Internet DRAFT - draft-amante-irs-topology-use-cases
draft-amante-irs-topology-use-cases
Internet Engineering Task Force J. Medved
Internet-Draft Cisco Systems, Inc.
Intended status: Informational T. Nadeau
Expires: February 17, 2014 Juniper Networks
S. Amante
August 16, 2013
Topology API Use Cases
draft-amante-irs-topology-use-cases-01
Abstract
This document describes use cases for gathering routing, forwarding
and policy information, (hereafter referred to as topology
information), about the network. It describes several applications
that need to view the topology of the underlying physical or logical
network. This document further demonstrates a need for a "Topology
Manager" and related functions that collects topology data from
network elements and other data sources, coalesces the collected data
into a coherent view of the overall network topology, and normalizes
the network topology view for use by clients -- namely, applications
that consume topology information.
Status of This Memo
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This Internet-Draft will expire on February 17, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Statistics Collection . . . . . . . . . . . . . . . . . . 4
1.2. Inventory Collection . . . . . . . . . . . . . . . . . . 5
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. The Orchestration, Collection & Presentation Framework . . . 7
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. The Topology Manager . . . . . . . . . . . . . . . . . . 8
3.3. The Policy Manager . . . . . . . . . . . . . . . . . . . 10
3.4. Orchestration Manager . . . . . . . . . . . . . . . . . . 10
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Virtualized Views of the Network . . . . . . . . . . . . 11
4.1.1. Capacity Planning and Traffic Engineering . . . . . . 11
4.1.1.1. Present Mode of Operation . . . . . . . . . . . . 12
4.1.1.2. Proposed Mode of Operation . . . . . . . . . . . 12
4.1.2. Services Provisioning . . . . . . . . . . . . . . . . 14
4.1.3. Troubleshooting & Monitoring . . . . . . . . . . . . 14
4.2. Path Computation Element (PCE) . . . . . . . . . . . . . 15
4.3. ALTO Server . . . . . . . . . . . . . . . . . . . . . . . 16
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
8.1. Normative References . . . . . . . . . . . . . . . . . . 18
8.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
In today's networks, a variety of applications, such as Traffic
Engineering, Capacity Planning, Security Auditing or Services
Provisioning (for example, Virtual Private Networks), have a common
need to acquire and consume network topology information.
Unfortunately, all of these applications are (typically) vertically
integrated: each uses its own proprietary normalized view of the
network and proprietary data collectors, interpreters and adapters,
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which speak a variety of protocols, (SNMP, CLI, SQL, etc.) directly
to network elements and to back-office systems. While some of the
topological information can be distributed using routing protocols,
unfortunately it is not desirable for some of these applications to
understand or participate in routing protocols.
This approach is incredibly inefficient for several reasons. First,
developers must write duplicate 'network discovery' functions, which
then become challenging to maintain over time, particularly as/when
new equipment are first introduced to the network. Second, since
there is no common "vocabulary" to describe various components in the
network, such as physical links, logical links, or IP prefixes, each
application has its own data model. To solve this, some solutions
have distributed this information in the normalized form of routing
distribution. However, this information still does not contain
"inactive" topological information, thus not containing information
considered to be part of a network's inventory.
These limitations lead to applications being unable to easily
exchange information with each other. For example, applications
cannot share changes with each other that are (to be) applied to the
physical and/or logical network, such as installation of new physical
links, or deployment of security ACL's. Each application must
frequently poll network elements and other data sources to ensure
that it has a consistent representation of the network so that it can
carry out its particular domain-specific tasks. In other cases,
applications that cannot speak routing protocols must use proprietary
CLI or other management interfaces which represent the topological
information in non-standard formats or worse, semantic models.
Overall, the software architecture described above at best results in
inefficient use of both software developer resources and network
resources, and at worst, it results in some applications simply not
having access to this information.
