Internet DRAFT - draft-li-dtn-sd-dtn-sat-net
draft-li-dtn-sd-dtn-sat-net
Delay Tolerant Networking Taixin Li
Internet Draft Huachun Zhou
Intended status: Informational Bohao Feng
Expires: May 5, 2019 Qi Xu
Guanwen Li
Beijing Jiaotong University
November 5, 2018
software defined dtn-based satellite networks
draft-li-dtn-sd-dtn-sat-net-05.txt
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Abstract
Delay/Disruption Tolerant Networking (DTN) is designed for a severe
environment where communication quality is not guaranteed. It works
as an overlay network associated with Bundle Protocol (BP) and some
convergence layer protocols like Licklider Transmission Protocol
(LTP). DTN is suitable for satellite networks. Because communication
delay is long and peer-to-peer communication is not guaranteed in
satellite networks. We implement SDN to solve the problems of
controllable, manageable, and flexible in satellite networks. In
this document, we propose a framework of Software Defined DTN-based
satellite networks, using Bundle tunnel and protocol translation
gateway.
Table of Contents
1. Introduction ................................................ 3
2. Conventions used in this document ........................... 3
3. Key points of the design .................................... 3
3.1. Separated control plane and forwarding plane ........... 4
3.2. Bundle tunnel .......................................... 5
3.3. Satellite gateway ...................................... 6
4. Use case .................................................... 7
5. Security Considerations ..................................... 8
6. IANA Considerations ......................................... 8
7. Conclusions ................................................. 8
8. References .................................................. 9
8.1. Normative References ................................... 9
8.2. Informative References ................................. 9
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9. Acknowledgments ............................................. 9
1. Introduction
Delay/Disruption Tolerant Networking (DTN) [RFC4838] is designed for
a severe environment where connectivity of network is intermittent
and communication quality is not guaranteed. It works as an overlay
network associated with Bundle Protocol (BP) [RFC5050] and
convergence layer protocols like Licklider Transmission Protocol
(LTP) [RFC5325] [RFC5326].
We implement DTN in the satellite networks to meet the need of high
transmission delay with the help of Interplanetary Overlay Network
(ION) [BURLEIGH07]. ION is an implementation of DTN architecture and
is designed to enable inexpensive insertion of DTN functionality
into embedded systems.
SDN [NUNES14] is a state-of-the-art network concept, introducing new
possibilities for network management and configuration methods by
decoupling the control decisions from forwarding hardware. A
controller communicates with the switches by southbound interface,
such as OpenFlow [LARA14], which is the core technology of SDN. We
apply the idea of SDN to satellite network by separating control
plane and forwarding plane in satellite network control structure
and taking advantage of the global view of a controller.
In this document, we propose a framework of Software Defined DTN-
based satellite networks, using Bundle tunnel to deploy OpenFlow
over DTN and protocol translation gateway to achieve protocol
translation between Bundle packets and IP packets.
2. Conventions used in this document
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].
3. Key points of the design
The idea of SDN is applied in the proposed framework. The control
link between the control plane and the forwarding plane is Bundle
tunnel. Because we use DTN protocol stack in space network and the
protocol stack of ground network is TCP/IP. There should be a
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protocol translation gateway to achieve protocol translation between
Bundle packets and IP packets.
3.1. Separated control plane and forwarding plane
+------------------------------------+
| +-------------+ |
|Control plane |GEO satellite| |
| +-------------+ |
+--------------+---------------------+
| Control link
| One set of ION
| configuration script
+--------------+---------------------+
| +-------------+ |
| +--+MEO satellite| |
| | +-------------+ |
|Forwarding | Data link |
| plane | Another set of ION |
| | configuration script|
| | +-------------+ |
| +--+LEO satellite| |
| +-------------+ |
+------------------------------------+
Figure 1 Illustration of the two planes
We apply the idea of SDN to satellite network by separating control
plane and forwarding plane in satellite network control structure
and taking advantage of the global view of a controller. The whole
space network is divided into two parts, control plane and
forwarding plane. The control plane contains Geosynchronous Earth
Orbit (GEO) satellites, on which SDN controllers are deployed. The
forwarding plane contains Medium Earth Orbit (MEO) satellites and
Low Earth Orbit (LEO) satellites, and OpenFlow enabled switches are
deployed on them.
