rfc1385.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

   The EIP Extension field holds the Source and Destination Network
   Numbers, which are only used for communications between different
   networks. For communications within the same network, the Network
   Numbers may be omitted. When the Extension field is omitted, there is
   little difference between an IP packet and an EIP packet.  Therefore,
   EIP hosts can maintain completely compatibility with IP hosts within
   one network.

   In EIP, the Network Numbers and Host Numbers are separate and the IP
   address field is used for the Host Number in EIP. There are a number
   of advantages:

   1) It maintains full compatibility between IP hosts and EIP hosts
      for communications within one network.  Note that the Network
      Number is not needed for communications within one network. A



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RFC 1385                          EIP                      November 1992


      host can omit the Extension field if it does not need any other
      information in the Extension field, when it communicates with
      another host within the same network.

   2) It allows the IP subnet routers to route EIP packet by treating
      the Host Number as the IP address during the transition period,
      therefore the subnet routers are not required to be updated
      along the border routers.

   3) It allows ARP/RARP to work with both EIP and IP hosts without
      any modifications.

   4) It allows the translation at the border routers much easier.
      During the transition period when the IP addresses are still
      unique, the network portion of the IP addresses can be directly
      extracted and mapped to EIP Network Numbers.

Modifications to IP Systems

   In this section, we outline the modifications to the IP systems that
   are needed for transition to EIP. Because of the similarity between
   the EIP and IP, the amount of modifications needed to current systems
   are substantially reduced.

   1) Network Numbers: Each network has to be assigned a new EIP Network
      Number based on the addressing scheme used. The mapping
      between the IP network numbers and the EIP Network Numbers can
      be used for translation service (see below).

   2) Host Numbers: There is no need for assigning EIP Host Numbers.
      All existing hosts can use their current IP addresses as their
      EIP Host Numbers. New machines may be allocated any number from
      the 32-bit Host Number space since the structure posed on IP
      addressing is no longer necessary. However, during the transition,
      allocation of EIP Host Numbers should still follow the IP
      addressing rule, so that the EIP Host Numbers are still globally
      unique and can still be interpreted as IP addresses.  This will
      allow a more gradual transition to EIP (see below).

   3) Translation Service: During the transition period when the EIP
      Host Numbers are still unique, an address translation service
      can be provided to IP hosts that need communicate with hosts in
      other networks cross the upgraded backbone networks.  The
      translation service can be provided by the border routers.  When a
      border router receives an IP packet, it obtains the Destination
      Network Number by looking up in the mapping table between IP
      network numbers and EIP Network Numbers. The border router then
      adds the Extension field with the Source and Destination Network



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RFC 1385                          EIP                      November 1992


      Numbers into the packet, and forwards to the backbone networks.
      It is only necessary to translate the out-going IP packets to
      the EIP packets.  There is no need to translate the EIP packets
      back to IP packets even when they are destined to IP hosts.
      This is because that the Extension field in the EIP packets
      appears to IP hosts just an unknown IP option and is ignored by
      the IP hosts during the processing.

   4) Border Routers: The new EIP Extension has to be implemented and
      routing has to be done based on the Network Number in the EIP
      Extension field. The border routers may have to provide the
      translation service for out-going IP packets during the transition
      period.

   5) Subnet Routers: No modifications are required during the transition
      period when EIP Host Numbers (which equals to the IP
      addresses) are still globally unique. The subnet routing is carried
      out based on the EIP Host Numbers and when the EIP Host
      IDs are still unique, subnet routers can determine, by treating
      the EIP Host Number as the IP addresses, whether a packet is
      destined to remote networks or not and forward correctly. The
      Extension field in the EIP packets also appear to the IP subnet
      routers an unknown IP option and is ignored in the processing.
      However, subnet routers eventually have to implement the EIP
      Extension and carry out routing based on Network Numbers when
      EIP Host Numbers are no longer globally unique.

   6) Hosts: The EIP Extension has to be implemented.  routing has to
      be done based on the Network Number in the EIP Extension field,
      and also based on the Host Number and subnet mask if subnetting
      is used. IP hosts may communication with any hosts within the
      same network at any time. During the transition period when the
      EIP Host Numbers are still unique, IP hosts can communicate with
      any hosts in other network via the translation service.

   7) DNS: A new resource record (RR) type "N" has to be added for EIP
      Network Numbers. The RR type "A", currently used for IP
      addresses, can still be used for EIP Host Numbers. RR type "N"
      entries have to be added and RR type "PTR" to be updated.  All
      other entries remain unchanged.

   8) ARP/RARP: No modifications are required. The ARP and RARP are
      used for mapping between EIP Host Numbers and physical
      addresses.

   9) ICMP: No modifications are required.

   10) TCP/UDP Checksum: No modifications are required. The pseudo



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RFC 1385                          EIP                      November 1992


       header includes the EIP Source and Destination IDs instead of
       the source and destination IP addresses.

   11) FTP: No modifications are required during the transition period
       when the IP hosts can still communicate with hosts in other
       networks via the translation service. After the transition period,
       however, the "DATA Port (Port)" command has to be modified to
       pass the port number only and ignore the IP address.  A new FTP
       command may be created to pass both the port number and the EIP
       address to allow a third party to be involved in the file
       transfer.

Transition to EIP

   In this section, we outline a plan for transition to EIP.

   EIP can greatly reduce the complexity of transition. In particular,
   there is no need for the updated hosts and subnet routers to run two
   protocols in parallel in order to achieve interoperability between
   old and new systems.  During the transition, IP hosts can still
   communicate with any machines in the same network without any
   changes.  When the EIP Host Numbers (i.e., the 32-bit IP addresses)
   are still globally unique, IP hosts can contact hosts in other
   networks via translation service provided in the border routers.

