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draft-ietf-quic-load-balancers
QUIC M. Duke
Internet-Draft F5 Networks, Inc.
Intended status: Standards Track May 10, 2019
Expires: November 11, 2019
QUIC-LB: Generating Routable QUIC Connection IDs
draft-duke-quic-load-balancers-04
Abstract
QUIC connection IDs allow continuation of connections across address/
port 4-tuple changes, and can store routing information for stateless
or low-state load balancers. They also can prevent linkability of
connections across deliberate address migration through the use of
protected communications between client and server. This creates
issues for load-balancing intermediaries. This specification
standardizes methods for encoding routing information and proposes an
optional protocol called QUIC-LB to exchange the parameters of that
encoding.
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 November 11, 2019.
Copyright Notice
Copyright (c) 2019 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
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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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Protocol Objectives . . . . . . . . . . . . . . . . . . . . . 4
2.1. Simplicity . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Security . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Robustness to Middleboxes . . . . . . . . . . . . . . . . 5
2.4. Load Balancer Chains . . . . . . . . . . . . . . . . . . 5
3. Routing Algorithms . . . . . . . . . . . . . . . . . . . . . 6
3.1. Plaintext CID Algorithm . . . . . . . . . . . . . . . . . 6
3.1.1. Load Balancer Actions . . . . . . . . . . . . . . . . 6
3.1.2. Server Actions . . . . . . . . . . . . . . . . . . . 6
3.2. Obfuscated CID Algorithm . . . . . . . . . . . . . . . . 7
3.2.1. Load Balancer Actions . . . . . . . . . . . . . . . . 7
3.2.2. Server Actions . . . . . . . . . . . . . . . . . . . 8
3.3. Stream Cipher CID Algorithm . . . . . . . . . . . . . . . 8
3.3.1. Load Balancer Actions . . . . . . . . . . . . . . . . 9
3.3.2. Server Actions . . . . . . . . . . . . . . . . . . . 9
3.4. Block Cipher CID Algorithm . . . . . . . . . . . . . . . 10
3.4.1. Load Balancer Actions . . . . . . . . . . . . . . . . 10
3.4.2. Server Actions . . . . . . . . . . . . . . . . . . . 11
4. Protocol Description . . . . . . . . . . . . . . . . . . . . 11
4.1. Out of band sharing . . . . . . . . . . . . . . . . . . . 11
4.2. QUIC-LB Message Exchange . . . . . . . . . . . . . . . . 12
4.3. QUIC-LB Packet . . . . . . . . . . . . . . . . . . . . . 12
4.4. Message Types and Formats . . . . . . . . . . . . . . . . 13
4.4.1. ACK_LB Message . . . . . . . . . . . . . . . . . . . 13
4.4.2. FAIL Message . . . . . . . . . . . . . . . . . . . . 13
4.4.3. ROUTING_INFO Message . . . . . . . . . . . . . . . . 14
4.4.4. STREAM_CID Message . . . . . . . . . . . . . . . . . 14
4.4.5. BLOCK_CID Message . . . . . . . . . . . . . . . . . . 15
4.4.6. SERVER_ID Message . . . . . . . . . . . . . . . . . . 16
4.4.7. MODULUS Message . . . . . . . . . . . . . . . . . . . 16
4.4.8. PLAINTEXT Message . . . . . . . . . . . . . . . . . . 16
5. Config Rotation . . . . . . . . . . . . . . . . . . . . . . . 17
5.1. Configuration Failover . . . . . . . . . . . . . . . . . 18
6. Configuration Requirements . . . . . . . . . . . . . . . . . 18
7. Security Considerations . . . . . . . . . . . . . . . . . . . 18
7.1. Outside attackers . . . . . . . . . . . . . . . . . . . . 19
7.2. Inside Attackers . . . . . . . . . . . . . . . . . . . . 19
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
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9.1. Normative References . . . . . . . . . . . . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . 20
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 20
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 20
B.1. Since draft-duke-quic-load-balancers-03 . . . . . . . . . 20
B.2. Since draft-duke-quic-load-balancers-02 . . . . . . . . . 20
B.3. Since draft-duke-quic-load-balancers-01 . . . . . . . . . 21
B.4. Since draft-duke-quic-load-balancers-00 . . . . . . . . . 21
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
QUIC packets usually contain a connection ID to allow endpoints to
associate packets with different address/port 4-tuples to the same
connection context. This feature makes connections robust in the
event of NAT rebinding. QUIC endpoints designate the connection ID
which peers use to address packets. Server-generated connection IDs
create a potential need for out-of-band communication to support
QUIC.
