Internet DRAFT - draft-stein-cloud-access
draft-stein-cloud-access
Network Working Group YJ. Stein
Internet-Draft Y. Gittik
Intended status: Informational RAD Data Communications
Expires: January 05, 2014 D. Kofman
K. Katsaros
LINCS
M. Morrow
L. Fang
Cisco Systems
W. Henderickx
Alcatel-Lucent
July 04, 2013
Accessing Cloud Services
draft-stein-cloud-access-03.txt
Abstract
Cloud services are revolutionizing the way computational resources
are provided, but at the expense of requiring an even more
revolutionary overhaul of the networking infrastructure needed to
deliver them. Much recent work has focused on intra- and inter-
datacenter connectivity requirements and architectures, while the
"access segment" connecting the cloud services user to the datacenter
still needs to be addressed. In this draft we consider tighter
integration between the network and the datacenter, in order to
improve end-to-end Quality of Experience, while minimizing both
networking and computational resource costs.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 05, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Model of Existing Cloud Services . . . . . . . . . . . . . . 4
3. Optimized Cloud Access . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Cloud services replace computational power and storage resources
traditionally located under the user's table or on the user's in-
house servers, with resources located in remote datacenters. The
cloud resources may be raw computing power and storage
(Infrastructure as a Service - IaaS), or computer systems along with
supported operating systems and tools (Platform as a Service - PaaS),
or even fully developed applications (Software as a Service - SaaS).
Processing power required for the operation of network devices can
also be provided (e.g., Routing as a Service - RaaS). The inter- and
intra-datacenter networking architectures needed to support cloud
services are described in [I-D.bitar-datacenter-vpn-applicability].
The advantages of cloud services over conventional IT services
include elasticity (the ability to increase or decrease resources on
demand rather than having to purchase enough resources for worst case
scenarios), scalability (allocating multiple resources and load-
balancing them), high-availability (resources may be backed up by
similar resources at other datacenters), and offloading of IT tasks
(such as applications upgrading, firewalling, load balancing, storage
backup, and disaster recovery). These translate to economic
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efficiencies if actually delivered. The disadvantages of cloud
service are lack of direct control by the customer, insecurity
regarding remote storage of sensitive data, and communications costs
(both direct monetary and technical such as lack of availability and
additional transaction latency).
The cloud service user connects to cloud resources over a networking
infrastructure. Today this infrastructure is often the public
Internet, but (for reasons to be explained below) is preferably a
network maintained by a Network Service Provider (NSP). The
datacenter(s) may belong to the NSP (which is the case considered by
[I-D.masum-chari-shc]), or may belong to a separate Cloud Service
Provider (CSP), and accessible from the NSP's network. In the latter
case there may or not be a business relationship between the NSP and
CSP, the strongest such relationship being when either the NSP or CSP
offers a unified "bundled" service to the customer.
In order to obtain the advantages of cloud service without many of
the disadvantages, the cloud services customer enters into a Service
Level Agreement (SLA) with the CSP. However, such an SLA by itself
will be unable to guarantee end-to-end service goals, since it does
not cover degradations introduced by the intervening network.
Indeed, if the datacenter is accessed over the public Internet, end-
to-end service goals may be unattainable. Thus an additional SLA
with the NSP (that may already be in effect for pre-cloud services)
is typically required. When the CSP and the NSP are the same entity
but not offering a bundled service, these SLAs may still be separate
documents.
Cloud services require a fundamental rethinking of the Information
Technology (IT) infrastructure, due to the requirement for dynamic
changes in IT resource configuration. Physical IT resources are
replaced by virtualized ones packaged in Virtual Machines (VMs). VMs
can be created, relocated while running (VM migration), and destroyed
on-demand. Since VMs need to interconnect, connect to physical
resources, and connect to the cloud services user, they need to be
allocated appropriate IP and layer 2 addresses. Since these
addresses need to be allocated, moved, and destroyed on-the-fly, the
cloud IT revolution directly impacts the networking infrastructure.
Recent work, such as [I-D.bitar-datacenter-vpn-applicability], has
focused on requirements and architectures for connectivity inside and
between datacenters. However, the "access segment", that is, the
networking infrastructure connecting the cloud services user to the
datacenter, has not been fully addressed.
The allocation, management, manipulation, and release of cloud
resources is called "orchestration" (see [I-D.dalela-orchestration]).
