Network Working Group                                         H. Kennedy

Request for Comments: 3252                                      Mimezine

Category: Informational                                     1 April 2002

                 Binary Lexical Octet Ad-hoc Transport

Status of this Memo

   This memo provides information for the Internet community.  It does

   not specify an Internet standard of any kind.  Distribution of this

   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document defines a reformulation of IP and two transport layer

   protocols (TCP and UDP) as XML applications.

1.   Introduction

1.1. Overview

   This document describes the Binary Lexical Octet Ad-hoc Transport

   (BLOAT): a reformulation of a widely-deployed network-layer protocol

   (IP [RFC791]), and two associated transport layer protocols (TCP

   [RFC793] and UDP [RFC768]) as XML [XML] applications.  It also

   describes methods for transporting BLOAT over Ethernet and IEEE 802

   networks as well as encapsulating BLOAT in IP for gatewaying BLOAT

   across the public Internet.

1.2. Motivation

   The wild popularity of XML as a basis for application-level protocols

   such as the Blocks Extensible Exchange Protocol [RFC3080], the Simple

   Object Access Protocol [SOAP], and Jabber [JABBER] prompted

   investigation into the possibility of extending the use of XML in the

   protocol stack.  Using XML at both the transport and network layer in

   addition to the application layer would provide for an amazing amount

   of power and flexibility while removing dependencies on proprietary

   and hard-to-understand binary protocols.  This protocol unification

   would also allow applications to use a single XML parser for all

   aspects of their operation, eliminating developer time spent figuring

   out the intricacies of each new protocol, and moving the hard work of

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   parsing to the XML toolset.  The use of XML also mitigates concerns

   over "network vs. host" byte ordering which is at the root of many

   network application bugs.

1.3. Relation to Existing Protocols

   The reformulations specified in this RFC follow as closely as

   possible the spirit of the RFCs on which they are based, and so MAY

   contain elements or attributes that would not be needed in a pure

   reworking (e.g. length attributes, which are implicit in XML.)

   The layering of network and transport protocols are maintained in

   this RFC despite the optimizations that could be made if the line

   were somewhat blurred (i.e. merging TCP and IP into a single, larger

   element in the DTD) in order to foster future use of this protocol as

   a basis for reformulating other protocols (such as ICMP.)

   Other than the encoding, the behavioral aspects of each of the

   existing protocols remain unchanged.  Routing, address spaces, TCP

   congestion control, etc. behave as specified in the extant standards.

   Adapting to new standards and experimental algorithm heuristics for

   improving performance will become much easier once the move to BLOAT

   has been completed.

1.4. Requirement Levels

   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 BCP 14, RFC 2119

   [RFC2119].

2.   IPoXML

   This protocol MUST be implemented to be compliant with this RFC.

   IPoXML is the root protocol REQUIRED for effective use of TCPoXML

   (section 3.) and higher-level application protocols.

   The DTD for this document type can be found in section 7.1.

   The routing of IPoXML can be easily implemented on hosts with an XML

   parser, as the regular structure lends itself handily to parsing and

   validation of the document/datagram and then processing the

   destination address, TTL, and checksum before sending it on to its

   next-hop.

   The reformulation of IPv4 was chosen over IPv6 [RFC2460] due to the

   wider deployment of IPv4 and the fact that implementing IPv6 as XML

   would have exceeded the 1500 byte Ethernet MTU.

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   All BLOAT implementations MUST use - and specify - the UTF-8 encoding

   of RFC 2279 [RFC2279].  All BLOAT document/datagrams MUST be well-

   formed and include the XMLDecl.

2.1. IP Description

   A number of items have changed (for the better) from the original IP

   specification.  Bit-masks, where present have been converted into

   human-readable values.  IP addresses are listed in their dotted-

   decimal notation [RFC1123].  Length and checksum values are present

   as decimal integers.

   To calculate the length and checksum fields of the IP element, a

   canonicalized form of the element MUST be used.  The canonical form

   SHALL have no whitespace (including newline characters) between

   elements and only one space character between attributes.  There

   SHALL NOT be a space following the last attribute in an element.

   An iterative method SHOULD be used to calculate checksums, as the

   length field will vary based on the size of the checksum.

   The payload element bears special attention.  Due to the character

   set restrictions of XML, the payload of IP datagrams (which MAY

   contain arbitrary data) MUST be encoded for transport. This RFC

   REQUIRES the contents of the payload to be encoded in the base-64

   encoding of RFC 2045 [RFC2045], but removes the requirement that the

   encoded output MUST be wrapped on 76-character lines.

