SDNRG Y. Xia, Ed.
Internet-Draft S. Jiang, Ed.
Intended status: Standards Track T. Zhou, Ed.
Expires: January 5, 2015 S. Hares
Huawei Technologies Co., Ltd
July 4, 2014
NEMO (NEtwork MOdeling) Language
draft-xia-sdnrg-nemo-language-00
Abstract
The North-Bound Interface (NBI), located between the network 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 anther NBI
fashion. Concept, model and syntax are introduced in the document.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Related work . . . . . . . . . . . . . . . . . . . . . . . . 4
4. The NEMO Language overview . . . . . . . . . . . . . . . . . 5
4.1. Network Model of the NEMO Language . . . . . . . . . . . 5
4.2. Primitives . . . . . . . . . . . . . . . . . . . . . . . 7
5. The NEMO Language Examples . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
9. Informative References . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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
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.
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 think from the user perspective and
abstract the network from the top down.
[I-D.sdnrg-service-description-language] describe the requirements
for a service description language and the design considerations.
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A top-down NBI 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 describe 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 proposed NEtwork MOdeling
(NEMO) 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, NEMO language is designed to help defining
service requirement to network, detailed configurations and
instructions performed by network devices are opaque to network
operators. So NEMO language should be declarative rather than
imperative.
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
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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".
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.
3. Related work
YANG is a data modeling language used to model configuration and
state data manipulated by the Network Configuration Protocol
(NETCONF), NETCONF remote procedure calls, and NETCONF notifications
[RFC6020]. Although it is extensible for more data modeling in
addition to NETCONF, YANG is not capable of describing high level
network requirements, such as SLA (Service Level Agreement). YANG is
designed for north-bound interfaces of the device, which is also the
south-bound of the controller. It is not proper to model the north-
bound interface of the controller, aka the NBI. Moreover, the YANG
is not capable of describing the service processing logic, which
typically includes transition of conditions and states.
UML (Unified Modeling Language) is a powerful modeling language,
which is domain agnostic. It is hard to describe the network demand,
and cannot be embedded in network applications. 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
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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 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.
4. The NEMO Language overview
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. With limited number
of key words and expressions, NEMO language defines the entity and
capability models for users with different view of network
abstraction, and enables network users/applications to describe their
demands for network resources, services and logical operations in an
intuitive expression. And finally the NEMO language description can
be explained and executed by a language engine.
4.1. Network Model of the NEMO Language
Behind the NEMO language, there is a set of meta-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,
link and flow. Each entity contains property and statistic
information. With a globally unique identifier, the network entity
is the basic object for operation.
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o Node model: describes the entity with the capability of packet
processing. According to the functionality, there are three types
of node
* The forwarding node (FN) only deals with L2/3 forwarding. It
forwards packets according to the forwarding table and modifies
packet heads.
* The processing node (PN) provides L4-7 network services, and
will modify the body of packets.
* The logical node (LN) describes a set of network elements and
their links, 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 Link model: describes the connectivity between node entities.
According to the forwarding capability, links are usually divided
into layer 2 and layer 3 types
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.
Network behavior includes the information and control operations.
The information operation 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 policy to describe the control operation.
o Policy: control the behavior of specific entities by APP, such as
flow policy, node policy. All the policies follow the same
pattern "with <condition>, to execute <action>", and can be
applied to any entity
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4.2. Primitives
The primitives of NEMO language are derived from the network model,
and fall into four categories.
a. Resource access primitives
Node/UnNode entity_id Type {FN|PN|LN}
Owner node_id
Properties key1 ,value1
Node/UnNode: create/delete a node
Entity id: system allocated URI for the node entity
Type: Node type of FN (forwarding node), PN (processing node)
or LN (logical node)
Owner: since the node can be nested, this primitive figures
out which node the new one belongs to
Properties: other properties to describe the node in the form of
(key, value).
Link/UnLink entity_id Endnodes (node1_id,node2_id)
SLA key,value
Properties key1 ,value1
Link/UnLink: create/delete a link.
Entity id: system allocated URI for the link entity
Endnodes: two end-node IDs of the link
SLA: SLA description for the link
Properties: other properties to describe the link in the form of
(key, value).
Flow/UnFlow entity_id Match/UnMatch key1, value1|
Range(value, value) |
Mask(value, value)
Properties key1 ,value1
Flow/UnFlow: create/delete a flow.
Match/UnMatch: create/delete match items for the flow
Range: describe the range of the value
Mask: use mask to describe a range of the value
Properties: other properties to describe the flow in the form of
(key, value).
b. Behavior primitives
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Query key Value {value}
From entity_id
Query: generate a synchronously query
key: the parameter name to be queried
Value: the return value for the query
From: the entity to be queried (define entity_id).
Policy/UnPolicy policy_id Appliesto entity_id
Condition {expression}
Action {"forwardto"|"drop"|"gothrough"|
"bypass"|"guaranteeSLA"|"Set"|
"Packetout"|Node|UnNode|Link|Unlink}
Policy/UnPolicy: create/delete a policy
Appliesto: apply the policy to an entity
Condition: condition to execute the policy
Action: actions to be executed when conditions are met
Notification/UnNotification entity_id On key
Every period
RegisterListener
callbackfunc
Notification/UnNotification: create/delete a notification for an
entity
On: the notification will monitor the state change of a
parameter identified by the "key"
Every: time period at which to report the state
RegisterListener: the callback function that is used to process the
notification.
c. Connection management primitives
Connect conn_id Address ip_address
Port port_num
Disconnect conn_id
Connect: set up a connection to the controller
Address: IP address of the controller to connect to
Port: port of the controller to connect to
Disconnect: disconnect to the controller.
d. Transaction primitives
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Transaction
Commit
Transaction: indicate the beginning of a transaction
Commit: commit to execute the transaction
5. The NEMO Language Examples
A tenant needs two connections to carry different service flows
between two datacenters.
one connection of the tenant is 40G bandwidth with less than 400ms
delay, another connection is 100M bandwidth with less than 50ms
delay.
{
Link Link1_id
Endnodes (DC1_node_id, DC2_node_id)
Property "NAME","DC1_DC2_link_one","Bandwith",40G,"Delay",400ms
Link Link2_id
Endnodes (DC1_node_id, DC2_node_id)
Property "NAME","DC1_DC2_link_two","Bandwith",100M,"Delay",50ms
}
The tenant has two types of traffic, CDN sync traffic uses high
bandwidth connection and online game traffic uses low latency
connection.
{
Flow flow1_id
Match "srcip","10.0.1.1/24","dstip","20.0.1.1/24","Port","55555"
Property "NAME","CDN sync flow","Bidirection","true"
Flow flow2_id
Match "srcip","10.0.1.1/24","dstip","20.0.1.1/24","Port","56663"
Property "NAME","online Game","Bidirection","true"
Policy policy1_id
Appliesto flow1_id
Action "forwardto",link1_id
Policy policy2_id
Appliesto flow2_id
Action "gothrough",link2_id
}
The tenant wants the online game traffic to go through WOC in
nighttime before it is carried by low latency connection.
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{
Policy policy3_id
Appliesto flow2_id
Condition {Time>18:00 or Time< 2:00}
Action "gothrough",{woc_node_id ,link2_id}
}
6. 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.
7. IANA Considerations
This memo includes no request to IANA.
8. Acknowledgements
The authors would like to thanks the valuable comments made by Wei
Cao, Xiaofei Xu, Fuyou Miao and Wenyang Lei.
This document was produced using the xml2rfc tool [RFC2629].
9. 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.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-00, Work in
progress", July 2014.
[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, March 1997.
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[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[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
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