Internet DRAFT - draft-hares-i2rs-info-model-service-topo
draft-hares-i2rs-info-model-service-topo
I2RS working group S. Hares
Internet-Draft Q. Wu
Intended status: Standards Track M. Wang
Expires: August 2, 2015 J. You
Huawei
January 29, 2015
An Information model for service topology
draft-hares-i2rs-info-model-service-topo-03
Abstract
As stated in [I.D-ietf-sfc-problem-statement], the service overlay is
independent of the network topology and allows operators to use
whatever overlay or underlay they prefer and to locate service nodes
in the network as needed.
This document extends the general topology model concept defined in
[I.D-medved-i2rs-topology-im] and focuses on defining information
model for service topology.
Status of This Memo
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This Internet-Draft will expire on August 2, 2015.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Service Topology Information Model . . . . . . . . . . . . . 3
3.1. Model Overview . . . . . . . . . . . . . . . . . . . . . 3
3.2. Abstract Topology Model: the Service-Topology Component . 3
3.3. Model Extension: Service Function Chain Topology
Component . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4. Model Extension: Inventory datastore Component . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Normative References . . . . . . . . . . . . . . . . . . 9
6.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Network topology information can be collected from network by using
IGP or BGP-LS [I.D-draft-ietf-idr-ls-distribution]. Information
model for network topology provided in [I.D-medved-i2rs-topology-im]
is built based on such network topology information.
A service specific overlay utilized by Service chaining creates the
service topology. The overlay creates a path between service
function(SF) nodes. Service functions can be co-located on one SF
Node or physically separated across several SF Nodes with each having
one or more Service Functions. In either case, a service function
may be running in its own virtualized system space or natively on the
hosting system.
Within the service topology, an ordered set of Service functions will
be invoked for each packet that belongs to a given flow for which a
SFC will be applied. Adding new service function to SF Node in the
topology is easily accomplished, and no underlying network changes
are required. Furthermore, additional service Functions or Service
Function instances, for redundancy or load distribution purpose, can
be added or removed to the service topology as required.
As stated in [I.D-ietf-sfc-problem-statement], the service overlay is
independent of the network topology and allows operators to use
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whatever overlay or underlay they prefer and to locate service nodes
in the network as needed.
This document extends the general topology model concept defined in
[I.D-medved-i2rs-topology-im] and focuses on defining information
model for service topology.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119].
3. Service Topology Information Model
This section specifies the service topology information model in
Routing Backus-Naur Form (RBNF, [RFC5511]). It also provides
diagrams of the main entities that the information model is comprised
of.
3.1. Model Overview
The abstract Topology Model contain a set of abstract nodes and a
list of abstract links. An abstract link connects two abstract
nodes. Service Function Chain Topo model and other service topo
model can be augumented from the abstract topology model with
topology specifics.
+-----------------+
| Abstract |
| Topology Model |
| |
+--------|--------+
|
+------------------------+
| | |
| | |
+--------V--------+ +--------V--------+
|Service Function | | |
| Chain | | Other Service |
| Topology Model | | Topology Model |
+-----------------+ +-----------------+
3.2. Abstract Topology Model: the Service-Topology Component
The following diagram contains an informal graphical depiction of the
main elements of the information model:
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+----------------+
| topology |<...
+----------------+ :
* * : :
| | :...:
| |
+--------+ +--------+
...>| node |<.......|segment |<...
: +--------+<.......+--------+ :
: : * : : * : :
:..... | : : | :...:
| : : |
.....>+--------+<........: : |
: | TP |<..........: |
: ...>+--------+ |
: : |
: : .....................+---------+
.........................|Direction|
+---------+
The basic information model works as follows: A service topology
contains service nodes and segments. A segment connects two nodes (a
source and a destination)and have direction, may be unidirectional or
bidirectional. unidirectional is one where traffic is passed through
any two service node or a set of service nodes in one forwarding
direction only. Bidirectional is one where traffic is passed through
any two service nodes or a set of service nodes in both forwarding
directions. Each serivce node contains termination points. It
occurs before or after other service node, therefore each node may
have its upstream service node and/or downstream service node.
