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Versions: 00 01 02 03 04                                                
INTERNET-DRAFT                                                T. Herbert
Intended Status: Standard                                     Quantonium
Expires: December 2018

                                                           June 25, 2018

                      Firewall and Service Tickets


   This document describes the Firewalls and Service Tickets protocol. A
   ticket is data that accompanies a packet and indicates a granted
   right to traverse a network or a request for network service to be
   applied. Applications request tickets from a local agent in the
   network and attach issued tickets to packets. Firewall tickets are
   issued to grant packets the right to traverse a network; service
   tickets indicate the desired service to be applied to a packets. A
   single ticket may provide both firewall and service ticket
   information. Tickets are sent in either IPv6 Destination options or
   Hop-by-Hop options.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as

   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."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

Copyright and License Notice

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   Copyright (c) 2018 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
   (http://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.

Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1 Current mechanisms . . . . . . . . . . . . . . . . . . . . .  4
       2.1.1 Stateful firewalls and proxies . . . . . . . . . . . . .  4
       2.1.2 QoS signaling  . . . . . . . . . . . . . . . . . . . . .  5
       2.1.3 Deep packet inspection . . . . . . . . . . . . . . . . .  5
     2.2 Alternative proposals  . . . . . . . . . . . . . . . . . . .  5
       2.2.1 SPUD/PLUS  . . . . . . . . . . . . . . . . . . . . . . .  5
       2.2.2 Path aware networking  . . . . . . . . . . . . . . . . .  6
     2.3 Emerging use cases . . . . . . . . . . . . . . . . . . . . .  7
   3  Architecture  . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.1 Example packet flow  . . . . . . . . . . . . . . . . . . . .  9
     3.2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 10
   4  Packet format . . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.1 Option format  . . . . . . . . . . . . . . . . . . . . . . . 11
     4.2 Option types . . . . . . . . . . . . . . . . . . . . . . . . 12
     4.3 Ticket format  . . . . . . . . . . . . . . . . . . . . . . . 12
   5  Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.1 Ticket types and ordering  . . . . . . . . . . . . . . . . . 13
     5.2 Origin application processing  . . . . . . . . . . . . . . . 14
       5.2.1 Ticket requests  . . . . . . . . . . . . . . . . . . . . 14
       5.2.2 Ticket identification  . . . . . . . . . . . . . . . . . 14
       5.2.3 Ticket use . . . . . . . . . . . . . . . . . . . . . . . 14
       5.2.4 Ticket scope . . . . . . . . . . . . . . . . . . . . . . 15
     5.3 Origin network processing  . . . . . . . . . . . . . . . . . 15
     5.4 Peer host processing . . . . . . . . . . . . . . . . . . . . 16
     5.5 Processing reflected tickets . . . . . . . . . . . . . . . . 16
       5.5.1 Network processing . . . . . . . . . . . . . . . . . . . 16
       5.5.2 Host processing  . . . . . . . . . . . . . . . . . . . . 17
     5.6 Handling dropped extension headers . . . . . . . . . . . . . 17
       5.6.1 Mitigation for dropped extension headers . . . . . . . . 17
       5.6.2 Fallback for dropped extension headers . . . . . . . . . 17

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   6  Implementation considerations . . . . . . . . . . . . . . . . . 18
     6.1 Origin applications  . . . . . . . . . . . . . . . . . . . . 18
     6.2 Ticket reflection  . . . . . . . . . . . . . . . . . . . . . 19
   7  Security Considerations . . . . . . . . . . . . . . . . . . . . 19
   8  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 19
   9  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     9.1  Normative References  . . . . . . . . . . . . . . . . . . . 20
     9.2  Informative References  . . . . . . . . . . . . . . . . . . 20
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 21

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1  Introduction

   Firewall and Service Tickets (FAST) is a technique to allow an
   application to signal to the network requests for admission and
   services for a flow. A ticket is data that is attached to a packet by
   the source that is inspected and validated by intermediate nodes in a
   network. Tickets express a grant or right for packets to traverse a
   network or have services applied to them.

