Dear all,
We have revised the document and handled all issues except the overlapping
prefixes. In the spirit of keeping the protocol simple, we propose the
following revision to handle the case. A fast action to resolve this final
issue will be greatly beneficial.
Thanks!
Richard
New text of Section 5.2:
---------------------------
5.2. Endpoint Addresses
The endpoints aggregated into a PID are denoted by endpoint
addresses. There are many types of addresses, such as IP addresses,
MAC addresses, or overlay IDs. This specification only considers IP
addresses.
5.2.1. IP Addresses
When either an ALTO Client or an ALTO Server needs to determine which
PID in a Network Map contains a particular IP address, longest-prefix
matching MUST be used.
A Network Map MUST define a PID for each possible address in the IP
address space for all of the address types contained in the map. A
RECOMMENDED way to satisfy this property is to define a PID with the
shortest enclosing prefix of the addresses provided in the map. For
a map with full IPv4 reachability, this would mean including the
0.0.0.0/0 prefix in a PID; for full IPv6 reachability, this would be
the ::/0 prefix.
This document focuses on Network Maps that do not define two or more
PIDs that contain an identical IP prefix. We refer to such Network
Maps as Non-Overlapping Network Maps. To illustrate Non-Overlapping
Network Maps, consider an example IPv4 Network Map NMa_A, which
consists of two PIDs, where the first PID contains {10.0.0.0/15,
0.0.0.0/0} and the second contains {10.0.0.0/16, 10.1.0.0/16}. This
is a Non-Overlapping Network Map. A variation of NMap_A, which can be
derived by merging the two IP prefixes defined in the second PID of
NMap_A as {10.0.0.0/15}, is not a Non-Overlapping Network Map.
A Non-Overlapping Network Map ensures that the longest-prefix
matching algorithm maps each endpoint represented by an IP address
into exactly one PID. Specifically, to map an IP address to its PID
in a Non-Overlapping Network Map, one considers the set S which
consists of all prefixes defined in the Network Map, applies the the
longest-prefix mapping algorithm to S to identify the longest prefix
containing the IP address, and assigns that the IP address belongs to
the PID containing the identified longest prefix. Consider the
preceding example Network Map NMap_A. The IP address 10.0.0.1 will be
identified as in the second PID.
To handle both Non-Overlapping and Overlapping Network Maps, an ALTO
Client moves any IP prefix that is defined in more than one PIDs into
a special PID named .OVERLAP, and then applies the longest-prefix
matching algorithm. A future extension of this document may redefine
how overlapping prefixes are handled.
5.3. Example Network Map
We use the Network Map shown in Figure 3 in most examples of this
document.
.------------------------------------------------------------.
| An ALTO Network Map |
| |
| .-----------------------------------. .----------------. |
| | NetLoc: PID-1 | | NetLoc: PID-3 | |
| | .------------------------------. | | | |
| | | 192.0.2.0/24 | | | .-----------. | |
| | | .--------------------------. | | | | 0.0.0.0/0 | | |
| | | | Endpoint: 192.0.2.34 | | | | `-----------` | |
| | | `--------------------------` | | | | |
| | `------------------------------` | | | |
| | .------------------------------. | | | |
| | | 198.51.100.0/25 | | | | |
| | | .--------------------------. | | | | |
| | | | Endpoint: 198.51.100.100 | | | | | |
| | | `--------------------------` | | | | |
| | `------------------------------` | | | |
| `-----------------------------------` | | |
| | | |
| .-----------------------------------. | | |
| | NetLoc: PID-2 | | | |
| | .------------------------------. | | | |
| | | 198.51.100.128/25 | | | | |
| | `------------------------------` | | | |
| `-----------------------------------` `----------------` |
`------------------------------------------------------------`
Figure 3: Example Network Map.
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