We implement DTN with the help of ION in space network. The topology
configuration mode of ION is reading the configuration scripts (.rc
file), which contains the information of connections and nodes. As
is shown in Figure 1, to achieve the goal of separating the control
plane and forwarding plane in the space network, we adopt two set of
unrelated ION configuration scripts when creating the topology. One
is the script of Bundle tunnel (or we can say the control link). The
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other one is the script of data link. Two ION processes run in the
MEO/LEO satellite nodes without affecting each other.
3.2. Bundle tunnel
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
X X
X Bundle tunnel header X
X X
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
X X
X Bundle tunnel payload X
X X
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
X +---------------------+--------------------+ X
X | Ethernet header | IP header | X
X +---------------------+--------------------+ X
X | UDP header | LTP header | X
X +---------------------+--------------------+ X
X |Primary Bundle header| Payload header | X
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
X | OpenFlow signaling data | X
X +------------------------------------------+ X
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Figure 2 Illustration of bundle tunnel
We deploy OpenFlow over DTN by a method of tunnel. That is,
signaling packets are transmitted in bundle tunnel when controller
(GEO satellite) sets up connection to switches (MEO satellites) and
when controllers send instructions to switches. The encapsulation
format of the bundle tunnel is shown in Figure 2. Because DTN is
implemented in ION in an overlay way, the first half of the Bundle
tunnel header is the same as normal IP packets. The difference is
that there are a 4-byte LTP header, a 14-byte Primary Bundle header,
and a 5-byte Payload header before the payload data field due to the
protocol stack of DTN. The link layer field is removed from the
OpenFlow signaling packets between controller and switches and then
the remaining fields are encapsulated in payload data.
The design of the Bundle tunnel adopts a dual process approach. One
process is responsible for receiving OpenFlow signaling packets from
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the local controller or switches. Then signaling data are separated
out and encapsulated in the Bundle packets. Finally, the Bundle
packets are sent to the control link. The other process is
responsible for receiving Bundle packets from the control link and
decapsulating the Bundle packets and get the OpenFlow signaling
data. Then the signaling data are sent to the local controller or
switches. In this way, the SDN controller in GEO satellite can
communicate with the OpenFlow enabled switches in MEO/LEO
satellites.
3.3. Satellite gateway
+------------+ +------------+
|Application <-----------------------------------> Application|
| data | | data |
+------------+ +----------+----------+ +------------+
| |ground| | Bundle |space | Bundle |
| | link | +----------+link +------------+
| TCP/UDP <------> TCP/UDP | LTP <------> LTP |
| | | +----------+ +------------+
| | | | UDP | | UDP |
+------------+ +---------------------+ +------------+
| IPv4/6 | | IPv4/6 | IPv4/6 | | IPv4/6 |
+------------+ +----------+----------+ +------------+
ground node satellite gateway satellite node
Figure 3 Protocol stacks
We use DTN protocol stack in space network and TCP/IP stack in the
terrestrial network, so there should be protocol translation for
data transmission and service delivery in the Software Defined DTN-
based satellite networks framework. We develop DTN to TCP/IP
bidirectional protocol translation and deploy this function on the
satellite gateways. We deploy DTN with Interplanetary Overlay
Network (ION) and modify ION to adapt to IPv6. In this way, ION is
IPv4/6 dual stack. If the ground nodes run in IPv6 stack, there is
no need for complex protocol translation between IPv4 and IPv6 at
the satellite gateway.
The protocol stacks of the ground node, satellite gateway node, and
satellite node are shown in Figure 3. The physical layer and the
data link layer are omitted because they are not involved in the
proposed framework. The bidirectional translation between IP packets
that belongs to TCP/IP stack and the Bundle packets that belongs to
DTN stack is achieved at the satellite gateway by adopting
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hierarchical, modular, and multi-process protocol translation
function.
