Network Working Group Young Lee (Huawei)
Internet Draft Dave McDysan (Verizon)
Intended Status: Informational Ning So (UTD)
Greg Bernstein (Grotto)
Tae Yeon Kim (ETRI)
Kohei Shiomoto (NTT)
Oscar Gonzalez de Dios (Telefonica)
October 20, 2010
Problem Statement for Network Stratum Query
draft-lee-network-stratum-query-problem-01.txt
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Abstract
This document describes the general problem of network stratum query
for application optimization. Network Stratum query is an ability to
query the network from an application controller such as those used
in Data Centers so that application controller decisions such as
server assignment or virtual machine instantiation/migration can be
performed with better knowledge of the underlying network conditions.
As application servers are distributed geographically across Data
Centers, many application-related decisions such as which server to
assign a new client or where to instantiate/migrate virtual machines
will suffer from sub-optimality unless the underlying network
conditions are factored in the decision process. The lack of network
awareness may result in not meeting the end-user service objective
for some key applications like video gaming/conferencing that require
stringent latency and bandwidth requirement.
Table of Contents
1. Introduction...................................................3
2. Network and Application Contexts...............................4
3. Problem Statement..............................................7
3.1. Limitation of existing probing schemes....................7
3.2. Lack of vertical query schemes............................8
3.3. Limitation of SNMP MIB network monitoring techniques......8
3.4. Lack of abstraction mechanisms............................8
4. High-level requirements........................................9
4.1. Application Profile.......................................9
4.2. Network Load Data to be queried..........................10
4.3. A Whole Network Query capability.........................10
4.4. Data Synchronization Mechanism...........................10
4.5. Responses to NS Query from network to application........11
5. Security Considerations.......................................11
6. IANA Considerations...........................................11
7. References....................................................12
7.1. Informative References...................................12
Author's Addresses...............................................13
Intellectual Property Statement..................................13
Disclaimer of Validity...........................................14
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1. Introduction
Cross Stratum Optimization is a joint optimization effort in
allocating resources to end-users that involves both the Application
Stratum and Network Stratum.
The application stratum is the functional block which manages and
controls application resources and provides application resources to
a variety of clients/end-users. Application resources are non-network
resources critical to achieving the application service
functionality. Examples include: application specific servers,
storage, content, large data sets, and computing power. Data Centers
are regarded as a tangible realization of the application stratum
architecture.
The network stratum is the functional block which manages and
controls network resources and provides transport of data between
clients/end-users to and among application resources. Network
Resources are resources of layer 3 or below (L1/L2/L3) such as
bandwidth, links, paths, path processing (creation, deletion, and
management), network databases, path computation, admission control,
and resource reservation capability.
Application services by their very nature utilize application
resources (e.g., servers, storage, memory, etc...) in Data Centers,
and the underlying network resources provided by LANs, MANs, and
carrier's transport networks. By "data center" is any location in the
network where applications resources, such as servers or storage, are
aggregated. We include in this definition extremely large data
centers with 10,000 or more servers, all the way down to small points
of presence co-located in network carrier facilities.
As the application servers are distributed geographically across many
Data Centers, decisions such as server assignment or new virtual
machine instantiation/migration will suffer from sub-optimality
unless the underlying network conditions are factored in the decision
process. The lack of network awareness may result in not meeting the
end-user service objective for some key applications like video
gaming/conferencing that require stringent latency and bandwidth
requirement.
This document describes the general problem of network stratum query
(NS Query) in Data Center environments. Network Stratum query is an
ability to query the network from application controllers in Data
Centers so that application server assignment or virtual machine
instantiation/migration decision would be jointly performed based on
both the application resource/load status and the network
resource/load status.
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The NS query is different from what is called "horizontal network
queries" performed as part of network management. These horizontal
queries are carried out by an entity (network management systems)
within the network and would have fairly complete access to network
information.
