ALTO Working Group M. Chen
Internet-Draft X. Wang
Intended status: Standards Track Tongji University
Expires: January 10, 2017 July 9, 2016
ALTO in Ethernet and Optical Converged Networks
draft-chen-alto-ethernet-optical-converged-network-00
Abstract
In conventional enterprise data centers, there are at least two
networks: Ethernet that allows users to access their applications on
servers, optical networks which built on Fiber Channel, that enables
those servers to access big data on storage network. Because of
their specialized hardware, they have vastly different management
tools and require completely different skill sets to build and
maintain.
The Application-Layer Traffic Optimization (ALTO) protocol is
designed to provide network related information to client
applications. It has developed a lot in Ethernet, and now we
consider to build a central control in a basic Ethernet and Optical
converged networks. Follow the concept of ALTO implementing in
Ethernet networks, an ALTO server can get the necessary information
from underlining Ethernet and Optical converged networks. After
abstracting the network information, ALTO server can achieve a
central resource allocation and organize them into a standard format
so as to provide useful information to ALTO clients. This document
designs a basic way of applying ALTO in converged networks.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.3. Changes Since Version -00 . . . . . . . . . . . . . . . . 4
2. ALTO Architecture in Converged Networks . . . . . . . . . . . 4
3. Ethernet and Optical Converged Networks Model . . . . . . . . 5
4. Optical Resource Abstraction and Allocation . . . . . . . . . 5
4.1. Optical Resource Abstraction . . . . . . . . . . . . . . 5
4.2. Optical Resource Allocation . . . . . . . . . . . . . . . 6
5. ALTO Standardized Converged Networks Information Construction 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Privacy And Security Considerations . . . . . . . . . . . . . 9
8. Normative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Reliability and Effectiveness are key metrics of the network
qualities. When facing multiple services, performance of networks
varies a lot. It seems that just one network would be more cost-
efficient. However, as a result of big data and cloud computing,
optical networks play an important role in meeting high speed demand.
Due to different mechanisms of packet and circuit networks' control,
management and transport technology, a unified control of the two
networks develops slowly. One highly scalable, high-performance
network with consistent management tools handling both Ethernet and
storage traffic is a promise of converged networking.
The initialize of converged networks was because 1Gbps Ethernet
couldn't handle the loads that enterprises throw at their 4Gbps and
8Gbps Fiber Channel-based storage networks. After that, Ethernet
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capability has increased but Fiber Channel still wins in an assured
delivery protocol. Using high-level protocols in Ethernet to
implement flow control and error correction is both complex and
expensive from a latency perspective.
ALTO is aimed at application layer optimization and it standardizes
the interaction between ALTO server and ALTO clients. How to extract
information from underlining networks and abstract them properly are
crucial. In practical, loading network information by an Agent, as
well as getting available information with OpenFlow protocol by
building an ALTO server on a SDN controller are both viable ways.
Here we point out a basic thread on how to achieve optical resource
abstraction and allocation based on OpenFlow extension. After that,
we use necessary information to reflect basic standard information of
ALTO server. In this case, bandwidth achievement is the significant
difference comparing with Ethernet, and other metrics like hop count,
cost can follow the Ethernet conception. Here we put optical
transport network (OTN) devices as the optical network elements and
discuss electrical switching, and the optical switching is out of
scope of this document.
This document is organized as follows. Section 2 proposal an ALTO
Architecture in Converged Networks. Based on it, Section 3 forward a
simple Ethernet and optical converged networks model. In the Optical
Networks Resource Abstraction module shown in Figure 1. Section 4
aims to illustrate it by explain optical resource abstraction and
allocation. In detail, Section 4.1 analyze the southbound interface
design based on OTN physical features. Section 4.2 illustrate a
simple rule on allocate the optical bandwidth resource and
configurations. At last, Section 5 discuss the central aspect from
ALTO server of Ethernet and optical converged networks and future
thinking.
1.1. Terminology
This document uses terms defined as follows:
o {1.2.3}: References of this form are to sections in the ALTO
protocol specification [RFC7285].
o And other terms defined in {8.2} of [RFC7285].
1.2. Requirements Language
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].
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1.3. Changes Since Version -00
o Change the format of API for clients' request. This design is
more concise and has better compatibility. It does not modify the
IRD of ECS. Section 3.1 introduces a new abstraction for Endpoint
which defines the ConnectionURI to represent an endpoint. And a
specific flow can be determined by a pair of ConnectionURI.
o Add some design principles in section 4.
o Give two strategies to solve the multi-path problem and handle
fine-grained path error in section 6. One option is to introduce
feedback mechanism, the other option is to implement exploring.
