Internet DRAFT - draft-herbert-ipv6-service-token-option
draft-herbert-ipv6-service-token-option
INTERNET-DRAFT T. Herbert
Intended Status: Standard Quantonium
Expires: November 2017
May 12, 2017
Service token option for IPv6
draft-herbert-ipv6-service-token-option-00
Abstract
This document describes the service token option in IPv6. The service
token option expresses to the network the services that should be
applied to a packet. The service token allows network infrastructure
to map packets to a service class for processing in the network. The
contents of service tokens are not globally defined, their meaning
and semantics are defined for individual networks. Applications
request service tokens from their network provider for the services
they wish to be applied. The service tokens are sent in either
Destination options or a Hop-By-Hop options IPv6.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright and License Notice
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Copyright (c) 2017 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
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described in the Simplified BSD License.
Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Current solutions . . . . . . . . . . . . . . . . . . . . . 3
1.2 SPUD and PLUS solution . . . . . . . . . . . . . . . . . . . 3
1.3 Emerging use cases . . . . . . . . . . . . . . . . . . . . . 4
2 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Example packet flow . . . . . . . . . . . . . . . . . . . . 6
2.2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Packet format . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 Option format . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 Option types . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3 Service token . . . . . . . . . . . . . . . . . . . . . . . 9
4 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1 Origin application operation . . . . . . . . . . . . . . . . 10
4.2 Origin network processing . . . . . . . . . . . . . . . . . 10
4.3 Peer processing . . . . . . . . . . . . . . . . . . . . . . 11
4.4 Handling dropped extension headers . . . . . . . . . . . . . 11
4.4.1 Mitigations for dropped extension headers . . . . . . . 11
4.4.2 Fallback for dropped extension headers . . . . . . . . . 11
5 Implementation considerations . . . . . . . . . . . . . . . . . 12
5.1 Origin applications . . . . . . . . . . . . . . . . . . . . 12
5.2 Reflection . . . . . . . . . . . . . . . . . . . . . . . . . 12
6 Security Considerations . . . . . . . . . . . . . . . . . . . . 13
7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 13
8 References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1 Normative References . . . . . . . . . . . . . . . . . . . 14
8.2 Informative References . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
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1 Introduction
Modern provider networks, such as those being designed for the 5G
mobile standard, offer a variety a services to applications for
processing packets. Applications need to coordinate with the network
get desired services applied to their packets. This coordination
entails that the applications signal to the network in some manner
what its characteristics are and what its requirements are for
service. This document describes a method for an application to
explicitly signal the network to request services.
1.1 Current solutions
In the current Internet, there is little coordination between hosts
and the network to provide services based on characteristics of the
application. Differentiated services provide some service
classification, however it is lacking in richness of expression and
pervasiveness in use. Some network operators have resorted to do Deep
Packet Inspection (DPI) whereby HTTP is parsed to determine URL,
content type, and other application level information the network is
interested in. DPI is limited only to the application layer protocols
that the device is programmed to parse and more importantly is being
effectively obsoleted in the network due the pervasive use of TLS.
1.2 SPUD and PLUS solution
SPUD (Session Protocol Underneath Datagrams) and its successor PLUS
(Path Layer UDP Substrate) proposed a UDP based protocol to allow
applications to signal a rich set of characteristics and service
requirements to the network.
SPUD has a number of drawbacks:
o SPUD is based on specific protocol over used over UDP. This
requires applications to change to use a new protocol. In
particular SPUD is incompatible with TCP which is the
predominant transport protocol on the Internet.
o SPUD requires that intermediate nodes parse and process UDP
payloads. Since UDP port numbers do not have global meaning
[RFC7605] this introduces the possibility of
misinterpretation and of silent data corruption if
intermediate nodes modify UDP payloads. SPUD attempts to
mitigate this issue with the use of magic numbers, however
that can only ever be probabilistically correct.
o SPUD included connection tracking in the network. This
problematic because:
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o Not all communications have well defined connection
semantics-- for instance a unidirectional data stream has
no connection semantics at all.
o Connection tracking breaks multi-homing; it assumes that
all packets of a connection in both directions are seen
by the node doing connection tracking. Firewalls for
instance require all packets for a flow to always go
through the same device in both directions. This
disallows flexibility and optimized traffic flow that a
multi-home network device affords.
o The meta data information in SPUD would have global
definition. This problematic because:
o Application specific information could be leaked to
unknown and untrusted parties.
o Establishing a specification on what data should be
conveyed in SPUD will be difficult. Different service
providers may want different pieces of information,
applications may also have different ideas about what
information is safe to make visible.