Orchestrators need to respond to user demands and uphold user SLAs
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(perhaps exploiting virtualization techniques such as VM migration)
while taking into account the location and availability of IT
resources, and optimizing the CSP's operational objectives. These
objectives include, for example, decreasing costs by consolidating
resources, balancing use of resources by reallocating computational
and storage resources, and enforcing engineering, business, and
security policies. Orchestrators of the present generation do not
attempt optimization of CSP's networking resources, but this
generalization is being studied [I-D.ietf-nvo3-framework].
Furthermore, these orchestrators are completely oblivious to the
NSP's resources and objectives. Hence, there is no mechanism for
maintaining end-to-end SLAs, or for optimizing end-to-end networking.
This goal of this Internet Draft is to kick off discussions on
requirements and possible mechanisms for improving end-to-end Quality
of Experience while minimizing both networking and computational
costs.
2. Model of Existing Cloud Services
-----
/- - - - - - - - - - - - - - - - - -I O I
-----
/ ------- I
I OSS I ----------
/ ------- I I
I I DC A I
/ -------- ----------- /I I
/ I I I I / ----------
-------- I I I NSP I--->---
I user I->-I CE I--->---I I
-------- I I I network I--->---
I I I I \ ----------
-------- ----------- \I I
I DC B I
I I
----------
Figure 1: Simplified model of cloud service provided over Service
Provider network to an enterprise customer behind a CE device
For concreteness, we will assume the scenario of Figure 1. On the
left we see a cloud services user attached to a customer site
network. This network connects to the outside world via a Customer
Edge (CE), which may be a branch-site router or switch, a special
purpose cloud demarcation device, or in degenerate cases the user's
computer itself. The NSP network is assumed to be a well-engineered
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network providing VPN and other SLA-based services to the customer
site. The NSP network is managed from an Operations Support System
(OSS), which may include a Business Support System (BSS), the latter
being needed for interfacing with the customer for approval of
service reconfiguration, billing issues, etc. In some cases, the
functionality needed here may be obtained by interfacing with a
Looking Glass server or a Policy and Charging Rules Function (PCRF).
Connected to this network are datacenters (two are shown - datacenter
A and datacenter B), which may belong to the NSP, or to a separate
CSP. The orchestrator of datacenter A is depicted as "O".
Additionally, Internet access may be available directly from the CE
(not shown) or from the NSP network.
In the usual cloud services orchestration model the user requests a
well-defined resource, for example over the telephone, via a web-
based portal, or via a function call. The orchestrator, after
checking correctness, availability, and updating the billing system,
allocates the resource, e.g., a VM on a particular CPU located in a
particular rack in datacenter A. In addition, the required networking
resources are allocated to the VM, e.g., an IP address, an Ethernet
MAC address, and a VLAN tag. The VM is now started and consumes CPU
power, memory, and disk space, as well as communications bandwidth
between itself and other VMs on the same CPU, within the same rack,
on other racks in the same datacenter, between datacenters, and
between itself and the user. If it becomes necessary to move the VM
from its allocated position to somewhere else (VM migration), the
orchestrator needs to reallocate the required computational and
communications resources. An example case is "cloudbursting" where a
customer who finds himself temporarily with insufficient local
resources reaches out to the cloud for supplementary ones
[I-D.mcdysan-sdnp-cloudbursting-usecase]. A priori this requires
allocating new addresses and rerouting all of the aforementioned
traffic types, while maintaining continuous operation of the VM.
When the user informs the CSP that it no longer requires the VM, the
orchestrator needs to clear the routing entries, withdraw the
communications resources, release storage and computational
resources, and update the billing system.
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The operations of the previous paragraph are all performed by the
orchestrator, with possible cooperation with orchestrators from other
datacenters. The needed routing information is advertised to the NSP
via standard routing protocols, without taking into account possible
effects on the NSP network. If, for example, the path in the NSP
network to datacenter A degrades, while the path to datacenter B is
performing well, this information is neither known by the
orchestrator, nor is there a method for the orchestrator to take it
into account. Instead, the NSP must find a way to reach datacenter
A, even if this path is expensive, or of high latency, or problematic
in some other way.
This predicament arises due to the orchestrator communicating
(indirectly) with the user, but not with the NSP's OSS. In addition,
although the CE may be capable of OAM functionality, fault and
performance monitoring of the communications path through the NSP
network are not employed. Finally, while the user can (indirectly)
communicate with the orchestrator, there is no coordinated path to
the NSP's OSS/BSS.
