SDNRG Y. Xia, Ed. Internet-Draft S. Jiang, Ed. Intended status: Standards Track T. Zhou, Ed. Expires: April 16, 2016 S. Hares Huawei Technologies Co., Ltd October 14, 2015 NEMO (NEtwork MOdeling) Language draft-xia-sdnrg-nemo-language-03 Abstract The North-Bound Interface (NBI), located between the control plane and the applications, is essential to enable the application innovations and nourish the eco-system of SDN. While most of the NBIs are provided in the form of API, this document proposes the NEtwork MOdeling (NEMO) language which is intent based interface with novel language fashion. Concept, model and syntax are introduced in the document. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 16, 2016. Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Xia, et al. Expires April 16, 2016 [Page 1] Internet-Draft NEtwork MOdeling Language October 2015 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements for the Intent Based NBI Language . . . . . . . 4 4. Related work . . . . . . . . . . . . . . . . . . . . . . . . 5 5. The NEMO Language Specifications . . . . . . . . . . . . . . 6 5.1. Network Model of the NEMO Language . . . . . . . . . . . 6 5.2. Notation . . . . . . . . . . . . . . . . . . . . . . . . 7 5.3. NEMO Language Overview . . . . . . . . . . . . . . . . . 8 5.4. Model Definition . . . . . . . . . . . . . . . . . . . . 9 5.4.1. Data Types . . . . . . . . . . . . . . . . . . . . . 9 5.4.2. Model Definition and Description Statement . . . . . 10 5.5. Resource Access Statements . . . . . . . . . . . . . . . 12 5.5.1. Node Operations . . . . . . . . . . . . . . . . . . . 12 5.5.2. Connection Operations . . . . . . . . . . . . . . . . 13 5.5.3. Flow Operations . . . . . . . . . . . . . . . . . . . 14 5.6. Behavior Statements . . . . . . . . . . . . . . . . . . . 15 5.6.1. Query Behavior . . . . . . . . . . . . . . . . . . . 16 5.6.2. Operation Behavior . . . . . . . . . . . . . . . . . 16 5.6.3. Notification Behavior . . . . . . . . . . . . . . . . 19 5.7. Transaction Statements . . . . . . . . . . . . . . . . . 20 6. The NEMO Language Examples . . . . . . . . . . . . . . . . . 20 7. Security Considerations . . . . . . . . . . . . . . . . . . . 21 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 10. Informative References . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 1. Introduction While SDN (Software Defined Network) is becoming one of the most important directions of network evolution, the essence of SDN is to make the network more flexible and easy to use. The North-Bound Interface (NBI), located between the control plane and the applications, is essential to enable the application innovations and nourish the eco-system of SDN by abstracting the network capabilities/information and opening the abstract/logic network to applications. The NBI is usually provided in the form of API (Application Programming Interface). Different vendors provide self-defined API Xia, et al. Expires April 16, 2016 [Page 2] Internet-Draft NEtwork MOdeling Language October 2015 sets. Each API set, such as OnePK from Cisco and OPS from Huawei, often contains hundreds of specific APIs. Diverse APIs without consistent style are hard to remember and use, and nearly impossible to be standardized. In addition, most of those APIs are designed by network domain experts, who are used to thinking from the network system perspective. The interface designer does not know how the users will use the device and exposes information details as much as possible. It enables better control of devices, but leaves huge burden of selecting useful information to users without well training. Since the NBI is used by network users, a more appropriate design is to express user intent and abstract the network from the top down. To implement such an NBI design, we can learn from the successful case of SQL (Structured Query Language), which simplified the complicated data operation to a unified and intuitive way in the form of language. Applications do not care about the way of data storage and data operation, but to describe the demand for the data storage and operation and then get the result. As a data domain DSL, SQL is simple and intuitive, and can be embedded in applications. So what we need for the network NBI is a set of "network domain SQL". [I-D.xia-sdnrg-service-description-language] describe the requirements for a service description language and the design considerations. This document will introduce an intent based NBI with novel language fashion. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] when they appear in ALL CAPS. When these words are not in ALL CAPS (such as "should" or "Should"), they have their usual English meanings, and are not to be interpreted as [RFC2119] key words. Network service also "service" for short, is the service logic that contains network operation requirements; Network APP also "APP" for short, is the application to implement the network service; Network user also "user" for short, is the network administrator or operator. Xia, et al. Expires April 16, 2016 [Page 3] Internet-Draft NEtwork MOdeling Language October 2015 3. Requirements for the Intent Based NBI Language An intent based NBI language design contains following features: o Express user intent To simplify the operation, applications or users can use the NBI directly to describe their requirements for the network without taking care of the implementation. All the parameters without user concern will be concealed by the NBI. o Platform independent With the NBI, the application or user can description of network demand in a generic way, so that any platform or system can get the identical knowledge and consequently execute to the same result. Any low-level and device/vendor specific configurations and dependencies should be avoided. o Intuitive Domain Specific Language (DSL) for network The expression of the DSL should be human-friendly and be easily understood by network operators. DSL should be directly used by the system. o Privilege control Every application or user is authorized within a specific network domain, which can be physical or virtual. While different network domains are isolated without impact, the application or user may have access to all the resource and capabilities within its domain. The user perception of the network does not have to be the same as the network operators. The NBI language works on the user's view so the users can create topologies based on the resources the network-operators allow them to have. o Declarative style As described above, the NBI language is designed to help defining service requirement to network, detailed configurations and instructions performed by network devices are opaque to network operators. So the NBI language should be declarative rather than imperative. Xia, et al. Expires April 16, 2016 [Page 4] Internet-Draft NEtwork MOdeling Language October 2015 4. Related work YANG [RFC6020] is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF) [RFC6241], NETCONF remote procedure calls, and NETCONF notifications. UML (Unified Modeling Language) is a powerful modeling language, which is domain agnostic. YANG and UML all focus on syntax specification which formulate grammatical structure of NBI language, however, they do not have the ability to express users' real semantics. NBI language should facilitate users to express their own intent explicitly, instead of general complying with grammar syntax. So YANG and UML is appropriate to describe the model behind the NBI language not the NBI itself. With the emergence of the SDN concept, it is a consensus to simplify the network operation, which leads to many cutting-edge explorations in the academic area. Nick McKeown from Stanford University proposed the SFNet [TSFNet], which translated the high level network demand to the underlying controller interfaces. By concealing the low level network details, the controller simplified the operation of resource, flow, and information for applications. The SFNet is used for the SDN architecture design, and does not go into the NBI design. Jennifer Rexford from Princeton University designed the Frenetic [Frenetic] based on the OpenFlow protocol. It is an advanced language for flow programming, and systematically defines the operating model and mode for the flow. However, the network requirement from the service is not only the flow operations, but also includes operations of resource, service conditions, and service logic. In the book [PBNM], John Strassner defined the policy concept and proposed the formal description for network operations by using the policy. The method for querying network information is absent in the book. Virtual tenant network and operations to the tenant network are not considered. All these investigations direct to the future SDN that use simple and intuitive interfaces to describe the network demands without complex programming. Xia, et al. Expires April 16, 2016 [Page 5] Internet-Draft NEtwork MOdeling Language October 2015 5. The NEMO Language Specifications NEMO language is a domain specific language (DSL) based on abstraction of network models and conclusion of operation patterns. It provides NBI fashion in the form of language. Instead of tons of abstruse APIs, with limited number of key words and expressions, NEMO language enables network users/applications to describe their demands for network resources, services and logical operations in an intuitive way. And finally the NEMO language description can be explained and executed by a language engine. 