draft-ietf-ccamp-tracereq-03.txt   draft-ietf-ccamp-tracereq-04.txt 
Internet Draft R. Bonica Internet Draft R. Bonica
Category: Informational MCI Category: Informational MCI
Expiration Date: November 2003 K. Kompella Expiration Date: December 2003 K. Kompella
Juniper Networks Juniper Networks
D. Meyer D. Meyer
Sprint Sprint
May 2003 June 2003
Tracing Requirements for Generic Tunnels Tracing Requirements for Generic Tunnels
draft-ietf-ccamp-tracereq-03 draft-ietf-ccamp-tracereq-04
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC-2026. all provisions of Section 10 of RFC-2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Internet-Drafts are draft documents valid for a maximum of Drafts. Internet-Drafts are draft documents valid for a maximum of
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12) Support tracing through the forwarding plane for all tunnel 12) Support tracing through the forwarding plane for all tunnel
types that implement TTL decrement, regardless of whether the types that implement TTL decrement, regardless of whether the
tunnel engages in TTL propagation. (That is, support tunnel tunnel engages in TTL propagation. (That is, support tunnel
tracing regardless of whether the TTL value is copied from an tracing regardless of whether the TTL value is copied from an
inner header to an outer header at tunnel ingress). inner header to an outer header at tunnel ingress).
Justification: Forwarding plane information is always available, Justification: Forwarding plane information is always available,
regardless of whether the tunnel engages in TTL propagation. regardless of whether the tunnel engages in TTL propagation.
13) When tracing through the control plane, display the MTU 13) When tracing through the control plane, display the MTU
associated with each hop. associated with interface that forwards datagrams through the
traced path.
Justification: MTU information is sometimes useful in identifying Justification: MTU information is sometimes useful in identifying
the root cause of forwarding plane failures. the root cause of forwarding and control plane failures.
14) When tracing through the forwarding plane, display the MTU 14) When tracing through the forwarding plane, display the MTU
associated with each hop in the reverse direction. associated with each interface that receives datagtrams along the
traced path.
Justification: MTU information is sometimes useful in identifying Justification: MTU information is sometimes useful in identifying
the root cause of forwarding plane failures. the root cause of forwarding and control plane failures.
15) Support partial traces through paths containing devices that 15) Support partial traces through paths containing devices that
do not provide protocol support for generic route tracing. When do not provide protocol support for generic route tracing. When
the application encounters such a device, it should inform the the application encounters such a device, it should inform the
user and attempt to descover details regarding the next interface user and attempt to discover details regarding the next interface
downstream. downstream.
Justification: The application must provide useful information Justification: The application must provide useful information
even if the supporting protocol is not universally deployed. even if the supporting protocol is not universally deployed.
Bonica, Kompella, Meyer [Page 5] Bonica, Kompella, Meyer [Page 5]
4. Protocol Requirements 4. Protocol Requirements
Implementors require a new protocol that supports the generic route- Implementors require a new protocol that supports the generic route-
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elicits exactly one response. Each response represents a hop that elicits exactly one response. Each response represents a hop that
that contributes to the path between two interfaces. A hop can be that contributes to the path between two interfaces. A hop can be
either a top-level IP hop or lower-level hop that is contained by a either a top-level IP hop or lower-level hop that is contained by a
tunnel. tunnel.
Justification: Because the generic route-tracing application must Justification: Because the generic route-tracing application must
trace through broken paths, the required protocol must use a separate trace through broken paths, the required protocol must use a separate
response message to deliver details regarding each hop. The protocol response message to deliver details regarding each hop. The protocol
must use a separate probe to elicit each response because the must use a separate probe to elicit each response because the
alternative approach, using the single probe with the IP Router Alert alternative approach, using the single probe with the IP Router Alert
Option, is unacceptable. Many network forward datagrams that specify Option, is unacceptable. Many networks forward datagrams that specify
IP options differently than they would forward datagrams that do not IP options differently than they would forward datagrams that do not
specify IP options. specify IP options. Therefore, the introductions of IP options would
cause the application to trace a forwarding path other than the path
that its user intended to trace.
4.2. Transport Layer Requirements 4.2. Transport Layer Requirements
UDP carries all protocol messages to their destinations. UDP carries all protocol messages to their destinations.
Justification: Because the probe/response scheme described above is Justification: Because the probe/response scheme described above is
stateless, a stateless transport is required. Candidate transports stateless, a stateless transport is required. Candidate transports
included UDP over IP, IP and ICMP. ICMP was disqualified because included UDP over IP, IP and ICMP. ICMP was disqualified because
carrying MPLS information in an ICMP datagram would constitute a carrying MPLS information in an ICMP datagram would constitute a
layer violation. IP was disqualified in order to conserve protocol layer violation. IP was disqualified in order to conserve protocol
 End of changes. 

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