1.3 Emerging use cases
In a typical client/server model of serving content, end host clients
communicate with Internet services. The clients are typically user
devices that are connected to the Internet through a provider
network. In the case of mobile devices, such as smart phones, the
devices are connected to the Internet through a carrier network.
Content providers (web servers) tend to be more directly connected to
the Internet, the largest of which can connect at exchange points.
Provider networks can be architected to provide different services
and levels of services to their users based on characteristics of
applications. For example, a mobile carrier network can provide
different latency and throughput guarantees for different types of
content. A network may offer different services for optimizing video:
streaming an HD movie might need high throughput but not particularly
low latency; a live video chat might have lower throughput demands
but have low latency requirements.
The emerging 3GPP standard for 5G defines a set of mechanisms to
provide a rich array of services for users. These mechanisms employ
Network Function Virtulization (NFV), Service Function Chaining
(SFC), and network slices that divide physical network resources into
different virtualized slices to provide different services. To make
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use of these services the applications running in UEs (User
Equipment) will need to indicate desired services of the RAN (Radio
Access Network). For instance, a video chat application may request
bounded latency that is implemented by the network as a network
slice; so packets sent by the application should be mapped to that
network slice.
Note that an application service applies to both packet sent by UE
and those sent from a peer towards the UE. For the latter case, the
network needs to be able to map packets sent from hosts on the
Internet to the services requested receiving application.
2 Architecture
The figure below illustrates an example network path between two
hosts on the Internet. Note that each host connects to the Internet
via a provider network and provider networks are connected in the
Internet by transit networks.
_____
__________ ( ) __________
+--------+ ( ) ( ) ( ) +--------+
| User 1 +---( Provider A )--( Transit )--( Provider B )---+ User 2 |
+--------+ (__________) ( ) (__________) +--------+
(_____)
Figure 1
Within each provider network, services may be provided on behalf of
the users of the network. In the example above, Provider 1 may
provide services and service agreements for users in its network
including User 1; and likewise Provider B can provide services to
users in its network including User 2. Transit networks service all
users and don't typically provide user specific services or service
differentiation.
Services provided by different provider networks may be very
different and dependent on the implementation of the network as well
as the policies of the provider.
Based on this model, services and service differentiation can be
considered local to each provider of the network. This document
describes a mechanism whereby each user and application can request
from its local provider the services to be applied to its traffic.
The request is made to "service token provider". The contents of the
request describe the service requirements that application desires.
The service token provider responds with a "service token" that the
application sets in its packets. When a packet is sent by the
application with a service token, the token is interpreted in the
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provider network to map the packet to the appropriate service. The
token is only relevant to the provider network, to both the
application and nodes outside of the provider network the token is an
opaque value.
To facilitate service mapping in the reverse direction for a flow,
that is packets sent from a peer host, peer hosts reflect the service
token without modification or interpretation.
The use of service tokens may be symmetric for a connection so that
each peer requests service. Therefore packets may contain two service
tokens: one that is set by the sending host to signal its local
provider network, and the other is the reflected service token that
is a signal to the provider network of the peer endpoint.
Service tokens are scoped values, they only have meaning in the
network for which they were defined. The destination option includes
an autonomous system value with each service option to indicate which
network interprets the value. The format, meaning, and interpretation
of service tokens is network (autonomous system) specific. By mutual
agreement, two networks may shared the policy and interpretations of
service tokens. For instance, there could be an agreement between two
autonomous systems to interpret each others service tokens or to use
a common format.
2.1 Example packet flow
Referencing the diagram in figure 1, consider that User 1 is
communicating with User 2 and wishes to have some service provided by
its local network (Provider 1). The flow of events may be:
1. User 1 wishes to create a live video chat with User 2
2. User 1 makes a service token request from service token
provider of Provider A that describes the video application and
may include detailed characteristics such as resolution, frame
rate, latency, etc.
3. Service token provider provides a token
4. Application sends packets with the service token set for the
video chat
5. Provider A interprets the service token and applies the
appropriate services to the packets
6. Packets traverse transit networks and Provider B network, the
service token is ignored
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7. Packet is received at User 2. The service token is saved in the
context for the video session
8. User 2 sends video chat packets to User 1. The service token
received from User 1 is reflected in these packets
9. Packets traverse Provider B network and transit networks
10. Provider A interprets the reflected service token and applies
appropriate services to the packets
11. Packets are received at User 1
2.2 Requirements
The requirements for this solution are:
o Service tokens should be connectionless
o Service tokens should work in multi-homed environments
o Service tokens should indicate the network for which they are
applicable
o Outside of the relevant network the service token should be
opaque and no application specific information should be
derivable from the token
o Service tokens should work with any transport protocol
o Service tokens should minimize the changes to an application.