QUIC allows servers (or load balancers) to designate an initial
connection ID to encode useful routing information for load
balancers. It also encourages servers, in packets protected by
cryptography, to provide additional connection IDs to the client.
This allows clients that know they are going to change IP address or
port to use a separate connection ID on the new path, thus reducing
linkability as clients move through the world.
There is a tension between the requirements to provide routing
information and mitigate linkability. Ultimately, because new
connection IDs are in protected packets, they must be generated at
the server if the load balancer does not have access to the
connection keys. However, it is the load balancer that has the
context necessary to generate a connection ID that encodes useful
routing information. In the absence of any shared state between load
balancer and server, the load balancer must maintain a relatively
expensive table of server-generated connection IDs, and will not
route packets correctly if they use a connection ID that was
originally communicated in a protected NEW_CONNECTION_ID frame.
This specification provides a method of coordination between QUIC
servers and low-state load balancers to support connection IDs that
encode routing information. It describes desirable properties of a
solution, and then specifies a protocol that provides those
properties. This protocol supports multiple encoding schemes that
increase in complexity as they address paths between load balancer
and server with weaker trust dynamics.
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1.1. Terminology
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].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying significance described in RFC 2119.
In this document, "client" and "server" refer to the endpoints of a
QUIC connection unless otherwise indicated. A "load balancer" is an
intermediary for that connection that does not possess QUIC
connection keys, but it may rewrite IP addresses or conduct other IP
or UDP processing.
Note that stateful load balancers that act as proxies, by terminating
a QUIC connection with the client and then retrieving data from the
server using QUIC or another protocol, are treated as a server with
respect to this specification.
When discussing security threats to QUIC-LB, we distinguish between
"inside observers" and "outside observers." The former lie on the
path between the load balancer and server, which often but not always
lies inside the server's data center or cloud deployment. Outside
observers are on the path between the load balancer and client.
"Off-path" attackers, though not on any data path, may also be
"inside" or "outside" depending on whether not they have network
access to the server without intermediation by the load balancer and/
or other security devices.
2. Protocol Objectives
2.1. Simplicity
QUIC is intended to provide unlinkability across connection
migration, but servers are not required to provide additional
connection IDs that effectively prevent linkability. If the
coordination scheme is too difficult to implement, servers behind
load balancers using connection IDs for routing will use trivially
linkable connection IDs. Clients will therefore be forced choose
between terminating the connection during migration or remaining
linkable, subverting a design objective of QUIC.
The solution should be both simple to implement and require little
additional infrastructure for cryptographic keys, etc.
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2.2. Security
In the limit where there are very few connections to a pool of
servers, no scheme can prevent the linking of two connection IDs with
high probability. In the opposite limit, where all servers have many
connections that start and end frequently, it will be difficult to
associate two connection IDs even if they are known to map to the
same server.
QUIC-LB is relevant in the region between these extremes: when the
information that two connection IDs map to the same server is helpful
to linking two connection IDs. Obviously, any scheme that
transparently communicates this mapping to outside observers
compromises QUIC's defenses against linkability.
However, concealing this mapping from inside observers is beyond the
scope of QUIC-LB. By simply observing Link-Layer and/or Network-
Layer addresses of packets containing distinct connection IDs, it is
trivial to determine that they map to the same server, even if
connection IDs are entirely random and do not encode routing
information. Schemes that conceal these addresses (e.g., IPsec) can
also conceal QUIC-LB messages.
Inside observers are generally able to mount Denial of Service (DoS)
attacks on QUIC connections regardless of Connection ID schemes.
However, QUIC-LB should protect against Denial of Service due to
inside off-path attackers in cases where such attackers are possible.
Though not an explicit goal of the QUIC-LB design, concealing the
server mapping also complicates attempts to focus attacks on a
specific server in the pool.
2.3. Robustness to Middleboxes
The path between load balancer and server may pass through
middleboxes that could drop the coordination messages in this
protocol. It is therefore advantageous to make messages resemble
QUIC traffic as much as possible, as any viable path must obviously
admit QUIC traffic.
