ALTO H. Song
Internet-Draft Y. Lee
Intended status: Informational Huawei
Expires: August 26, 2013 Feb 22, 2013
Infrastructure to Application Information Exposure
draft-song-alto-i2rs-01
Abstract
This document describes the scenarios that applications can use the
network layer especially the network routing system exposed
information, so as to optimize application layer traffic. The use
cases in this document include the ISP broadband network (using P2P
and CDN as examples) and the data center network. This document
also describes what information should be collected for
ALTO service for traffic optimization.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. ISP network . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Data Center Network . . . . . . . . . . . . . . . . . . . . 4
4. Open Discussion . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Informative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
ALTO provides an interface to applications and appropriate
information to guide an optimal node selection when there are more
than one application node providing the same service, through
aggregated network map and cost map. It usually aggregates network
locations into PIDs, and assigns lower cost value for a PID pair that
are topologically closer. So when application node follows the advice
from ALTO server to choose one resource provider within a PID that
has lower cost from its own PID, with higher probability the
application node can keep the content request and response traffic
flow intra domain. This can reduce interdomain traffic for ISPs, and
avoid the congestion in the backbone network. More factors for node
selection can be considered, such as pricing, congestion, and etc.
In order to assure optimality, the underlying infrastructure needs
to expose its topology information, node/link status information,
pricing information for path selection to ALTO server, which will
either be abstracted as the network map or as the impacting input
factor of cost map.
2. Terminology
I2AEX: Infrastructure to Application Exposure.
ALTO: application layer traffic optimization.
IaaS: Infrastructure as a Service.
3. Use Cases
3.1. ISP network
ISP broadband networks are consisted of interconnected autonomous
systems. They run BGP protocols between the boarder gateway routers,
and run IGP protocols intra autonomous systems. There are core
routers, and access routers (BRAS) which fullfill the admission
control through RADIUS servers, the access router connects to
multiple aggregation switches. And an aggregation switch connects to
multiple DSLAMs or OLTs. And the DSLAM or OLT connect to the home
gateways or ONUs, which connect to the user devices. [It's better to
give a figure here.]
The ISP network usually hide all its information to applications.
But in the trend of big traffic use case, the main motivation is to
reduce the backbone and interdomain traffic. CDN and P2P are the two
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target applications. In a P2P application, the content requester
requests contents from peers in the same swarm. It may choose a peer
that is far way ignoring a peer that is topologically closer to it.
Due to the topology ignorance, the application may creates
unnecessary backbone and interdomain traffic.
In another application of CDN, a popular resource usually is stored
in multiple data centers. Without the knowledge of the network
topology, the CDN's DNS server can redirects the content requester to
a sub-optimal edge server, which is not always topolocially close to
the content requester. Even with measuring the round trip time
between its edge servers and the requester's local DNS server, it may
not get the accurate result because RTT is dynamic and user can
specify its own DNS server.
For the above two broadband network use cases, the infrastructure
information from the home to the access router does not help much.
But more attendtion should be paid to the information from the access
router to the routing system, which can provide important input for
the ALTO maps. An ALTO server needs the following information as
input:
o The network segments information. Every access router manages one
or more IP address pools, to be assigned to the users through DHCP or
other ways.
o The IP addresses of the interfaces of routers, and the routing
table information(IGP or BGP). This information can help to
construct the whole network topology.
o The congestion status of the router interfaces, but this
information could be reflected in the routing table change.
o Policy information. For example, one multi-homing AS prefers to
use which AS to transit its traffic, including the pricing
information.
ALTO can use the collected information mentioned above to be able to
select a node topologically closer, with lower transit price and
less congested link.
3.2. Data Center Network
Infrastructure as a service (IaaS) is a way how the data center
provides its services. There are different kinds of resources in a
data center, physical machines, virtual machines, switches,
firewalls, computing power, storage space, and electric power.
[I-D.lee-alto-ext-dc-resource] proposes collecting data
center resource information to make use of such information for a key
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decision to allocate the application request to an "optimal" Data
Center location in which to host the application request. Key
constraints in this decision include resource availability (e.g.,
memory, storage, CPU, etc.), DC network cost, DC network resource
constraints (e.g., bandwidth), structure constraints (e.g., Data
Center power consumption) and others.
Combined computing and network resource optimization is of value to
both application owners and data center operators. For example a
data center operator with multiple buildings in a metropolitan area
may also want to balance compute and network costs.
+--------------+
Resource Request | Application |
-----------> | Orchestrator |
+-------+------+
|
+--------+ +----+----+ +--------+
| | | | | |
| DC 1 |<--------+------->| ALTO |<-------+------->| DC 2 |
| | ALTO-interface | Client | ALTO-interface | |
+--------+ +---------+ +--------+
/|\
|
+ ALTO-interface
|
\|/
+---------+
| |
| DC 3 |
| |
+---------+
The ALTO server needs to collect the following information so as to
provide this kind of service.
o All switches' network capacity information
o All physical servers' information(CPU, memory) in the data center
o The storage space information in the data center
o The physical links information
o The virtual machines' information(CPU, memory) and its affinity
o Pricing models
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Based on the aforementioned information, ALTO server can provide the
load balancing/traffic optimization information to ALTO client for
data centers, through map or ranking.
4. Open Discussion
In order to optimize the application traffic, network layer needs to
provide necessary information to the according applications in the
previous section, with a method (request/response, or subscription/
notification) to make the underlying information changes be timely
sent to the ALTO server. This requires more interactions between the
network layer and the application layer. I2RS seems to consider more
configuration use cases such like policy based routing, but what ALTO
protocol needs is the part that discloses the network information.
So there could be two ways to go forward.
(1) Defining a new protocol to cover all required functions such as
configuration and information disclosure required by I2RS. This
protocol covers ALTO's south bound information requirements on network
topology, with its one component. But this protocol will be
tremendously complicated. It will be related and overlapped with
other existing protocols, such like NetConf and YANG.
(2) Defining the south bound interface for ALTO, to collect the
infrastructure information, and bring the requirements discussion in
I2RS, and identify the final scope, to avoid the overlap between
different WGs(ALTO, NetConf, NetMod). In this case, the protocol
development will belong to ALTO WG.
5. Informative References
[I-D.lee-alto-ext-dc-resource]
Lee, Y., Bernstein, G., and D. Dhody, "ALTO Extensions for
Collecting Data Center Resource Information",
draft-lee-alto-ext-dc-resource-01 (work in progress),
January 2013.
[I-D.ietf-alto-protocol]
Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol",
draft-ietf-alto-protocol-13 (work in progress),
September 2012.
[RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic
Optimization (ALTO) Problem Statement", RFC 5693,
October 2009.
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Authors' Addresses
Haibin Song
Huawei
Email: haibin.song@huawei.com
Young Lee
Huawei
Email: leeyoung@huawei.com
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