Their use should should be an "add-on" to the existing
communications of an application
o Service tokens should prevent spoofing and other misuse that
might result in illegitimate use of network services or denial
of service attack
o Deep packet inspection is not needed
o Service tokens must allow services to be applied in the reverse
path. In a client/server application it is often the packets in
the reverse path that require the most service (for instance if
a video is being streamed to a client).
o A fallback exists if packets with extension headers are dropped
3 Packet format
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The service token is sent as Destination option or a Hop-By-Hop
option.
3.1 Option format
The same option types and format are used for both a Destination and
Hop-By-Hop option. The format of the option is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len | Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Autonomous number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Service Token ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fields:
o ICMP Option type: 0x4F or 0x6F
o Opt Data Len: Length of the option data field. This is 6 + the
length of the service token field
o Type: Indicates the type and action of the service token. This
is one of:
o 0x0: Service token from origin, don't reflect at receiver
o 0x1: Service token from origin, reflect at receiver
o 0x2: Reflected service token
o 0x3-0xf: Reserved
o Autonomous number: AS for for the network in which the service
token is valid. A value of zero indicates the locally attached
network of the origin.
3.2 Option types
The service token may be sent as a Destination option or Hop-By-Hop
option. The rationale is that the two methods exhibit different drop
rates. For instance, [RFC7872] indicates that the drop rate to
Alexa's Top 1M Sites for Destination options was 10.91%, whereas Hop-
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By-Hop options have a drop rate of 39.03%
The are two option numbers requested for the service token option:
0x4F and 0x6F. The latter allows modification. This would be used in
situations where the network nodes needed to modify the option with
new information. If the option is modifiable it should be a Hop-By-
Hop option.
3.3 Service token
The service token contains service parameters that describe the
desired services as well as additional fields that would be used to
provide private and integrity.
The format of the service token is defined by the network in which
the service token originates. The service token should be obfuscated
or encrypted for privacy. It should also be resistant to spoofing
when an attacker uses a service token seen on other flows to
illegitimately have service applied to its packets.
It is recommended that service tokens are encrypted and each token
has an expiration time. For instance, a service token may be created
by encrypting the token data with an expiration time and using the
source address, destination address, and a shared key as the key for
encryption.
For example, the security token for a network may have the format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Expiration time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Service parameters ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where the expiration time is in a format that are understood by the
provider network nodes which maintain synchronized time. The Service
parameters are relevant to network nodes and describe the services to
be applied. The service parameters could simply be a set of flags for
services, an index to a service profile known by the network nodes,
or possibly have more elaborate structure that could indicate
numerical values for characteristics that have a range. The service
parameters could also include a type field to allow a network to
define different representations of service parameters.
A simple service token containing a service protocol index might be:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Expiration time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Service Profile Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 Operation
4.1 Origin application operation
An application that wishes to request services first requests a
service token from a service token provider. The application request
could be in the form of an XML structure with a canonical format (the
definition is outside the scope of this document). The application
makes a request to a service token provider for the local network.
This could be done a web service using HTTP PUT/GET. Internally in
the host the security token provider might be accessed through a
library that interfaces to a service token provider daemon that in
turn arbitrates requests between the applications and the network
infrastructure.
When the service token provider returns a token, the application sets
the token as Hop-By-Hop option or Destination option as indicated.
This is typically done by setting socket option on a socket (in the
case of TCP) or by indicating the option in the ancillary data when
sending on a socket (in the case of UDP).
The service token provider should return an expiration time with the
service token. An application can use the token until the expiration
time, at which point it must request a new service token. The service
token itself is opaque to the application and the application should
no attempt to interpret any meaning from it.
4.2 Origin network processing
When a packet with a service token enters a network referred to by
the autonomous system number it should be processed. The service
token is decrypted if necessary and the expiration time is checked.
If the service token is valid then the packet is mapped to be
processed by the requested services. For instance, in a 5G network
the packet may be forwarded on a network slice for the
characteristics the application has requested (real-time video for
instance).
Note that there are two points at which the provider needs to process
the service token: when a local user sends a packet into the provider
network, and when a packet from an external network enters the
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provider's network with a reflected security token. Once the service
token is processed and mapped to the network's mechanism it should
not need further examination.
4.3 Peer processing
When an application receives a packet with a service token whose type
is "from origin and needs to be reflected", it should save the
service option in its flow context and reflect it on subsequent
packets. When the application reflects the option is copies the whole
option and only modifies the type to indicate a reflected option. The
application continues to reflect the service token until a different
one is received from the origin or a packet without a service token
option is received for the flow.