NS Query can be thought of as a two-stage query that consists of:
. First Stage: A vertical query from an application entity (i.e.,
the Application Control Gateway (ACG) in Data Center) to an
entity representing the network (i.e., the Network Control
Gateway (NCG))for highly summarized and abstracted network
related information; and
. Second Stage: Internal "horizontal queries" at the network work
layer along with summarization and abstraction of the network
information in a form that preserves network confidentiality
and significantly reduces the amount of information that needs
to be transferred. The raw information needed to perform this
summarization/abstraction is defined in existing and emerging
network management standards and protocols (SNMP, Netflow,
sFlow, IPPM, IGP, RIB, etc...).
NS Query would not necessarily standardize how the above "internal
horizontal queries" and summarization would be performed but would
illustrate how such processes can be accomplished via standards,
emerging standards or common commercial practices.
2. Network and Application Contexts
Figure 1 shows a typical application architecture where an end-user
(the point of consuming resource) needs to be connected for its
application (e.g., gaming) to a server located in one of the
geographically distributed data centers.
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,-----. ---------------
---------- / App \ | DC 1 |
| End-user |. . .>( Control ) | o o o |
| | \ / | \|/ |
---------- `-----' | O |
| ----- --|------
| |
| |
| --------------------------|--
| / PE1 | \
| / ...................O \ --------------
| | . | | o o o DC 2 |
| | PE4 . PE2 | | \|/ |
----|---O.........................O---|---|---O |
| . | | |
| . PE3 | --------------
\ ..........O Carrier /
\ | Network /
---------------|-------------
|
--------|------
| O |
| /|\ |
| o o o |
| DC 3 |
---------------
Figure 1. Data Center Architecture
Figure 1 shows that the user application can be served by any of the
servers in DC1, DC2 or DC3. When the initial request arrives to the
application controller, the controller (aka, a global load balancer)
would ideally assign an "optimal" server based on both server
resource/load status and the network resources/load status. This
server assignment decision today, however, is limited due to the lack
of network awareness in this decision making process in the
application.
For example, the application controller needs to find a good server
that can serve the client. Assume that this particular application
requires x amount of minimum bandwidth guarantee and with less than y
ms of latency limit. The route that serves Data Center 1 traffic to
the end-user (PE1 - PE4) may not have enough capacity at a moment of
service instantiation and therefore the service objective of the end-
user may not be satisfied had such route been taken.
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On the other hand, there may be good servers available in Data
Centers 2 and 3 and their routes (PE2-PE4 and PE3-PE4) may have
enough capacity to meet the service requirement.
This example illustrates the benefit of and the need for the joint
optimization across the application and network strata. NS Query is
the ability to query the network from an application controller to
collect a certain level of network information. No such mechanisms
exist in the today's Internet Protocol technologies.
Figure 2 shows the context of NS Query in a more detail within the
overarching data center architecture shown in Figure 1.
+--------------------------------------------+
| +-------------+ |
| | Application | |
| | Controller | Application Overlay |
| +------|------+ (Data Centers) |
| | |
---------- | ------|------- -------------- |
| End-User | | | Application |. . . .| Application | |
| |. . . >| | Control | | Processes | |
---------- | | Gateway (ACG)| -------------- |
| | | -------------- |
| ------------- . . . . | Application | |
| /\ | Related Data | |
| || -------------- |
----------||--------------------------------
||
|| Network Stratum Query (First Stage)
||
+----------||--------------------------------+
| \/ Network Underlay |
| |
| -------------- ---------------- |
| | Network |. . . | Network | |
| | Control | | Processes | |
| | Gateway (NCG)| ---------------- |
| | | ---------------- |
| ------------- | Network | |
| |------------->| Related Data | |
| (Second Stage) ---------------- |
+--------------------------------------------+
Figure 2. NS Query Architecture
Figure 2 shows key architectural components that enable NS Query
capability. The application controller, e.g., global load balancer,
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utilizes the Application Control Gateway (ACG) to interface with the
network and generate queries to network. The ACG can query various
metric values that may contribute to meeting the overall service
objective of an application. This is a vertical query (Stage 1).