Figure 1 is an illustration of how individual applications collect
data from the underlying network. Applications retrieve inventory,
network topology, state and statistics information by communicating
directly with underlying Network Elements as well as with
intermediary proxies of the information. In addition, applications
transmit changes required of a Network Element's configuration and/or
state directly to individual Network Elements, (most commonly using
CLI or Netconf). It is important to note that the "data models" or
semantics of this information contained within Network Elements are
largely proprietary with respect to most configuration and state
information, hence why a proprietary CLI is often the only choice to
reflect changes in a NE's configuration or state. This remains the
case even when standards-based mechanisms such as Netconf are used
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which provide a standard syntax model, but still often lack due to
the proprietary semantics associated with the internal representation
of the information.
+---------------+
+----------------+ |
| Applications |-+
+----------------+
^ ^ ^
SQL, RPC, ReST # | * SQL, RPC, ReST ...
########################## | **********************
# | *
+------------+ | +------------+
| Statistics | | | Inventory |
| Collection | | | Collection |
+------------+ | +------------+
^ | NETCONF, I2RS, SNMP, ^
| | CLI, TL1, ... |
+------------------------+-----------------------+
| | |
| | |
+---------------+ +---------------+ +---------------+
|Network Element| |Network Element| |Network Element|
| +-----------+ | | +-----------+ | | +-----------+ |
| |Information| |<-LLDP->| |Information| |<-LMP->| |Information| |
| | Model | | | | Model | | | | Model | |
| +-----------+ | | +-----------+ | | +-----------+ |
+---------------+ +---------------+ +---------------+
Figure 1: Applications getting topology data
Figure 1 shows how current management interfaces such as NETCONF,
SNMP, CLI, etc. are used to transmit or receive information to/from
various Network Elements. The figure also shows that protocols such
as LLDP and LMP participate in topology discovery, specifically to
discover adjacent network elements.
The following sections describe the "Statistics Collection" and
"Inventory Collection" functions.
1.1. Statistics Collection
In Figure 1, "Statistics Collection" is a dedicated infrastructure
that collects statistics from Network Elements. It periodically (for
example, every 5-minutes) polls Network Elements for octets
transferred per interface, per LSP, etc. Collected statistics are
stored and collated within a statistics data warehouse. Applications
typically query the statistics data warehouse rather than poll
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Network Elements directly to get the appropriate set of link
utilization figures for their analysis.
1.2. Inventory Collection
"Inventory Collection" is a network function responsible for
collecting component and state information directly from Network
Elements, as well as for storing inventory information about physical
network assets that are not retrievable from Network Elements. The
collected data is hereafter referred to as the 'Inventory Asset
Database. Examples of information collected from Network Elements
are: interface up/down status, the type of SFP/XFP optics inserted
into physical port, etc.
The Inventory Collection function may use SNMP and CLI to acquire
inventory information from Network Elements. The information housed
in the Inventory Manager is retrieved by applications via a variety
of protocols: SQL, RPC, REST etc. Inventory information, retrieved
from Network Elements, is periodically updated in the Inventory
Collection system to reflect changes in the physical and/or logical
network assets. The polling interval to retrieve updated information
is varied depending on scaling constraints of the Inventory
Collection systems and expected intervals at which changes to the
physical and/or logical assets are expected to occur.
Examples of changes in network inventory that need be learned by the
Inventory Collection function are as follows:
o Discovery of new Network Elements. These elements may or may not
be actively used in the network (i.e.: provisioned but not yet
activated).
o Insertion or removal of line cards or other modules, such as
optics modules, during service or equipment provisioning.
o Changes made to a specific Network Element through a management
interface by a field technician.
o Indication of an NE's physical location and associated cable run
list, at the time of installation.
o Insertion of removal of cables that result in dynamic discovery of
a new or lost adjacent neighbor, etc.
1.3. Requirements Language
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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 RFC 2119 [RFC2119]
2. Terminology
The following briefly defines some of the terminology used within
this document.
Inventory Manager is a function that collects Network Element
inventory and state information directly from Network Elements and
from associated offline inventory databases. Inventory
information may only be visible at a specific network layer; for
example, a physical link is visible within the IGP, but a Layer-2
switch through which the physical link traverses is unknown to the
Layer-3 IGP.
