LTP Fragmentation
draft-templin-dtn-ltpfrag-00
|
| Document |
Type |
|
Active Internet-Draft (individual)
|
|
Last updated |
|
2020-04-10
|
|
Stream |
|
(None)
|
|
Intended RFC status |
|
(None)
|
|
Formats |
|
plain text
xml
pdf
htmlized (tools)
htmlized
bibtex
|
| Stream |
Stream state |
|
(No stream defined) |
|
Consensus Boilerplate |
|
Unknown
|
|
RFC Editor Note |
|
(None)
|
| IESG |
IESG state |
|
I-D Exists
|
|
Telechat date |
|
|
|
Responsible AD |
|
(None)
|
|
Send notices to |
|
(None)
|
Network Working Group F. Templin, Ed.
Internet-Draft Boeing Research & Technology
Intended status: Informational April 10, 2020
Expires: October 12, 2020
LTP Fragmentation
draft-templin-dtn-ltpfrag-00
Abstract
The Licklider Transmission Protocol (LTP) provides a reliable
datagram "covergence layer" for the Delay/Disruption Tolerant
Networking (DTN) Bundle Protocol. In common practice, LTP is often
configured over UDP/IP sockets and inherits its maximum segment size
from the maximum-sized UDP datagram. This document discussses LTP
interactions with IP fragmentation and mitigations for managing the
amount of IP fragmentation employed.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 12, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Templin Expires October 12, 2020 [Page 1]
Internet-Draft LTP Fragmentation April 2020
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. LTP Fragmentation . . . . . . . . . . . . . . . . . . . . . . 3
4. Implementation Status . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Licklider Transmission Protocol (LTP) [RFC5326] provides a
reliable datagram "covergence layer" for the Delay/Disruption
Tolerant Networking (DTN) Bundle Protocol (BP) [I-D.ietf-dtn-bpbis].
In common practice, LTP is often configured over UDP/IP sockets and
inherits its maximum segment size from the maximum-sized UDP datagram
(i.e. 2^16 bytes minus header sizes).
LTP breaks BP bundles into "blocks", then further breaks these blocks
into "segments". The segment size is a configurable option and
represents the largest atomic block of data that LTP will require
underlying layers to deliver as a single unit. The segment size is
therefore also known as the "retransmission unit", since each lost
segment must be retransmitted in its entireity.
When LTP presents a segment to the operating system kernel (e.g., via
a sendmsg() system call), the UDP layer frames the segment in a UDP
header. The UDP layer then presents the resulting datagram to the IP
layer for packet framing and transmission over a networked path. The
path is further characterized by the path Maximum Transmission Unit
(Path-MTU) which is a measure of the smallest link MTU (Link-MTU)
among all links in the path.
When LTP presents a segment to the kernel that is larger than the
Path-MTU, the IP layer performs IP fragmentation to break the
datagram into fragments that are no larger than the Path-MTU. For
example, if the LTP segment size is 64000 bytes and the Path-MTU is
1280 bytes IP fragmentation results in 50+ fragments that are
transmitted as individual IP packets.
Templin Expires October 12, 2020 [Page 2]
Internet-Draft LTP Fragmentation April 2020
Show full document text