MARBEN OSIAM Protocol Suite

MARBEN OSIAM Protocols suite comes with a set of off-the-shelf portable C source OSI protocols.

These products cover OSI layer 3 to 7 :

• Network Layers and Routing Protocols;
• Transport Layer;
• Session Layer;
• ACSE/ROSE/Presentation Layer.

Lower layers

The MARBEN OSIAM Network Layers provide the Connection-Oriented Network Service (CONS) and the Connection-Less Network Service (CLNS). The CLNP layer is a high performance and portable implementation of the Connection-Less Network Protocol (CLNP), as specified by the ISO 8473 recommendations.

The CLNP layer supports:

• full non-segmenting and null subset protocols;
• relay function (may be used as an Intermediate System);
• multiple subnets.

Optional modules are:

• End System to Intermediate System (ES-IS) routing protocol as specified in ISO 9542;
• Intermediate System to Intermediate System (IS-IS) routing protocol (level 1 and level 2) as specified in ISO 10589;
• SubNetwork Dependent Convergence Function (SNDCF -IP/X.25) as specified in ISO 8473/add1.

The CONL layer provides the means to establish, maintain and terminate switched connections between end-systems. It conforms to ISO 8348 and is able to deal with:

• the X.25/84/88 protocol following ISO 8878;
• the X.25/80 protocol following ISO 8878-annex A or following a "pre-ISO 8878" common usage;
• multiple subnets as well as Closed User Group, Reverse Charging,….

Routing protocols

In addition to the MARBEN OSIAM Network layers, routing is provided by two optional modules:

• End System to Intermediate System (ES-IS) routing protocol as specified in ISO 9542;
• Intermediate System to Intermediate System (IS-IS) routing protocol (level 1 and level 2) as specified in ISO 10589.

ES-IS protocol operates in conjunction with or without the IS-IS protocol inside the OSI connectionless network layer protocol (CLNP). This allows to build and adjust the routing information base (RIB) automatically in End Systems (where applications are located), as well as in Intermediate Systems (network relays).

MARBEN OSIAM ES-IS supports the following procedures:

• Report Configuration by ES and by IS;
• Record Configuration by ES and by IS;
• Flush Old Configuration (ESH and ISH);
• Query Configuration;
• Configuration response;
• Request redirect;
• Refresh redirect;
• Configuration Notification;
• Flush Old Redirect;
• Assign Address on the sender side (Intermediate systems);
• Request Address on the receiver side (Intermediate systems).

The IS-IS protocol allows cooperation between every Intermediate Systems (IS) within a network in order to exchange some topology information. The knowledge by every IS of the whole network topology at a given time allows the computation of the optimal (less costly) route to any possible destination (End system or ES) on the network.

MARBEN OSIAM IS-IS encloses the following functions:

• Operation of the Level 1 and Level 2 protocol, over broadcast, static point to point sub networks and Level 1 virtual links;
• Support of the LSP database overload and overloaded IS exclusion mechanism;
• Support of the two-way connectivity mechanism. This mechanism prevents chaotic IS-IS protocol behaviors when some (broken) link-level controllers work only on one transfer side (i.e. able to receive, but not to send, or the opposite);
• Support of up to 12 area addresses per Level 1 area. This mechanism may be helpful for bypassing some topology constraints when implementing IS-IS over an existing network;
• Support of 6 bytes long system identifiers;
• Support of Level 1 manual ES adjacencies. This allows IS-IS to take into account End Systems that, for any reason, do not implement the ES-IS protocol (and therefore, that cannot be discovered dynamically);
• Support of Level 2 Reachable Address Prefixes. This allows to take into account routes to domains that do not implement IS-IS, inside the whole network domain managed by IS-IS;
• Support of the partition repair mechanism. This mechanism allows using an alternate path though Level 2 systems when the last path between two systems in the same area disappears. The related procedures may be removed if partition repair is not needed.

Transport Layer

The MARBEN OSIAM Transport layer is a high performance and portable implementation of the ISO 8073 / CCITT X.224. It provides the end-to-end control and information interchange with the level of reliability that is needed for applications.

The MARBEN OSIAM Transport layer is available as a multi-option package:

• OSI Transport Protocol Class 0;
• OSI Transport Protocol Classes 0, 2, 3 and 4 over CONS;
• OSI Transport Protocol Class 4 over CLNS;
• OSI Connection-Less Transport Service (CLTS) over CLNS;
• The MSDSG Transport Relay, also known as Active Transport Relay (ATR), allows connection between the two Transport entities. It provides a gateway between a LAN and a WAN;
• The RFC1006 module allows OSI applicative layers such as Session, Presentation, etc., to be connected using a TCP/IP network.

Both MARBEN OSIAM Transport options (over CONS or over CLNS) provide the same Connection-Oriented Transport Service (COTS).

The MARBEN OSIAM Transport layer provides:

• full Class negotiation;
• data Transfer Optimization (header prediction);
• user data in connection and disconnection phases;
• infinite Transport Service Data Unit (TSDU) size;
• implicit or explicit flow control in class 2;
• quality of service parameters;
• support of Teletex special Protocol Identifier;
• parameters which can be changed dynamically: PDU size, outgoing and incoming multiplexing, credit and ACK strategy, TS1 and TS2 timers,checksum computation, and more ...

Session Layer

The MARBEN OSIAM Session layer is a high performance portable implementation of the ISO 8327 / CCITT X.225 specifications.

It provides all the Session Subsets in version 1 and version 2: BCS, BAS, BSS.

The MARBEN OSIAM Session layer supports all functional units and particularly:

• infinite SSDU (Session Service Data Unit) size;
• optional reuse of the Transport connections;
• dynamic selection of the functional units;
• basic concatenation;
• extended concatenation (for half-duplex, full-duplex and minor synchronization functional units).

The MARBEN OSIAM Session layer uses the MARBEN OSIAM Transport CONS and/or CLNS services in a transparent mode.

Presentation, ROSE, ACSE layer

The MARBEN OSIAM Presentation layer provides the ISO services allowing application processes to interpret the meaning of the information exchanged. This layer identifies and negotiates the abstract and transfer syntax used for the communication.

MARBEN OSIAM ACSE (Association Control Service Element), and MARBEN OSIAM ROSE (Remote Operations Service Element) directly serve the end-user, which is the application process, by providing distributed information service to support and manage the communication.

MARBEN OSIAM Presentation layer supports two functional units: Kernel and Context Management. It can use Session V1 and V2.

The MARBEN OSIAM Presentation layer can be mapped onto any ISO compliant Session layer such as the MARBEN OSIAM Session layer.