Policy Manager is a function that attaches metadata to network
components/attributes. Such metadata may include security,
routing, L2 VLAN ID, IP numbering, etc. policies, which enable the
Topology Manager to:
* Assemble a normalized view of the network for clients (or
upper-layer applications
* Allow clients (or upper-layer applications) access to
information collected from various network layers and/or
network components, etc.
The Policy Manager function may be a sub-component of the Topology
Manager or it may be a standalone function.
Topology Manager is a function that collects topological information
from a variety of sources in the network and provides a normalized
view of the network topology to clients and/or higher-layer
applications.
Orchestration Manager is a function that stitches together
resources, such as compute or storage, and/or services with the
network or vice-versa. To realize a complete service, the
Orchestration Manager relies on capabilities provided by the other
"Managers" listed above.
Normalized Topology Information Model is an open, standards-based
information model of the network topology.
Information Model Abstraction: The notion that one is able to
represent the same set of elements in an information model at
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different levels of "focus" in order to limit the amount of
information exchanged in order to convey this information.
Multi-Layer Topology: Topology is commonly referred to using the OSI
protocol layering model. For example, Layer 3 represents routed
topologies that typically use IPv4 or IPv6 addresses. It is
envisioned that, eventually, multiple layers of the network may be
represented in a single, normalized view of the network to certain
applications, (i.e.: Capacity Planning, Traffic Engineering, etc.)
Network Element (NE) refers to a network device that typically is
addressable (but not always), or a host. It is sometimes referred
to as a 'Node'.
Links: Every NE contains at least 1 link. These are used to connect
the NE to other NEs in the network. Links may be in a variety of
states, such as up, down, administratively down, internally
testing, or dormant. Links are often synonymous with network
ports on NEs.
3. The Orchestration, Collection & Presentation Framework
3.1. Overview
Section 1 demonstrates the need for a network function that would
provide a common, standards-based topology view to applications.
Such topology collection/management/presentation function would be a
part of a wider framework that should also include policy management
and orchestration. The framework is shown in Figure 2.
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+---------------+
+----------------+ |
| Applications |-+
+----------------+
^ Websockets, ReST, XMPP...
+------------------------+-------------------------+
| | |
+------------+ +------------------------+ +-------------+
| Policy |<----| Topology Manager |---->|Orchestration|
| Manager | | +--------------------+ | | Manager |
+------------+ | |Topology Information| | +-------------+
| | Model | |
| +--------------------+ |
+------------------------+
^ ^ ^
Websockets, ReST, XMPP # | * Websockets, ReST, XMPP
####################### | ************************
# | *
+------------+ | +------------+
| Statistics | | | Inventory |
| Collection | | | Collection |
+------------+ | +------------+
^ | I2RS, NETCONF, SNMP, ^
| | TL1 ... |
+------------------------+------------------------+
| | |
+---------------+ +---------------+ +---------------+
|Network Element| |Network Element| |Network Element|
| +-----------+ | | +-----------+ | | +-----------+ |
| |Information| |<-LLDP->| |Information| |<-LMP-->| |Information| |
| | Model | | | | Model | | | | Model | |
| +-----------+ | | +-----------+ | | +-----------+ |
+---------------+ +---------------+ +---------------+
Figure 2: Topology Manager
The following sections describe in detail the Topology Manager,
Policy Manager and Orchestration Manager functions.
3.2. The Topology Manager
The Topology Manager is a function that collects topological
information from a variety of sources in the network and provides a
cohesive, abstracted view of the network topology to clients and/or
higher-layer applications. The topology view is based on a
standards-based, normalized topology information model.
Topology information sources can be:
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o The "live" Layer 3 IGP or an equivalent mechanism that provides
information about links that are components of the active
topology. Active topology links are present in the Link State
Database (LSDB) and are eligible for forwarding. Layer 3 IGP
information can be obtained by listening to IGP updates flooded
through an IGP domain, or from Network Elements.
o The Inventory Collection system that provides information for
network components not visible within the Layer 3 IGP's LSDB,
(i.e.: links or nodes, or properties of those links or nodes, at
lower layers of the network).
o The Statistics Collection system that provides traffic
information, such as traffic demands or link utilizations.
