Network Working Group                                              M. Xu
Internet-Draft                                                     J. Wu
Intended status: Standards Track                     Tsinghua University
Expires: 25 September 2022                                       S. Yang
                                                                  L. Cui
                                                     Shenzhen University
                                                                 D. Wang
                                        Hong Kong Polytechnic University
                                                           24 March 2022


                Two Dimensional IP Routing Architecture
                   draft-xu-rtgwg-twod-ip-routing-01

Abstract

   This document describes Two Dimensional IP (TwoD-IP) routing, a new
   Internet routing architecture which makes forwarding decisions based
   on both source address and destination address.  This presents a
   fundamental extension for traditional routing mechanism, which makes
   forwarding decisions based on destination addresses to provides
   reachability services.  Such extension provides rooms to solve
   fundamental problems of the past and foster great innovations in the
   future.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 25 September 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Benefits of Introducing TwoD-IP Routing . . . . . . . . . . .   3
     2.1.  Multi-homing  . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Load Balancing  . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Policy Routing  . . . . . . . . . . . . . . . . . . . . .   5
     2.4.  Others  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Framework . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Routing Protocol Design . . . . . . . . . . . . . . . . . . .   7
     4.1.  Protocol Overview . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Router Actions  . . . . . . . . . . . . . . . . . . . . .   8
     4.3.  TwoD-IP Routing Table Construction  . . . . . . . . . . .   9
   5.  Forwarding Table Design . . . . . . . . . . . . . . . . . . .  10
   6.  Deployment  . . . . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Implementation Status . . . . . . . . . . . . . . . . . . . .  11
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Since IP routing took place, the current Internet has been making
   forwarding decisions based on destination addresses.  The
   destination-based routing system provides limited semantics with only
   a single path towards each destination.  Many services, such as
   multi-homing, multi-path and traffic engineering, face difficulties
   within the current Internet routing system.  Due to the important
   semantics of source address, recent years see increasing works on
   adding source addresses into routing controls.









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   IP source routing [3] carries the routes in packet header.  However,
   IP source routing is disabled in most networks due to security
   reasons.  MPLS [4] uses label switching to manage traffic per-flow.
   However, MPLS raises scalability issues when the number of label
   switching paths (LSPs) increases [5].  What's more, many ISPs prefer
   pure-IP networks.

   In this draft, we describe Two Dimensional IP (TwoD-IP) routing,
   which makes forwarding decisions based on both source and destination
   addresses.  TwoD-IP routing presents a fundamental extension of the
   semantics from the current Internet.  The network will become more
   flexible, manageable, reliable, etc.  Such extension provides rooms
   to solve problems of the past and foster innovations in the future.

   This document also presents the deployment issues and objectives of
   the TwoD-IP routing.

2.  Benefits of Introducing TwoD-IP Routing

   In this section, we list the use cases that can benefit from TwoD-IP
   routing.

2.1.  Multi-homing

   Multi-homing is prevalent among ISPs for better traffic distribution
   and reliability.  Traditionally, Provider Independent (PI) address is
   used.  Because PI address can not be aggregated by higher level ISPs,
   it will cause explosion of routing table.  To solve the problem,
   Provider Aggregatable (PA) address is proposed.  However, PA address
   complicates network configurations for ISP operators.  Besides, due
   to destination-based routing in traditional networks, PA address has
   difficulties when facing failures, i.e., the network has to re-
   compute a new path when failures happen.


















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                       +--------------------+
                       |                    |
                       |       Internet     |
                       |                    |
                       +--+---------------+-+
                          |               |
                          |  l3           | l4
                          |               |
                   +------+----+       +--+--------+
                   |   ISP1    |       |   ISP2    |
                   | Prefix P1 |       | Prefix P2 |
                   +--------+--+       +-+---------+
                            |            |
                            | l1         | l2
                         +--+------------+--+
                         |                  |
                         | Multi-homed Site |        +---------+
                         |                  +--------+  Host   |
                         +------------------+        +---------+
                                                   ISP1 address: A
                                                   ISP2 address: B


                 Figure 1: TwoD-IP routing for multi-homing

   For example, in Figure 1, assume a multi-homed site is connected to
   two ISPs: ISP1 and ISP2.  ISP1 has a prefix P1, and ISP2 has a prefix
   P2.  A host connect to the multi-homed site has two addresses,
   address A that can be aggregated into P1, and address B that can be
   aggregated into P2.  With TwoD-IP routing, the multi-homed site can
   deliver the traffic from A towards the Internet to ISP1, and deliver
   the traffic from B towards the Internet to ISP2.  If the host is
   using address A, and the link l1 or l3 fails.  Then the host can
   immediately detect the failure, then switch to address B, and
   continue to communicate with the Internet via ISP2.  With TwoD-IP,
   the host does not have to wait for routing convergence in the multi-
   homed site when failures happen.

