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RICOCHET ROUTING

Ricochet routing, a method of sequential bankshot addressing, was originally developed to handle situations where there were more than 200 local users at a single post office (simple ricochet routing). A modified version of ricochet routing can be used to set up centrally administered and controlled mailing lists for any size organization (complex ricochet routing).

SIMPLE RICOCHET ROUTING

Simple ricochet routing requires one post office where there are over 200 local users and one router post office. The first step in setting up simple ricochet routing is to divide up all of the local users into groups of less than 200 and then to create a series of mailing lists containing less than 200 users each. In simple ricochet routing some 'r' user may be included in the mailing lists also but the number of 'r' users included in the series of mailing lists must be well under 200. The mailing lists in the series will be referred to as 'ricochet mailing lists'.

Ricochet routing delivers a message to a series of mailing lists. This is done by addressing a message in such a way as to have it sent back and forth between a router post office and the post office where the series mailing lists reside. Each time the cc:Router delivers the message to mailing list a copy of that message is sent back to the router post office then delivered to the next mailing list, etc..

NOTE: The technical reason why the number of 'r' users is limited in simple ricochet routing to well under 200 is that when the cc:Router delivers a message to a mailing list, the names of 'r' users, as opposed to local users, are enumerated in the cc:Mail message header. This is so that local users can see who, other than the users at their own post office, got the message. For ricochet routing, however, the consequence of this is that the header of the message that is
returned to the router post office will contain the cc:Mail names and addresses of the 'r' users that the message has been delivered to. On delivery of the message to one of the series of mailing lists the names of the 'r' users accumulate in the message header so that if there are close to 200 of them, the 4K message header buffer will overflow and the message will become undeliverable. This is the reason why complex ricochet routing was developed.

To set up simple ricochet routing, the list names of the ricochet mailing lists are entered into the cc:Mail directory of a router post office and a series of router mailing lists are created. Each router mailing list contains only the list name of one ricochet mailing lists at the originating post office. The first router mailing list contains the list name of the second ricochet mailing list at the originating post office and the second router mailing list contains the list name of the third ricochet mailing list at the originating post office, etc. The list names of the router mailing lists are then entered into the cc:Mail directory of the originating post office. Next, the list name of the first router mailing list is added to the first ricochet mailing list, and the name of the second router mailing list is added to the second ricochet mailing list, etc.

When messages are sent to the first ricochet mailing list they are delivered immediately to the users on that list but also sent to the first router mailing list at the router post office. When messages are delivered to the first router mailing list, they are sent back to the originating post office, addressed to the second ricochet mailing list. When messages addressed to the second ricochet mailing list are delivered, they are also sent to the second router mailing list at the router post office, etc. The last ricochet mailing list in the series does not contain the name of a router mailing list because when a message is delivered to that mailing list it has been delivered to all of the users of the series of mailing lists.

1. Create a series of ricochet mailing lists at the originating post office. Each list should contain less that 200 users.

2. Add the list names of the ricochet mailing lists to the cc:Mail directory of a router post office.

3. Create a series of router mailing lists at the router post office. The first router mailing list will contain the list name of the second ricochet mailing list; the second router mailing list will contain the list name of the third ricochet mailing list, etc.

4. Add the list names of the router mailing lists to the cc:Mail directory of the originating post office.

5. Add the list name of the first router mailing list to the first ricochet mailing list at the originating post office; add the list name of the second ricochet mailing list to the second ricochet mailing list at the originating post office, etc.

6. Add the list name of the first ricochet mailing list to the cc:Mail directories of other post offices.

7. Advise users of procedures to:

a) Address messages to the list name of the first ricochet mailing list in their cc:Mail directory in order to address messages to everyone in the mail system;

NOTE: If ricochet routing is set up exactly as described in the example, local users at the originating post office will address messages directly to the first ricochet mailing list, rather than using a list name in the cc:Mail directory, as in bankshot addressing. To create a standard procedure for all users an initial router mailing list must be created. This is discussed below.

b) Use the forward feature to send a reply to everyone by addressing the forwarded message to the list name of the first ricochet mailing list.

ORIGINATING POST OFFICE

Mailing Lists at Originating Post Office

Mailing List Name Contents of lists:

#users_a-h 166 user names + list name of #router_list1
#users_i-p 166 user names + list name of #router_list2
#users_q-z 168 user names

cc:Mail Directory of Originating Post Office:

Name Loc Address Comments
#router_list1 r router router list 1
#router_list2 r router router list 2

Mailing Lists at Router Post Office:

Mailing List Name Contents of mailing lists

#router_list1 list name #users_i-p
#router_list2 list name #users_q-z

cc:Mail Directory of Router Post Office:

Name Loc Address Comments
#users_i-p r originating po second ricochet list
#users_q-z r originating po final ricochet list

NOTE: The naming conventions of the list names in this example of simple ricochet routing are intended for illustrative purposes only. In a real-world implementation of ricochet routing the lists should be named in a way that would prevent users from accidentally sending a message to all or part of the series of ricochet mailing lists. In complex ricochet routing the ricochet mailing lists do not contain the list names of any router mailing lists, hence the lists may be used separately either directly or via bankshot addressing without accidentally causing the message to ricochet down the series of mailing lists.

In the example above users could send messages to everyone in their cc:Mail system by addressing them to the list name #all_users in their cc:Mail directories. Notice that this is not the same procedure as using an ordinary mailing list. Users at the ricochet post office may directly address messages to the first ricochet mailing list, however they would never directly address a message any other ricochet mailing lists (see above note). To create a standard procedure for all users an initial router mailing lists must be used.