   An application requests tickets for admission or services from a
   ticket agent in their local network. The agent issues tickets to the
   application which in turn attaches these to its packets. In the
   forwarding path, intermediate network nodes interpret tickets and
   apply requested services on packets.

   Tickets are validated for authenticity by the network and contain an
   expiration time so that they cannot be easily forged. Tickets do not
   have a global interpretation, they can only be interpreted within the
   network that issues them. In order to apply services to inbound
   packets for a communication, remote peers reflect received tickets in
   packets they send without interpreting them. Tickets are stateless
   within the network, however can be used to attain per flow semantics.
   Firewall and service tickets are are non-transferable and revocable.

   Tickets are coded in IPv6 Hop-by-Hop or Destination options.

2  Motivation

   This section presents the motivation for Firewall and Service

2.1 Current mechanisms

   Current solutions for controlling admission to the network and
   requesting services are mostly ad hoc and architecturally limiting.

2.1.1 Stateful firewalls and proxies

   Stateful firewalls and proxies are the predominantly deployed
   techniques to control access to a network on a per flow basis. While
   they provide some benefits of security, they have also break the end-
   to-end model and have otherwise restricted the Internet in several

     o They require parsing over transport layer headers in the fast
       path of forwarding.

     o They are limited to work only with a handful of protocols and

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       protocol features thereby ossifying protocols.

     o They break the ability to use mulithoming and multipath. All
       packets for a flow must traverse a specific network device in
       both directions of a communication.

     o They can break end to end security. NAT for instance breaks the
       TCP authentication option.

     o They have created single points of failure and become network

2.1.2 QoS signaling

   In the current Internet, there is little coordination between hosts
   and the network to provide services based on characteristics of the
   application. Differentiated services provides an IP layer means to
   classify and manage traffic, however it is lacking in richness of
   expression and lacks a ubiquitous interface that allows applications
   to request service with any granularity. Without additional state,
   there is no means for the network infrastructure to validate that a
   third party application has requested QoS that adheres to network

2.1.3 Deep packet inspection

   Some network devices perform Deep Packet Inspection (DPI) into the
   application data to determine whether to admit packets or what
   services to apply. For instance, HTTP is commonly parsed to determine
   URL, content type, and other application level information the
   network is interested in. DPI can only be effective with the
   application layer protocols that a device is programmed to parse.
   More importantly, application level DPI is being effectively
   obsoleted in the network due the pervasive use of TLS. TLS
   interception and SSL inspection, whereby an intermediate node
   implements a proxy that decrypts a TLS session and re-encrypts, is
   considered a security vulnerability [TLSCERT].

2.2 Alternative proposals

   This section surveys some proposals to address the need for
   applications to signal the network.


   SPUD (Session Protocol Underneath Datagrams) [SPUD] and its successor
   PLUS (Path Layer UDP Substrate) [PLUS] proposed a UDP based protocol
   to allow applications to signal a rich set of characteristics and

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   service requirements to the network.

   SPUD has a number of drawbacks:

     o SPUD is based on a specific protocol 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] there is 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 stateful flow tracking in the network. This
       problematic because:

        o Not all communications have well defined connection semantics.
          For instance, a unidirectional data stream has no connection
          semantics at all.

        o Stateful network devices breaks multi-homing; they assume that
          all packets of a flow in both directions are seen by the node
          doing tracking flow state. Stateful 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-homed network 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

2.2.2 Path aware networking

   Path aware networking (PAN) [PAN] is an IRTF effort to allow
   applications to select paths through the Internet for their traffic.
   The idea is that in choosing different paths an application can
   select form the different characteristics that are associated with

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   different paths. Path aware networking requires a means to express
   the various paths and their associated characteristics to
   applications. In the data path, a method to express desired path for
   a packet is needed-- this presumably could be by a mechanism such as
   segment routing.