2.2.  Load Balancing

   Compared to destination-based routing, TwoD-IP routing can manipulate
   traffic in a finer-grained granularity.  Such that TwoD-IP can
   achieve better traffic distribution.  For example, in Figure 2,
   assume that there are 5 hosts that are communicating with the same
   server at 10Mbps.  Our goal is to minimize the maximum link
   utilization over the network.  Within destination-based routing,
   traffic towards the same destination has to travel along the same
   path in the network.  Thus the best traffic distribution is to let



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   all traffic take the north route via router b, and the Min-max link
   utilization is 83.3%.


          +-----+
          |Host1+---+
          +-----+   |
          +-----+   |       60Mbps  +-----+   60Mbps
          |Host2+---+      +--------+  b  +---------+
          +-----+   |      |        +-----+         |
          +-----+   |   +--+--+                  +--+--+        +------+
          |Host3+---+---+  a  |                  |  c  +--------+Server|
          +-----+   |   +--+--+                  +--+--+        +------+
          +-----+   |      |        +-----+         |
          |Host4+---+      +________+  d  |_________+
          +-----+   |       40Mbps  +-----+   40Mbps
          +-----+   |
          |Host5+---+
          +-----+


                Figure 2: TwoD-IP routing for load balancing

   With TwoD-IP routing, we can let the traffic of three hosts (e.g.,
   Host1, Host2 and Host3) take the north route via b, and let the
   traffic of the other two hsots (e.g., Host4 and Host5) take the south
   route via d.  Thus the Min-max link utilization is only 50.0%.

2.3.  Policy Routing

   Assume in an ISP network, ISP operator wants that the traffic from
   source address A towards destination address B passes by router C.
   With TwoD-IP routing, routers make forwarding decisions based on both
   destination and source addresses, thus can easily identify the
   traffic from A towards B, and divert it to the next hop towards C.

2.4.  Others

   Besides the above-mentioned use cases, TwoD-IP routing is beneficial
   in many other use-cases.  We list the other use-cases briefly.

   *  Reliability: TwoD-IP provides multiple paths towards destination,
      rather than the shortest path only.  When one path breaks down,
      routers can immediately switch to another path.







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   *  Multi-path: TwoD-IP can forward packets towards the same
      destination, and from different sources to different next hops.
      If a host has multiple source addresses, the host will have
      multiple paths towards the same destination.

   *  Security: Traditional network pushes the security devices to the
      border routers, the intermediate network just delivers the
      packets.  With TwoD-IP, intermediate routers also have source
      checking functionality.  Thus, the whole network rather than the
      border network, can defense attacks.

3.  Framework

   In traditional routing, the control plane is concerned with the
   network status, e.g., network topology.  Within TwoD-IP routing, the
   control plane is concerned with both network status and user demands.
   TwoD-IP routing not only provides basic connectivity service, but
   also satisfies kinds of user demands, e.g., policy routing, multi-
   path and traffic engineering.  TwoD-IP routing protocol has two
   components:

   *  Destination-based routing protocol: To be compatible with
      traditional routing (especially when most networks only support
      destination-based routing), TwoD-IP routing protocol should
      support destination-based routing.  Such that ISPs can provide the
      same connectivity service, while upgrading routers with TwoD-IP
      functionality.  To provide better connectivity services,
      destination-based routing protocol should respond instantly to the
      changes of network topology.

   *  Source-related routing protocol: Combined with source addresses,
      TwoD-IP routing can make better forwarding decisions for users.
      Source-related routing protocols focus on providing services that
      are related with source addresses.  They may need to collect
      demands from users, and compute the routing table to satisfy these
      demands.  Depending on the specific user demands, some source-
      related routing protocols need real-time updates, while others do
      not.  The newly designed source-related routing protocols should
      be:

      -  Consistent, they should be consistent with other routing
         protocols, including the destination-based routing protocol and
         other new source-related routing protocols;

      -  Efficient, they should not bring lots of additional overheads
         to the network.