5.1. Network Model of the NEMO Language Behind the NEMO language, there is a set of basic network models abstracting the network demands from the top down according to the service requirement. Those demands can be divided into two types: the demand for network resources and the demands for network behaviors. The network resource is composed of three kinds of entities: node, connection and flow. Each entity contains property and statistic information. With a globally unique identifier, the network entity is the basic object for operation. Users can construct their own topology or network traffic arbitrarily with these basic objects without considering about real physical topology. In addition, NEMO Engine also has the ability of obtaining available resources automatically as operation objects when users don't define them. o Node model: describes the entity with the capability of packet processing. According to the functionality, there are two types of node * The function node (FN) provides network services or forwarding with user concern, such as, firewall, load balance, vrouter, etc. * The business node (BN) describes a set of network elements and their connections, such as subnet, autonomous system, and internet. It conceals the internal topology and exposes properties as one entity. It also enables iteration, i.e., a network entity may include other network entities. o Connection model: describes the connectivity network resource between node entities. With Connection model, user could apply for link resources between nodes and user can assign specific bandwidth for them. Connection constructs the foundation of communication, namely, the necessary condition for communications between nodes is there are available resources between them. By Xia, et al. Expires April 16, 2016 [Page 6] Internet-Draft NEtwork MOdeling Language October 2015 default, the communication is allowed if there are direct connections between them. The Connection is not limited to the connectivity between single entity and single entity, but it can also express the connectivity between single entity and multiply entities, or multiply entities and multiply entities. o Flow model: describes a sequence of packets with certain common characters, such as source/destination IP address, port, and protocol. From the northbound perspective, flow is the special traffic with user concern, which may be per device or across many devices. So the flow characters also include ingress/egress node, and so on. The Flow model together with the associated operations describe reachability of specific traffic between nodes in the virtual network, which is different from the connection resource between nodes. Network behavior includes the information aquisition and the control operations. The NEMO language provides two methods to get the network information for users. o Query: a synchronous mode to get the information, i.e., one can get the response when a request is sent out. o Notification: an asynchronous mode to get the information, i.e., with one request, one or multiple responses will be sent to the subscriber automatically whenever trigger conditions meet. The NEMO language uses operations to control the network. o Operation: control the behavior of specific entities by APP, such as flow operation, node operation. All the operations follow the same pattern "when , do , with ", and can be applied to any entity. But some of operation elements can be omitted according to users' requirement. Operation has the similar meaning with policy in some sense which also emphasizes the dynamic adjustment of objects. 5.2. Notation The syntactic notation used in this specification is an extended version of BNF ("Backus Naur Form" or "Backus Normal Form"). In BNF, each syntactic element of the language is defined by means of a production rule. This defines the element in terms of a formula consisting of the characters, character strings, and syntactic elements that can be used to form an instance of it. The version of BNF used in this specification makes use of the following symbols: Xia, et al. Expires April 16, 2016 [Page 7] Internet-Draft NEtwork MOdeling Language October 2015 < > Angle brackets delimit character strings that are the names of syntactic elements. ::= The definition operator. This is used in a production rule to separate the element defined by the rule from its definition. The element being defined appears to the left of the operator and the formula that defines the element appears to the right. [ ] Square brackets indicate optional elements in a formula. The portion of the formula within the brackets may be explicitly specified or may be omitted. { } Braces group elements in a formula. The portion of the formula within the braces shall be explicitly specified. | The alternative operator. The vertical bar indicates that the portion of the formula following the bar is an alternative to the portion preceding the bar. If the vertical bar appears at a position where it is not enclosed in braces or square brackets, it specifies a complete alternative for the element defined by the production rule. If the vertical bar appears in a portion of a formula enclosed in braces or square brackets, it specifies alternatives for the contents of the innermost pair of such braces or brackets. !! Introduces ordinary English text. This is used when the definition of a syntactic element is not expressed in BNF. 5.3. NEMO Language Overview NEMO language provides 5 classes of commands: model definition, resource access, behavior, connection management, transaction