3. Optimized Cloud Access
-----
/------/--------------I O I
/ / -----
/ ------- I
-----I OSS I ----------
/ ------- /I I
/ I / I DC A I
-------- / ----------- / /I I
I I/ I I--->-' / ----------
-------- I I--->---I NSP I--->---
I user I->-I CE I I I
-------- I I--->---I network I--->---
I I I I \ ----------
-------- ----------- \I I
I DC B I
I I
----------
Figure 2: Cloud service with dual homing between a cloud-aware CE and
NSP network, and coordination between CE, NSP OSS/BSS, and
orchestrator
Figure 2. depicts two enhancements to the previous scenario. The
trivial enhancement is the providing of dual-homing between the CE
and the NSP network. This is a well-known and widely deployed
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feature, which may be implemented regardless of the cloud services.
We shall see that it acquires additional meaning in the context of
the solution described below.
More significantly, Figure 2 depicts three new control communications
channels. The CE device is now assumed to be cloud-aware, and may
communicate directly with the NSP OSS/BSS, and with the CSP
orchestrator. In addition, the latter two may communicate with each
other. These control channels facilitate new capabilities, that may
improve end-to-end QoE while optimizing operational cost. An
alternative to a combined cloud/network CE is a separate "cloud
demarcation device" placed behind the network CE.
Consider the provisioning of a new cloud service. With this new
architecture the user's request is proxied by the cloud-aware CE to
both the OSS/BSS and to the orchestrator. Before commissioning the
service, the orchestrator initiates network testing between the
datacenter and the CE, and with the NSP's assistance QoS parameters
are determined for alternative paths to various relevant datacenters.
The NSP and CSP (whether a single SP or two) can now jointly decide
on placement of the VM in order to optimize the user's end-to-end
Quality of Experience (QoE) while minimizing costs to both SPs. The
best placement will necessitate the solution of a joint CSP + NSP
optimization problem, while the latter minimization may only be
reliable when a single SP provides networking and cloud resources.
The joint optimization calculation will input the status of
computational and storage resources at all relevant datacenters; as
well as network delay, throughput, and packet loss to each
datacenter. In some cases re-allocation of existing computational
and networking resources may needed.
Similarly, the NSP OSS may trigger VM migration if network conditions
degrade to the point where user QoE is no longer at the desired
level, or may veto a CSP initiated VM migration when its effect would
be too onerous on the NSP network.
The cloud-aware CE may be configured to periodically test path
continuity and measure QoS parameters. The CE can then report that
the estimated QoE drops under that specified in the SLA (or
dangerously approaches it), in order to promote SLA assurance even
when neither OSS nor orchestrator would otherwise know of the
problem. Additionally, the cloud-aware CE may report workload
changes detected by monitoring the number of active sessions (e.g.,
the number of "flows" or n-tuple pairs). The OSS and orchestrator
can jointly perform root cause analysis and decide to trigger VM
migration or network allocation changes or both. Finally, over-
extended network segments may be identified, and pro-active VM
migration and/or rerouting performed to better distribute the load.
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When the CE is dual homed to the NSP network, the secondary link may
be utilized in the conventional manner when the primary link fails,
or may be selected as part of the overall optimization of QoE vs.
cost. Load balancing over both links may also employed. The
datacenters may also be connected to the network with multiple links
(as depicted for DC A in Figure 2), enabling further connectivity
optimization.
In addition, popular yet stationary content may be cached in the NSP
network, and optimization may lead to the NSP network providing this
content without the need to access the datacenter at all. In certain
cases (e.g., catastrophic failure in the NSP network or of the
connectivity between that network and the datacenter), the cloud-
aware CE may choose to bypass the NSP network altogether and reach
the datacenter over the public Internet (with consequent QoE
reduction). In other cases, it may make sense to locally provide
standalone resources at the cloud demarcation device itself.
4. Security Considerations
Perceived insecurity of the customer's data sent to the cloud or
stored in a datacenter is perhaps the single most important factor
impeding the wide adoption of cloud services. At present, the only
solutions have been end-to-end authentication and confidentiality,
with the high cost these place on user equipment. The cloud-aware CE
may assume the responsibility for securing the cloud services from
the edge of the customer's walled garden, all the way to the
datacenter.