2.4. Load Balancer Chains
While it is possible to construct a scheme that supports multiple
low-state load balancers in the path, by using different parts of the
connection ID to encoding routing information for each load balancer,
this use case is out of scope for QUIC-LB.
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3. Routing Algorithms
In QUIC-LB, load balancers do not send individual connection IDs to
servers. Instead, they communicate the parameters of an algorithm to
generate routable connection IDs.
The algorithms differ in the complexity of configuration at both load
balancer and server. Increasing complexity improves obfuscation of
the server mapping.
The load balancer SHOULD route Initial and 0-RTT packets from the
client using an alternate algorithm. Note that the SCID in these
packets may not be long enough to represent all the routing bits.
This algorithm SHOULD generate consistent results for Initial and
0RTT packets that arrive with the same source and destination
connection ID. The load balancer algorithms below apply to all
incoming Handshake and 1-RTT packets.
There are situations where a server pool might be operating two or
more routing algorithms or parameter sets simultaneously. The load
balancer uses the first two bits of the connection ID to multiplex
incoming SCIDs over these schemes.
3.1. Plaintext CID Algorithm
3.1.1. Load Balancer Actions
The load balancer selects a number of bytes of the server connection
ID (SCID) that it will use to route to a given server, called the
"routing bytes". The number of bytes MUST have enough entropy to
have a different code point for each server.
The load balancer shares this value with servers, as explained in
Section 4, along with the value that represents that server.
On each incoming packet, the load balancer extracts consecutive
octets, beginning with the second byte. These bytes represent the
server ID.
3.1.2. Server Actions
The server chooses a connection ID length. This MUST be at least one
byte longer than the routing bytes.
When a server needs a new connection ID, it encodes its assigned
server ID in consecutive octets beginning with the second. All other
bits in the connection ID, except for the config rotation bits, MAY
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be set to any other value. These other bits SHOULD appear random to
observers.
The figure below clarifies the format. The first two bits are
reserved for config rotation. The server can assign the next 6 bits
to any value. The specified number of bytes encodes the server ID,
and the server may decide how many trailing octets of information to
include up to the QUIC limit of 18-octet CIDs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C R| Any | Server ID (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Any (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Plaintext CID Format
3.2. Obfuscated CID Algorithm
3.2.1. Load Balancer Actions
The load balancer selects an arbitrary set of bits of the server
connection ID (SCID) that it will use to route to a given server,
called the "routing bits". The number of bits MUST have enough
entropy to have a different code point for each server, and SHOULD
have enough entropy so that there are many codepoints for each
server.
The load balancer MUST NOT select a routing mask that with more than
126 routing bits set to 1, which allows at least 2 bits for config
rotation (see Section 5) and 16 for server purposes in a maximum-
length connection ID.
The first two bits of an SCID MUST NOT be routing bits; these are
reserved for config rotation.
The load balancer selects a divisor that MUST be larger than the
number of servers. It SHOULD be large enough to accommodate
reasonable increases in the number of servers. The divisor MUST be
an odd integer so certain addition operations do not always produce
an even number.
The load balancer also assigns each server a "modulus", an integer
between 0 and the divisor minus 1. These MUST be unique for each
server, and SHOULD be distributed across the entire number space
between zero and the divisor.
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The load balancer shares these three values with servers, as
explained in Section 4.
Upon receipt of a QUIC packet that is not of type Initial or 0-RTT,
the load balancer extracts the selected bits of the SCID and
expresses them as an unsigned integer of that length. The load
balancer then divides the result by the chosen divisor. The modulus
of this operation maps to the modulus for the destination server.
Note that any SCID that contains a server's modulus, plus an
arbitrary integer multiple of the divisor, in the routing bits is
routable to that server regardless of the contents of the non-routing
bits. Outside observers that do not know the divisor or the routing
bits will therefore have difficulty identifying that two SCIDs route
to the same server.
Note also that not all Connection IDs are necessarily routable, as
the computed modulus may not match one assigned to any server. Load
balancers SHOULD drop these packets if not a QUIC Initial or 0-RTT
packet.
3.2.2. Server Actions
The server chooses a connection ID length. This MUST contain all of
the routing bits and MUST be at least 8 octets to provide adequate
entropy.
When a server needs a new connection ID, it adds an arbitrary
nonnegative integer multiple of the divisor to its modulus, without
exceeding the maximum integer value implied by the number of routing
bits. The choice of multiple should appear random within these
constraints.