   The transition goes as follows:

   Phase 0:
        a) Choose an addressing and routing scheme for the Internet.
        b) Implement the routing protocol.
        c) Assign new Network Numbers to existing networks.

   Phase 1:
        a) Update all backbone routers and border routers.
        b) Update DNS servers.
        c) Start translation service.

   Phase 2:
        a) Update first the key hosts such as mail servers, DNS servers,
        FTP servers and central machines.
        b) Update gradually the rest of the hosts.

   Phase 3:
        a) Update subnet routers
        b) Withdraw the translation service.

   The translation service can be provided as long as the Host IDs
   (i.e., the 32-bit IP address) are still globally unique. When the IP



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RFC 1385                          EIP                      November 1992


   address space is exhausted, the translation service will be withdrawn
   and the remaining IP hosts can only communicate with hosts within the
   the same network. At the same time, networks can use any numbers in
   the 32-bit space for addressing their hosts.

Related Work

   A recent proposal called IPAE by Hinden and Crocker also attempts to
   minimize the modifications to the current IP system yet to extend the
   addressing space [12]. IPAE uses encapsulation so that the extended
   space is carried as IP data. However, it has been found that the 64
   bits IP data returned by an ICMP packet is too small to hold the
   Global IP addresses. Thus, when a router receives an ICMP generated
   by an old IP host, it is not able to convert it into a proper ICMP
   packet. More details can be found in [13].

Discussions

   EIP does not necessary increase the header length significantly as
   most of the fields in the current IP will be still needed in the new
   internet protocol. There are debates as to whether fragmentation and
   header checksum are necessary in the new internet protocol but no
   consensus has been reached.

   EIP assumes that IP hosts and routers ignore unknown IP option
   silently as required by [15,16].  Some people have expressed some
   concerns as to whether current IP routers and hosts in the Internet
   can deal with unknown IP options properly.

   In order to look into the issues further, we carried out a number of
   experiments over the use of IP option. We selected 35 hosts over 30
   countries across the Internet. A TCP test program (based on ttcp.c)
   then transmitted data to the echo port (tcp port 7) of each of the
   hosts. Two tests were carried out for each host, one with an unknown
   option (type 0x8A, length 40 bytes) and the other without any
   options.

   It is difficult to ensure that the conditions under which the two
   tests run are identical but we tried to make them as close as
   possible. The two tests (test-opt and test-noopt) run on the same
   machine a Sun4) in parallel, i.e., "test-opt& ; test-noopt&" and then
   again in the reverse order, i.e., "test-noopt& ; test-opt&", so each
   test pair actually run twice.  Each host was ping'ed before the tests
   so that the domain name information was cached before the name
   lookup.

   The experiments were carried out at three sites: UCL, Bellcore and
   Cambridge University. The tcp echo throughput (KB/Sec) results are



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RFC 1385                          EIP                      November 1992


   listed in Appendix.

   The results show that the IP option was dealt with properly and there
   is no visible performance difference under the test setup.

References

   [1] Chiappa, N., "The IP Addressing Issue", Work in Progress, October
       1990.

   [2] Clark, D., Chapin, L., Cerf, V., Braden, R., and R. Hobby,
       "Towards the Future Architecture", RFC 1287, MIT, BBN, CNRI, ISI,
       UCDavis , December 1991.

   [3] Solensky, F. and F. Kastenholz, "A Revision to IP Address
       Classifications", Work in Progress, March 1992.

   [4] Fuller, V., Li, T., Yu, J., and K. Varadhan, "Supernetting: an
       Address Assignment and Aggregation Strategy", RFC 1338, BARRNet,
       cisco, Merit, OARnet, June 1992.

   [5] Wang, Z., and J. Crowcroft, "A Two-Tier Address Structure for the
       Internet: a solution to the problem of address space exhaustion",
       RFC 1335, University College London, May 1992.

   [6] Callon, R., "TCP and UDP with Bigger Addresses (TUBA), a Simple
       Proposal for Internet Addressing and Routing", RFC 1347, DEC,
       June 1992.

   [7] Tsuchiya, P., "Pip: The 'P' Internet Protocol", Work in Progress,
       May 1992

   [8] Chiappa N., "A New IP Routing and Addressing Architecture", Work
       in Progress, 1992.

   [9] Colella, R., Gardner, E., and R. Callon, "Guidelines for OSI NSAP
       Allocation in the Internet" RFC 1237, NIST, Mitre, DEC, July
       1991.

  [10] Deering, S., "City Codes: An Alternative Scheme for OSI NSAP
       Allocation in the Internet", Work in Progress, January 1992.

  [11] Clark, D., "Building routers for the routing of tomorrow", in his
       message to [e-mail], 14 July 1992.

  [12] Hinden, R., and D. Crocker, "A Proposal for IP Address
       Encapsulation (IPAE): A Compatible Version of IP with Large
       Addresses", Work in Progress, July 1992.



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RFC 1385                          EIP                      November 1992


  [13] Partridge, C., "Re: Note on implementing IPAE", in his message to
       [e-mail], 17 July 1992.

  [14] Deering, S., "SIP: Simple Internet Protocol", Work in Progress,
       September 1992.

  [15] Braden, R., Editor, "Requirements for Internet Hosts
        -- Communication Layers", RFC 1122, ISI, October 1989.

  [16] Almquist, P., Editor, "Requirements for IP Routers", Work in
       Progress, October 1991.

Appendix

       Throughput Test from UCL (sartre.cs.ucl.ac.uk)