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Versions: 00 01 02 03 04 RFC 3609
Internet Draft R. Bonica
Expiration Date: October 2003 WorldCom
K. Kompella
Juniper Networks
D. Meyer
Sprint
April 2003
Tracing Requirements for Generic Tunnels
draft-ietf-ccamp-tracereq-01
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC-2026.
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Abstract
This document specifies requirements for a generic route-tracing
application. It also specifies requirements for a protocol that will
support the generic route-tracing application. Network operators will
use the generic route-tracing application to verify proper operation
of the IP forwarding plane. They also use the generic route-tracing
application to discover details regarding tunnels that support IP
forwarding.
1. Introduction
Currently, the IETF supports several tunneling technologies.
Although these tunneling technologies provide operators with many
useful features, they also present management challenges. Operators
require a generic route-tracing application that they can use to
verify tunnel paths and diagnose tunnel faults.
This document specifies requirements for that generic route-tracing
application. It also specifies requirements for a protocol that will
support the generic route-tracing application. Network operators will
use the generic route-tracing application to verify proper operation
of the IP forwarding plane. They also use the generic route-tracing
application to discover details regarding tunnels that support IP
forwarding.
2. Review of Existing Functionality
Currently, network operators use "traceroute" to identify the path
toward any destination in an IP network. Section 3.4 of [RFC-2151]
provides a thorough description of traceroute. Although traceroute
is very reliable and very widely deployed, it is deficient with
regard to tunnel tracing.
Depending upon tunnel type, traceroute may display an entire tunnel
as a single IP hop, or it may display a tunnel as a collection of IP
hops, without indicating that they are part of a tunnel.
For example, assume that engineers deploy IP tunnels in an IP
network. Assume also that they configure a tunnel so that the head-
end router does not copy the TTL value from the inner IP header to
outer IP header. Instead, the head-end router always sets the outer
TTL value to its maximum permitted value. When engineers trace
routes through the network, traceroute will always display the tunnel
as a single IP hop, hiding all components except the tail-end
interface.
Now assume that engineers deploy MPLS in an IP network. Assume also
that engineers configure an MPLS LSP so that the ingress router
propagates the TTL value from the IP header to the MPLS header. When
engineers trace routes through the network, traceroute will display
the LSP as a series of IP hops, without indicating that they are part
of a tunnel.
3. Application Requirements
Network operators require a new route-tracing application. The new
application must provide all functionality that traceroute currently
provides. It also must provide enhanced tunnel tracing capabilities.
The following list provides specific requirements for the new route-
tracing application:
1) Support the notion of a security token as part of the tunnel
trace request. The security token identifies the tracer's
privileges in tracing tunnels. Network elements will use this
security token to determine whether or not to return the requested
information to the tracer. In particular, appropriate privileges
are required for items (2), (3), (5), (8), (9), (12), and (13).
2) Support in-line traces. An in-line trace reveals the path
between the host upon which the route-tracing application executes
and any interface in an IP network.
3) Support third party traces. A third party trace reveals the
path between any two points in an IP network. The application
that initiates a third party trace need not execute upon a host or
router that is part of the traced path. Unlike existing solutions
[RFC-2151] [RFC-2925], the application will not rely upon IP
options or require access to the SNMP agent in order to support
third-party traces.
4) When tracing through a tunnel, either as part of an in-line
trace or a third party trace, display the tunnel either as a
single IP hop or in detail. The user's request determines how the
application displays tunnels, subject to the user having
permission to do this.
5) When displaying a tunnel in detail, include the tunnel type
(e.g., GRE, MPLS), the tunnel name (if applicable) and the tunnel
identifier (if applicable). Also, include tunnel components and
round trip delay across each component.
6) Support the following tunneling technologies: GRE, MPLS, IPSEC,
GMPLS, IP-in-IP, L2TP. Be easily extensible to suppport new tunnel
technologies.
7) Trace through nested, heterogeneous tunnels (e.g., IP-in-IP
over MPLS).
8) At the users request, trace through the forwarding plane, the
control plane or both.
9) Support control plane tracing for all tunnel types. When
tracing through the control plane, the device at the head-end of a
hop reports hop details.
10) Support tracing through forwarding plane for all tunnel types
that implement TTL decrement (or some similar mechanism). When
tracing through the forwarding plane, the device at the tail-end
of a hop reports hop details.
11) Support tracing through the forwarding plane for all tunnel
types that implement TTL decrement, regardless of whether the
tunnel engages in TTL propagation. (That is, support tunnel
tracing regardless of whether the TTL value is copied from an
inner header to an outer header at tunnel ingress).
12) When tracing through the control plane, display the MTU
associated with each hop.
13) When tracing through the forwarding plane, display the MTU
associated with each hop in the reverse direction.
4. Protocol Requirements
Implementers require a new protocol that supports the application
described above. This protocol reveals the path between two points
in an IP network. When access policy permits, the protocol also
reveals tunnel details.
4.1. Information Requirements
The protocol consists of probes and probe responses. Each probe
elicits exactly one response. Each response represents a hop that
connects the head-end of the traced path to the tail-end of the
traced path. A hop can be either a top-level IP hop or lower-level
hop that is contained by a tunnel.
4.2. Transport Layer Requirements
UDP carries all protocol messages to their destinations.
4.3. Routing Requirements
The device that hosts the route-tracing application must maintain an
IP route to the head-end of the traced path. It must also maintain an
IP route to the head-end of each tunnel for which it is requesting
tunnel details. The device that hosts the tunnel tracing application
need not maintain a route to any other device that supports the
traced path.
All of the devices mentioned above must maintain an IP route back to
the device that hosts the route-tracing application.
In order for the protocol to provide tunnel details, all devices
contained by a tunnel must maintain an IP route to the tunnel
ingress.
4.4. Stateless Protocol
The protocol must be stateless. That is, no node should have to
maintain state between successive traceroute messages.
5. Security Considerations
A configurable access control policy determines the degree to which
features described herein are delivered. The access control policy
requires user identification and authorization.
As stated above, the new protocol must not introduce security holes
nor consume excessive resources (e.g., CPU, bandwidth). It also must
not be exploitable by those launching DoS attacks or replaying
messages.
6. Informative References
[RFC-2151], Kessler, G., Shepard, S., A Primer On Internet and TCP/IP
Tools and Ut ilities, RFC 2151, Hill Associates, Inc., June 1997
[RFC-2925], White, K., "Definitions of Managed Objects for Remote
Ping, Traceroute, and Lookup Operations", RFC 2925, September, 2000.
7. Acknowledgements
Thanks to Randy Bush and Steve Bellovin for their comments.
8. Author's Addresses
Ronald P. Bonica
WorldCom
22001 Loudoun County Pkwy
Ashburn, Virginia, 20147
Phone: 703 886 1681
Email: rbonica@mci.net
Kireeti Kompella
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, California 94089
Email: kireeti@juniper.net
Dave Myers
Email: dmm@sprint.net
9. Full Copyright Statement
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