The Topology Manager provides topology information to Clients or
higher-layer applications via a northbound interface, such as ReST,
Websockets, or XMPP.
The Topology Manager will contain topology information for multiple
layers of the network: Transport, Ethernet and IP/MPLS, as well as
information for multiple Layer 3 IGP areas and multiple Autonomous
Systems (ASes). The topology information can be used by higher-level
applications, such as Traffic Engineering, Capacity Planning and
Provisioning. Such applications are typically used to design,
augment and optimize IP/MPLS networks, and require knowledge of
underlying Shared Risk Link Groups (SRLG) within the Transport and/or
Ethernet layers of the network.
The Topology Manager must be able to discover Network Elements that
are not visible in the "live" L3 IGP's Link State Database (LSDB).
Such Network Elements can either be inactive, or active but invisible
in the L3 LSDB (e.g.: L2 Ethernet switches, ROADM's, or Network
Elements that are in an underlying transport network).
In addition static inventory information collected from the Inventory
Manager, the Topology Manager will also collect dynamic inventory
information. For example, Network Elements utilize various Link
Layer Discovery Protocols (i.e.: LLDP, LMP, etc.) to automatically
identify adjacent nodes and ports. This information can be pushed to
or pulled by the Topology Manager in order to create an accurate
representation of the physical topology of the network
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3.3. The Policy Manager
The Policy Manager is the function used to enforce and program
policies applicable to network component/attribute data. Policy
enforcement is a network-wide function that can be consumed by
various Network Elements and services, including the Inventory
Manager, the Topology Manager and other Network Elements. Such
policies are likely to encompass the following:
o Logical Identifier Numbering Policies
* Correlation of IP prefix to link based on link type, such as
P-P, P-PE, or PE-CE.
* Correlation of IP Prefix to IGP Area
* Layer-2 VLAN ID assignments, etc.
o Routing Configuration Policies
* OSPF Area or IS-IS Net-ID to Node (Type) Correlation
* BGP routing policies, such as nodes designated for injection of
aggregate routes, max-prefix policies, or AFI/SAFI to node
correlation..
o Security Policies
* Access Control Lists
* Rate-limiting
o Network Component/Attribute Data Access Policies. Client's
(upper-layer application) access to Network Components/Attributes
contained in the "Inventory Manager" as well as Policies contained
within the "Policy Manager" itself.
The Policy Manager function may be either a sub-component of the
Topology or Orchestration Manager or a standalone component.
3.4. Orchestration Manager
The Orchestration Manager provides the ability to stitch together
resources (such as compute or storage) and/or services with the
network or vice-versa. Examples of 'generic' services may include
the following:
o Application-specific Load Balancing
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o Application-specific Network (Bandwidth) Optimization
o Application or End-User specific Class-of-Service
o Application or End-User specific Network Access Control
The above services could then enable coupling of resources with the
network to realize the following:
o Network Optimization: Creation and Migration of Virtual Machines
(VM's) so they are adjacent to storage in the same DataCenter.
o Network Access Control: Coupling of available (generic) compute
nodes within the appropriate point of the data-path to perform
firewall, NAT, etc. functions on data traffic.
The Orchestration Manager will exchange information models with the
Topology Manager, the Policy Manager and the Inventory Manager. In
addition, the Orchestration Manager must support publish and
subscribe capabilities to those functions, as well as to Clients.
The Orchestration Manager may receive requests from Clients
(applications) for immediate access to specific network resources.
However, Clients may request to schedule future appointments to
reserve appropriate network resources when, for example, a special
event is scheduled to start and end.
Finally, the Orchestration Manager should have the flexibility to
determine what network layer(s) may be able to satisfy a given
Client's request, based on constraints received from the Client as
well as constraints learned from the Policy and Topology Managers.
This could allow the Orchestration Manager to, for example, satisfy a
given service request for a given Client using the optical network
(via OTN service) if there is insufficient IP/MPLS capacity at the
specific moment the Client's request is received.
The operational model is shown in the following figure.
TBD.