4. Use case
GEO satellite
+---+XX+---+
+---+XX+---+
X X X X
XX X X XX
XX X X X
Bundle tunnels XX X X X Bundle tunnels
XXX X X X
XXX X X XX
XX X +---+XX+---+ XX
+---+XX+---+ X +---+XX+---+ XX
+---+XX+---+ X MEO/LEO XX
MEO/LEO X satellite3 XX
satellite1 X ^ + XX
X | | X
X | | +---+XX+---+
X | +---------> +---+XX+---+
+---+XX+---+ | Space links MEO/LEO
+---+XX+---+----+ satellite4
MEO/LEO +
satellite2 |
^ |
| |
+---------+ +----------+
| |
+ v
+-----------+ X X +--------+
|Data Center+------------->XXX XXX+------> User |
+-----------+ Ground XXXXX XXXXX +--------+
links Satellite Satellite
gateway 1 gateway 2
Figure 4 Use case of the proposed framework
The use case of proposed framework is shown in Figure 4. The GEO
satellite set up control link to the four MEO/LEO satellites. The
data center data are transmitted among the four MEO/LEO satellites.
The ION configuration script of the control plane is about the
connections of one GEO satellite to four MEO/LEO satellites. The ION
configuration script of the forwarding plane is about the
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connections among the four MEO/LEO satellites. That is to say, two
sets of unrelated ION processes are running in the four MEO/LEO
satellites.
A user applies for data from the data center via satellite networks.
The traffic is sent to satellite gateway 1 and converted from IP
packets to Bundle packets. The controller in GEO satellite send
instructions to the MEO/LEO satellites and configure the flow tables
of the switches in MEO/LEO satellites. Then the traffic is forwarded
via the path: satellite2-->satellite3-->satellite4 under control of
GEO satellite. Then, the traffic is sent to satellite gateway 2 and
converted from Bundle packets to IP packets. Finally, the data are
sent to the user.
5. Security Considerations
Introducing SDN in DTN-based space network can bring in some
problems that any SDN-based frameworks have. The proposed framework
adopts a centralized control architecture. So if GEO satellite is
attacked (by viruses or physical attack), security problem should be
considered. The possible solution may be reserving spare GEO
satellite. When the GEO satellite in use breaks down, the spare one
will take on the responsibility.
6. IANA Considerations
This document does not update or create any IANA registries.
7. Conclusions
This document describes the key points of the design of the proposed
Software Defined DTN-based satellite networks framework: Separated
control plane and forwarding plane in space network, Bundle tunnel,
and satellite protocol translation gateway. And we describe the use
case of the proposed framework in this document.
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8. References
8.1. Normative References
[RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
R., Scott, K., Fall, K., and Weiss, H., "Delay-Tolerant
Networking Architecture", RFC 4838, April 2007.
[RFC5050] Scott, K., and Burleigh, S., "Bundle Protocol
Specification", RFC 5050, RFC5050, November 2007.
[RFC5325] Burleigh, S., Ramadas, M., and Farrell, S., "Licklider
Transmission Protocol - Motivation", RFC 5325, September
2008.
[RFC5326] Ramadas, M., Burleigh, S., and Farrell, S., "Licklider
Transmission Protocol - Specification", RFC 5326,
September 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[BURLEIGH07] Burleigh S. "Interplanetary Overlay Network: An
Implementation of the DTN Bundle Protocol" Consumer
Communications and NETWORKING Conference (CCNC), 2007,
pp. 222-226, 2007.
[NUNES14] B. Nunes, M. Mendonca, X. Nguyen, K. Obraczka, & T,
Turletti, "A survey of software-defined networking: Past,
present, and future of programmable networks," IEEE
Communications Surveys & Tutorials, vol. 16 (3), pp. 1617-
1634, Feb. 2014.
[LARA14] A. Lara, A. Kolasani, & B. Ramamurthy, "Network Innovation
using Openflow: A Survey," IEEE Communications Surveys &
Tutorials, vol. 16(1), pp. 493-512, Feb. 2014.
9. Acknowledgments
This work in this document was supported by National High Technology
of China ("863 program") under Grant No.2015AA015702.
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Authors' Addresses
Taixin Li
Beijing Jiaotong University
Beijing, 100044, P.R. China
Email: 14111040@bjtu.edu.cn
Huachun Zhou
Beijing Jiaotong University
Beijing 100044, P.R. China
Email: hchzhou@bjtu.edu.cn
Bohao Feng
Beijing Jiaotong University
Beijing, 100044, P.R. China
Email: 11111021@bjtu.edu.cn
Qi Xu
Beijing Jiaotong University
Beijing, 100044, P.R. China
Email: 15111046@bjtu.edu.cn
Guanwen Li
Beijing Jiaotong University
Beijing, 100044, P.R. China
Email: 16111011@bjtu.edu.cn
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