The server encodes the result in the routing bits. It MAY put any
other value into the non-routing bits except the config rotation
bits. The non-routing bits SHOULD appear random to observers.
3.3. Stream Cipher CID Algorithm
The Encrypted CID algorithm provides true cryptographic protection,
rather than mere obfuscation, at the cost of additional per-packet
processing at the load balancer to decrypt every incoming connection
ID except for Initial and 0RTT packets.
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3.3.1. Load Balancer Actions
The load balancer assigns a server ID to every server in its pool,
and determines a server ID length (in octets) sufficiently large to
encode all server IDs, including potential future servers.
The load balancer also selects a nonce length and an 16-octet AES-ECB
key to use for connection ID decryption. The nonce length MUST be at
least eight octets and no more than 16 octets. The nonce length and
server ID length MUST sum to 18 or fewer octets.
The load balancer shares these three values with servers, as
explained in Section 4.
Upon receipt of a QUIC packet that is not of type Initial or 0-RTT,
the load balancer extracts as many of the earliest octets from the
destination connection ID as necessary to match the nonce length.
The server ID immediately follows.
The load balancer decrypts the server ID using 128-bit AES Electronic
Codebook (ECB) mode, much like QUIC header protection. The nonce
octets are padded to 16 octets using the as many of the first octets
of the token as necessary. AES-ECB encrypts this nonce using its key
to generate a mask which it applies to the encrypted server id.
server_id = encrypted_server_id ^ AES-ECB(key, padded-nonce)
For example, if the nonce length is 10 octets and the server ID
length is 2 octets, the connection ID can be as small as 12 octets.
The load balancer uses the first 10 octets (including the config
rotation bits) of the connection ID for the nonce, pads it to 16
octets using the first 6 octets of the token, and uses this to
decrypt the server ID in the eleventh and twelfth octet.
The output of the decryption is the server ID that the load balancer
uses for routing.
3.3.2. Server Actions
When generating a routable connection ID, the server writes arbitrary
bits into its nonce octets, and its provided server ID into the
server ID octets. Servers MAY opt to have a longer connection ID
beyond the nonce and server ID. The nonce and additional bits MAY
encode additional information, but SHOULD appear essentially random
to observers. The first two bits of the first octet are reserved for
config rotation Section 5, but form part of the nonce.
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The server decrypts the server ID using 128-bit AES Electronic
Codebook (ECB) mode, much like QUIC header protection. The nonce
octets are padded to 16 octets using the as many of the first octets
of the token as necessary. AES-ECB encrypts this nonce using its key
to generate a mask which it applies to the server id.
encrypted_server_id = server_id ^ AES-ECB(key, padded-nonce)
3.4. Block Cipher CID Algorithm
The Block Cipher CID Algorithm, by using a full 16 octets of
Plaintext and a 128-bit cipher, provides higher cryptographic
protection and detection of spurious connection IDs. However, it
also requires connection IDs of at least 17 octets, increasing
overhead of client-to-server packets.
3.4.1. Load Balancer Actions
The load balancer assigns a server ID to every server in its pool,
and determines a server ID length (in octets) sufficiently large to
encode all server IDs, including potential future servers. The
server ID will start in the second octet of the decrypted connection
ID and occupy continuous octets beyond that.
The load balancer selects a zero-padding length. This SHOULD be at
least four octets to allow detection of spurious connection IDs. The
server ID and zero- padding length MUST sum to no more than 16
octets. They SHOULD sum to no more than 12 octets, to provide
servers adequate space to encode their own opaque data.
The load balancer also selects an 16-octet AES-ECB key to use for
connection ID decryption.
The load balancer shares these four values with servers, as explained
in Section 4.
Upon receipt of a QUIC packet that is not of type Initial or 0-RTT,
the load balancer reads the first octet to obtain the config rotation
bits. It then decrypts the subsequent 16 octets using AES-ECB
decryption and the chosen key.
The decrypted plaintext contains the server id, zero padding, and
opaque server data in that order. If the zero padding octets are not
zero, the load balancer MUST drop the packet. The load balancer uses
the server ID octets for routing.