A service node may be dedicated to a tenant(e.g., an IPVPN customer),
globally shared among tenants, or available to be assigned in whole
or in part to a tenant or a set of tenants. Therefore service Nodes
can map onto and be supported by other network elements in the
underlying network, while Segment can map onto and be supported by
other links in the underlying network,e.g., one segment can be mapped
to two consecutive links stitching together. Service Topologies can
map onto other, underlay topologies.
The information model for the Service-Topology component is more
formally shown in the following diagram.
/* exterior definitions for service topology */
<service-topology> ::= (<topology>...)
/* Topology definitions */
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<topology> ::= <TOPOLOGY_IDENTIFIER>
[<node-count>]
(<segment>...)
(<node>...)
[<topology-type>]
[<underlay-topologies>]
[<topology-extension>]
<node-count> ::= INTEGER-32;
<topology-type> ::= (
(<netconf> [<netconf-topology-type>])|
(<i2rs> [<i2rs-topology-type>])
<underlay-topologies> ::= (<TOPOLOGY_IDENTIFIER>...)
<topology-extension> ::=
<netconf-topology-extension> |
...
<segment> ::= <Segment_IDENTIFIER>
<source>
<destination>
[<direction>]
[<segment-extension> ]
<source> ::= <termination-point-reference>
<destination> ::= <termination-point-reference>
<termination-point-reference> ::= <SF_NODE_IDENTIFIER>
<direction> ::= (<Unidirection>)|
(<Bidirection>)
<segment-extension> ::= <netconf-segment-extension> |
<i2rs-segment-extension> |
...
<node> ::= <SF_NODE_IDENTIFIER>
(<termination-point>...)
[<NODE_TYPE>]
[<NEXT-HOP>]
[<node-extension>]
<termination-point> ::= <TERMINATION_POINT_IDENTIFIER>
[<supporting-termination-points>]
[<termination-point-extension>]
<supporting-termination-points> ::=
(<TERMINATION_POINT_IDENTIFIER>...)
< NODE-TYPE> ::=
(<Classifier-Node>)|
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(<SF-Node>)|
(<SFF-Node>)
...
<NEXT-HOP> ::= (<NODE_IDENTIFIER>...)
<node-extension> ::= <Classifier-extension> |
<SF-Node-extension> |
<SFF-Node-extension>
...
The elements of the Service-Topology information model are as
follows:
o A service overlay can contain multiple topologies. Each topology
is captured in its own list element, distinguished via a topology-
id.
o A topology has a certain type, such as NETCONF or I2RS. A
topology can even have multiple types simultaneously. The type,
or types, are captured in the list of "topology-type" components.
o A topology contains segments and nodes, each captured in their own
list.
o A node has a node-id. This distinguishes the node from other
nodes in the list. In addition, a node has a list of termination
points, used to terminate segment. An examples of a termination
point might be a physical or logical port or, more generally, an
interface.
o A segment is identified by a segment-identifier, uniquely
identifying the portion of the network bounded by two service
nodes within the topology. segment are point-to- point and has
direction. The direction can be unidirectional or bidirectional.
Accordingly, a segment contains a source and a destination. Both
source and destination reference a corresponding node, as well as
a termination point on that node.
o The topology, node, segment and direction elements can be extended
with topology-specific components (topology-extensions, node-
extension, segment-extension and direction-extension
respectively).
The topology model includes segment that are either bidirectional
unidirectional. Service function chain path is analogue to linked
list data structure and can be represented through a set of Ordered
segments from source to destination. Each node in the service
overlay may be located at different layer. The segment can be setup
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to steer traffic through these specific service nodes at different
layers or bypass some specific service nodes at different layers.
The topology model only supports point to point and does not support
multipoint. Therefore Segments are terminated by a single
termination point, not sets of termination points. Connections
involving multihoming or segment aggregation schemes need to be
modeled using multiple point-to-point segment,e.g., connection from
service node A at lower layer to service node D at higher layer can
comprise a segment 1 from service node A to service node B and
segment 2 from service node B to service node C and segment 3 from
service node C to service node D. By using segment aggregation, we
can define a new segment from service A to service node D which is
supported by segment 1,2 and 3.