to facilitate the user intent description. Xia, et al. Expires April 16, 2016 [Page 8] Internet-Draft NEtwork MOdeling Language October 2015 := | | := | | | := | | | | | | | | | := | | | | | | := | NEMO language provides limited number of key words to enables network users/applications to describe their intent. The key words supported by the language are as follows: := Boolean | Integer | String | Date | UUID | EthAddr | IPPrefix | NodeModel | ConnectionModel | FlowModel | ActionModel | Description | Porperty | Node | Connection| Flow | EndNodes | Type | Contain | Match | List | Range| Query | From | Notification | Listener | Operation | Target | Priority | Condition | Action | Transaction | Commit | CREATE | IMPORT | UPDATE | DELETE 5.4. Model Definition 5.4.1. Data Types NEMO language provides several build-in data types: Boolean This data type is used for simple flags that track true/ false conditions. There are only two possible values: true and false. The Boolean literal is represented by the token . Integer A number with an integer value, within the range from -(2^63) to +(2^63)-1. The Integer literal is represented by the token . String A sequence of characters. The string is always in the quotation marks. The String literal is represented by the token . Date A string in the format yyyy-mm-dd hh:mm:ss, or yyyy-mm-dd, or hh:mm:ss. The Date literal is represented by the token . UUID A string in the form of Universally Unique IDentifier [RFC4122], e.g. "6ba7b814-9dad-11d1-80b4-00c04fd430c8". A Xia, et al. Expires April 16, 2016 [Page 9] Internet-Draft NEtwork MOdeling Language October 2015 typical usage of the UUID is to identify network entities, policies, actions and so on. The UUID literal is represented by the token . EthAddr A string in the form of MAC address, e.g. "00:00:00:00:00:01". The EthAddr literal is represented by the token . IPPrefix A string in the form of IP address, e.g. "192.0.2.1". The mask can be used in the IP address description, e.g. "192.0.2.0/24". The IPPrefix literal is represented by the token . The token can be defined as follows: := Boolean | Integer | String | Date | UUID | EthAddr | IPPrefix And a generic literal is represented by the token := | | | | | | 5.4.2. Model Definition and Description Statement In addition to default build-in network models, NEMO language facilitates users to define new model types. The token is a string that MUST start with a letter and followed by any number of letters and digits. More specific naming can be defined as follows: := !!type name of the node model := !!type name of the connection model := !!type name of the flow model := | | := !!type name of the action model := | := !!name of the property in a model The statement is used to create a node model: := NodeModel Property { : }; The NodeModel specifies a new node type. Xia, et al. Expires April 16, 2016 [Page 10] Internet-Draft NEtwork MOdeling Language October 2015 The Property is followed by a list of " : " pairs to specify properties for the new node type. Since belonging network is the intrinsic property for a node model, there is no need to redefine the belonging network in the property list. Example: NodeModel "DPI" Property String : "name", Boolean : "is_enable"; The statement generates a new node model named DPI with two properties, "name" and "is_enable". The statement is used to create a connection model: := ConnectionModel Property { : }; The ConnectionModel specifies a new connection type. The Property is followed by a list of " : " pairs to specify properties for the new connection type. Since end nodes are intrinsic properties for a connection model, there is no need to redefine the end nodes in the property list. The statement is used to create a flow model: := FlowModel Property { : }; The FlowModel specifies a new flow type. The Property is followed by a list of " : " pairs to specify fields for the new flow type. The statement is used to create an action model: := ActionModel Property { : }; The ActionModel specifies a new action type. The Property is followed by a list of " : " pairs to specify properties for the new action. NEMO language also supports querying the description of a defined model by using the statement: := Description ; Xia, et al. Expires April 16, 2016 [Page 11] Internet-Draft NEtwork MOdeling Language October 2015 The keyword Description is followed by a model type name. The description of the queried model will return from the language engine. 