ScopeControl » History » Version 3
Junxiao Shi, 11/06/2016 07:48 AM
| 1 | 1 | Junxiao Shi | # Namespace-based Scope Control |
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| 3 | NFD performs scope control of Interest and Data according to their namespace. |
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| 4 | |||
| 5 | ## localhost Scope |
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| 7 | The localhost scope limits propagation to the applications on the originating host. |
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| 9 | Interest and Data packets under prefix `ndn:/localhost` are restricted by these rules: |
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| 11 | 2 | Junxiao Shi | * Interest can come from and go to local faces only. |
| 12 | * Data can come from and go to local faces only. |
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| 13 | 1 | Junxiao Shi | |
| 14 | ### local face |
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| 16 | Whether a face is considered "local" for scope control purpose is determined by the face implementation. |
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| 17 | 2 | Junxiao Shi | [[FaceMgmt#Static-Face-Attributes|FaceScope]] attribute indicates whether a face is local or non-local. |
| 18 | 1 | Junxiao Shi | |
| 19 | Generally, the following faces are local: |
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| 21 | 2 | Junxiao Shi | * internal face for NFD [[Management]] |
| 22 | 1 | Junxiao Shi | * UNIX-domain socket face |
| 23 | * TCP face whose remote address is a loopback address |
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| 24 | * WebSocket face whose remote address is a loopback address |
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| 26 | 2 | Junxiao Shi | A local process may connect as non-local by establishing a TCP or WebSocket connection to the IP address of a non-loopback NIC of the local machine. |
| 27 | 1 | Junxiao Shi | Since this IP address is not a loopback address, the face would be non-local. |
| 28 | This is desirable in scenarios such as a protocol translator. |
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| 30 | ## localhop Scope |
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| 32 | 3 | Junxiao Shi | The localhop scope limits propagation to no further than the next node. This scope is applied to `ndn:/localhop` namespace. |
| 33 | 1 | Junxiao Shi | |
| 34 | 3 | Junxiao Shi | Interest packets are restricted by these rules: |
| 35 | 1 | Junxiao Shi | |
| 36 | 3 | Junxiao Shi | * If an Interest is received from a local face, it can be forwarded to a non-local face. |
| 37 | * If an Interest is received from a non-local face, it cannot be forwarded to a non-local face. |
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| 38 | * In either case the Interest can be forwarded to a local face. |
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| 39 | 1 | Junxiao Shi | * PIT entry can be satisfied by Data from any source. |
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| 41 | 3 | Junxiao Shi | Data packets are unrestricted. |
| 42 | 1 | Junxiao Shi | |
| 43 | The localhop scope allows an Interest packet to travel only one hop from the consumer host, but a Data packet may travel multiple hops from the producer host. |
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| 44 | Suppose we have three hosts A-B-C in a linear topology, B can retrieve a Data under /localhop namespace from C, and this Data is cached in B's ContentStore. |
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| 45 | Later A sends an Interest to B; although B cannot forward this Interest to C, the cached Data can satisfy the Interest and would be returned to A. |