Re: M3UA AS override mode from SGP perspective
Chris Benson <[email protected]>
| Newsgroups | gmane.ietf.sigtran |
|---|---|
| Message-ID | <[email protected]> |
Mikhail, It is the individual ASPs (endpoints) that are active or not active - rather than M3UA connections (or SCTP associations) being active or not active. The number of current connections is not equivalent to whether they can be used to tranfer user data to the AS. An M3UA traffic mode specifies how one side wishes to RECEIVE traffic. In the example you cite, the whole AS (all four ASPs) are in "Override mode". This means that within the AS there can only be one currently active ASP (except for a tiny window of time when changing from one ASP to another). This rule (only one ASP in use) must be honoured by both SGP1 and SGP2. This means in your example, that there must be two M3UA connections at all [active] times: for example between SGP1 and ASP3 as well as between SGP2 and ASP3. Later this may change to these two connections: SGP1 <==> ASP2 and SGP2 <==> ASP2. There may be other M3UA connections, but they cannot be used to transfer user data (nor most other messages) from any SGP to a non-active ASP. This sounds a little more complicated when considering IPSP-DE mode, where within the same connection, one side can be ACTIVE (can receive data) and the other side INACTIVE or DOWN (cannot receive data). This only discussed how the AS wishes to RECEIVE traffic (one ASP at a time), and does not consider that the SG has an independent traffic mode for how it wishes to share traffic coming in to SGP1 or SGP2. With thanks, from Chris Benson. On Fri, 1 Oct 2010, Mikhail Plotkin wrote: >> Date: Fri, 1 Oct 2010 01:19:32 +0400 >> From: Mikhail Plotkin <[email protected]> >> To: <[email protected]> >> Subject: [Sigtran] M3UA AS override mode from SGP perspective >> >> Hi, >> >> It is not obvious for me how the M3UA "Override mode" should be understood from the description in RFC4666 (ch. 4.3.4.3). >> >> Consider the following configuration: Local side is SG and it has two SGPs each connected with two remote ASPs. Note that both SGPs are handled by the same SW process! The consideration is within the same AS, which is served by all 4 ASPs: >> >> Local Side Remote Side >> +------------+ >> -------assoc11-------|ASP_1 | >> +----------+ / | | >> | SGP_1| --------assoc12-------|ASP_2 | >> | | | | >> | SG | | AS | >> | | | | >> | SGP_2| --------assoc23-------|ASP_3 | >> +----------+ \ | | >> -------assoc24-------|ASP_4 | >> +------------+ >> >> If the AS works in an Override mode, then how many associations (max) may be simultaneously active in this configuration? I see two options: >> >> Option 1. There can be only one association active within the AS at the same time. So if any of the remote ASPs activates, all other ASPs will receive Notify(Alternative ASP active). >> >> Option 2. There can be two associations active within the AS at the same time: one of {assoc11, assoc12} and one of {assoc23, assoc24}. So activation of ASP_1 or ASP_2 does not affect SGP_2. >> >> >> BR/ Mikhail >> >> _______________________________________________ >> Sigtran mailing list >> [email protected] >> https://www.ietf.org/mailman/listinfo/sigtran >>