In the network stratum, the Network Control Gateway (NCG) serves the
interface to the network stratum. The NCG receives the query request
from the ACG, makes use of current and/or historical network
information (IPPM, IGP, MIB, TED, etc...), abstracts and summaries
this information implemented in the network stratum. This is the
horizontal query and summarization stage (Stage 2).
Further, the NCG provides the responses to the original query sent
from the ACG. The data collected by the NCG needs to be abstracted.
This abstraction is needed on two grounds.
First, the network does not usually reveal its details to the
outside entity. Although the Data Center providers and the carriers
are business partners in providing application services to the end-
users and to the application providers (e.g., gaming providers),
detail network data may not be leaked to the Data Centers, and vice
versa.
Secondly, detail network data may not be understood by the
application. Link or node level data in and of themselves may not
help the application to process the detail data. For instance,
latency or bandwidth on a link level is too detail for application
to handle. Instead, latency or bandwidth on a route level (i.e., PE1
- PE4 in Figure 1) will help the application make its server
selection/instantiation decision.
The abstraction function needs to be provided by the NCG. Note that
NCG plays gate keeper role to information concerning the network. a
Within the network the NCG collects and or probes network
performance/management data (e.g., IPPM, MIB, etc.) or routing data
[MRT] (e.g., LSDB, TED, BGP-RIB, etc.) and others. Once the basic
data is collected, the NCG will need to abstract/summary before it
sends to the application.
3. Problem Statement
3.1. Limitation of existing probing schemes
The current state-of-the art application network awareness schemes
for an entity external to the network are based on ping, trace route,
or vendor specific probing mechanisms based on the assumption that
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the underlying transport network is L3 network and that the routing
is simple IP forwarding.
In reality, the carrier's routing schemes are likely to include IP
tunneling or MPLS tunneling on top of or in place of IP forwarding.
In some cases, the actual network may be VPN, MPLS-TE or GMPLS-TE
networks where trace route does not work.
This implies that network status estimation technique made from
application stratum may have limited accuracy. Thus, application
resource allocation to end-users can suffer sub-optimality and fail
to meet performance objective for the application.
3.2. Lack of vertical query schemes
There is no standard "vertical" query scheme that allows an
application control gateway in a Data Center to query network stratum
in a way suitable for a third party (i.e. an entity "outside" the
network).
Due to the lack of standard vertical query scheme, there is a
limitation on exchanging information between application and network
that would increase efficiency of joint optimization across
application to network. For instance, the ability to exchange the
application profile information (defined in Section 4.1) or network
capability information between application and network would increase
efficiency of resource allocation across application to network.
3.3. Limitation of SNMP MIB network monitoring techniques
SNMP MIB Network Monitoring lacks a whole network query capability. A
whole network query is a query to gather information across many
boxes simultaneously under the control of a single administration
domain (AD) as defined in RFC 1136. A single AD means the single AS
or multiple ASes under the control of a single AD.
3.4. Lack of abstraction mechanisms
Most of the information needed to provide NS Query is currently
available from the network; however, it is not aggregated into a form
suitable for use by the application stratum. For example from
commonly monitored SNMP based link statistics and current routing
tables one can easily compute average available bandwidth and many
other statistical performance measures such as packet loss, latency,
etc.
However, neither the raw SNMP nor routing table data should be
delivered to the application stratum since (a) this reveals too much
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information concerning the carriers network, (b) presents too much
information to transfer to each application. This warrants some work
on abstraction from network side to preserve the privacy of network
stratum details from the application stratum.
4. High-level requirements
This section discusses high-level requirements to support NS Query in
the Data Center environments.
The ACG plays the key role functioning as an application gateway to
network and runs the NS Query. The ACG has access to the end-user
profile for the application and the candidate servers' locations
locally and remotely located. How the ACG access these information is
beyond the scope of this work.
4.1. Application Profile
The application Stratum needs to provide the application profile to
network as part of a query.