Figure 3: Overall Reference Model
4. Use Cases
4.1. Virtualized Views of the Network
4.1.1. Capacity Planning and Traffic Engineering
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4.1.1.1. Present Mode of Operation
When performing Traffic Engineering and/or Capacity Planning of an IP
/MPLS network, it is important to account for SRLG's that exist
within the underlying physical, optical and Ethernet networks.
Currently, it's quite common to take "snapshots" at infrequent
intervals that comprise the inventory data of the underlying physical
and optical layer networks. This inventory data is then normalized
to conform to data import requirements of sometimes separate Traffic
Engineering and/or Capacity Planning tools. This process is error-
prone and inefficient, particularly as the underlying network
inventory information changes due to introduction of new network
element makes or models, line cards, capabilities, etc..
The present mode of operation is inefficient with respect to Software
Development, Capacity Planning and Traffic Engineering resources.
Due to this inefficiency, the underlying physical network inventory
information (containing SRLG and corresponding critical network
assets information) is not updated frequently, thus exposing the
network to, at minimum, inefficient utilization and, at worst,
critical impairments.
4.1.1.2. Proposed Mode of Operation
First, the Inventory Manager will extract inventory information from
network elements and associated inventory databases. Information
extracted from inventory databases will include physical cross-
connects and other information that is not available directly from
network elements. Standards-based information models and associated
vocabulary will be required to represent not only components inside
or directly connected to network elements, but also to represent
components of a physical layer path (i.e.: cross-connect panels,
etc.) The inventory data will comprise the complete set of inactive
and active network components.
Second, the Topology Manager will augment the inventory information
with topology information obtained from Network Elements and other
sources, and provide an IGP-based view of the active topology of the
network. The Topology Manager will also include non-topology dynamic
information from IGPs, such as Available Bandwidth, Reserved
Bandwidth, Traffic Engineering (TE) attributes associated with links,
etc.
Finally, the Statistics Collector will collect utilization statistics
from Network Elements, and archive and aggregate them in a statistics
data warehouse. Selected statistics and other dynamic data may be
distributed through IGP routing protocols
([I-D.ietf-isis-te-metric-extensions] and
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[I-D.ietf-ospf-te-metric-extensions]) and then collected at the
Statistics Collection Function via BGP-LS
([I-D.ietf-idr-ls-distribution]). Statistics summaries then will be
exposed in normalized information models to the Topology Manager,
which can use them to, for example, build trended utilization models
to forecast expected changes to physical and logical network
components.
It is important to recognize that extracting topology information
from the network solely from Network Elements and IGPs (IS-IS TE or
OSPF TE), is inadequate for this use case. First, IGPs only expose
the active components (e.g. vertices of the SPF tree) of the IP
network, and are not aware of "hidden" or inactive interfaces within
IP/MPLS network elements, such as unused line cards or ports. IGPs
are also not aware of components that reside at a layer lower than IP
/MPLS, such as Ethernet switches, or Optical transport systems.
Second, IGP's only convey SRLG information that have been first
applied within a router's configurations, either manually or
programatically. As mentioned previously, this SRLG information in
the IP/MPLS network is subject to being infrequently updated and, as
a result, may inadequately account for critical, underlying network
fate sharing properties that are necessary to properly design
resilient circuits and/or paths through the network.
Once the Topology Manager has assembled a normalized view of the
topology and metadata associated with each component of the topology,
it can expose this information via its northbound API to the Capacity
Planning and Traffic Engineering applications. The applications only
require generalized information about nodes and links that comprise
the network, e.g.: links used to interconnect nodes, SRLG information
(from the underlying network), utilization rates of each link over
some period of time, etc.
Note that any client/application that understands the Topology
Manager's northbound API and its topology information model can
communicate with the Topology Manager. Note also that topology
information may be provided by Network Elements from different
vendors, which may use different information models. If a Client
wanted to retrieve topology information directly from Network
Elements, it would have to translate and normalize these different
representations.
A Traffic Engineering application may run a variety of CSPF
algorithms that create a list of TE tunnels that globally optimize
the packing efficiency of physical links throughout the network. The
TE tunnels are then programmed into the network either directly or
through a controller. Programming of TE tunnels into the network is
outside the scope of this document.