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3.4.2. Server Actions
When generating a routable connection ID, the server MUST choose a
connection ID length of 17 or 18 octets. The server writes its
provided server ID into the server ID octets, zeroes into the zero-
padding octets, and arbitrary bits into the remaining bits. These
arbitrary bits MAY encode additional information. Bits in the first
and eighteenth octets SHOULD appear essentially random to observers.
The first two bits of the first octet are reserved for config
rotation Section 5.
The server then encrypts the second through seventeenth octets using
the 128-bit AES-ECB cipher.
4. Protocol Description
The fundamental protocol requirement is to share the choice of
routing algorithm, and the relevant parameters for that algorithm,
between load balancer and server.
For Obfuscated CID Routing, this consists of the Routing Bits,
Divisor, and Modulus. The Modulus is unique to each server, but the
others MUST be global.
For Stream Cipher CID Routing, this consists of the Server ID, Server
ID Length, Key, and Nonce Length. The Server ID is unique to each
server, but the others MUST be global. The authentication token MUST
be distributed out of band for this algorithm to operate.
For Block Cipher CID Routing, this consists of the Server ID, Server
ID Length, Key, and Zero-Padding Length. The Server ID is unique to
each server, but the others MUST be global.
Each routing configuration also requires a unique two-bit config
rotation codepoint (see Section 5) to identify it.
4.1. Out of band sharing
When there are concerns about the integrity of the path between load
balancer and server, operators MAY share routing information using an
out-of-band technique, which is out of the scope of this
specification.
To simplify configuration, the global parameters can be shared out-
of-band, while the load balancer sends the unique server IDs via the
truncated message formats presented below.
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4.2. QUIC-LB Message Exchange
QUIC-LB load balancers and servers exchange messages via the QUIC-
LBv1 protocol, which uses the QUIC invariants with version number
0xF1000000. The QUIC-LB load balancers send the encoding parameters
to servers and periodically retransmit until that server responds
with an acknowledgement. Specifics of this retransmission are
implementation-dependent.
4.3. QUIC-LB Packet
A QUIC-LB packet uses a long header. It carries configuration
information from the load balancer and acknowledgements from the
servers. They are sent when a load balancer boots up, detects a new
server in the pool or needs to update the server configuration.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
|1|C R| Reserved|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x00 | 0x00 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Authentication Token (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type |
+-+-+-+-+-+-+-+-+
Figure 2: QUIC-LB Packet Format
The Version field allows QUIC-LB to use the Version Negotiation
mechanism. All messages in this specification are specific to QUIC-
LBv1. It should be set to 0xF1000000.
Load balancers MUST cease sending QUIC-LB packets of this version to
a server when that server sends a Version Negotiation packet that
does not advertise the version.
The length of the DCIL and SCIL fields are 0x00.
CR The 2-bit. CR field indicates the Config Rotation described in
Section 5.
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Authentication Token The Authentication Token is an 8-byte field
that both entities obtain at configuration time. It is used to
verify that the sender is not an inside off-path attacker.
Servers and load balancers SHOULD silently discard QUIC-LB packets
with an incorrect token.
Message Type The Message Type indicates the type of message payload
that follows the QUIC-LB header.
4.4. Message Types and Formats
As described in Section 4.3, QUIC-LB packets contain a single
message. This section describes the format and semantics of the
QUIC-LB message types.
4.4.1. ACK_LB Message
A server uses the ACK_LB message (type=0x00) to acknowledge a QUIC-LB
packet received from the load balancer. The ACK-LB message has no
additional payload beyond the QUIC-LB packet header.
Load balancers SHOULD continue to retransmit a QUIC-LB packet until a
valid ACK_LB message, FAIL message or Version Negotiation Packet is
received from the server.
4.4.2. FAIL Message
A server uses the FAIL message (type=0x01) to indicate the
configuration received from the load balancer is unsupported.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Supp. Type | Supp. Type | ...
+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Servers MUST send a FAIL message upon receipt of a message type which
they do not support, or if they do not possess all of the implied
out-of-band configuration to support a particular message type.
The payload of the FAIL message consists of a list of all the message
types supported by the server.
Upon receipt of a FAIL message, Load Balancers MUST either send a
QUIC-LB message the server supports or remove the server from the
server pool.
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4.4.3. ROUTING_INFO Message
A load balancer uses the ROUTING_INFO message (type=0x02) to exchange
all the parameters for the Obfuscated CID algorithm.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Routing Bit Mask (144) +
| |
+ +
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Modulus (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Divisor (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Routing Bit Mask The Routing Bit Mask encodes a '1' at every bit
position in the server connection ID that will encode routing
information.
