Networking basics © 2006 IBM Corporation Introduction to the Mainframe: Networking basics.

Networking basics

© 2006 IBM Corporation

Introduction to the Mainframe:

Networking basics

Networking basics


Chapter 1

Mainframes and Networks

Networking basics

© 2006 IBM Corporation3

Objectives

Understand the role of the network in your company's business objectives and corporate infrastructure.

After completing this chapter, you will be able to:

–Explain the use of data networks in high volume industry transaction processing

–List at least three typical advantages of a mainframe in network communications

–Describe the role of a network administrator in a large network

–List the major software components of the z/OS Communications Server.

Networking basics


Key Terms

APPN

Fiber optics

Intranet

OLTP

Backbone

Infrastructure

Mainframe

Connectivity

Integrated supply chain

Network

OSI

Extranet

Internet

Network Protocol

OSA

Networking basics


Mainframes, networks, and you

What is a network?

Definition depends on who is using the network

– IT Professional

– Engineer

Our definition of a network

Where are mainframes used today?

– ATMs

– Credit Card Payments

– Online Purchasing

Networking basics


Networks and online systems

Categories of Networks

–Internet

–Intranet

–Extranet

Terminals

Online Transaction processing

–Characteristics of OLTP

What activities add to network traffic?

Networking basics


The importance of networks

Why are networks important?

–Satisfy an objective or need.

–Provide a means for transmitting data.

–Accuracy and speed is essential to business

–Numerous businesses depend on their networks.

Examples of mainframe-based networks

–1.4.1 ATM Cash withdrawal

–1.4.2 Credit purchase at a retail store

–1.4.3 Technology choices abound in network technology

Networking basics


Who supports the network?

Separated into hardware and software

Network administrator is responsible for both

Responsibilities of a Network Administrator

–Definition, maintenance, and modification of an existing z/Series network

–Problem, isolation, and correction

–Performance tuning

–Capacity planning recommendations

–Development of operational procedures

–Training of network operators

Networking basics


What are basic elements of a data network? Basic elements are hardware, software, and protocols.

What is a network infrastructure?

Protocols

–“Traffic Rules” of the network

–Define how two devices in a network communicate

Layered network architecture model.

Networking basics


Overview of System z network capabilities

System z is capable of handling many network nodes that are dispersed over a large area.

Internal network capabilities.

–Guest machines

–LPARs

–Cluster

External network capabilities

–TCP/IP applications, protocols, and equipment

–Subarea System Network Architecture

–Advanced Peer-to-Peer Networking

–Integration of SNA into IP networks using EE

Networking basics


z/OS Communication Server

Implements the SNA and TCP/IP protocols.

Provides a set of protocols to support peer-to-peer connectivity.

Performance enhancements that can benefit a variety of TCP/IP applications.

Networking basics


SNA and TCP/IP on z/OS

What is SNA?

When were the protocols developed?

What is the advantage of SNA?

Why is TCP/IP more popular?

Networking basics


Data integrity, security, and availability in a network Data Integrity

–Modification

–Non-repudiation

–Error-free transmission

Security

–Procedures

• Preventing unauthorized disclosure of transmitted data• Detecting unauthorized modification of data• Non-repudiation using proof of origin, receipt, and digital certificates.

–Products

• IBM Security Server and Commutations Server components include RACF and Farewell.• Communications server components include parameters to encrypt network traffic• Major IBM subsystems have security mechanisms.

–Availability

• Degree to which a system is ready when needed to process data.• Enhance availability through redundancy.• Parallel Sysplex

Networking basics


Summary

A network is the hardware and software that enables computers to share files and resources and exchange data.

To support changing requirements protocols such as SNA and TCP/IP can be combined to optimize performance.

z/OS network capability includes a fully-featured communications server with integration of SNA and TCP/IP protocols.

Many technologies exists to protect data between the server and authorized clients.

Networking basics


Chapter 2

Network Protocols

Networking basics


Objectives

This chapter discusses various networking protocols.

Networking basics


Network protocols

Point to point - direct link between two hosts

Point to multipoint - direct link from one point to many others

Broadcast - multi-access with ability to address all hosts on the network

Local Area Network - LAN segment

Wide Area Network (WAN)

Networking basics


Local Area Network (LAN) Ethernet

Ethernet is believed to consist of 90% of network installations.

–Standard defined in 1985 known as IEEE 802.3

–CSMA/CD access method

–Ethernet 10 mbps

–Fast Ethernet 100 mbps

–Dual Speed Products

Gigabit Ethernet

–Retains the standard 10/100 base-T and CSMA/CD but it uses the fiber channel’s physical layer as the underlying transport mechanism

–Full Duplex does not require the CSMA/CD scheme, but retains support for the Ethernet frame format.