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2.2. Example Datagram

   The following is an example IPoXML datagram with an empty payload:

   <?xml version="1.0" encoding="UTF-8"?>

   <!DOCTYPE ip PUBLIC "-//IETF//DTD BLOAT 1.0 IP//EN" "bloat.dtd">

   <ip>

   <header length="474">

   <version value="4"/>

   <tos precedence="Routine" delay="Normal" throughput="Normal"

        relibility="Normal" reserved="0"/>

   <total.length value="461"/>

   <id value="1"/>

   <flags reserved="0" df="dont" mf="last"/>

   <offset value="0"/>

   <ttl value="255"/>

   <protocol value="6"/>

   <checksum value="8707"/>

   <source address="10.0.0.22"/>

   <destination address="10.0.0.1"/>

   <options>

   <end copied="0" class="0" number="0"/>

   </options>

   <padding pad="0"/>

   </header>

   <payload>

   </payload>

   </ip>

3.   TCPoXML

   This protocol MUST be implemented to be compliant with this RFC.  The

   DTD for this document type can be found in section 7.2.

3.1. TCP Description

   A number of items have changed from the original TCP specification.

   Bit-masks, where present have been converted into human-readable

   values.  Length and checksum and port values are present as decimal

   integers.

   To calculate the length and checksum fields of the TCP element, a

   canonicalized form of the element MUST be used as in section 2.1.

   An iterative method SHOULD be used to calculate checksums as in

   section 2.1.

   The payload element MUST be encoded as in section 2.1.

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   The TCP offset element was expanded to a maximum of 255 from 16 to

   allow for the increased size of the header in XML.

   TCPoXML datagrams encapsulated by IPoXML MAY omit the <?xml?> header

   as well as the <!DOCTYPE> declaration.

3.2. Example Datagram

   The following is an example TCPoXML datagram with an empty payload:

   <?xml version="1.0" encoding="UTF-8"?>

   <!DOCTYPE tcp PUBLIC "-//IETF//DTD BLOAT 1.0 TCP//EN" "bloat.dtd">

   <tcp>

   <tcp.header>

   <src port="31415"/>

   <dest port="42424"/>

   <sequence number="322622954"/>

   <acknowledgement number="689715995"/>

   <offset number=""/>

   <reserved value="0"/>

   <control syn="1" ack="1"/>

   <window size="1"/>

   <urgent pointer="0"/>

   <checksum value="2988"/>

   <tcp.options>

   <tcp.end kind="0"/>

   </tcp.options>

   <padding pad="0"/>

   </tcp.header>

   <payload>

   </payload>

   </tcp>

4.   UDPoXML

   This protocol MUST be implemented to be compliant with this RFC.  The

   DTD for this document type can be found in section 7.3.

4.1. UDP Description

   A number of items have changed from the original UDP specification.

   Bit-masks, where present have been converted into human-readable

   values.  Length and checksum and port values are present as decimal

   integers.

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   To calculate the length and checksum fields of the UDP element, a

   canonicalized form of the element MUST be used as in section 2.1.  An

   iterative method SHOULD be used to calculate checksums as in section

   2.1.

   The payload element MUST be encoded as in section 2.1.

   UDPoXML datagrams encapsulated by IPoXML MAY omit the <?xml?> header

   as well as the <!DOCTYPE> declaration.

4.2. Example Datagram

   The following is an example UDPoXML datagram with an empty payload:

   <?xml version="1.0" encoding="UTF-8"?>

   <!DOCTYPE udp PUBLIC "-//IETF//DTD BLOAT 1.0 UDP//EN" "bloat.dtd">

   <udp>

   <udp.header>

   <src port="31415"/>

   <dest port="42424"/>

   <udp.length value="143"/>

   <checksum value="2988"/>

   </udp.header>

   <payload>

   </payload>

   </udp>

5.   Network Transport

   This document provides for the transmission of BLOAT datagrams over

   two common families of physical layer transport.  Future RFCs will

   address additional transports as routing vendors catch up to the

   specification, and we begin to see BLOAT routed across the Internet

   backbone.

5.1. Ethernet

   BLOAT is encapsulated in Ethernet datagrams as in [RFC894] with the

   exception that the type field of the Ethernet frame MUST contain the

   value 0xBEEF.  The first 5 octets of the Ethernet frame payload will

   be 0x3c 3f 78 6d 6c ("<?xml".)

5.2. IEEE 802

   BLOAT is encapsulated in IEEE 802 Networks as in [RFC1042] except

   that the protocol type code for IPoXML is 0xBEEF.

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6. Gatewaying over IP

   In order to facilitate the gradual introduction of BLOAT into the

   public Internet, BLOAT MAY be encapsulated in IP as in [RFC2003] to

   gateway between networks that run BLOAT natively on their LANs.

7. DTDs

   The Transport DTDs (7.2. and 7.3.) build on the definitions in the

   Network DTD (7.1.)

   The DTDs are referenced by their PubidLiteral and SystemLiteral (from

   [XML]) although it is understood that most IPoXML implementations

   will not need to pull down the DTD, as it will normally be embedded

   in the implementation, and presents something of a catch-22 if you

   need to load part of your network protocol over the network.