   PAN and FAST have similar characteristics, particularly with respect
   to the need for applications and networks to communicate about
   network path characteristics. However, where PAN presumably endeavors
   to allow path selection by an application, FAST allows applications
   to select their desired path characteristics and it is up to the
   network to select the actual path. This distinction is important to
   maximize flexibility, especially in situations where providing any
   detailed path information to untrusted end device is a security risk
   (which would be the typical case in a provider network).

2.3 Emerging use cases

   In a typical client/server model of serving content, end host clients
   communicate with servers on the Internet. 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 mobile provider
   network. Content providers (web servers and content caches) 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 stringent 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
   use of these mechanisms 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.

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   Note that an application service applies to both packets sent by an
   end node and those sent from a peer towards the end node. For the
   latter case, the network needs to be able to map packets sent from
   hosts on the Internet to the services requested by the receiving

3  Architecture

   The figure below illustrates an example network path between two
   hosts on the Internet. 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 figure 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

   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 network provider. FAST is a mechanism
   whereby each user and application can request from its local provider
   the services to be applied to its traffic. A request for service is
   made to a FAST "ticket agent". The contents of the request describe
   the services that application desires. The ticket agent responds with
   a "ticket" that the application sets in its packets. When a packet is
   sent by the application with a ticket attached, the ticket is
   interpreted in the provider network to allow the packet to traverse
   the network and to map the packet to the appropriate services. The
   ticket is only relevant to the provider network of the application,
   to the application itself and nodes outside of the provider network
   the ticket is only an uinterpretable opaque object.

   To facilitate network traversal and service mapping in the reverse

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   direction for a flow, that is packets sent from a peer host, peer
   hosts reflect tickets without modification or interpretation. This is
   done by saving the ticket received in packets of a flow and attaching
   that as a reflected ticket to packets being sent on the flow.

   The use of tickets may be bilateral for a connection so that each
   peer requests service from its local network. Therefore packets may
   contain two types of tickets: one that is set by the sending host to
   signal its local provider network, and the other is the reflected
   ticket that is a signal to the provider network of the peer endpoint.

   Tickets are scoped values, they only have meaning in the network in
   which they were issued. The format, meaning, and interpretation of
   tickets is network specific. By mutual agreement, two networks may
   share the policy and interpretations of tickets. For instance, there
   could be an agreement between two provider networks to interpret each
   others tickets or to use a common format.

3.1 Example packet flow

   Referencing the diagram in figure 1, consider that User 1 is
   establishing a video chat with User 2 and wishes to have low latency
   service for video applied by its local network (Provider 1). The flow
   of events may be:

      1. User 1 makes a ticket request to a ticket agent of Provider A
         that describes the video application and may include detailed
         characteristics such as resolution, frame rate, latency, etc.

      2. The ticket agent issues a ticket to User 1 that indicates that
         packets of the flow have a right to traverse the network and
         the services to be applied to the packets of the flow.

      3. The video chat application sends packets with the ticket
         attached for the video chat.

      4. The first hop node in Provider A's network interprets the
         ticket in packets and applies the appropriate services (e.g.
         sets diffserv, forwards on a network slice, encapsulates in
         MPLS, etc.).

      5. Packets traverse Provider A's network with the appropriate
         services being applied.

      6. Packets traverse transit networks and Provider B network, the
         attached tickets are ignored.

      7. Packets are received at User 2. Attached tickets are saved in

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         the context of the flow for the video chat.

      8. User 2's video chat application sends packets to User 1. The
         last ticket previously received from User 1 is now reflected in
         these packets.

      9. Packets traverse Provider B network and transit networks, the
         reflected ticket is ignored.

      10. An ingress node in Provider A's network interprets the
         reflected tickets and applies appropriate services to the
         packets for traversing the local network.

      11. Packets are forwarded within Provider's A network with the
         appropriate services applied. No other intermediate nodes
         should need to interpret the tickets.