To clarify how this works, let's follow the route of a cc:Mail message through this scenario:

1. At the originating post office, a user addresses a message to the first ricochet mailing list (or a user at another post office addresses a message to the list name of the first ricochet mailing list in their cc:Mail directory), #users_a-h.

2. The message is delivered to all of the first 166 users on the first ricochet mailing list, but also on this list is the list name of the first router mailing list at the router post office, router_list1 (see above example).

3. At the router post office, the message is delivered to the first router mailing list. On this list is the list name of the second ricochet mailing list, #users_i-p.

4. Back at the originating post office, the message is now delivered to next 166 users on the second ricochet mailing list, #users_i-p, but also on this list is the list name of the second router mailing list, #router_list2.

5. Again at the router post office, the message is delivered to the second router mailing list, #router_list2. On this list is the list name of the third and final ricochet mailing list at the originating post office, #users_q-z.

6. Finally, at the originating post office, the message is delivered to the last 168 users on the third ricochet mailing list, #users_q-z. This mailing list does not contain the list name of a router mailing list because it is the last mailing list in the ricochet series.

LIMITATIONS OF RICOCHET ROUTING

PROBLEM: Users whose names are on ricochet mailing lists other than the first one cannot directly reply to a message because replies will only go to the names of users on the ricochet mailing list that the user who replies is on and to all the users further down in the series of ricochet mailing lists.

SOLUTION: To reply to everyone, users must use the forward feature of cc:Mail and forward their reply to the list name of the first ricochet mailing list.

PROBLEM: If ricochet addressing is set up exactly as described in the example above, users at the ricochet post office will address messages directly to the first ricochet mailing list, while users at other post offices will address messages to the list name of first ricochet mailing list in their cc:Mail directory. The problem is, that there are two different procedures for users depending upon the post office where their mailbox is located.

SOLUTION: This problem can be solved by adding one additional router mailing list at the router post office that points to the first ricochet mailing list at the originating post office. The name of this initial router mailing list can then be used by all users to address messages using the same procedure.

NOTE: In the example above, the ricochet mailing list was used directly by local users at the originating post office and messages addressed to this mailing list cascaded down the whole series of ricochet mailing lists. Technically, this is optimal for a single post office with over 200 local users because at the time that the message is sent, it is immediately delivered to the users on the first ricochet mailing list rather than being sent to the router post office first.

PROBLEM: If ricochet addressing is set up exactly as described in the example above, it's possible for local users at the originating post to accidentally address messages to one of the ricochet mailing lists resulting in a partial mailing to the ricochet mailing lists after the one to which the message was addressed.

SOLUTION: First, assign names to the ricochet mailing lists that indicate that their function is internal to cc:Mail. An ordinary mailing list might be called #Sales, so the ricochet mailing lists should be given names that will prevent addressing errors. For example, the ricochet mailing lists might be called #~ricochet_1, #~ricochet_2, etc. It would be difficult for a user to know who would be on these lists hence an addressing error would be very unlikely.

COMPLEX RICOCHET ROUTING

Complex ricochet routing offers two important advantages over simple ricochet routing. First, complex ricochet routing allows for the mailing lists at the ricochet hub post office to used independently because messages addressed to specific mailing lists are no longer forwarded to the next mailing list in the ricochet series. Second, it allows for central administration of enterprise-wide mailing lists. In complex ricochet routing, two router post offices are used and a dedicated cc:Mail router is required.

Three post offices are used to construct the complex ricochet routing loop. The post office where the ordinary mailing lists exist is referred to as the ricochet hub post office (this will usually be an ordinary routing hub post office). The first router post office is referred to as the ricochet master post office and it is at this post office that the dedicated cc:Mail router will run. The third post office is referred to as the ricochet slave post office.

The idea is that, as in simple ricochet routing a message will be sent back and forth between a series of mailing lists at two post offices, except that in complex ricochet routing, the two post offices are the ricochet master and the ricochet slave. Each time a message is delivered to the ricochet master post office one copy is sent from the ricochet master a mailing list at the ricochet hub and another copy is sent to the ricochet slave. The message bounces back and forth through a series of mailing lists between the ricochet master and the ricochet slave until the ricochet master has sent a copy of the message to all of the mailing lists at the ricochet hub post office.

Mailing lists at the ricochet hub post office will be referred to as ricochet mailing lists (see RICOCHET MAILING LIST TYPE B). Mailing lists at the ricochet master post office will be referred to as router mailing lists. Mailing lists at the ricochet slave post office will be referred to as shadow mailing lists.

Messages will be cycled through a series of mailing lists at the ricochet slave and ricochet router mailing lists at the ricochet master. Each time a message returns to the ricochet master it is sent back to both the next shadow mailing list at the ricochet slave (actually a router mailing list) and to the next ricochet mailing list at the ricochet hub (ordinary mailing lists).

NOTE: The reason why a second router post office and a dedicated cc:Mail router are required for complex ricochet routing has to do with the enumeration of 'r' user addresses in the message header. Whenever the router delivers a message to a mailing list the cc:Mail addresses of 'r' users are enumerated in the message header. If simple ricochet routing is used, the header of a message will fill up with addresses just like a mailing list with over 200 addresses. Similarly, even with a complex ricochet routing configuration, if the cc:Mail router is located at the same post office as the ricochet mailing lists, i.e., at the ricochet hub post office, messages returned to the master-slave ricochet routing loop via the ricochet hub post office, will have the 'r' addressees enumerated in the message header and after a few passes through the ricochet routing loop the message header buffer will overflow. This is because a cc:Mail router at the ricochet hub post office would actually use only one copy of a message to both deliver to a ricochet mailing list and to pass on to the ricochet slave, thus the ricochet slave would get a copy of the message with the 'r' users enumerated in the message header. This is why ricochet routing requires a dedicated cc:Mail router.