5.5. Resource Access Statements In NEMO language, each resource entity instance is identified by a which MUST be unique. We use the following token to indicate the identifier given to the resource entity instance. := !! name to identify the node instance := !! name to identify the connection instance := !! name to identify the flow instance := || 5.5.1. Node Operations NEMO model defines basic method for the node instances, and uses intuitive keyword to indicate the specific method. User could create, import, update and delete a node instance. The statement is used to create or update a node instance: := CREATE Node Type [Contain {}] [Property {: }]; The statement is used to import an existing external node instance: := IMPORT Node Type [Contain {}] [Property {: }]; The statement is used to update an existing node instance: := UPDATE Node [Contain {}] [Property {: }]; In all the above three statements, the Node is followed by a user specified . According to the method, system will take corresponding action for the node instance. If the method is CREATE or IMPORT and the is new in the system, a new node will be created automatically. If the method is UPDATE and the Xia, et al. Expires April 16, 2016 [Page 12] Internet-Draft NEtwork MOdeling Language October 2015 exists in the system, the corresponding node identified by will be updated with the following information. The Type specifies the type of the node to operate. The Contain is an optional keyword specifying the internal nodes which are included in this node instance. The Property is an optional keyword followed by a list of ": " pairs. Multiple ": " pairs are separated by commas. The MUST be selected from the property definition of the corresponding node definition. An example of creating a node instance is as follows: CREATE Node Headquarter Type l3group Contain LN-1 Property location : "Beijing"; The statement creates a layer 3 virtual network which contains a predefined node "LN-1". The l3 virtual network is located in Beijing. The statement is used to delete a node instance: := DELETE Node ; The DELETE Node is to delete a node in user's network. 5.5.2. Connection Operations NEMO model defines basic method for the connection instances, and use intuitive keyword to indicate the specific method. User could create, update and delete a connection instance. The statement is used to create a connection: := CREATE Connection Type EndNodes , [Property {: }]; The statement is used to update a connection: Xia, et al. Expires April 16, 2016 [Page 13] Internet-Draft NEtwork MOdeling Language October 2015 := UPDATE Connection [EndNodes {}, {}] [Property {: }]; The Connection is followed by a user specified . If the method is CREATE and the is new in the system, a new connection will be created automatically. If the method is UPDATE and the exists in the system, the corresponding connection identified by the will be updated with the following information. The Type specifies the type of the connection to use. For example there will be point to point connection, or point to multiple points connection. The EndNodes specifies the end nodes of a connection. For each connection there will be left nodes and right nodes stand for the two ends. The Property is an optional keyword followed by a list of ": " pairs. Multiple ": " pairs are separated by commas. The MUST be selected from the property definition of the corresponding connection definition. An example of creating a connection instance is as follows: CREATE Connection connection-1 Type p2p EndNodes S1, S2 Property bandwidth : 1000, delay : 40; The statement creates a connection between two nodes, and sets the connection property. The statement is used to delete a connection instance: := DELETE Connection ; The DELETE Connection is to delete a connection in user's network. 5.5.3. Flow Operations NEMO model defines basic method for the flow instances, and use intuitive keyword to indicate the specific method. User could create, update and delete a flow instance. Xia, et al. Expires April 16, 2016 [Page 14] Internet-Draft NEtwork MOdeling Language October 2015 The statement is used to create a flow: := CREATE Flow Match {: | Range (, ) | List({})} The statement is used to update a flow: := UPDATE Flow Match {: | Range (, ) | List({})} The Flow is followed by a user defined . If the method is CREATE and the is new in the system, a new flow identifier will be created automatically. If the method is UPDATE and the exists in the system, the corresponding flow identified by the will be updated with the following information. The Match specifies a flow by indicate match fields. NEMO language also provides two keywords to assist the expression of values: o The List is used to store a collection of data with the same data type. o The Range is used to express a range of values. An example of creating a flow instance is as follows: CREATE Flow flow-1 Match src_ip : Range ("192.0.2.1", "192.0.2.243"); The statement describes a flow with the source IP address ranging from 192.0.2.1 to 192.0.2.243. The statement is used to delete a flow instance: := DELETE Flow ; The DELETE Flow is to delete a flow in user's network. 5.6. Behavior Statements Xia, et al. Expires April 16, 2016 [Page 15] Internet-Draft NEtwork MOdeling Language October 2015 5.6.1. Query Behavior The query statement is to retrieve selected data from specified model object. The generate a query: := Query {} From {|} The Query is followed by one or more s which are defined properties of the object to be queried. The From is followed by the one or more queried objects. NENO language support query operation to network entities and the policy. 