      12. Packets are received at the host for User 1. The reflected
         ticket is validated by comparing the received ticket with that
         being sent for the flow. It the ticket is determined valid then
         the packet is accepted.

3.2 Requirements

   The requirements for Firewall and Service Tickets are:

      o Tickets MUST be stateless within the network. In particular
        intermediate nodes MUST NOT be required to create and maintain
        state for transport layer connections.

      o Tickets MUST work in a multi-homed and multi-path environments.

      o Outside of the network that issued a ticket, tickets MUST be
        opaque and obfuscated so that no application specific
        information is derivable.

      o Tickets MUST work with any transport protocol as well as in the
        presence of any IP protocol feature (e.g. other extension
        headers are present).

      o Tickets SHOULD minimize the changes to an application. Their use
        should be an "add-on" to the existing communications of an

      o Tickets MUST deter spoofing and other misuse that might result
        in illegitimate use of network services or denial of service

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      o Tickets MUST be contained in the IP layer protocol. In
        particular, tickets MUST NOT require parsing transport layer

      o Tickets MUST allow services to be applied in the return path of
        a communication. 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 MUST be present to handle the case that extension
        headers are dropped within the network or a peer node does not
        reflect tickets. A fallback allows functional communications but
        provides it in a degrade mode of service.

4  Packet format

   A ticket is sent as Destination option or a Hop-by-Hop option.

4.1 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  |                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                       +
   |                                                               |
   ~                            Ticket                             ~
   |                                                               |


      o Option type: Type of Hop-by-Hop or Destination option. This
        document proposes two possible values for ticket: an
        unmodifiable and a modifiable variant.

      o Opt Data Len: Length of the option data field. This is two plus
        the length of the ticket field

      o Type: Indicates the type and reflection property of the ticket.
        This is one of:

         o 0x0: Ticket from origin, don't reflect at receiver

         o 0x1: Ticket from origin, reflect at receiver

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         o 0x2: Reflected ticket

         o 0x3-0xf: Reserved

4.2 Option types

   A ticket 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-by-Hop
   options have a drop rate of 39.03%

   The are two option numbers requested for the ticket option: 0x0F and
   0x2F. 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.

4.3 Ticket format

   A ticket encodes service parameters that describe the desired
   services as well as additional fields that would be used to provide
   privacy and integrity.

   The format of a ticket is defined by the network in which the ticket
   is issued. A ticket should be obfuscated or encrypted for privacy so
   that only the local network can interpret it. It should be
   uniterpretable to any nodes outside the network and to the
   application or host that is granted a ticket. It should be resistant
   to spoofing so that an attacker cannot illegitimately get service by
   applying a ticket seen on other flows.

   It is recommended that tickets are encrypted and each ticket has an
   expiration time. For instance, a ticket may be created by encrypting
   the ticket data with an expiration time and using the source address,
   destination address, and a shared key as the key for encryption.

   For example, a ticket with an expiration time 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                         ~
   |                                                               |

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   Where the expiration time is in a format understood by the local
   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 ticket containing a service protocol index might be:

    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                       |

   Where Type indicates the type of ticket and in this case indicates it
   is a service profile index. Service Profile Index could be an index
   into a table that describes the services to be applied.

5  Operation

5.1 Ticket types and ordering

   There are three types of tickets that may be contained in a packet:

     o origin tickets that are not reflected

     o origin tickets to be reflected

     o reflected tickets

   Origin tickets are those set by an application that was issued a
   ticket and have an additional property indicating whether they are to
   be reflected by a peer host. Reflected tickets are those that have
   been received and reflected by a peer host.

   A sender SHOULD set at most one of each type of ticket in a packet.
   If different types of ticket are sent with single packet they SHOULD
   have the following ordering:

     1. origin tickets that are not reflected

     2. origin tickets to be reflected

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     3. reflected tickets

5.2 Origin application processing

   An origin application requests tickets, sets them in packets, and
   validates reflected tickets.