7.1.  IPoXML DTD

   <!--

    DTD for IP over XML.

    Refer to this DTD as:

    <!DOCTYPE ip PUBLIC "-//IETF//DTD BLOAT 1.0 IP//EN" "bloat.dtd">

   -->

   <!--

    DTD data types:

      Digits      [0..9]+

      Precedence  "NetworkControl | InternetworkControl |

                   CRITIC | FlashOverride | Flash | Immediate |

                   Priority | Routine"

      IP4Addr     "dotted-decimal" notation of [RFC1123]

      Class       [0..3]

      Sec          "Unclassified | Confidential | EFTO | MMMM | PROG |

                    Restricted | Secret | Top Secret | Reserved"

      Compartments [0..65535]

      Handling     [0..65535]

      TCC          [0..16777216]

   -->

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   <!ENTITY % Digits "CDATA">

   <!ENTITY % Precedence "CDATA">

   <!ENTITY % IP4Addr "CDATA">

   <!ENTITY % Class "CDATA">

   <!ENTITY % Sec "CDATA">

   <!ENTITY % Compartments "CDATA">

   <!ENTITY % Handling "CDATA">

   <!ENTITY % TCC "CDATA">

   <!ELEMENT ip (header, payload)>

   <!ELEMENT header (version, tos, total.length, id, flags, offset, ttl,

                    protocol, checksum, source, destination, options,

                    padding)>

   <!-- length of header in 32-bit words -->

   <!ATTLIST header

             length %Digits; #REQUIRED>

   <!ELEMENT version EMPTY>

   <!-- ip version. SHOULD be "4" -->

   <!ATTLIST version

             value   %Digits;  #REQUIRED>

   <!ELEMENT tos EMPTY>

   <!ATTLIST tos

             precedence   %Precedence;    #REQUIRED

             delay    (normal | low)  #REQUIRED

             throughput   (normal | high) #REQUIRED

             relibility   (normal | high) #REQUIRED

             reserved     CDATA #FIXED "0">

   <!ELEMENT total.length EMPTY>

   <!--

    total length of datagram (header and payload) in octets, MUST be

    less than 65,535 (and SHOULD be less than 1024 for IPoXML on local

    ethernets).

   -->

   <!ATTLIST total.length

             value %Digits; #REQUIRED>

   <!ELEMENT id EMPTY>

   <!-- 0 <= id <= 65,535  -->

   <!ATTLIST id

             value %Digits; #REQUIRED>

   <!ELEMENT flags EMPTY>

   <!-- df = don't fragment, mf = more fragments  -->

   <!ATTLIST flags

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          reserved CDATA  #FIXED "0"

          df (may|dont)   #REQUIRED

          mf (last|more)  #REQUIRED>

   <!ELEMENT offset EMPTY>

   <!-- 0 <= offset <= 8192 measured in 8 octet (64-bit) chunks -->

   <!ATTLIST offset

             value %Digits; #REQUIRED>

   <!ELEMENT ttl EMPTY>

   <!-- 0 <= ttl <= 255 -->

   <!ATTLIST ttl

             value %Digits; #REQUIRED>

   <!ELEMENT protocol EMPTY>

   <!-- 0 <= protocol <= 255 (per IANA) -->

   <!ATTLIST protocol

             value %Digits; #REQUIRED>

   <!ELEMENT checksum EMPTY>

   <!-- 0 <= checksum <= 65535 (over header only) -->

   <!ATTLIST checksum

             value %Digits; #REQUIRED>

   <!ELEMENT source EMPTY>

   <!ATTLIST source

             address %IP4Addr; #REQUIRED>

   <!ELEMENT destination EMPTY>

   <!ATTLIST destination

             address %IP4Addr; #REQUIRED>

   <!ELEMENT options ( end | noop | security | loose | strict | record

                     | stream | timestamp )*>

   <!ELEMENT end EMPTY>

   <!ATTLIST end

             copied (0|1) #REQUIRED

             class  CDATA #FIXED "0"

             number CDATA #FIXED "0">

   <!ELEMENT noop EMPTY>

   <!ATTLIST noop

             copied (0|1) #REQUIRED

             class  CDATA #FIXED "0"

             number CDATA #FIXED "1">

   <!ELEMENT security EMPTY>

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   <!ATTLIST security

             copied CDATA #FIXED "1"

             class  CDATA #FIXED "0"

             number CDATA #FIXED "2"

             length CDATA #FIXED "11"

             security %Sec; #REQUIRED

             compartments %Compartments; #REQUIRED

             handling %Handling; #REQUIRED

             tcc %TCC; #REQUIRED>

   <!ELEMENT loose (hop)+>

   <!ATTLIST loose

             copied CDATA #FIXED "1"

             class  CDATA #FIXED "0"

             number CDATA #FIXED "3"

             length %Digits; #REQUIRED

             pointer %Digits; #REQUIRED>

   <!ELEMENT hop EMPTY>