Isolation of CSP customers is addressed in [I-D.masum-chari-shc].
Security measures such as hiding of network topology, as well as on-
the-fly inspection and modification of transactions are listed as
requirements in [I-D.dalela-orchestration], while [I-D.dalela-sop]
specifies encryption and authentication of orchestration protocol
messages.
A further extension to the model is to explicitly include security
levels as parameters of the QoE optimization process. This parameter
may be relatively coarse-grained (for example, 1 for services which
must be provided only over secure links, 0.5 for those for which
access paths under direct control of the NSP is sufficient, 0 for
general services that may run over out-of-footprint connections).
Security may also take regulatory restrictions into account, such as
limitations on database migration across national boundaries. Thus,
the placement and movement of a VM will be accomplished based on full
optimization of computational and storage resources; network delay,
throughput, and packet loss; and security levels. For example, for
an application for which the user can not afford denial of service
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the joint optimizaton would need to find the needed resources as
close as possible to the end user.
5. IANA Considerations
This document requires no IANA actions.
6. Acknowledgements
The work of Y(J)S, YG, DK, and KK was conducted under the aegis of
ETICS (Economics and Technologies for Inter-Carrier Services), a
European collaborative research project within the ICT theme of the
7th Framework Programme of the European Union that contributes to the
objective "Network of the Future".
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7. References
[I-D.bitar-datacenter-vpn-applicability]
Bitar, N., Balus, F., Lasserre, M., Henderickx, W.,
Sajassi, A., Fang, L., Ikejiri, Y., and M. Pisica, "Cloud
Networking: Framework and VPN Applicability", draft-bitar-
datacenter-vpn-applicability-02 (work in progress), May
2012.
[I-D.bitar-datacenter-vpn-applicability]
Bitar, N., Balus, F., Lasserre, M., Henderickx, W.,
Sajassi, A., Fang, L., Ikejiri, Y., and M. Pisica, "Cloud
Networking: Framework and VPN Applicability", draft-bitar-
datacenter-vpn-applicability-02 (work in progress), May
2012.
[I-D.dalela-orchestration]
Dalela, A. and M. Hammer, "Service Orchestration Protocol
(SOP) Requirements", draft-dalela-orchestration-00 (work
in progress), January 2012.
[I-D.dalela-sop]
Dalela, A. and M. Hammer, "Service Orchestration
Protocol", draft-dalela-sop-00 (work in progress), January
2012.
[I-D.masum-chari-shc]
Hasan, M., Chari, A., Fahed, D., Tucker, L., Morrow, M.,
and M. Malyon, "A framework for controlling Multitenant
Isolation, Connectivity and Reachability in a Hybrid Cloud
Environment", draft-masum-chari-shc-00 (work in progress),
February 2012.
[I-D.mcdysan-sdnp-cloudbursting-usecase]
McDysan, D., "Cloud Bursting Use Case", draft-mcdysan-
sdnp-cloudbursting-usecase-00 (work in progress), October
2011.
[I-D.ietf-nvo3-framework]
Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
Rekhter, "Framework for DC Network Virtualization", draft-
ietf-nvo3-framework-02 (work in progress), February 2013.
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Authors' Addresses
Yaakov (Jonathan) Stein
RAD Data Communications
24 Raoul Wallenberg St., Bldg C
Tel Aviv 69719
Israel
Email: yaakov_s@rad.com
Yuri Gittik
RAD Data Communications
24 Raoul Wallenberg St., Bldg C
Tel Aviv 69719
Israel
Email: yuri_g@rad.com
Daniel Kofman
LINCS
23 Avenue d'Italie
Paris 75013
France
Email: daniel.kofman@telecom-paristech.fr
Konstantinos Katsaros
LINCS
23 Avenue d'Italie
Paris 75013
France
Email: katsaros@telecom-paristech.fr
Monique Morrow
Cisco Systems
Richtistrase 7
CH-8304 Wallisellen
Switzerland
Email: mmorrow@cisco.com
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Luyuan Fang
Cisco Systems
300 Beaver Brook Road
Boxborough, MA 01719
US
Email: lufang@cisco.com
Wim Henderickx
Alcatel-Lucent
Copernicuslaan 50
2018 Antwerp
Belgium
Email: wim.henderickx@alcatel-lucent.com
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