2. ALTO Architecture in Converged Networks
As we introduce optical network resource into the underlining network
environment. Some modules should addict to the ALTO server
reasonably. Here is a ALTO Architecture in Ethernet and optical
converged networks in Figure 1. In this architecture, we describe
the underlining converged networks and Optical Networks Resource
Abstraction further more in Section 3 and Section 4. Over the
Ethernet Network Resource Extraction and Optical Networks Resource
Abstraction modules, there is a Converged Network Resource
Integration module which we may infer some aspects from it in the
following.
+---------------+ +---------------+
| ALTO Client A | | ALTO Client B |
+-------^-------+ +-------^-------+
+----------------------------------------------+
| ALTO Server |
| +----------------------------------------+ |
| |Converged Network Resource Integration | |
| +----------------------------------------+ |
| +----------------------------------------+ |
| |Ethernet |Optical Networks | |
| |Resource Extraction|Resource Abstraction| |
| +-------^----------------------^---------+ |
+----------------------------------------------+
+---------------------+ +----------------------+
| Ethernet | |Optical Networks |
| | | |
+---------------------+ +----------------------+
Figure 1: ALTO architecture in converged networks.
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3. Ethernet and Optical Converged Networks Model
The variety of services requires controllable and flexible mechanism
of networks in a certain degree. Dynamic scheduling service
depending on specific situation can improve source utilization. And
reasonably intelligent network control does not only save costs of
network operation and maintenance, but also cater to the needs of
various services much more.
We proposed a simple Ethernet and optical converged networks model
which has considered the physical characteristics of optical
transport networks. The switching granularity is at time slot level,
or optical fiber. In the model. Optical networks bear the large
transmission tasks and locate in the core position. At the edge of
the network model, Ethernet plays an access role of the network
environment and face the applications directly. Consider the
electrical switch character and separation design between control
plane and data plane of optical networks, it seems to be less
significant in applying ALTO to optical networks as the origin design
can achieve the same effect as ALTO. But ALTO in Ethernet and
optical converged network is of value to provide a better service for
ALTO clients due to the converged network resource integration.
Imagine that, ALTO server obtain a global view both on Ethernet and
optical networks, the schedule and false detection will be more
direct.
4. Optical Resource Abstraction and Allocation
The feasible proposed architecture has to consider the
programmability of network configuration based on physical device and
application. Switching in optical NE can be supported in both
electrical and optical domains. For time division multiplexing (TDM)
circuits with guaranteed bandwidths, electrical switching is at
tributary slot level. Generally, TDM is defined by the OTN optical
data unit (ODUk) standards with a rigid bandwidth hierarchy, and
provides fixed and guaranteed bandwidth for client ports. Networks
can make an appropriate combination of electrical and optical
switching based on the application requirements.
4.1. Optical Resource Abstraction
Figure 2 illustrates OTN device abstraction and information mapping.
Software defined networking principles can be applied to many
different optical transport network architectures. So we leave a
field to express feature type. In this case, we set it as OTN Layer
Stack, and then list OTN layer entries. Each of layer entries'
information refines layer class, signal type, adaptation. Layer
class and signal type, as the most important optical port
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information, will reflect some certain performance of optical
networks. ODU client (ODUCLT) Layer represents client-side
information and it is always Ethernet signal type. ODU Layer
influences the length and allocation of tributary slot, it represents
the switching granularity. The signal type of optical transform unit
(OTU) Layer indicates a certain bandwidth. Optical Channel (OCh)
Layer corresponds to the optical signal type. Here we discuss
electrical switching only.
+-----+ . +-----+ +-----+ . +-----+ . +-----+
|Eth | ---- | | | | . | | . | |
|If | . | | | | . | | . | |
+-----+ . | | |ODUk | . |OTUk | . |OCh |
. | | ---- | | ---- | | ---- | | ----
+-----+ . |ODUk | |Sw | . |Proc | . |Sw |
|OTUk | ---- | | | | . | | . +-----+
|If | . |Proc | | | . | | .
+-----+ . | | | | . | | .
. | | | | . | | .
+-----+ . | | +-----+ . | | .
|Other| ---- | | . | | .
|If | . | | ----------------- | | -----------------
+-----+ . +-----+ . +-----+ .
