usually of the form CG##X, where ## is a two digit number and X is a letter, usually referring to a patch code or revision code. The current release is PCR 10.1.1.

Worked examples

Example 1 — a first encounter with Passport Carrier Release

Start with the simplest possible case. Write down what Passport Carrier Release claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Passport Carrier Release before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Passport Carrier Release ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Passport Carrier Release

In research: Passport Carrier Release appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Passport Carrier Release in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Passport Carrier Release is common in secondary-school and first-year university syllabi. It links to neighbouring topics Embedded operating systems, Internet Protocol based network software, Networking hardware, so understanding it makes those chapters shorter.
In everyday life: Look for Passport Carrier Release outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Passport Carrier Release in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Passport Carrier Release means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Passport Carrier Release out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Passport Carrier Release in simple terms?

Passport Carrier Release (PCR) is a version of the Passport Switch (now Multiservice Switch) software designed to run in telecommunications carrier environments. It was formerly developed by Nortel.

Why does Passport Carrier Release matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Passport Carrier Release?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Passport Carrier Release.