These bits, along with the Modulus and Divisor, are chosen by the
load balancer as described in Section 3.2.
4.4.4. STREAM_CID Message
A load balancer uses the STREAM_CID message (type=0x03) to exchange
all the parameters for using Stream Cipher CIDs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce Len (8) | SIDL (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server ID (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Key (128) +
| |
+ +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Stream CID Payload
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Nonce Len The Nonce Len field is a one-octet unsigned integer that
describes the nonce length necessary to use this routing
algorithm, in octets.
SIDL The SIDL field is a one-octet unsigned integer that describes
the server ID length necessary to use this routing algorithm, in
octets.
Server ID The Server ID is the unique value assigned to the
receiving server. Its length is determined by the SIDL field.
Key The Key is an 16-octet field that contains the key that the load
balancer will use to decrypt server IDs on QUIC packets. See
Section 7 to understand why sending keys in plaintext may be a
safe strategy.
4.4.5. BLOCK_CID Message
A load balancer uses the BLOCK_CID message (type=0x04) to exchange
all the parameters for using Stream Cipher CIDs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ZP Len (8) | SIDL (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server ID (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Key (128) +
| |
+ +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Block CID Payload
ZP Len The ZP Len field is a one-octet unsigned integer that
describes the zero-padding length necessary to use this routing
algorithm, in octets.
SIDL The SIDL field is a one-octet unsigned integer that describes
the server ID length necessary to use this routing algorithm, in
octets.
Server ID The Server ID is the unique value assigned to the
receiving server. Its length is determined by the SIDL field.
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Key The Key is an 16-octet field that contains the key that the load
balancer will use to decrypt server IDs on QUIC packets. See
Section 7 to understand why sending keys in plaintext may be a
safe strategy.
4.4.6. SERVER_ID Message
A load balancer uses the SERVER_ID message (type=0x05) to exchange
explicit server IDs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SIDL (8) | Server ID (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Load balancers send the SERVER_ID message when all global values for
Stream or Block CIDs are sent out-of-band, so that only the server-
unique values must be sent in-band. The fields are identical to
their counterparts in the Section 4.4.4 payload.
4.4.7. MODULUS Message
A load balancer uses the MODULUS message (type=0x06) to exchange just
the modulus used in the Obfuscated CID algorithm.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Modulus (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Token (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Load balancers send the MODULUS when all global values for Obfuscated
CIDs are sent out-of-band, so that only the server-unique values must
be sent in-band. The Modulus field is identical to its counterpart
in the ROUTING_INFO message.
4.4.8. PLAINTEXT Message
A load balancer uses the PLAINTEXT message (type=0x07) to exchange
all parameters needed for the Plaintext CID algorithm.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SIDL (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Server ID (variable) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The SIDL field indicates the length of the server ID field. The
Server ID field indicates the encoding that represents the
destination server.
5. Config Rotation
The first two bits of any connection-ID MUST encode the configuration
phase of that ID. QUIC-LB messages indicate the phase of the
algorithm and parameters that they encode.
A new configuration may change one or more parameters of the old
configuration, or change the algorithm used.
It is possible for servers to have mutually exclusive sets of
supported algorithms, or for a transition from one algorithm to
another to result in Fail Payloads. The four states encoded in these
two bits allow two mutually exclusive server pools to coexist, and
for each of them to transition to a new set of parameters.
When new configuration is distributed to servers, there will be a
transition period when connection IDs reflecting old and new
configuration coexist in the network. The rotation bits allow load
balancers to apply the correct routing algorithm and parameters to
incoming packets.
Servers MUST NOT generate new connection IDs using an old
configuration when it has sent an Ack payload for a new
configuration.
Load balancers SHOULD NOT use a codepoint to represent a new
configuration until it takes precautions to make sure that all
connections using IDs with an old configuration at that codepoint
have closed or transitioned. They MAY drop connection IDs with the
old configuration after a reasonable interval to accelerate this
process.
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5.1. Configuration Failover
If a server is configured to expect QUIC-LB messages, and it has not
received these, it MUST generate connection IDs with the config
rotation bits set to '0b11' and MUST use the "disable_migration"
transport parameter in all new QUIC connections. It MUST NOT send
NEW_CONNECTION_ID frames with new values.
