Comparing ALPS and Half-RTT Data
draft-davidben-tls-alps-half-rtt-00
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David Benjamin
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2020-12-03
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TLS D. Benjamin
Internet-Draft Google LLC
Intended status: Informational 3 December 2020
Expires: 6 June 2021
Comparing ALPS and Half-RTT Data
draft-davidben-tls-alps-half-rtt-00
Abstract
This document compares the Application Layer Protocols Settings
extension with the half-RTT feature in TLS 1.3.
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 6 June 2021.
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 the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Benjamin Expires 6 June 2021 [Page 1]
Internet-Draft Comparing ALPS and Half-RTT Data December 2020
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Using Half-RTT Data . . . . . . . . . . . . . . . . . . . . . 3
2.1. Half-RTT Delimiter . . . . . . . . . . . . . . . . . . . 3
2.2. Non-Integer HTTP Settings . . . . . . . . . . . . . . . . 4
2.3. Early Data and Session Tickets . . . . . . . . . . . . . 4
2.4. Client Certificates . . . . . . . . . . . . . . . . . . . 5
2.5. TLS Terminators . . . . . . . . . . . . . . . . . . . . . 6
2.6. TCP Flow Control . . . . . . . . . . . . . . . . . . . . 7
3. Using ALPS . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Half-RTT Delimiter . . . . . . . . . . . . . . . . . . . 8
3.2. Non-Integer HTTP Settings . . . . . . . . . . . . . . . . 8
3.3. Early Data and Session Tickets . . . . . . . . . . . . . 8
3.4. Client Certificates . . . . . . . . . . . . . . . . . . . 8
3.5. TLS Terminators . . . . . . . . . . . . . . . . . . . . . 8
3.6. TCP Flow Control . . . . . . . . . . . . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Informative References . . . . . . . . . . . . . . . . . . . 9
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
An application-layer protocol often starts with both parties
negotiating parameters under which the protocol operates; for
instance, HTTP/2 [RFC7540] and HTTP/3 [I-D.ietf-quic-http] use a
SETTINGS frame to exchange the list of protocol parameters supported
by each endpoint. This can achieved by waiting for TLS handshake
[RFC8446] to complete and then performing the application-layer
handshake within the application protocol itself.
This approach, however, means application protocols must wait for a
secondary negotiation to complete, often incurring network round-
trip. HTTP/2 and HTTP/3 mitigate this with a best-effort negotiation
scheme: clients do not wait for server SETTINGS before sending a
request. But then, by the time the client applies the setting, it
has already sent the first request based on the default values. This
limits the kinds of extensions possible. For example, the SETTINGS
frame cannot support negotiate header compression [QUIC-3622] or a
different static table [HTTP2-788] without changing the protocol to
disable compression by default and switch partway through.
Protocol selection is another example of application-level
negotiation with these trade-offs. The Application Layer Protocol
Negotiation (ALPN) extension [RFC7301] adds protocol selection into
the TLS handshake. ALPN is instead consistently ordered before all
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