Path: A sequence of adjacent path elements over which a packet can be transmitted, starting and ending with a node. A path is unidirectional. Paths are time-dependent, i.e., the sequence of path elements over which packets are sent from one node to another may change. A path is defined between two nodes. For multicast or broadcast, a packet may be sent by one node and received by multiple nodes. In this case, the packet is sent over multiple paths at once, one path for each combination of sending and receiving node; these paths do not have to be disjoint. Note that an entity may have only partial visibility of the path elements that comprise a path and visibility may change over time. Different entities may have different visibility of a path and/or treat path elements at different levels of abstraction.
For purposes of this document, "path aware networking" describes endpoint discovery of the properties of paths they use for communication across an internetwork, and endpoint reaction to these properties that affects routing and/or data transfer. Note that this can and already does happen to some extent in the current Internet architecture; this definition expands current techniques of path discovery and manipulation to cross administrative domain boundaries and up to the transport and application layers at the endpoints. Expanding on this definition, a "path aware internetwork" is one in which endpoint discovery of path properties and endpoint selection of paths used by traffic exchanged by the endpoint are explicitly supported, regardless of the specific design of the protocol features which enable this discovery and selection.
Lesson | Category |
---|---|
Justifying Deployment ( |
Invariant |
Providing Benefits for Early Adopters ( |
Invariant |
Providing Benefits during Partial Deployment ( |
Invariant |
Outperforming End-to-End Protocol Mechanisms ( |
Variable |
Paying for Path Aware Techniques ( |
Invariant |
Impact on Operational Practices ( |
Invariant |
Per-Connection State ( |
Variable |
Keeping Traffic on Fast Paths ( |
Variable |
Endpoints Trusting Intermediate Nodes ( |
Not Now |
Intermediate Nodes Trusting Endpoints ( |
Not Now |
Reacting to Distant Signals ( |
Variable |
Support in Endpoint Protocol Stacks ( |
Variable |
Planning for Failure ( |
Invariant |
IGD problem #1: one of the most popular versions from one of the most popular vendors. When a data packet arrives with either ECT(0) or ECT(1) (indicating successful ECN capability negotiation) indicated, router crashed. Cannot be recovered at TCP layer [sic]