[netmod] Key selection for next hop list in RFC8349

[Qin Wu <[e-mail]>]

Hi, Acee, Lada, Yingzhen:
In RFC8349, a string type index parameter is defined as the key for next hop list, this index has no semantics and can be used as unique ID for each next hop entry.
I am wondering why not select next hop address as the key instead of using no semantic meaning index? What's the rationale behind, when we will use index as the key, when we will use next hop address as the key?
Thanks in advance.
The following YANG data model snippets is for reference.
     grouping next-hop-content {
       description
         "Generic parameters of next hops in static routes.";
       choice next-hop-options {
         mandatory true;
         description
           "Options for next hops in static routes.

            It is expected that further cases will be added through
            augments from other modules.";
         case next-hop-list {
           container next-hop-list {
             description
               "Container for multiple next hops.";
             list next-hop {
               key "index";
               description
                 "An entry in a next-hop list.
                  Modules for address families MUST augment this list
                  with a leaf containing a next-hop address of that
                  address family.";
               leaf index {
                 type string;
                 description
                   "A user-specified identifier utilized to uniquely
                    reference the next-hop entry in the next-hop list.
                    The value of this index has no semantic meaning
                    other than for referencing the entry.";
               }
               leaf outgoing-interface {
                 type if:interface-ref;
                 description
                   "Name of the outgoing interface.";
               }
             }
           }
         }
       }
     }

-Qin