Example service profile information that can be useful to network to
understand is as follows:
. End user IP address;
. User access router IP address;
. Authentication Profile: Authentication Key;
. Bandwidth Profile: Minimum bandwidth required for the
application;
. Connectivity Profile: P-P, P-MP, Anycast (Multi-destination);
. Directionality of the connectivity: unidirectional, bi-
directional;
. Path Estimation Objective Function: Min latency, etc.
Additional profile information can be added depending on the network
capability.
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4.2. Network Load Data to be queried
For a given location mapping information (i.e., from the server
location to end-user location), the query from an application can ask
the following network load data:
. Type of networks and the technical capabilities of the networks;
. Bandwidth capabilities and availability;
. latency;
. jitter;
. packet loss;
. And other Network Performance Objective (NPO) as defined in
section 5 of [ITU-T Y.1541].
Note that this can be asked in a different way. For example, the
query can simply ask:
. Can you give me a route with x amount of b/w (from server to
end-user) within y ms of latency?
. Can you give me a route with x amount of b/w (from server to
end-user) with no packet loss?
4.3. A Whole Network Query capability
Upon the request from application (specifically, the ACG in Figure
2), the network (specifically the NCG in Figure 2) should perform "a
whole network query" of information.
A whole network query is a query to gather information across many
boxes simultaneously under the control of a single administration
domain (AD) as defined in RFC 1136. A single AD means the single AS
or multiple ASes under the control of a single AD.
The scope of a whole network query can include the topology of the
network, the bandwidth availability for the routes of interest, the
capabilities and congestion of links and routes, and an indication of
the contribution to delay and jitter that each link and route will
contribute and so on.
4.4. Data Synchronization Mechanism
When querying the network there are two general categories of
information that are of interest (a) current data, and (b) historical
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data. Current data information tells us information about the current
state of the network, this data represent current network "state" and
over time is subject to change. Application servers would use
abstracted versions of this information to make decisions regarding
current application activities.
Historical data can be used by the application controller to schedule
application events at future times. Such historical data must be time
stamped so that inferences can be drawn from the data. For example,
consider the backup and synchronization of large application
databases between two data centers. Not only would we like to know
how much bandwidth is available, and importantly when is the best
time to perform such synchronization (given there is flexibility on
when to perform the backup).
4.5. Responses to NS Query from network to application
Given the network query from application, the network should provide
the following mechanisms:
- For a given location mapping information from application (i.e.,
from the server location to end-user location) and the gathered
information by the second stage query discussed in section 4.3.,
the network needs to present the requested information in a
standard format and respond to the application.
The actual abstraction mechanism is beyond the scope of this
document.
5. Security Considerations
TBD
6. IANA Considerations
This informational document does not make any requests for IANA
action.
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7. References
7.1. Informative References
[RFC2261] D. Harrington, et al., "An Architecture for Describing SNMP
Management Frameworks," January, 1998.
[RFC2265] B. Wijnen, et al., "View-based Access Control Model (VACM)
for the Simple Network Management Protocol (SNMP),"
January, 1998.
[Y.1541] Network performance objectives for IP-based services,
February, 2002.
[Y.2011] General principles and general reference model for Next
Generation Networks, October, 2004.
[Y.2012] Functional Requirements and architecture of the NGN, April,
2010.
[MRT] L. Blunk, M. Karir, and C. Labovitz, "MRT routing
information export format," draft-ietf-grow-mrt, work in
progress.
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Author's Addresses
Young Lee
Huawei Technologies
1700 Alma Drive, Suite 500
Plano, TX 75075
USA
Phone: (972) 509-5599
Email: ylee@huawei.com
Ning So
Univerity of Texas at Dallas
Email: ningso@yahoo.com
Dave McDysan
Verizon Business
Email: dave.mcdysan@verizon.com
Greg M. Bernstein
Grotto Networking
Fremont California, USA
Phone: (510) 573-2237
Email: gregb@grotto-networking.com
Tae Yeon Kim
ETRI
tykim@etri.or.kr
Kohei Shiomoto
NTT
Email : shiomoto.kohei@lab.ntt.co.jp
Oscar Gonzalez de Dios
Telefonica
Email : ogondio@tid.es
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