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   *  There are multiple ways to implement source-related routing
      protocol, such as, 1) updating OSPF [8] or IS-IS [7] protocols to
      support source-related protocols; 2) using segment routing [9] or
      software defined network controller to divert traffic according to
      user demands.

4.  Routing Protocol Design

4.1.  Protocol Overview

   In this section, to illustrate TwoD-IP routing protocol, we design a
   simple policy routing protocol.  The routing protocol provides a
   flexible tool for ISPs to divert traffic (that is from some customer
   networks towards the foreign Internet) to another path.


          +---------+
          |0.0.0.*  |     +-----------------------+     +----------+
          |         +-----+-B0       I3 ------ E0-+-----+          |
          +---------+     |   )    (              |     | 1.0.0.*  |
         Domain number=0  |    )  (               |     |          |
       The first customer |     I0                |     | 1.0.1.*  |
          +---------+     |    )  (               |     |          |
          |0.0.1.*  |     |   )    (              |     | 1.0.2.*  |
          |         +-----+-B1       I1---I2---E1-+-----+          |
          +---------+     +-----------------------+     +----------+
         Domain number=1      ISP network              Foreign Internet
      The second customer


                 Figure 3: A simple policy routing protocol

   For example, in Figure 3, the ISP has two customer networks, the
   first customer network has domain number of 0 and one prefix of
   0.0.0.*, the second customer network has domain number of 1 and one
   prefix of 0.0.1.*. The first customer network is conneted to provider
   edge router (PE router) B0 and the second customer network is
   connected to PE router B1.  The ISP is connected to the foreign
   Internet through two edge routers, E0 and E1, besides, it has four
   intermediate routers (P router), I0, I1, I2 and I3.  The shortest
   paths from the customer networks to the foreign Internet are
   B0-I0-I3-E0 and B1-I0-I3-E0.  However, due to congestion on E0, the
   ISP operator wants to divert the traffic of the second customer
   network (behind B1) to the path through E1, i.e., B1-I0-I1-I2-E1.

   We design the protocol based on the extension of OSPF [2], which can
   disseminate the information within the network.  To illustrate the
   protocol, we first clarify the following aspects.



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   *  Through e-BGP, edge routers know the prefixes of foreign Internet,
      e.g., both E0 and E1 know that there are three foreign Internet
      prefixes, 1.0.0.*, 1.0.1.*, 1.0.2.*;

   *  Through OSPF, PE routers know the prefixes of the customer
      networks behind them, e.g., B0 knows that prefix 0.0.0.* belong to
      the first customer network in Figure 3.  Besides, PE routers know
      the customer domain number of the customer networks behind them,
      e.g, B0 knows that the customer domain number of the first
      customer network is 0.  Through manual configuration or automatic
      selection (e.g., selecting the router that has lower utilization),
      edge routers know the preferences of customer networks on edge
      routers, e.g., B1 knows that the second customer network in
      Figure 3 prefers to pass by E1.

   With these preconditions, each edge router can announce the foreign
   Internet prefixes combined with its own router identification to the
   network, each PE router can announce the customer prefixes combined
   with the corresponding customer domain number, PE routers are also
   responsible for announcing the preference of customer networks on
   edge routers.  When receiving all necessary information, both PE and
   P routers will construct the routing table, which can be used to
   generate the forwarding table.

4.2.  Router Actions

   We first define three types of messages.

   Announce(Prefixes, Router_ID):  Edge routers send this message, to
      announce the binding relations between foreign IP perfixes and the
      edge router identification (can be represented by the IP address
      of the edge router).  This message indicates that traffic can
      reach the foreign Internet through the edge router.

   Bind(Prefixes, Domain_Number):  PE routers send this message, to
      announce the binding relations between customer network IP
      prefixes and customer domain number.  This message indicates that
      the customer network IP prefixes belong to the cusomter network
      that owns the Domain_Number.

   Pref(Domain_Number, Router_ID):  PE routers send this message, to
      announces the preference of a customer network on an edge router.
      This message indicates that the customer network that owns the
      Domain_Number prefers to pass by the edge router that owns the
      Router_ID.

   Then the actions on different types of routers are as follows.




