RFC3252
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.
Contents
Introduction
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.
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
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.
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.
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.
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.
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.
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.
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>
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.
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.
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.
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>
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.
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.
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.
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>
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.
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".)
IEEE 802
BLOAT is encapsulated in IEEE 802 Networks as in RFC1042 except that the protocol type code for IPoXML is 0xBEEF.
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.
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.
IPoXML DTD
<!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)>
<!ATTLIST header
length %Digits; #REQUIRED>
<!ELEMENT version EMPTY> <!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> <!ATTLIST total.length
value %Digits; #REQUIRED>
<!ELEMENT id EMPTY> <!ATTLIST id
value %Digits; #REQUIRED>
<!ELEMENT flags EMPTY> <!ATTLIST flags
reserved CDATA #FIXED "0"
df (may|dont) #REQUIRED
mf (last|more) #REQUIRED>
<!ELEMENT offset EMPTY> <!ATTLIST offset
value %Digits; #REQUIRED>
<!ELEMENT ttl EMPTY> <!ATTLIST ttl
value %Digits; #REQUIRED>
<!ELEMENT protocol EMPTY> <!ATTLIST protocol
value %Digits; #REQUIRED>
<!ELEMENT checksum EMPTY> <!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>
<!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> <!ATTLIST hop
address %IP4Addr; #REQUIRED>
<!ELEMENT strict (hop)+> <!ATTLIST strict
copied CDATA #FIXED "1"
class CDATA #FIXED "0"
number CDATA #FIXED "9"
length %Digits; #REQUIRED
pointer %Digits; #REQUIRED>
<!ELEMENT record (hop)+> <!ATTLIST record
copied CDATA #FIXED "0"
class CDATA #FIXED "0"
number CDATA #FIXED "7"
length %Digits; #REQUIRED
pointer %Digits; #REQUIRED>
<!ELEMENT stream EMPTY> <!ATTLIST stream
copied CDATA #FIXED "1"
class CDATA #FIXED "0"
number CDATA #FIXED "8"
length CDATA #FIXED "4"
id %Digits; #REQUIRED>
<!ELEMENT timestamp (tstamp)+>
<!ATTLIST timestamp
copied CDATA #FIXED "0"
class CDATA #FIXED "2"
number CDATA #FIXED "4"
length %Digits; #REQUIRED
pointer %Digits; #REQUIRED
oflw %Digits; #REQUIRED
flag (0 | 1 | 3) #REQUIRED>
<!ELEMENT tstamp EMPTY> <!ATTLIST tstamp
time %Digits; #REQUIRED
address %IP4Addr; #IMPLIED>
<!ELEMENT padding EMPTY> <!ATTLIST padding
pad CDATA #REQUIRED>
<!ELEMENT payload (CDATA)>
TCPoXML DTD
<!ELEMENT tcp (tcp.pseudoheader?, tcp.header, payload)>
<!ELEMENT tcp.header (src, dest, sequence, acknowledgement, offset,
reserved, control, window, checksum, urgent,
tcp.options, padding)>
<!ELEMENT src EMPTY> <!ATTLIST src
port %Digits; #REQUIRED>
<!ELEMENT dest EMPTY>
<!ATTLIST dest
port %Digits; #REQUIRED>
<!ELEMENT sequence EMPTY> <!ATTLIST sequence
number %Digits; #REQUIRED>
<!ELEMENT acknowledgement EMPTY> <!ATTLIST acknowledgement
number %Digits; #REQUIRED>
<!ELEMENT offset EMPTY> <!ATTLIST offset
number %Digits; #REQUIRED>
<!ELEMENT reserved EMPTY> <!ATTLIST reserved
value CDATA #FIXED "0">
<!ELEMENT control EMPTY> <!ATTLIST control
urg (0|1) #IMPLIED
ack (0|1) #IMPLIED
psh (0|1) #IMPLIED
rst (0|1) #IMPLIED
syn (0|1) #IMPLIED
fin (0|1) #IMPLIED>
<!ELEMENT window EMPTY> <!ATTLIST window
size %Digits; #REQUIRED>
<!ELEMENT tcp.pseudoheader (source, destination, protocol,
tcp.length)>
<!ELEMENT tcp.length EMPTY>
<!ATTLIST tcp.length
value %Digits; #REQUIRED>
<!ELEMENT urgent EMPTY> <!ATTLIST urgent
pointer %Digits; #REQUIRED>
<!ELEMENT tcp.options (tcp.end | tcp.noop | tcp.mss)+>
<!ELEMENT tcp.end EMPTY> <!ATTLIST tcp.end
kind CDATA #FIXED "0">
<!ELEMENT tcp.noop EMPTY> <!ATTLIST tcp.noop
kind CDATA #FIXED "1">
<!ELEMENT tcp.mss EMPTY> <!ATTLIST tcp.mss
kind CDATA #FIXED "2"
length CDATA #FIXED "4"
size %Digits; #REQUIRED>
UDPoXML DTD
<!ELEMENT udp (udp.pseudoheader?, udp.header, payload)>
<!ELEMENT udp.header (src, dest, udp.length, checksum)>
<!ELEMENT udp.pseudoheader (source, destination, protocol,
udp.length)>
<!ELEMENT udp.length EMPTY> <!ATTLIST udp.length
value %Digits; #REQUIRED>
Security Considerations
XML, as a subset of SGML, has the same security considerations as specified in SGML Media Types RFC1874. Security considerations that apply to IP, TCP and UDP also likely apply to BLOAT as it does not attempt to correct for issues not related to message format.
References
[JABBER] Miller, J., "Jabber", draft-miller-jabber-00.txt,
February 2002. (Work in Progress)
RFC768 Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
RFC791 Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
RFC793 Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
RFC894 Hornig, C., "Standard for the Transmission of IP
Datagrams over Ethernet Networks.", RFC 894, April 1984.
RFC1042 Postel, J. and J. Reynolds, "Standard for the
Transmission of IP Datagrams Over IEEE 802 Networks", STD
43, RFC 1042, February 1988.
RFC1123 Braden, R., "Requirements for Internet Hosts -
Application and Support", RFC 1123, October 1989.
RFC1874 Levinson, E., "SGML Media Types", RFC 1874, December
1995.
RFC2003 Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996.
RFC2045 Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
RFC2119 Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
RFC2279 Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 2279, January 1998.
RFC2460 Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
RFC3080 Rose, M., "The Blocks Extensible Exchange Protocol Core",
RFC 3080, March 2001.
[SOAP] Box, D., Ehnebuske, D., Kakivaya, G., Layman, A.,
Mendelsohn, N., Nielsen, H. F., Thatte, S. Winer, D.,
"Simple Object Access Protocol (SOAP) 1.1" World Wide Web
Consortium Note, May 2000 http://www.w3.org/TR/SOAP/
[XML] Bray, T., Paoli, J., Sperberg-McQueen, C. M., "Extensible
Markup Language (XML)" World Wide Web Consortium
Recommendation REC- xml-19980210.
http://www.w3.org/TR/1998/REC-xml-19980210
10. Author's Address
Hugh Kennedy Mimezine 1060 West Addison Chicago, IL 60613 USA
EMail: [email protected]
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Acknowledgement
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