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A Capacity Planning application may run a variety of algorithms the
result of which is a list of new inventory that is required for
purchase or redeployment, as well as associated work orders for field
technicians to augment the network for expected growth.
4.1.2. Services Provisioning
Beyond Capacity Planning and Traffic Engineering applications, having
a normalized view of just the IP/MPLS layer of the network is still
very important for other mission critical applications, such as
Security Auditing and IP/MPLS Services Provisioning, (e.g.: L2VPN,
L3VPN, etc.). With respect to the latter, these types of
applications should not need a detailed understanding of, for
example, SRLG information, assuming that the underlying MPLS Tunnel
LSP's are known to account for the resiliency requirements of all
services that ride over them. Nonetheless, for both types of
applications it is critical to have a common and up-to-date
normalized view of the IP/MPLS network to, for example, instantiate
new services at optimal locations in the network, or to validate
proper ACL configuration to protect associated routing, signaling and
management protocols on the network.
A VPN Service Provisioning application must perform the following
resource selection operations:
o Identify Service PE's in all markets/cities where the customer has
identified they want service
o Identify one or more existing Servies PE's in each city with
connectivity to the access network(s), e.g.: SONET/TDM, used to
deliver the PE-CE tail circuits to the Service's PE.
o Determine that the Services PE have available capacity on both the
PE-CE access interface and its uplinks to terminate the tail
circuit
The VPN Provisioning application would iteratively query the Topology
Manager to narrow down the scope of resources to the set of Services
PEs with the appropriate uplink bandwidth and access circuit
capability plus capacity to realize the requested VPN service. Once
the VPN Provisioning application has a candidate list of resources it
requests programming of the Service PE's and associated access
circuits to set up a customer's VPN service into the network.
Programming of Service PEs is outside the scope of this document.
4.1.3. Troubleshooting & Monitoring
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Once the Topology Manager has a normalized view of several layers of
the network, it can expose a rich set of data to network operators
who are performing diagnosis, troubleshooting and repairs on the
network. Specifically, there is a need to (rapidly) assemble a
current, accurate and comprehensive network diagram of a L2VPN or
L3VPN service for a particular customer when either: a) attempting to
diagnose a service fault/error; or, b) attempting to augment the
customer's existing service. Information that may be assembled into
a comprehensive picture could include physical and logical components
related specifically to that customer's service, i.e.: VLAN's or
channels used by the PE-CE access circuits, CoS policies, historical
PE-CE circuit utilization, etc. The Topology Manager would assemble
this information, on behalf of each of the network elements and other
data sources in and associated with the network, and would present
this information in a vendor-independent data model to applications
to be displayed allowing the operator (or, potentially, the customer
through a SP's Web portal) to visualize the information.
4.2. Path Computation Element (PCE)
As described in [RFC4655] a PCE can be used to compute MPLS-TE paths
within a "domain" (such as an IGP area) or across multiple domains
(such as a multi-area AS, or multiple ASes).
o Within a single area, the PCE offers enhanced computational power
that may not be available on individual routers, sophisticated
policy control and algorithms, and coordination of computation
across the whole area.
o If a router wants to compute a MPLS-TE path across IGP areas its
own TED lacks visibility of the complete topology. That means
that the router cannot determine the end-to-end path, and cannot
even select the right exit router (Area Border Router - ABR) for
an optimal path. This is an issue for large-scale networks that
need to segment their core networks into distinct areas, but which
still want to take advantage of MPLS-TE.
The PCE presents a computation server that may have visibility into
more than one IGP area or AS, or may cooperate with other PCEs to
perform distributed path computation. The PCE needs access to the
topology and the Traffic Engineering Database (TED) for the area(s)
it serves, but [RFC4655] does not describe how this is achieved.
Many implementations make the PCE a passive participant in the IGP so
that it can learn the latest state of the network, but this may be
sub-optimal when the network is subject to a high degree of churn, or
when the PCE is responsible for multiple areas.