5.2.1 Ticket requests

   An application that wishes to use network services first requests
   tickets from a ticket agent. The application request could be in the
   form of an XML structure with a canonical elements (the definition is
   outside the scope of this document). The application makes a request
   to the ticket agent for the local network. This could be done via a
   web service using HTTP PUT/GET. Internally in the host, the ticket
   agent might be accessed through a library that interfaces to a ticket
   daemon that in turn arbitrates requests between the applications and
   a ticket agent in the network.

   An issued ticket is opaque to the application and the application
   should not attempt to interpret it or take any other action other
   than attaching the ticket to its packets.

   A ticket agent MAY provide both a origin ticket not to be reflected
   and one that is to be reflected. The intent is that different tickets
   can be used between the outbound and inbound paths for the flow. In
   the case that two tickets are provided, the origin ticket not to be
   reflected MUST appear first in the options list.

5.2.2 Ticket identification

   Tickets are valid for a specific IP source and destination address
   for which they were issued. Transport layer ports and other transport
   layer information are not included ticket identification, however an
   application can request tickets and validate reflected tickets on a
   per flow basis. Issued tickets are stored in the flow context and the
   saved information is used to validate reflected tickets.

5.2.3 Ticket use

   When the ticket agent issues an returns a ticket, the application
   sets the ticket as a Hop-by-Hop option or Destination option as
   specified. 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 unconnected socket (in the case of
   UDP). The application SHOULD continue to use the same ticket for the
   flow until it is updated with a new ticket.

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   The ticket agent SHOULD return an expiration time with the ticket. An
   application can use the ticket until the expiration time, at which
   point it can request a new ticket to continue communications. In
   order to make the ticket transition process seamless an application
   MAY request a new ticket before the old one expires.

   A host SHOULD set in a packet at most one origin ticket not to be
   reflected and one origin ticket to be reflected.

5.2.4 Ticket scope

   Tickets are valid for a specific IP source and destination address
   for which they were issued. Transport layer ports and other transport
   layer information are not included ticket identification, however an
   application can request tickets and validate reflected tickets on a
   per flow basis. Issued tickets are stored in the flow context and the
   saved information is used to validate reflected tickets.

   A network MAY delegate creation of tickets to hosts in a limited
   fashion. This would entail the network ticket agent issuing a master
   ticket to a host ticket agent which in turn can use the master ticket
   to create a limited number of tickets. The details of ticket agent
   delegation are outside the scope of this document.

5.3 Origin network processing

   When a packet with a ticket enters a network, a network node can
   determine if the ticket originated in its network and must be
   processed. This is done by considering the origin of the ticket and
   the source or destination IP address. For an origin ticket (i.e.
   ticket is not reflected), the source address is considered. If the
   source address is local to the network then the ticket can be
   interpreted. For a reflected ticket, the destination address is
   considered. If the destination address is local to the network then
   the ticket can be interpreted.

   If a ticket origin is determined to be the local network then the
   ticket is processed. The ticket is decrypted if necessary and the
   expiration time is checked. If the ticket is verified to be authentic
   and 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 logically only two ingress points into the
   network at which a provider needs to process tickets: when a local
   user sends a packet into the provider network with an origin ticket,
   and when a packet from an external network enters the provider's

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   network with a reflected ticket. Any ticket should be processed at
   most once within a network. Once a ticket is processed and mapped to
   the network's service mechanisms it should not need further

   If there is more than one origin ticket present, then the first one
   encountered is processed and any additional origin tickets SHOULD be
   ignored by a network node. Note that this will be the case if a
   ticket agent issued both a origin ticket not to be reflected and one
   to be reflected; the ticket not to be reflected should appear first
   in the packet and thus would be the one processed by the node.

   If there is more than one reflected ticket present, then the first
   one encountered is processed and any additional reflected tickets
   SHOULD be ignored.