A load balancer that sees a connection ID with config rotation bits
set to '0b11' MUST revert to 5-tuple routing.
6. Configuration Requirements
QUIC-LB strives to minimize the configuration load to enable, as much
as possible, a "plug-and-play" model. However, there are some
configuration requirements based on algorithm and protocol choices
above.
There are three levels of configuration that correspond to increasing
levels of concern about the security of the load balancer-server
path.
The complete information requirements are described in Section 4.
Load balancers MUST have configuration for all parameters of each
routing algorithm they support.
If there is any in-band communication, servers MUST be explicitly
configured with the token of the load balancer they expect to
interface with. Endpoints that use Stream Cipher CIDs MUST have this
token regardless of the configuration method.
Optionally, servers MAY be configured with the global parameters of
supported routing algorithms. This allows load balancers to use
Server ID and Modulus Payloads, limiting the information sent in-
band.
Finally, servers MAY be directly configured with their unique server
IDs or modulus, eliminating need for in-band messaging at all. In
this case, servers and load balancers MUST enable only one routing
algorithm, as there is no explicit message to agree on one or the
other.
7. Security Considerations
QUIC-LB is intended to preserve routability and prevent linkability.
Attacks on the protocol would compromise at least one of these
objectives.
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Note that the Plaintext CID algorithm makes no attempt to obscure the
server mapping, and therefore does not address these concerns. It
exists to allow consistent CID encoding for compatibility across a
network infrastructure. Servers that are running the Plaintext CID
algorithm SHOULD only use it to generate new CIDs for the Server
Initial Packet, and SHOULD NOT send CIDs in QUIC NEW_CONNECTION_ID
frames. Doing so might falsely suggest to the client that said CIDs
were generated in a secure fashion.
A routability attack would inject QUIC-LB messages so that load
balancers incorrectly route QUIC connections.
A linkability attack would find some means of determining that two
connection IDs route to the same server. As described above, there
is no scheme that strictly prevents linkability for all traffic
patterns, and therefore efforts to frustrate any analysis of server
ID encoding have diminishing returns.
7.1. Outside attackers
For an outside attacker to break routability, it must inject packets
that correctly guess the 64-bit token, and servers must be reachable
from these outside hosts. Load balancers SHOULD drop QUIC-LB packets
that arrive on its external interface.
Off-path outside attackers cannot observe connection IDs, and will
therefore struggle to link them.
On-path outside attackers might try to link connection IDs to the
same QUIC connection. The Encrypted CID algorithm provides robust
entropy to making any sort of linkage. The Obfuscated CID obscures
the mapping and prevents trivial brute-force attacks to determine the
routing parameters, but does not provide robust protection against
sophisticated attacks.
7.2. Inside Attackers
As described above, on-path inside attackers are intrinsically able
to map two connection IDs to the same server. The QUIC-LB algorithms
do prevent the linkage of two connection IDs to the same individual
connection if servers make reasonable selections when generating new
IDs for that connection.
On-path inside attackers can break routability for new and migrating
connections by copying the token from QUIC-LB messages. From this
privileged position, however, there are many other attacks that can
break QUIC connections to the server during the handshake.
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Off-path inside attackers cannot observe connection IDs to link them.
To successfully break routability, they must correctly guess the
token.
8. IANA Considerations
There are no IANA requirements.
9. References
9.1. Normative References
[QUIC-TRANSPORT]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", draft-ietf-quic-
transport (work in progress).
9.2. Informative 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>.
Appendix A. Acknowledgments
Appendix B. Change Log
*RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document.
B.1. Since draft-duke-quic-load-balancers-03
o Renamed Plaintext CID algorithm as Obfuscated CID
o Added new Plaintext CID algorithm
B.2. Since draft-duke-quic-load-balancers-02
o Added Config Rotation
o Added failover mode
o Tweaks to existing CID algorithms
o Added Block Cipher CID algorithm
o Reformatted QUIC-LB packets
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B.3. Since draft-duke-quic-load-balancers-01
o Complete rewrite
o Supports multiple security levels
o Lightweight messages
B.4. Since draft-duke-quic-load-balancers-00
o Converted to markdown
o Added variable length connection IDs
Author's Address
Martin Duke
F5 Networks, Inc.
Email: martin.h.duke@gmail.com
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