| Thomas Vachuska | 83e090e | 2014-10-22 14:25:35 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Licensed to the Apache Software Foundation (ASF) under one |
| 3 | * or more contributor license agreements. See the NOTICE file |
| 4 | * distributed with this work for additional information |
| 5 | * regarding copyright ownership. The ASF licenses this file |
| 6 | * to you under the Apache License, Version 2.0 (the |
| 7 | * "License"); you may not use this file except in compliance |
| 8 | * with the License. You may obtain a copy of the License at |
| 9 | * |
| 10 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | * |
| 12 | * Unless required by applicable law or agreed to in writing, |
| 13 | * software distributed under the License is distributed on an |
| 14 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| 15 | * KIND, either express or implied. See the License for the |
| 16 | * specific language governing permissions and limitations |
| 17 | * under the License. |
| 18 | */ |
| 19 | |
| Brian O'Connor | b876bf1 | 2014-10-02 14:59:37 -0700 | [diff] [blame] | 20 | /** |
| tom | a1d16b6 | 2014-10-02 23:45:11 -0700 | [diff] [blame] | 21 | * Set of abstractions for conveying high-level intents for treatment of |
| 22 | * selected network traffic by allowing applications to express the |
| 23 | * <em>what</em> rather than the <em>how</em>. This makes such instructions |
| 24 | * largely independent of topology and device specifics, thus allowing them to |
| 25 | * survive topology mutations. |
| tom | 6db1f0a | 2014-10-07 09:12:29 -0700 | [diff] [blame] | 26 | * <p/> |
| 27 | * The controller core provides a suite of built-in intents and their compilers |
| 28 | * and installers. However, the intent framework is extensible in that it allows |
| 29 | * additional intents and their compilers or installers to be added |
| 30 | * dynamically at run-time. This allows others to enhance the initial arsenal of |
| 31 | * connectivity and policy-based intents available in base controller software. |
| 32 | * <p/> |
| 33 | * The following diagram depicts the state transition diagram for each top-level intent:<br> |
| 34 | * <img src="doc-files/intent-states.png" alt="ONOS intent states"> |
| 35 | * <p/> |
| 36 | * The controller core accepts the intent specifications and translates them, via a |
| 37 | * process referred to as intent compilation, to installable intents, which are |
| 38 | * essentially actionable operations on the network environment. |
| 39 | * These actions are carried out by intent installation process, which results |
| 40 | * in some changes to the environment, e.g. tunnel links being provisioned, |
| 41 | * flow rules being installed on the data-plane, optical lambdas being reserved. |
| 42 | * <p/> |
| 43 | * After an intent is submitted by an application, it will be sent immediately |
| 44 | * (but asynchronously) into a compiling phase, then to installing phase and if |
| 45 | * all goes according to plan into installed state. Once an application decides |
| 46 | * it no longer wishes the intent to hold, it can withdraw it. This describes |
| 47 | * the nominal flow. However, it may happen that some issue is encountered. |
| 48 | * For example, an application may ask for an objective that is not currently |
| 49 | * achievable, e.g. connectivity across to unconnected network segments. |
| 50 | * If this is the case, the compiling phase may fail to produce a set of |
| 51 | * installable intents and instead result in a failed compile. If this occurs, |
| 52 | * only a change in the environment can trigger a transition back to the |
| 53 | * compiling state. |
| 54 | * <p/> |
| 55 | * Similarly, an issue may be encountered during the installation phase in |
| 56 | * which case the framework will attempt to recompile the intent to see if an |
| 57 | * alternate approach is available. If so, the intent will be sent back to |
| 58 | * installing phase. Otherwise, it will be parked in the failed state. Another |
| 59 | * scenario that’s very likely to be encountered is where the intent is |
| 60 | * successfully compiled and installed, but due to some topology event, such |
| 61 | * as a downed or downgraded link, loss of throughput may occur or connectivity |
| 62 | * may be lost altogether, thus impacting the viability of a previously |
| 63 | * satisfied intent. If this occurs, the framework will attempt to recompile |
| 64 | * the intent, and if an alternate approach is available, its installation |
| 65 | * will be attempted. Otherwise, the original top-level intent will be parked |
| 66 | * in the failed state. |
| 67 | * <p/> |
| 68 | * Please note that all *ing states, depicted in orange, are transitional and |
| 69 | * are expected to last only a brief amount of time. The rest of the states |
| 70 | * are parking states where the intent may spent some time; except for the |
| 71 | * submitted state of course. There, the intent may pause, but only briefly, |
| 72 | * while the system determines where to perform the compilation or while it |
| 73 | * performs global recomputation/optimization across all prior intents. |
| Brian O'Connor | b876bf1 | 2014-10-02 14:59:37 -0700 | [diff] [blame] | 74 | */ |
| Toshio Koide | d32809b | 2014-10-09 10:58:54 -0700 | [diff] [blame] | 75 | package org.onlab.onos.net.intent; |