5.4 Peer host processing

   When a host receives a packet with a ticket whose type is "from
   origin and needs to be reflected", it SHOULD save the ticket in its
   flow context and reflect it on subsequent packets. When the
   application reflects the option, it copies the whole option and only
   modifies the type to indicate a "reflected ticket". The application
   SHOULD continue to reflect the ticket until a different one is
   received from the origin or a packet without a service ticket option
   is received on the flow. Note that the latest ticket that is received
   is the one to be reflected, if packets have been received out of
   order for a flow it is possible that the reflected ticket is from an
   earlier packet in a flow.

   If there is more than one origin ticket to be reflected present, then
   the first one encountered is processed and any additional origin
   tickets to be reflected SHOULD be ignored.

   A peer host MUST ignore received origin tickets that are not to be

5.5 Processing reflected tickets

5.5.1 Network processing

   When a packet with a reflected ticket enters the origin network of
   the ticket, the ticket MUST be processed. The ticket is validated.
   Validation entails decoding or decrypting the ticket and checking the
   expiration time. If the ticket is valid and has not expired time then
   the packet is verified for forwarding.

   A network MAY accept expired reflected tickets for some configurable

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   period after the expiration time. Rate limiting SHOULD be applied to
   packets with expired reflected tickets. Accepting expired tickets is
   useful in the case that a connection goes idle and after sometime the
   remote peer starts to send. The ticket it reflects may be expired and
   presumably the receiving host will quickly respond with a new ticket.

5.5.2 Host processing

   Upon receiving a packet with a reflected ticket an end host MUST
   validate the ticket before accepting the packet. This verification is
   done by comparing the received ticket to that which is set to be sent
   on the corresponding flow. If the tickets do not match then the
   packet is dropped and the event SHOULD be logged.

   A host SHOULD retain and validate expired tickets that are reflected
   to allow a peer time to receive and reflect an updated ticket.

5.6 Handling dropped extension headers

   The downside of using IPv6 extension headers on the Internet is that
   they are currently not completely reliable. Some intermediate nodes
   will drop extension headers with rates described in [RFC7872].

5.6.1 Mitigation for dropped extension headers

   There are some mitigating factors for this problem:

      o A provider network that implements tickets would need to ensure
        that extension headers are at least usable within their 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.

      o The requirement that nodes must process Hop-by-hop options has
        been relaxed in [RFC8200]. It is permissible for intermediate
        nodes to ignore them.

      o Increased deployment of IPv6 and viable use cases of extension
        headers, such as described here, may motivate vendors to fix
        issues with extension headers.

5.6.2 Fallback for dropped extension headers

   Since the possibility that extension headers are dropped cannot be

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   completely eliminated, a fallback is included for use with tickets.

   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 a host to send a
   number of packets with and without tickets. The application can
   observe whether packets with tickets are being dropped or not being

   There are a few possible outcomes of this process:

      o A packet with a ticket is dropped and an ICMP for extension
        headers [ICMPEH] processing limits is received. This is a strong
        signal that extension headers are not viable to the destination
        and should not be used for the flow.

      o A packet with a ticket 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 tickets, then extension headers should be considered not
        viable for the flow.

      o Packets with tickets are not being dropped, however tickets are
        not being reflected. This is a signal that the peer application
        does not support reflection. Tickets may be sent, however they
        are only useful in the outbound path.

      o Packet with tickets are not being dropped and tickets are
        properly being reflected. Tickets are useful in both directions.

   If extension headers are found to not be viable or tickets are not
   being properly reflected, a possible fallback is to not use tickets.
   In this case, communications might remain functional, however they
   would be operate in a degraded mode of service. The network may
   fallback to creating per flow state in the network; the ticket that
   an application sent with packets during probing could be used to
   instantiate the service characteristics maintained in a flow state.

6  Implementation considerations

6.1 Origin applications

   Existing client applications can be modified to request tickets and
   set them in packets. The kernel may need some small changes or
   configuration to enable an application to specify the option for its

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   The interface to the ticket agent would likely be via a library API.

