Path Aware Networking Research Group S. Zheng
Internet-Draft P. Liu
Intended status: Informational Z. Chen
Expires: August 26, 2021 China Mobile
February 22, 2021
Required path properties for applying path aware networking in
integrated space-terrestrial networks
draft-zheng-panrg-path-properties-istn-00
Abstract
Integrated space-terrestrial networks are heterogeneous networks with
various path characteristic, and usually belong to different
administrative domains. Therefore integrated space-terrestrial
networks can be seen as a use case of path-aware networking. This
memo introduces requirements on path properties when applying path-
aware-network in integrated space-terrestrial networks.
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 [RFC2119].
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 26, 2021.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Abbreviation . . . . . . . . . . . . . . . . 3
3. Path properties . . . . . . . . . . . . . . . . . . . . . . . 3
4. Fine granular properties . . . . . . . . . . . . . . . . . . 3
4.1. node properties . . . . . . . . . . . . . . . . . . . . . 4
4.2. Link properties . . . . . . . . . . . . . . . . . . . . . 4
5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
In the integrated space-terrestrial networks, endpoint is capable to
access space networks, mobile networks, and fixed networks. These
heterogeneous networks have essential difference on characteristics
and come from different service providers, which makes it difficult
to carry out unified management and control. Furthermore, different
with ground networks, the quality of links in space is fluctuating,
the network topology changes dynamically, and the resources of space
node is limited. It is necessary to come out a system to release the
burden of networks(especially space nodes with limited resource) and
leaving the complex function to endpoint. In other words, the path-
aware network may help to cope with the dynamics of this kind of
network.
According to the definition of [RFC5136], a path is a series of links
that connect a series of nodes from the source node to destination.
The properties of path can be seen from the overall point of view, or
decomposed into node properties and link properties. Corresponding
granular path awareness can be performed in the basis of the
capability of the endpoint and/or the required quality of service.
This memo will describe the required path properties from different
granularity in integrated space-terrestrial networks.
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2. Terminology and Abbreviation
Integrated space-terrestrial Networks(ISTN): A network system that
comprehensively utilizes a variety of communication network
technologies including space networks and terrestrial networks to
achieve global coverage. The integrated system includes ground
segment and space segment. The ground segment includes terrestrial
network nodes such as ground stations, terminals, servers controllers
and terrestrial links such as cable, fiber. Space segment includes
space node such as satellites and space links such as laser and
radio.
3. Path properties
The path properties describe the overall properties of the whole path
from an end-to-end perspective.
Space and ground networks share some common properties, but due to
the essential differences between the space network and the
terrestrial network on characteristics such as mobility, link
stability, resources etc., some additional properties are required to
support path selection at the endpoint.
Common path properties
1. Properties in path
properties[I-D.irtf-panrg-path-properties],such as one way delay and
one way packet loss.
Additional path properties in space
1.Available time: path available time; due to the topological
dynamics of the space link, the path in the world-ground integrated
network is not always available. Therefore, it is necessary to set
an available time for each path;
4. Fine granular properties
In addition to the fluctuating latency, and bandwidth, the complex
space environment will lead to unpredictable wireless link
disconnection.The mobility of space nodes will lead to periodic
dynamic topology change. Therefore, the performance of the path
changes more frequently, and the fine granular properties can help
the integrated space-terrestrial networks to quickly locate
unpredictable faults and find the optimal alternative link instead of
discarding the entire path. For example, path properties can be
decomposed into node properties and link properties.
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4.1. node properties
Common properties of nodes
1.Node computing resources: computing resources available on ground
nodes/space nodes. When the available computing resource is less, it
indicates that the node is heavy-loaded, and the path that contains
the node should be avoided when selecting a path.
2.Node storage resources: available storage resources of ground
nodes/space nodes.
Additional node properties in space
1.Node power: This is actually the most important property of space,
because the energy of satellite in space comes from solar panels,
which make the node energy fluctuating with time. If the power of
the satellite node is not sufficient to support additional computing/
communication functions, the satellite node is not available; it can
be simply set to 0/1 to indicate whether the node supports additional
computing/communication functions.
2.Available interfaces of the node. The interface that can be used
to establish a link, it may contain a set of information indicating
the direction of interface and available next hop. This property can
be use to derive the topology information. The specific link status
is excluded and needs to query the link properties described below.
3.The future available interfaces of the node. The movement of
satellite nodes is periodic. Periodicity can be used to predict the
topology in the future to help make routing decisions. This property
can be sent in different manners, depending on the mechanism the
system used to deal with the network mobility. This property can be
sent in each time slot if the system use snapshot. Or to reduce the
interaction cost, event triggered property notification can be used,
that is the notification only executes when the available interfaces
changes due to unexpected event.
4.2. Link properties
Common link properties
1.Propagation delay:When a data packet propagates from the source
node to the destination node, the time required for the transmission
from the beginning to the end of the link is the propagation delay.
Data packets are propagated at the propagation rate of the link, and
its rate depends on the physical medium of the link. The propagation
delay is equal to the ratio of the distance between the nodes and the
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propagation rate. As the distance between the nodes changes as space
node moves, the delay changes as well.
2.Link media: the link media can be laser/cable/radio etc., and the
different media can have different priority and cost, which should be
used to do the path selection decision.
3.Quality of link: This property can be indicated by bit error rate
or packet loss rate, depending on the network system.
Additional link properties in space
1. Available time: When the nodes at both ends of a link are
constantly moving relative to each other, the link may be unavailable
because the nodes move out of mutual visible area. Therefore, it is
necessary to know the available time of the link.
2. Link status: different from bit error rate, this property
indicates the state of link, for example, when the link is
temporarily unavailable due to space environment, it can be set in
leave and; when the link is unavailable due to mobility, it can be
set to down . The link state information may not come from space node
itself but from ground measurement and control station.
5. Summary
Integrated space-terrestrial Networks can take advantage of the PAN
and can be seen as a typical use cases. When PAN is introduced into
ISTN, it will have some different requirements on the path
properties, and this memo study the first question in
[I-D.irtf-panrg-questions] by list and explain some potential path
properties.
6. Security Considerations
It should be noticed that under the Integrated space-terrestrial
Networks background, the topology information comes from different
operators, they may not willing to expose their network information
to other operators or other 3rd parties, so it is crucial to find a
way to supply the information to end user while not expose to others.
7. IANA Considerations
This document has no requests to IANA.
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8. Normative References
[I-D.irtf-panrg-path-properties]
Enghardt, T. and C. Krahenbuhl, "A Vocabulary of Path
Properties", draft-irtf-panrg-path-properties-01 (work in
progress), September 2020.
[I-D.irtf-panrg-questions]
Trammell, B., "Current Open Questions in Path Aware
Networking", draft-irtf-panrg-questions-08 (work in
progress), December 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5136] Chimento, P. and J. Ishac, "Defining Network Capacity",
RFC 5136, DOI 10.17487/RFC5136, February 2008,
<https://www.rfc-editor.org/info/rfc5136>.
Authors' Addresses
Shaowen Zheng
China Mobile
Beijing 100053
China
Email: zhengshaowen@chinamobile.com
Peng Liu
China Mobile
Beijing 100053
China
Email: liupengyjy@chinamobile.com
Danyang Chen
China Mobile
Beijing 100053
China
Email: chendanyang@chinamobile.com
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