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   Edge Routers:  Edge routers have to send Announce(Prefixes,
      Router_ID) to announce the foreign Internet prefixes to the
      network.  For example, in Figure 3, E0 will send Announce(1.0.0.*,
      E0), Announce(1.0.1.*, EO) and Announce(1.0.2.*, EO).  E1 will
      send Announce(1.0.0.*, E1), Announce(1.0.1.*, E1) and
      Announce(1.0.2.*, E1).

   PE Routers:
      1.  PE routers have to send Bind(Prefixes, Domain_Number) to
          announce the customer network prefixes to the network.  For
          example, B0 will send Bind(0.0.0.*, 0), B1 will send
          Bind(0.0.1.*, 1).

      2.  PE routers have to send Pref(Domain_Number, Router_ID) to
          announce the preference of the cusomter network on an edge
          routers.  For example, B1 will send Pref(1, E1).

      3.  After receiving Announce(Prefixes, Router_ID) from edge
          routers, PE routers should construct the routing table.

   Intermediate Routers:  After receiving Announce(Prefixes, Router_ID)
      from edge routers, Bind(Prefixes, Domain_Number) and
      Pref(Domain_Number, Router_ID) from PE routers, P routers should
      construct the routing table.

4.3.  TwoD-IP Routing Table Construction

   Receiving the necessary information (including customer network
   prefixes, foreign Internet prefixes and preferences of customer
   networks), both PE and P routers should construct the routing table.
   Edge routers do not need to construct the routing table, unless they
   also belong to PE/P routers.

   The routing table consists of two parts, the first part (traditional
   routing table) is constructed based on OSPF, the second part (TwoD-IP
   routing table) is construted based on our TwoD-IP policy routing
   protocol.  When forwarding a packet to the destination, routers first
   lookup the TwoD-IP routing table, if there does not exist a matched
   entry, routers will lookup the traditional routing table.  We focus
   on the construction of TwoD-IP routing table in this document.  For
   simplicity, we assume that there are only threee fields in each entry
   of TwoD-IP routing table, i.e., (Destination, Source, Next hop).
   Both the destination and source fields represent an IP prefix, the
   next hop field denotes the outgoing router interface to use (see
   Section 11 of [1] for more details).

   The routing table construction process is as follows.




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   1.  For each received Pref(Domain_Number, Router_ID), lookup the
       traditional table, and obtain the next hop towards the edge
       router that owns Router_ID.  We use Next_Hop to denote the
       obtained next hop.

   2.  For each foreign Internet prefix (Foreign_Prefix), lookup the
       traditional table, and obtain the next hop towards the
       Foreign_Prefix.  We use Next_Hop' to denote the obtained next
       hop.

   3.  If Next_Hop!=Next_Hop', for each customer network prefix
       (Customer_Prefix) that belongs to the customer network that own
       Domain_Number, we add a new entry (Foreign_Prefix,
       Customer_Prefix, Next_Hop) to the TwoD-IP routing table.

   For example, we continue the example in Figure 3, the TwoD-IP routing
   table on the P router I0 is shown in Figure 4.


           Destination          Source            Next hop
       _______________________________________________________
            1.0.0.*             0.0.1.*             I1
            1.0.1.*             0.0.1.*             I1
            1.0.2.*             0.0.1.*             I1



             Figure 4: TwoD-IP routing table on the P router I0

5.  Forwarding Table Design

   The forwarding table stores a set of 3-tuple rules, {pd, ps, nh},
   where pd is a destination prefix, ps is a source prefix, and nh
   indicates the next hop.  When a packet arrives, if its destination
   address matches pd according to LMF (longest match first) rule among
   all rules, and its source address matches ps according to LMF rule
   among all rules that are associated with pd.  Then the router will
   forward the packet to the next hop nh.

   The forwarding table design could be based on extension to TCAM, or
   algorithmic lookup in SRAM.  The newly designed forwarding table
   should satisfy the following requirements.

   *  Storage requirement: The new forwarding table should not cause
      forwarding table explosion problem.  Current storage technology
      should be able to accomodate the table.





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   *  Speed requirement: The new forwarding table should match line-
      speeds.

6.  Deployment

   TwoD-IP should support incremental deployment, and during deployment,
   the following requirements should be satisfied.

   Backward compatibility:  During deployment, reachability should be
      guaranteed, and loops should be avoided.

   Incentive:  After deploying partial routers, ISPs should be able to
      see visible gains, e.g., their policies are implemented, traffic
      distribution is improved or security level is enhanced.