   Using the BSD sockets interface, for a connected socket (TCP, SCTP,
   or connected UDP socket) a Hop-by-Hop or Destination option can be
   set on the socket via the setsockopt system call. For an unconnected
   socket (UDP) the ticket option can be set as ancillary data in the
   sendmsg system call.

   Happy Eyeballs for extension headers, described in section 5.6.2,
   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.

6.2 Ticket reflection

   To perform ticket reflection, servers must be updated. In the case of
   a connected socket (TCP, SCTP, or a connected UDP socket) this can be
   done as relatively minor change to the kernel networking stack which
   would be transparent to applications. For unconnected UDP, an
   application could receive the ticket as part of the ancillary data in
   recvmsg system call, and then send the reflected ticket in a reply
   using ancillary data in sendmsg.

7  Security Considerations

   There are two main security considerations:

      o Leakage of content specific information to untrusted third
        parties must be avoided.

      o Tickets cannot be forged or illegitimately used.

   Tickets may be visible to the Internet including untrusted and
   unknown networks in the path of sent packets. Therefore, tickets
   should be encrypted or obfuscated by the origin network.

   Tickets need to have an expiration time, must be resistant to
   forgery, and must be nontransferable. A ticket should be valid for
   the specific source and destination addresses that it was issued for.
   Tickets are revocable by implemented a black-list contained revoked

8  IANA Considerations

   IANA is requested to assigned the following Destination and Hop-By-
   Hop options:

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      | Hex Value | Binary value  | Description | Reference     |
      |           | act chg rest  |             |               |
      | 0x0F      | 00   0  01111 | Firewall    | This document |
      |           |               | and Service |               |
      |           |               | Ticket      |               |
      | 0x2F      | 00   1  01111 | Modifiable  | This document |
      |           |               | Firewall    |               |
      |           |               | and Service |               |
      |           |               | Ticket      |               |

   IANA is requested to set up a registry for the Ticket types. These
   types are 4 bit values. New values for control types 0x3-0xf are
   assigned via Standards Action [RFC5226].

      | Ticket type    | Description        | Reference     |
      | 0x0            | Ticket from origin | This document |
      |                | and don't reflect  |               |
      | 0x1            | Ticket from origin | This document |
      |                | and reflect        |               |
      | 0x2            | Reflected ticket   | This document |

9  References

9.1  Normative References

   [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
             (IPv6) Specification", STD 86, RFC 8200, DOI
             10.17487/RFC8200, July 2017, <https://www.rfc-

   [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
             IANA Considerations Section in RFCs", RFC 5226, DOI
             10.17487/RFC5226, May 2008, <https://www.rfc-

9.2  Informative References

   [RFC7605] Touch, J., "Recommendations on Using Assigned Transport
             Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605,

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             August 2015, <http://www.rfc-editor.org/info/rfc7605>.

   [RFC7872] Got, 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,

   [TLSCERT] United States Computer Emergency Readiness Team (US-CERT),
             "Alert (TA17-075A), HTTPS Interception Weakens TLS
             Security, March 2017

   [SPUD]    Hildebrand, J. and Trammell, B., "Substrate Protocol for
             User Datagrams (SPUD) Prototype", draft-hildebrand-spud-
             prototype-03, March 2015

   [PLUS]    Trammell, B. and Kuehlewind, M., "Path Layer UDP Substrate
             Specification", draft-trammell-plus-spec-01, March 2017

   [PAN]     Trammell, B., "Open Questions in Path Aware Networking",
             draft-trammell-panrg-questions-02, December 2017

   [ICMPEH]  Herbert, T., "ICMPv6 errors for discarding packets due to
             processing limits", draft-herbert-6man-icmp-limits-00.txt

Author's Address

   Tom Herbert
   Santa Clara, CA

   Email: tom@quantonium.net

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