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The following figure shows how a PCE can get its TED information
using a Topology Server.
+----------+
| ----- | TED synchronization via Topology API
| | TED |<-+----------------------------------+
| ----- | |
| | | |
| | | |
| v | |
| ----- | |
| | PCE | | |
| ----- | |
+----------+ |
^ |
| Request/ |
| Response |
v |
Service +----------+ Signaling +----------+ +----------+
Request | Head-End | Protocol | Adjacent | | Topology |
-------->| Node |<------------>| Node | | Manager |
+----------+ +----------+ +----------+
Figure 4: Topology use case: Path Computation Element
4.3. ALTO Server
An ALTO Server [RFC5693] is an entity that generates an abstracted
network topology and provides it to network-aware applications over a
web service based API. Example applications are p2p clients or
trackers, or CDNs. The abstracted network topology comes in the form
of two maps: a Network Map that specifies allocation of prefixes to
PIDs, and a Cost Map that specifies the cost between PIDs listed in
the Network Map. For more details, see [I-D.ietf-alto-protocol].
ALTO abstract network topologies can be auto-generated from the
physical topology of the underlying network. The generation would
typically be based on policies and rules set by the operator. Both
prefix and TE data are required: prefix data is required to generate
ALTO Network Maps, TE (topology) data is required to generate ALTO
Cost Maps. Prefix data is carried and originated in BGP, TE data is
originated and carried in an IGP. The mechanism defined in this
document provides a single interface through which an ALTO Server can
retrieve all the necessary prefix and network topology data from the
underlying network. Note an ALTO Server can use other mechanisms to
get network data, for example, peering with multiple IGP and BGP
Speakers.
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The following figure shows how an ALTO Server can get network
topology information from the underlying network using the Topology
API.
+--------+
| Client |<--+
+--------+ |
| ALTO +--------+ +----------+
+--------+ | Protocol | ALTO | Network Topology | Topology |
| Client |<--+------------| Server |<-----------------| Manager |
+--------+ | | | | |
| +--------+ +----------+
+--------+ |
| Client |<--+
+--------+
Figure 5: Topology use case: ALTO Server
5. Acknowledgements
The authors wish to thank Alia Atlas, Dave Ward, Hannes Gredler,
Stafano Previdi for their valuable contributions and feedback to this
draft.
6. IANA Considerations
This memo includes no request to IANA.
7. Security Considerations
At the moment, the Use Cases covered in this document apply
specifically to a single Service Provider or Enterprise network.
Therefore, network administrations should take appropriate
precautions to ensure appropriate access controls exist so that only
internal applications and end-users have physical or logical access
to the Topology Manager. This should be similar to precautions that
are already taken by Network Administrators to secure their existing
Network Management, OSS and BSS systems.
As this work evolves, it will be important to determine the
appropriate granularity of access controls in terms of what
individuals or groups may have read and/or write access to various
types of information contained with the Topology Manager. It would
be ideal, if these access control mechanisms were centralized within
the Topology Manager itself.
8. References
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8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[I-D.ietf-alto-protocol]
Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol", draft-
ietf-alto-protocol-17 (work in progress), July 2013.
[I-D.ietf-idr-ls-distribution]
Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
Ray, "North-Bound Distribution of Link-State and TE
Information using BGP", draft-ietf-idr-ls-distribution-03
(work in progress), May 2013.
[I-D.ietf-isis-te-metric-extensions]
Previdi, S., Giacalone, S., Ward, D., Drake, J., Atlas,
A., and C. Filsfils, "IS-IS Traffic Engineering (TE)
Metric Extensions", draft-ietf-isis-te-metric-
extensions-00 (work in progress), June 2013.
[I-D.ietf-ospf-te-metric-extensions]
Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", draft-ietf-ospf-te-metric-extensions-04 (work
in progress), June 2013.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-05 (work in progress), July 2013.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic
Optimization (ALTO) Problem Statement", RFC 5693, October
2009.
Authors' Addresses
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Jan Medved
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134
USA
Email: jmedved@cisco.com
Thomas D. Nadeau
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: tnadeau@juniper.net
Shane Amante
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