1 University of California, Irvine Done By : Ala Khalifeh (Note : Not Presented)

2 APPN: Advanced Peer-to-Peer Networking This survey done by  Ala’ Khalifeh- Overview  Link g4/nd2006.htm# g4/nd2006.htm# / /  Application/Issue A Peer to Peer architecture proposed by IBM as an improvement to the SNA architecture.

3 Overview SNA (Systems Network Architecture) is one of the most popular network architecture models, proposed by IBM. SNA was designed around the host-to-terminal communication model that IBM's mainframes use. IBM expanded the SNA protocol to support peer-to-peer networking. This expansion was deemed Advanced Peer-to-Peer Networking (APPN) and Advanced Program-to-Program Communication (APPC). Advanced Peer-to-Peer Networking (APPN) represents IBM's second-generation SNA. In creating APPN. IBM moved SNA from a hierarchical, mainframe-centric environment to a peer-to-peer (P2P) networking environment.

4 Overview (Continued) Cisco’s IBM Internetworking Strategy  Cisco is the industry leader in the integration of IBM SNA networks within the framework of today’s expanding multiprotocol global internetworks. In 1993, Cisco held over 67 percent of the SNA router market, according to an IDC study. Cisco Implementation of APPN  Cisco licensed the APPN source code from IBM and then ported it to the Cisco IOS software using network services from the data-link controls (DLCs).

5 Overview (Continued) Cisco Implementation of APPN  Cisco licensed the APPN source code from IBM and then ported it to the Cisco IOS software using network services from the data-link controls (DLCs).

6 APPN Features APPN features include: Better distributed network control; because the organization is peer- to-peer rather than solely hierarchical, failed nodes can be isolated. Dynamic peer-to-peer exchange of information about network topology, which enables easier connections, reconfigurations, and routing. Dynamic definition of available network resources Automation of resource registration and directory lookup Flexibility, which allows APPN to be used in any type of network topology

7 Network Architecture An APPN network is composed of three types of APPN node:  Low Entry Networking (LEN) Node – The End user peripheral  End Node- An End Node is similar to a LEN node in that it participates at the periphery of an APPN network. An End Node includes a Control Point (CP) for network control information exchange with an adjacent network node.  Network Node - The backbone of an APPN network is composed of one or more Network Nodes which provide network services to attached LEN and End Nodes.

8 Network Architecture (Continued)

9 Session Initialization In order for an APPN session to be established, the following must occur: 1. The end user requests a session with an application, which causes the end node to begin the process of session establishment by sending a LOCATE message to its network node server. For session initiation, the network node server provides the path to the destination end node, which allows the originating end node to send messages directly to the destination.

10 Session Initialization (Continued) 2. The network node uses directory services to locate the destination by first checking its internal directories.  If the destination is not included in the internal directory, the network node sends a LOCATE request to the central directory server if one is available.  If a central directory server is not available, the network node sends a LOCATE broadcast to the adjacent network nodes that in turn propagate the LOCATE throughout the network.  The network node server of the destination returns a reply that indicates the location of the destination.

11 Session Initialization (Continued) 3. Based on the location of the destination, the network node server of the originator selects the least expensive path that provides the appropriate level of service. 4. The originating network node server sends a LOCATE reply to the originating end node. The LOCATE reply provides the path to the destination.

12 Session Initialization (Continued) 5. The originating end node is then responsible for initiating the session. A BIND is sent from the originating end node to the destination end node, requesting a session. After the destination replies to the BIND, session traffic can flow.

13 Routing Session connectors are used in place of routing tables in APPN. The unique session identifier and port from one side of the node are mapped to the unique session identifier and port on the other side. As data traffic passes through the node, the unique session identifier in the header is swapped for the outgoing identifier and sent out on the appropriate port, as shown in FigureFigure

14 Routing (Continued)

15 Topology Management Bootstrapping  APPN is a link-state protocol. Like other link- state-based algorithms, it maintains a database of the entire topology information of the network.  Every APPN network node in the network sends out TDU (Topology Database Update) packets that describe the current state of all its links to its adjacent network nodes.

16 Topology Management (Continued) The TDU contains information that identifies the following:  The characteristics of the sending node  The node and link characteristics of the various resources in the network  The sequence number of the most recent update for each described resource. A network node that receives a TDU packet propagates this information to its adjacent network nodes using a flow reduction technique

17 Topology Management (Continued) APPN network node maintains full knowledge of the network and how the network is interconnected. Once a network node detects a change to the network (either a change to the link, or the node), it floods TDUs throughout the network to ensure rapid convergence. If there is an unstable link in the network, it can potentially cause many TDU flows in a network. As the number of network nodes and links increases, so does the number of TDU flows in the network. This type of distributing topology can consume significant CPU cycles, memory, and bandwidth. Maintaining routes and a large, complete topology subnet can require a significant amount of dynamic memory.

18 Categorization-1 Yes Download Yes Centralized Hybrid yes YesDecentralized SearchStorageTopologyInitialization Functional Criteria The degree of decentralization

19 Categorization-2 Download Yes Structured Loosely structured Yes Unstructured SearchStorageTopologyInitialization Functional Criteria The degree of structure

20 Categorization-3 Download Security full redund ancy Reliability Scalability Uses topology database updates (TDUs) Adaptability Uses LOCATE search requests. Efficiency SearchStorageTopologyInitialization Functional Criteria Requirements