   Effectivity:  The deployment should maximize the benefits for ISPs,
      e.g., the deployment sequence should be carefully scheduled, such
      that ISPs can obtain maximum benefits in each step.

7.  Implementation Status

   We have developed a prototype of the TwoD-IP policy routing protocol
   (see Section 4) based on Quagga, and set up tests with a small scale
   testbed.

8.  Security Considerations

   TwoD-IP routing will enhance the security level of the networks,
   because routers will check source addresses, which is an important
   identity of the senders.  Distributed attack defenses will be an
   important topic of TwoD-IP routing, because source checking
   functionality is deployed deeper in the network.

   However, TwoD-IP routing protocols must be carefully designed, to
   avoid to be used by hackers.

9.  IANA Considerations

   Some newly designed TwoD-IP routing protocols may need new protocol
   numbers assigned by IANA.

10.  References

10.1.  Normative References

   [1]        Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,
              <https://www.rfc-editor.org/info/rfc2328>.



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   [2]        Zinin, A., Roy, A., Nguyen, L., Friedman, B., and D.
              Yeung, "OSPF Link-Local Signaling", RFC 5613,
              DOI 10.17487/RFC5613, August 2009,
              <https://www.rfc-editor.org/info/rfc5613>.

   [3]        Estrin, D., Li, T., Rekhter, Y., Varadhan, K., and D.
              Zappala, "Source Demand Routing: Packet Format and
              Forwarding Specification (Version 1)", RFC 1940,
              DOI 10.17487/RFC1940, May 1996,
              <https://www.rfc-editor.org/info/rfc1940>.

   [4]        Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [5]        Yasukawa, S., Farrel, A., and O. Komolafe, "An Analysis of
              Scaling Issues in MPLS-TE Core Networks", RFC 5439,
              DOI 10.17487/RFC5439, February 2009,
              <https://www.rfc-editor.org/info/rfc5439>.

10.2.  Informative References

   [6]        Breitbart, Y., Chan, Chee-Yong., Garofalakis, M., Rastogi,
              R., and A. Silberschatz, "Efficiently monitoring bandwidth
              and latency in IP networks", INFOCOM 2001, April 2001.

   [7]        Baker, F. and D. Lamparter, "IPv6 Source/Destination
              Routing using IS-IS", Work in Progress, Internet-Draft,
              draft-baker-ipv6-isis-dst-src-routing-07, 18 July 2017,
              <https://www.ietf.org/archive/id/draft-baker-ipv6-isis-
              dst-src-routing-07.txt>.

   [8]        Baker, F., "IPv6 Source/Destination Routing using OSPFv3",
              Work in Progress, Internet-Draft, draft-baker-ipv6-ospf-
              dst-src-routing-03, 28 August 2013,
              <https://www.ietf.org/archive/id/draft-baker-ipv6-ospf-
              dst-src-routing-03.txt>.

   [9]        Xu, M., Wang, B., Wang, T., Yang, S., and J. Wu, "Segment
              Routing in Two Dimensional IP Routing", Work in Progress,
              Internet-Draft, draft-xu-spring-segment-twod-ip-routing-
              01, 24 February 2022, <https://www.ietf.org/archive/id/
              draft-xu-spring-segment-twod-ip-routing-01.txt>.

Authors' Addresses





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   Mingwei Xu
   Tsinghua University
   Department of Computer Science, Tsinghua University
   Beijing
   100084
   P.R. China
   Phone: +86-10-6278-5822
   Email: xmw@cernet.edu.cn


   Jianping Wu
   Tsinghua University
   Department of Computer Science, Tsinghua University
   Beijing
   100084
   P.R. China
   Phone: +86-10-6278-5983
   Email: jianping@cernet.edu.cn


   Shu Yang
   Shenzhen University
   South Campus, Shenzhen University
   Shenzhen
   518060
   P.R. China
   Phone: +86-755-2653-4078
   Email: yang.shu@szu.edu.cn


   Laizhong Cui
   Shenzhen University
   South Campus, Shenzhen University
   Shenzhen
   518060
   P.R. China
   Phone: +86-755-8695-6280
   Email: cuilz@szu.edu.cn


   Dan Wang
   Hong Kong Polytechnic University
   Department of Computing, Hong Kong Polytechnic University
   Hong Kong
   P.R. China
   Phone: +852-2766-7267
   Email: csdwang@comp.polyu.edu.hk




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