5.6.2. Operation Behavior NEMO model defines basic method for the operation instances, and use intuitive keyword to indicate the specific method. User could create, update and delete a operation instance. In NEMO language, each operation instance is identified by a which MUST be unique. := !! name to identify the operation instance Create and update a policy := CREATE Operation Target Priority [Condition ] Action { : {}}; := UPDATE Operation [Target ] [Priority ] [Condition ] [Action { : {}}]; The Operation is followed by a user defined . If the method is CREATE and the is new in the system, a new operation will be created automatically. If the method is UPDATE and the exists in the system, the corresponding operation identified by the will be updated with the following information. Xia, et al. Expires April 16, 2016 [Page 16] Internet-Draft NEtwork MOdeling Language October 2015 The Target specifies the entity to which the operation will apply. The Priority specifies the globe priority of the operation in the tenant name space. The with lower number has a higher priority, i.e. priority 0 holds the highest priority. The Condition is an optional keyword follow by an expression. It tells your program to execute the following actions only if a particular test described by the expression evaluates to true. And users also can define which objects won't need to execute these actions with Constraint. A NEMO language expression is a construct made up of variables, operators, and method invocations, which are constructed according to the syntax of the language and evaluates to a single value. NEMO language supports many operators to facilitate the construction of expressions. Assume variable A holds 10 and variable B holds 0, then: Xia, et al. Expires April 16, 2016 [Page 17] Internet-Draft NEtwork MOdeling Language October 2015 +----------+----------------------------------------------+---------+ | Operator | Description | Example | +----------+----------------------------------------------+---------+ | && | Called Logical AND operator. If both the | (A && | | | operands are non-zero, then the condition | B) is | | | becomes true. | false. | | || | Called Logical OR Operator. If any of the | (A || | | | two operands are non-zero, then the | B) is | | | condition becomes true. | true. | | ! | Called Logical NOT Operator. Use to reverses | !(A && | | | the logical state of its operand. If a | B) is | | | condition is true then Logical NOT operator | true. | | | will make false. | | | == | Checks if the values of two operands are | (A == | | | equal or not, if yes then condition becomes | B) is | | | true. | not | | | | true. | | != | Checks if the values of two operands are | (A != | | | equal or not, if values are not equal then | B) is | | | condition becomes true. | true. | | > | Checks if the value of left operand is | (A > B) | | | greater than the value of right operand, if | is not | | | yes then condition becomes true. | true. | | >= | Checks if the value of left operand is | (A >= | | | greater than or equal to the value of right | B) is | | | operand, if yes then condition becomes true. | not | | | | true. | | < | Checks if the value of left operand is less | (A < B) | | | than the value of right operand, if yes then | is | | | condition becomes true. | true. | | <= | Checks if the value of left operand is less | (A <= | | | than or equal to the value of right operand, | B) is | | | if yes then condition becomes true. | true. | +----------+----------------------------------------------+---------+ The Action specifies the execution when conditions meet. An example of creating anoperation is as follows: CREATE Operation operation-1 Target flow-1 Priority 100 Condition (time>"18:00") || (time<"21:00") Action redirect : "backup_connection"; The statement creates an operation which indicates the flow to go through backup connection from 18:00 to 21:00. Xia, et al. Expires April 16, 2016 [Page 18] Internet-Draft NEtwork MOdeling Language October 2015 Delete an operation: := DELETE Operation ; The DELETE Operation is to delete a policy in user's network. 5.6.3. Notification Behavior In NEMO language, each notification instance is identified by a := !! name to identify the notification instance Create and update a notification := CREATE Notification [(Query {} From {})] Condition {} Listener ; := UPDATE Notification [(Query {} From {})] Condition {} Listener ; The Notification is followed by a user defined . If the method is CREATE and the is new in the system, a new notification will be created automatically. If the method is UPDATE and the exists in the system, the corresponding notification identified by the will be updated with the following information. The Query clause is nested in the notification statement to indicate the information acquisition. The Condition clause is the same as in operation statement, which triggers the notification. The Listener specifies the callback function that is used to process the notification. Delete a notification: := DELETE Notification ; Xia, et al. Expires April 16, 2016 [Page 19] Internet-Draft NEtwork MOdeling Language October 2015 The DELETE Notification is to delete a notification in user's network. 