Unlike network topology collection, the service topology information
may be not available from each SF by using IGP advertisement or BGP-
LS northbound distribution since SF may be not located at network
layer. However these SF at different layer may have affinity with
one SF node(e.g., SF egress node or SF ingress node or SF enabled
node),therefore service topology information associated with Service
nodes can be collected using RESTCONF/NETCONF interface or I2RS
interface for interrogation of a virtual device's state, statistics
and configuration.
3.3. Model Extension: Service Function Chain Topology Component
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<Classifier-extension>::= <SFP>
<SFC-Policy>
<Matching-RULE>
<SFP> :: = <SF-List>
<SFF-List>
<SF-Node-extension> :: = <SF-Node-Locator>
<Support-Context-Type>
<SF-Type>
<SF-Inventory-data>
<SF-type> ::=
<firewall> |
<loadbalancer>|
<NAT44>|
<NAT64>|
<DPI>
<SFF-Node-extension>::=<SFFN-address>
<SFFN-Virtual-Context>
<Attached-service-add>
<Customer-Support-List>
<Customer-Support-Resource-List>
<SFFN-VNTopo>
<SFFN-Virtual-Context>::= <id>
3.4. Model Extension: Inventory datastore Component
Inventory Data for service overlay can be obtained by using NETCONF
or I2RS and share to PCE, ALTO server or other topology manager
defined in [I.D-ietf-i2rs-architecture]. Information shared by them
is defined as the component, "inventory database". This component
defines a set of groupings with auxiliary information required and
shared by those other components.
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<SF-inventory-data> ::=
<SF-capabilities>
<SF-administrative-info>
<SF-capabilities> ::=
(<supported-ACL-number >)|
(<virtual-context-number >)|
(<supported-packet-rate>)|
(<supported-bandwidth>)
<SF-administrative-info> :: =
(<Packet-rate-utilization>)|
(<Bandwidth-utilization-per-CoS>)|
(<Packet-rate-utilization-per-Cos>)|
(<Memory-utilization>)|
(<available-memory>)|
(<RIB-utilization-per-address-family>)|
(<FIB-utilization-per-address-family>)|
(<CPU-utilization>)|
(<Available storage>)|
(<Bandwidth-utilization>)|
(<Flow-resource-utilization-per-flow-type>)
This module details inventory node attributes:
o Inventory node attributes include SF-type,SF-capabilities and SF-
administrative-info.
4. Security Considerations
This document does not introduce any new security issues above those
identified in [RFC5511].
5. IANA Considerations
This draft includes no request to IANA.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2009.
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6.2. Informative References
[I.D-bitar-i2rs-service-chaining]
Bitar, N., Heron, G., and L. Fang, "Interface to the
Routing System (I2RS) for Service Chaining: Use Cases and
Requirements", ID draft-bitar-i2rs-service-chaining-00,
July 2013.
[I.D-draft-ietf-idr-ls-distribution]
Gredler, H., "North-Bound Distribution of Link-State and
TE Information using BGP", ID draft-ietf-idr-ls-
distribution-03, May 2013.
[I.D-ietf-sfc-problem-statement]
Quinn, P., "Service Function Chaining Problem Statement",
ID draft-ietf-sfc-problem-statement-10, August 2014.
[I.D-medved-i2rs-topology-im]
Medved, J., Bahadur, N., Clemm, A., and H.
Ananthakrishnan, "An Information Model for Network
Topologies", ID draft-medved-i2rs-topology-im-01, October
2003.
Authors' Addresses
Susan Hares
Huawei
7453 Hickory Hill
Saline, MI 48176
USA
Email: shares@ndzh.com
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: sunseawq@huawei.com
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Michael Wang
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: wangzitao@huawei.com
Jianjie You
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: youjianjie@huawei.com
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