Internet-Draft TwoD-IP Routing Architecture March 2022
Xu, et al. Expires 25 September 2022 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-xu-rtgwg-twod-ip-routing-01
Published:
Intended Status:
Standards Track
Expires:
Authors:
M. Xu
Tsinghua University
J. Wu
Tsinghua University
S. Yang
Shenzhen University
L. Cui
Shenzhen University
D. Wang
Hong Kong Polytechnic University

Two Dimensional IP Routing Architecture

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

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

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This Internet-Draft will expire on 25 September 2022.

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Table of Contents

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.

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.




                    +--------------------+
                    |                    |
                    |       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 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.

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:

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.

  • 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.

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.

  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.

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, , <https://www.rfc-editor.org/info/rfc2328>.
[2]
Zinin, A., Roy, A., Nguyen, L., Friedman, B., and D. Yeung, "OSPF Link-Local Signaling", RFC 5613, DOI 10.17487/RFC5613, , <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, , <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, , <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, , <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, .
[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, , <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, , <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, , <https://www.ietf.org/archive/id/draft-xu-spring-segment-twod-ip-routing-01.txt>.

Authors' Addresses

Mingwei Xu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing
100084
P.R. China
Phone: +86-10-6278-5822
Jianping Wu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing
100084
P.R. China
Phone: +86-10-6278-5983
Shu Yang
Shenzhen University
South Campus, Shenzhen University
Shenzhen
518060
P.R. China
Phone: +86-755-2653-4078
Laizhong Cui
Shenzhen University
South Campus, Shenzhen University
Shenzhen
518060
P.R. China
Phone: +86-755-8695-6280
Dan Wang
Hong Kong Polytechnic University
Department of Computing, Hong Kong Polytechnic University
Hong Kong
P.R. China
Phone: +852-2766-7267