5.7. Transaction Statements := Transaction := Commit The keywords Transaction and Commit are used to tag begin and end of a transaction. The code between the two key words will be interpreted as a transaction and executed by the NEMO language engine. 6. The NEMO Language Examples An enterprise with geographically distributed headquarter and branch sites has the requirement to dynamically balance the backup traffic. In order to implement this scenario, the virtual WAN tenant creates two logicnw, and generates two connections with different SLA to carry diverse service flows. One connection has 100M bandwidth with less than 50ms delay, which is used for normal traffic. And the other connection has 40G bandwidth with less than 400ms delay, which is used for backup traffic after work (from 19:00 to 23:00). With self defined flow operations, the tenant can manage the connection load balancing conveniently. Real-time Connection +--------------------+ 192.0.2.0/24 198.51.100.0/24 +---------+ +-------------+ | Branch |------------------| Headquarter | +---------+ +-------------+ | | +--------------------+ Broadband Connection The detailed operation and code are shown as follows. o Step1: Create two virtual logicnw nodes in the WAN CREATE Node Branch Type l2group Property ipv4Prefix : 192.0.2.0/24; CREATE Node Headquarter Type l2group Property ipv4Prefix : 198.51.100.0/24; Xia, et al. Expires April 16, 2016 [Page 20] Internet-Draft NEtwork MOdeling Language October 2015 o Step2: Connect the two virtual nodes with two virtual connections with different SLA. CREATE Connection broadband_connection EndNodes Branch, Headquater Property bandwidth : 40000, delay : 400; CREATE Connection realtime_connection EndNodes Branch, Headquater Property bandwidth : 100, delay : 50; o Step3: Indicate the flow to be operated. CREATE Flow flow_all Match src_ip : "192.0.2.0/24", dst_ip: "198.51.100.0/24"; CREATE Flow flow_backup Match src_ip : "192.0.2.0/24", dst_ip: "198.51.100.0/24", port: 55555; o Step4: Apply policies to corresponding flows. P1: CREATE Operation operation4all Target flow_all Priority 200 Action redirect: "realtime_connection"; P2: CREATE Operation operation4backup Target flow_backup Priority 100 Condition (time>"19:00:00") || (time<"23:00:00") Action redirect: "broadband_connection"; 7. Security Considerations Because the network customers are allowed to customize their own services, they may bring potentially big impacts to a running IP network. A strong user authentication mechanism is needed for the northbound interface of the SDN controller. User authorization should be carefully managed by the network administrator to avoid any dangerous operations and prevent any abuse of network resources. 8. IANA Considerations This memo includes no request to IANA. Xia, et al. Expires April 16, 2016 [Page 21] Internet-Draft NEtwork MOdeling Language October 2015 9. Acknowledgements The authors would like to thanks the valuable comments made by Wei Cao, Xiaofei Xu, Fuyou Miao, Yali Zhang and Wenyang Lei. This document was produced using the xml2rfc tool [RFC2629]. 10. Informative References [Frenetic] Foster, N., Harrison, R., Freedman, M., Monsanto, C., Rexford, J., Story, A., and D. Walker, "Frenetic: A Network Programming Languages, ICFP' 11". [I-D.xia-sdnrg-service-description-language] Xia, Y., Jiang, S., and S. Hares, "Requirements for a Service Description Language and Design Considerations", draft-xia-sdnrg-service-description-language-02 (work in progress), May 2015. [PBNM] Strassner, J., "Policy-Based Network Management: Solutions for the Next Generation, Morgan Kaufmann Publishers Inc. San Francisco, CA, USA.", 2003. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, DOI 10.17487/RFC2629, June 1999, . [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, DOI 10.17487/RFC4122, July 2005, . [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, . Xia, et al. Expires April 16, 2016 [Page 22] Internet-Draft NEtwork MOdeling Language October 2015 [TSFNet] Yap, K., Huang, T., Dodson, B., Lam, M., and N. McKeown, "Towards Software-Friendly Networks, APSys 2010, pp:49-54, 2010, New Delhi, India.". Authors' Addresses Yinben Xia (editor) Huawei Technologies Co., Ltd Q14, Huawei Campus, No.156 Beiqing Road Hai-Dian District, Beijing, 100095 P.R. China Email: xiayinben@huawei.com Sheng Jiang (editor) Huawei Technologies Co., Ltd Q14, Huawei Campus, No.156 Beiqing Road Hai-Dian District, Beijing, 100095 P.R. China Email: jiangsheng@huawei.com Tianran Zhou (editor) Huawei Technologies Co., Ltd Q14, Huawei Campus, No.156 Beiqing Road Hai-Dian District, Beijing, 100095 P.R. China Email: zhoutianran@huawei.com Susan Hares Huawei Technologies Co., Ltd 7453 Hickory Hill Saline, CA 48176 USA Email: shares@ndzh.com Xia, et al. Expires April 16, 2016 [Page 23]