INTERNET-DRAFT Thomas C. Shaw, Unisys Corporation Malcolm Lloyd, Unisys Corporation Expires July 2001 Submitted January 2001 Host Ip Routing, Version 1 STATUS OF THIS MEMO This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as work in progress. The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document specifies an additional ip routing technique. A host will use a route table to determine how to best transmit a network datagram packet to the destination host. The destination address is compared to a locally maintained routing table to determine the specific gateway. The best route and/or lowest metric is used to determine the gateway to use to reach the destination host. A default gateway is used if no matches are found in the routing table. This type of routing works when there is only one route to the destination address. A problem is encountered when a computer is connected to more than one network. All of the destination networks must be defined in the routing table to properly route the request back to the originating host. The default gateway will not always be able to route to the destination address. This consumes routing resources when the routing table is significantly large and impossible when dealing with the world wide Internet. Tom Shaw, Malcolm Lloyd [Page 1] INTERNET-DRAFT Host-Ip-Routing January 2001 ---- ---- -- --- -- --- - Network - - Network - -- --- -- --- ---- ---- | | ---------- ---------- - Router - - Router - ---------- ---------- | | ---------- ---------- - Switch - - Switch - ---------- ---------- | | | ++++> -------- <---- | ________________- Host -__________________ -------- <++++ <---- This diagram describes today's environment when the user networks are not known and all traffic relies on the default gateway. The incoming traffic will come in from both networks but the response will go out only on the single network. A failure in a switch or router on the response network would make the system unusable even though the other network is available. Furthermore, when hosts are connected to more than one network, as in web servers with dual ISP access, the return route is always to the default gateway. Therefore the return traffic may go out a different ISP than the way it entered the network. Solution This memo proposes using the source address to route traffic back out the same network it came in. This problem is currently being addressed in a number of ways. One of them being the use of "Hide" in firewalls and devices with similar capabilities like proxies. The hosts see the destination address as the firewall or proxy and can route using the IP routing table. Many products produce reports about a web servers usage. It is important to maintain the originators IP address to produce accurate reports. Today's reports will show the originating user as the firewall or the proxy. Tom Shaw, Malcolm Lloyd [Page 2] INTERNET-DRAFT Host-Ip-Routing January 2001 ---- ---- -- --- -- --- - Network - - Network - -- --- -- --- ---- ---- | | ---------- ---------- - Router - - Router - ---------- ---------- | | ---------- ---------- - Switch - - Switch - ---------- ---------- | | | ++++> -------- <---- | ________________- Host -__________________ -------- <++++ ----> This memo proposes allowing each network to have a default gateway. This will ensure that any incoming packet will be returned to the same network. This will simplify routing tables for hosts connected to more than one network. IP will continue to use the routing table as it does today. This change will only occur if the default gateway is used and multiple gateways are configured. IP will compare the source address of the multiple default gateways to find the originating network and use the configured gateway. Comments or suggestions can be mailed to thomas.shaw@unisys.com and malcolm.lloyd@unisys.com. AUTHORS' ADDRESSES Thomas C. Shaw Unisys Corporation 3199 Pilot Knob Road Eagan, MN 55121 Email: thomas.shaw@unisys.com Phone: 651-687-3355 Malcolm Lloyd Unisys Corporation 3199 Pilot Knob Road Eagan, MN 55121 Email: malcolm.lloyd@unisys.com Phone: 651-687-2752 Expires July 2001 Submitted January 2001 Tom Shaw, Malcolm Lloyd [Page 3]