computer science

Private Network-to-Network Interface

Private Network-to-Network Interface 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 Private Network-to-Network Interface rather than just read about it. In short: The Private Network-to-Network Interface (PNNI) is a link-state routing protocol used in Asynchronous Transfer Mode (ATM) networks. PNNI is similar to the Open Shortest Path First (OSPF) used for IP routing.

Key takeaways

Private Network-to-Network Interface 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 Private Network-to-Network Interface to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Private Network-to-Network Interface from memory before moving on to harder problems.

Reference excerpt

The Private Network-to-Network Interface (PNNI) is a link-state routing protocol used in Asynchronous Transfer Mode (ATM) networks. PNNI is similar to the Open Shortest Path First (OSPF) used for IP routing. PNNI is a suite of network protocols that can be used to discover an ATM network topology, create a database of topology information, and route calls over the discovered topology. PNNI is a link-state routing protocol, which means that the protocol collects information about the current state of links and nodes in the network to build a network database. The PNNI network database can be used to determine the network structure and the current state of network components. To build the PNNI network database, each PNNI node must receive topology information from all the other devices in the network. To keep the database current, the node must receive regular updates from other nodes. The PNNI protocol communicates the state of a PNNI network in PNNI Topology State Elements (PTSEs). PTSEs are discrete messages that contain information about one of the following types of network components:

PNNI nodes Reachable addresses PNNI links between nodes To enable communications with other nodes, each switch needs to have all the PTSE information for each switch in the network. Each node is responsible for flooding out its own PTSE information to all the other switches in the network. Since up-to-date PTSE information is required for optimal routing decisions to be made, there are several different mechanisms in place to help ensure that all nodes have reasonably accurate PTSE information. The five common reasons for updating PTSEs are as follows:

Resources administratively added, removed or altered on a node. Resource failure such as a loss of signal (LOS) on a link. A significant change in link resources due to virtual circuits (VCs) routing or derouting. Periodic updates defined by the PTSE refresh and PTSE lifetime interval timers. A processor switch module (PXM) switchover. PTSE information is passed between nodes using PNNI topology state packets (PTSPs). These packets utilize the routing control channel (RCC; VPI = 0 and VCI = 18) between adjacent nodes. The RCC is also used for Hello packets and other PNNI messages. If the switch is unable to establish the RCC with the adjacent node, then PTSE information is not exchanged. Once a node receives PTSE information, the node stores the contents, or element information, in the database. This information is used to generate precomputed routing tables that identify routes to other network devices. PNNI uses the Dijkstra's algorithm for shortest path first (SPF) calculation. The PNNI database is also used to perform on-demand routing when the appropriate routing table does not contain a viable path. PNNI measures line capacities and delays in addition to simple cost metrics.

References

External links "Cisco PNNI Network Planning Guide for MGX and SES Products, Release 5.2; Chapter: Introduction to PNNI". Cisco.com. Cisco Systems. Retrieved August 7, 2017.

Worked examples

Example 1 — a first encounter with Private Network-to-Network Interface

Start with the simplest possible case. Write down what Private Network-to-Network Interface 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 Private Network-to-Network Interface 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 Private Network-to-Network Interface 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 Private Network-to-Network Interface

In research: Private Network-to-Network Interface 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 Private Network-to-Network Interface 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: Private Network-to-Network Interface is common in secondary-school and first-year university syllabi. It links to neighbouring topics Asynchronous Transfer Mode, ITU-T recommendations, Networking standards, so understanding it makes those chapters shorter.
In everyday life: Look for Private Network-to-Network Interface 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 Private Network-to-Network Interface in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Private Network-to-Network Interface 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 Private Network-to-Network Interface out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Private Network-to-Network Interface in simple terms?

Why does Private Network-to-Network Interface 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 Private Network-to-Network Interface?

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 Private Network-to-Network Interface.