Internet DRAFT - draft-blanchet-dtn-http-over-bp
draft-blanchet-dtn-http-over-bp
Internet Engineering Task Force M. Blanchet
Internet-Draft 4 March 2024
Intended status: Standards Track
Expires: 5 September 2024
Encapsulation of HTTP over Delay-Tolerant Networks(DTN) using the Bundle
Protocol
draft-blanchet-dtn-http-over-bp-01
Abstract
This document describes the encapsulation of HTTP requests and
responses in the payload of bundles of the Bundle Protocol for the
use case of Delay-Tolerant Networks(DTN) such as in space
communications.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
1.2. Vocabulary . . . . . . . . . . . . . . . . . . . . . . . 3
2. Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Negotiation, Redirect and other Considerations . . . . . . . 4
4. Encapsulation Format . . . . . . . . . . . . . . . . . . . . 4
5. Considerations . . . . . . . . . . . . . . . . . . . . . . . 5
6. Use case where the endpoint is only a BP agent . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
An important use case of Delay-Tolerant Networks(DTN) using the
Bundle Protocol[RFC9171](BP) is in space communications. Current
scenarios by space agencies[ioag] involves the use of an Internet
Protocol (IP) network on the planetary body and the use of the Bundle
Protocol between planetary bodies, including Earth. Therefore, there
are IP endpoints at both ends, and then bundles could be used as a
transport of Internet related application payload. This document
describes the encapsulation of http requests and responses over
bundles so that end-users on the remote end (aka on a planetary body
such as Moon or Mars) or processes can use typical Internet HTTP
software and tools to use http-based applications, while the http
requests and responses when transiting in space is encapsulated into
bundles of the Bundle Protocol.
It should be noted that in DTNs, delays may be very large compared to
normal delays on (Earth) Internet. In theory, there should be no
timeout at the HTTP layer, but timeouts are typical at the transport
layer. Therefore, care should be taken on how to setup the whole
path to avoid those potential issues. This document describes some
possible solutions.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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1.2. Vocabulary
* Internet: identifies the global IP network on Earth as we know it
* Planetary body: describes Moon, Mars and others. In this
document, we only care about ones that would have some IP
networking installed.
2. Encapsulation
Similar to [draft-blanchet-dtn-over-email], this document defines the
encapsulation of HTTP requests and responses into bundles of the
Bundle Protocol
Since HTTP is a query-response protocol, the client must keep a
handle of its communication with the server to get the response. On
regular IP networks, this is done together with the transport which
accomplishes a direct connection between the two peers. That notion
of direct //connection does not exist when using BP. Therefore, the
encapsulation is prepended with a connection ID and a sequence
number. The connection ID is generated by the client. The
connection ID is a random number which should have similar
characteristics to UUIDs. The actual details of the connection ID is
left to the implementation, however, the connection ID appears as a
string of ASCII characters, with the same restrictions as [RFC4122].
The sequence number is a positive integer and is set by the client
and the server. It is zero if the query or response is complete in
the single return. In case of long responses such as real-time
media, the response is continuous and in this case, the server starts
with the value 1 and increase the sequence number by one each time it
sends a new packet for the same response and the same connection id.
The client may also use the sequence number to tell the server that
the query is still not finished in the first packet, for example,
when a POST is used with an embedded large file. Similarly, the
client increments the sequence number by one for each packet.
Herein, the client and server are in fact a small piece of software
between the bundle protocol agent and the HTTP client or server.
In case the http request or response is too large for the bundle
agent and that the client or server did not slice the request or
response into smaller pieces as described in the previous paragraph,
then the bundle agent uses bundle fragmentation as described in
section 5.8 of RFC9171 to slice the http data in multiple bundles.
It is the responsability of the receiving bundle agent to properly
reassemble the http data into the source http content. Both sides
may use their sequence numbers and they are independent and can be
used at the same time. Both the client and the server keeps track of
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the connection ids and sequence numbers. When multiple packets are
sent and therefore sequence numbers were incremented from 1, the last
packet of the sending agent is indicated with sequence number zero.