4.4 Handling dropped extension headers
The downside of using IPv6 extension headers on the Internet is that
they are unreliable. Some intermediate nodes will drop extension
headers with rates described in [RFC7872].
4.4.1 Mitigations for dropped extension headers
There are some mitigating factors for this problem:
o A provider network that implements the service token protocol
defined in this document would need to ensure that the service
token option is usable within the network
o Transit networks are less likely to arbitrarily drop packets
with extension headers
o Many content providers, especially the larger ones, may be
directly connected to the Internet. For example, front end web
servers may be co-located as exchange points.
4.4.2 Fallback for dropped extension headers
Since the possibility that extension headers are dropped cannot be
eliminated, a fallback is included for use with service tokens.
When an application connects to a new destination for which it has no
history about the viability of extension headers, it can perform a
type of Happy Eyeballs probing. The concept is for the to send a
number of packets with and without the service token. The application
should observe whether packets with service tokens are being dropped.
There are a few possible outcomes of this process:
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o A packet with a service token is dropped and an ICMP for
extension headers [ICMPEH] processing limits is received. This
is a signal that extension headers are not viable and should not
be used for the flow.
o A packet with a service token is dropped and no ICMP error is
received. This is a signal that extension headers may not be
usable. If such drops are observed for all or a significant
fraction of packets and there are no drops for packets that were
sent without the service token, then extension headers should be
considered not viable for the flow.
o Packets with service tokens are not being dropped, however
service tokens are not being reflected. This is a signal that
the peer application does not support reflection. Service tokens
may be sent, however they are only useful in the outbound path.
o Packet with service tokens are not being dropped and service
tokens are being reflected. Service tokens are useful in both
direction.
5 Implementation considerations
5.1 Origin applications
Existing client applications can be modified to request service
tokens and set them in packets. The kernel may need some small
changes or configuration to enable an application to specify the
option for its packets.
The interface to the service provider would likely be via a library
API.
Using the BSD sockets interface, for a connected socket (TCP, SCTP,
or connected UDP socket) the destination option can be set on the
socket via the setsockopt system call. For an unconnected socket
(UDP) the service token option can be set as ancillary data in the
sendmsg system call.
Extension header probing, described in section 4.4.2, could be
implemented in the kernel for a connection oriented transport
protocol such a TCP. For connectionless protocols, probing could be
handled by an application library.
5.2 Reflection
To perform reflection of the service option, a server must be
updated. In the case of a connected socket (TCP, SCTP, or a connected
UDP socket) this can be done as relatively minro change to the kernel
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networking stack which would be transparent to application. For
unconnected UDP, an application could receive the security token as
part of the ancillary data in recvmsg system call, and then send the
security option in a reply using ancillary data in sendmsg.
6 Security Considerations
Service token options may be visible to the Internet including
untrusted and unknown networks in the path of sent packets. As such
the token should be encrypted or obfuscated by the origin network.
7 IANA Considerations
IANA is requested to assigned the following Destination and Hop-By-
Hop options:
+-----------+---------------+-------------+---------------+
| Hex Value | Binary value | Description | Reference |
| | act chg rest | | |
+-----------+---------------+-------------+---------------+
| 0x0F | 00 0 01111 | Service | This document |
| | | Token | |
+-----------+---------------+-------------+---------------+
| 0x2F | 00 0 01111 | Modifiable | This document |
| | | Service | |
| | | Token | |
+-----------+---------------+-------------+---------------+
IANA is requested to set up a registry for the Service Token option
types. These types are 4 bit values. New values for control types
0x3-0xf are assigned via Standards Action [RFC5226].
+----------------+--------------------+---------------+
| Service Token | Description | Reference |
| option type | | |
+----------------+--------------------+---------------+
| 0x0 | Token from origin | This document |
| | and don't reflect | |
+----------------+--------------------+---------------+
| 0x1 | Token from origin | This document |
| | and reflect | |
+----------------+--------------------+---------------+
| 0x2 | Token not from | This document |
| | origin and reflect | |
+----------------+--------------------+---------------+
8 References
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8.1 Normative References
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
8.2 Informative References
[RFC7605] Touch, J., "Recommendations on Using Assigned Transport
Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605,
August 2015, <http://www.rfc-editor.org/info/rfc7605>.
[RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu, "Observations
on the Dropping of Packets with IPv6 Extension Headers in
the Real World", RFC 7872, DOI 10.17487/RFC7872, June 2016,
<http://www.rfc-editor.org/info/rfc7872>.
[ICMPEH] Herbert, T., "ICMPv6 errors for discarding packets due to
processing limits", draft-herbert-6man-icmp-limits-00.txt
Author's Address
Tom Herbert
Quantonium
Santa Clara, CA
USA
Email: tom@herbertland.com
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