. . .
| | | |
| | | |
+--|-----------------|--------------------|-----------|--------+
| | | OTN Layer Stack | | |
| V V V V |
+--------------+---------------+---------------+---------------+
|ODUCLT-Layer | ODU_Layer | OTU_Layer | OCh_Layer |
+--------------+---------------+---------------+---------------+
|Layer-|Signal-|Layer-|Signal- |Layer-|Signal- |Layer-|Signal- |
|Class |Type |Class |Type |Class |Type |Class |Type |
+--------------+---------------+---------------+---------------+
Figure 2: Resource abstraction on optical NE.
4.2. Optical Resource Allocation
Configuring tables of network element (NE) is another challenge.
Based on signal types of NE, ODUx is a good candidate to become a
match principle. Besides allocation tributary slot according to
ODUx, we should also consider Ethernet signal types. A simple
simulation scene presents two kind of services implementation based
on bandwidth demand. Besides the specific technical realisation of
optical NE table configuration. We would like to show an example of
the service based clients use case in converged networks.
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Tributary slot allocation plays an important role in electrical
switching. As a direct influence factor of granularity, ODUx leads
ways for matching flow entries namely resource allocation. In
Figure 3, suppose electrical switching granularity of an optical NE
is ODU0 which represents 1.25GE bandwidth. ODU0 presents a match
principle of match field, i.e., ODU_SIGTYPE. And ODU_SIGID manages
output ways as an action principle. Similarly, OTU Layer signal type
OTU2 indicates a given bandwidth 10GE. Conclusively, bandwidth
reflexed by OTUx and ODUx indicates numbers of tributary slot (TSLEN)
gotten by OTUx's dividing by ODUx's, so we get a value of TSLEN: 8 to
provide services in this case. In figure 3, suppose an client A
requires 1GE bandwidth accesses Port 1 of Optical NE:1 (NE:1:1) .
From above we can deduce that one tributary slot is occupied by the
service namely tributary port number (TPN) equals 1. It should be
noticed that tributary slot map (TSMAP) is presented by binary array.
So the value of it is a result of transform from binary value to
decimal value. In this situation, suppose client A is routed from
NE:1:4 to NE:2:2. Apparently, the action principle of service in
NE:1 turns to be match principle of NE:2 to a large extent. A small
difference may be presented in TSMAP allocation. Referred to the
action principle of NE:2, the output field is NE:2:4.
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NE:1
+----------+------------------------+
|Sig-Type: | |Sig-Type: |
|OTU2 | |ODUCLT |
+-----------------------------------+
| 1 | +------+ 1 |----- Client A
+----------+ | +----------+ 1GE
| 2 | | | 2 |
+----------+ | +----------+
| 3 | | | 3 |
+----------+ | +----------+
+-----+ 4 |------+ | 4 |
| +----------+-------------+----------+
|
|
| NE:2
| +----------+------------------------+
| |Sig-Type: | |Sig-Type: |
| |OTU2 | |ODUCLT |
| +-----------------------------------+
| | 1 | | 1 |
| +----------+ +----------+
+---->| 2 |------+ | 2 |
+----------+ | +----------+
| 3 | | | 3 |
+----------+ | +----------+
| 4 | +----->| 4 |----- Client B
+------------------------+----------+ 1GE
Figure 3: Route configuration based on bandwidth.
5. ALTO Standardized Converged Networks Information Construction
For OTN device, we know that the numbers of unused tributary slot can
deduce to the remaining bandwidth resource. From the aspect of ALTO
Clients, there is no need for them to know the underlining networks
but just the remaining network resource and other parameters on
transport. As we mentioned at the beginning, we can extract the
optical networks information by extending OpenFlow protocol and
abstract the information into useful resource. We can get the
tributary slot information by changing a little bit on the port reply
message of OpenFlow. This document put forward a possibility on
integrating the Ethernet and optical converged networks by deploying
an ALTO server. In the future, we will combine optical network
resource with ALTO in protocol level.
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6. IANA Considerations
This document does not define any new media type or introduce any new
IANA consideration.
7. Privacy And Security Considerations
This document does not introduce any privacy or security issue not
already present in the ALTO protocol.
8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S.,
Previdi, S., Roome, W., Shalunov, S., and R. Woundy,
"Application-Layer Traffic Optimization (ALTO) Protocol",
RFC 7285, DOI 10.17487/RFC7285, September 2014,
<http://www.rfc-editor.org/info/rfc7285>.
Authors' Addresses
Mingming Chen
Tongji University
4800 Cao'an Road, Jiading District
Shanghai
China
Email: mingmingminne@126.com
Xin Tony Wang
Tongji University
4800 Cao'an Road, Jiading District
Shanghai
China
Email: xinwang2014@hotmail.com
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