In other words, sequence number zero means no more packets.
The receiving bundle agent will receive the http-containing bundle(s)
on the specific assigned IANA service number. It is expected that
the agent will transfer the http data to a http listener that will
deliver to the appropriate location as normal practice on (Earth)
Internet.
3. Negotiation, Redirect and other Considerations
Given the nature of DTN networks, negotiations such as HTTP version
negotiations, URL redirection, and other techniques are still
possible and working in this proposal, but not recommended as they
would trigger additional bundles over a long delay network, which may
end up triggering timeouts at some level, such as the application.
Therefore, careful configuration of both endpoints to avoid that
extra trafic is advised. Initial key negotiation is however
difficult to avoid, unless offpath or static key configuration is
done. Given that http2 and http3 create possible long standing
connections, then the extra initial key negotiation is not too costly
compared to the possible duration of the connection between the two
peers.
4. Encapsulation Format
The encapsulation is done as follows inside a bundle: First appears
at the beginning of all bundles the connection idm which is a string
of undefined length terminated with ASCII CR-LF. Then the sequence
number follows for all bundles, as a string representing a positive
integer of undefined length terminated with ASCII CR-LF. As
described above, the sequence number can be zero when no other packet
will come. Following the CR-LF of the sequence number is the actual
HTTP content. For example, for an HTTP1.1 query, the HTTP content
after the terminated sequence number could be: "GET /index.html
HTTP/1.1". Various HTTP headers may be added as needed. After the
terminated sequence number could be any HTTP content of any HTTP
version, including binary frames. This specification is agnostic of
the HTTP version.
TBD: artwork of bundle encapsulation
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5. Considerations
Configuring and deploying an isolated IP network on a planetary body
with local HTTP servers or clients, DNS servers or other
infrastructure needs careful considerations. These operational
considerations are not described here and are outside the scope of
this document.
6. Use case where the endpoint is only a BP agent
There are cases such as a spacecraft currently moving in space where
there might be no IP network attached to it and has only a BP agent.
However, this specification works as is, if that device is augmented
by a local IP stack, with an HTTP listener, where the final source or
destination of the HTTP packet is within the spacecraft.
7. IANA Considerations
This document requests IANA to allocate a new Bundle Protocol service
number under the current CBHE Service Numbers and assign it to this
document. Description should be: "HTTP content". If the registry is
updated to indicate the Bundle Protocol version, this specification
do apply for both BPv6 and BPv7, as it is agnostic of the BP version.
8. Security Considerations
Sending any payload with bad data over a space link is a somewhat DOS
attack. It is expected that this environment will be highly managed
and controlled, therefore, before a bundle is sent, the payload is
properly verified and access control to the space network will be
tightly controlled.
BPSEC[RFC9172] can be used to provide authentication and encryption
at the Bundle layer.
9. References
9.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC9171] Burleigh, S., Fall, K., and E. Birrane, III, "Bundle
Protocol Version 7", RFC 9171, DOI 10.17487/RFC9171,
January 2022, <https://www.rfc-editor.org/info/rfc9171>.
9.2. Informative References
[RFC9172] Birrane, III, E. and K. McKeever, "Bundle Protocol
Security (BPSec)", RFC 9172, DOI 10.17487/RFC9172, January
2022, <https://www.rfc-editor.org/info/rfc9172>.
[ioag] Lunar Communications Architecture Working Group,
Interagency Operations Advisory Group, "The Future Lunar
Communications Architecture, Report of the Interagency
Operations Advisory Group", January 2022.
[draft-blanchet-dtn-over-email]
Blanchet, MB., "Encapsulation of Email over Delay-Tolerant
Networks(DTN) using the Bundle Protocol", 17 January 2023,
<draft-blanchet-dtn-over-email-00>.
Acknowledgements
The following people have reviewed and provided comments to improve
this document (in no particular order): Stuart Card, Mark Nottingham,
Ed Birrane.
Author's Address
Marc Blanchet
Email: marc.blanchet@viagenie.ca
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