Traceroute Using an IP Option
RFC 1393
Document | Type |
RFC - Historic
(January 1993; No errata)
Obsoleted by RFC 6814
Was draft-malkin-traceroute (individual)
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Author | Gary Malkin | ||
Last updated | 2013-03-02 | ||
Stream | Legacy | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 1393 (Historic) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group G. Malkin Request for Comments: 1393 Xylogics, Inc. January 1993 Traceroute Using an IP Option Status of this Memo This memo defines an Experimental Protocol for the Internet community. Discussion and suggestions for improvement are requested. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract Traceroute serves as a valuable network debugging tool. The way in which it is currently implemented has the advantage of being automatically supported by all of the routers. It's two problems are the number of packets it generates and the amount of time it takes to run. This document specifies a new IP option and ICMP message type which duplicates the functionality of the existing traceroute method while generating fewer packets and completing in a shorter time. Table of Contents 1. Traceroute Today . . . . . . . . . . . . . . . . . . . . . 2 2. Traceroute Tomorrow . . . . . . . . . . . . . . . . . . . . 2 2.1 Basic Algorithm . . . . . . . . . . . . . . . . . . . . . . 2 2.2 IP Traceroute option format . . . . . . . . . . . . . . . . 3 2.3 ICMP Traceroute message format . . . . . . . . . . . . . . 4 3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1 Hop Counts . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2 Destination Node Operation . . . . . . . . . . . . . . . . 6 3.3 Router Operation . . . . . . . . . . . . . . . . . . . . . 6 4. References . . . . . . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . 7 6. Author's Address . . . . . . . . . . . . . . . . . . . . . 7 Malkin [Page 1] RFC 1393 Traceroute January 1993 1. Traceroute Today The existing traceroute operates by sending out a packet with a Time To Live (TTL) of 1. The first hop then sends back an ICMP [1] error message indicating that the packet could not be forwarded because the TTL expired. The packet is then resent with a TTL of 2, and the second hop returns the TTL expired. This process continues until the destination is reached. The purpose behind this is to record the source of each ICMP TTL exceeded message to provide a trace of the path the packet took to reach the destination. The advantage of this algorithm, is that every router already has the ability to send TTL exceeded messages. No special code is required. The disadvantages are the number of packets generated (2n, where n is the number of hops), the time it takes to duplicate all the nearer hops with each successive packet, and the fact that the path may change during this process. Also, this algorithm does not trace the return path, which may differ from the outbound path. 2. Traceroute Tomorrow The proposed traceroute would use a different algorithm to achieve the same goal, namely, to trace the path to a host. Because the new traceroute uses an ICMP message designed for the purpose, additional information, unavailable to the original traceroute user, can be made available. 2.1 Basic Algorithm A new IP Traceroute option will be defined. The presence of this option in an ICMP Echo (or any other) packet, hereinafter referred to as the Outbound Packet, will cause a router to send the newly defined ICMP Traceroute message to the originator of the Outbound Packet. In this way, the path of the Outbound Packet will be logged by the originator with only n+1 (instead of 2n) packets. This algorithm does not suffer from a changing path and allows the response to the Outbound Packet, hereinafter refered to as the Return Packet, to be traced (provided the Outbound Packet's destination preserves the IP Traceroute option in the Return Packet). The disadvantage of this method is that the traceroute function will have to be put into the routers. To counter this disadvantage, however, is the fact that this mechanism may be easily ported to a new IP version. Malkin [Page 2] RFC 1393 Traceroute January 1993 2.2 IP Traceroute option format 0 8 16 24 +-+-+-+-+-+-+-+-+---------------+---------------+---------------+ |F| C | Number | Length | ID Number | +-+-+-+-+-+-+-+-+---------------+---------------+---------------+ | Outbound Hop Count | Return Hop Count | +---------------+---------------+---------------+---------------+Show full document text