Networking basics


Wide area networking

Network Interface Card (NIC)

Wide Area Networking (WAN)

–The subscriber loop• What is a subscriber loop?• Asymmetric Digital Subscriber Line (ADSL)• Integrated Services Digital Network (ISDN)• ISDN Basic rate interface (BRI)• ISDN primary rate interface (PRI)

–WAN Connection type• Point to Point• Circuit switching• T1/E1• Packet switching• Frame relay

Networking basics


Network routing

Static - manual entry of routes into a table

Dynamic – populating routing tables by protocols

–Routing Information Protocol (RIP)

–Open Shortest Path First (OSPF)

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Security

Firewalls and gateways

Security protocols

Protection

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Summary

Understand the terminology

Understand the layers

–physical layer

–data link layer (Ethernet)

–network layer (IP and routing)

–transport layer (TCP and UDP)

Networking basics


Chapter 3

Network Hardware on the Mainframe

Networking basics


Objectives

Understand the different types of network links

Explain why OSA-Express is the future direction for network connectivity

Set the different OSA modes

Explain how to associate protocols with the OSA-Express

Networking basics


Key Terms

HiperSocket

Escon

Ose

VLAN

Qdio

Escon Converter

Osd

Ccl

Parallel

OSA

LPAR

NCP

Networking basics


The System z channel subsystem and network links

Each server has a channel subsystem

The CSS allows channel I/O operations to continue independently of other operations.

The purpose is to permit a z990 system to have more than 256 channels

Components

–Logical partition name

–Logical partition identifier

–MIF Image ID

–Physical Channel ID

–Channel ID

–Control Unit

–I/O Device

Networking basics


The System z channel subsystem and network links

Networking basics


Hardware channels

Parallel Channel

–Byte Multiplexer

–Block Multiplexer

Enterprise System Connectivity Channel

Networking basics


Hardware channels

Open Systems Adapter

–Integrates several hardware features and supports many networking transport protocols

–Three main versions• OSA-Express 2• OSA-Express• OSA-2

–QDIO verses non-QDIO

–QDIO incorporates a number of features:• LPAR-to-LPAR• DMA (Direct Access Memory)• Priority queuing• Enhanced IP network availability• VLAN Support• ARP Takeover

–Communication Controller for LINUX (CCL)

Networking basics


HiperSockets

Provides high-speed TCP/IP connectivity within a Central Electronics Complex.

Based on the OSA-Express queued direct input/output protocol.

–HiperSockets with CHIPD FC

–HiperSockets with CHPID FD

–HiperSockets with CHPID FE

–HiperSockets with CHIPID FF

Networking basics


Summary

The mainframe originally relied upon the channel subsystem to offload I/O processing to channel programs. DASD is still accessed using FICON and ESCON channels, but for networking connectivity, OSA-Express cards offer better performance and availability.

Networking basics


Chapter 4

Sample Configuration

Networking basics


Objectives

The objective of this chapter is to provide an introduction to the type of System z networking components and environment that many organizations deploy


–List the components of a typical System z networking infrastructure

–Give three reasons why organizations implement this type of configuration.

Networking basics


Key Terms

CF

CICS

CPC

DB2

LPAR

OSA

OMPROUTE

RAS

Service Level Agreement (SLA)

Stub Area

Sysplex

Switch

VIPA

VTAM

Networking basics


Example case Requirements for a reliable network

The ZOS Company data center•Processing is divided up physically by central processor complexes and logically by logical partitions.

•Production LPAR•Development LPAR•Systems programming LPAR•Fencing off the Production LPARs

–Key mainframe network availability aspects•Reliability, availability, serviceability (RAS)

–Component Failure–Dual and Diverse Paths–Performance–Failure Process

•Security•Scalability•Continuing compatibility•Evolving architecture

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Continued

Hardware Availability

–Switches

–OSA Cards

–CPC

–Coupling Facility

Software Availability

–OSPF

–TCP/IP

–VTAM

Networking basics


Summary

Organizations run many of their mission-critical applications on System z and system availability is a key factor in maintain an organization’s business.

Key Points

–Most organizations will have two central processor complexes (CPCs) to allow for scheduled and unscheduled outages

–Most organizations will have a geographically isolated site to allow for a disaster recover situations

–OSA card can be shared among LPARs on a CPC.

–TCP/IP VIPAs are not associated with a physical interface and assist in maintaining availability for applications and users.

Networking basics


Chapter 5

TCP/IP on z/OS

Networking basics


Objectives


–Explain the usage of the TCP/IP profile configuration file

–Explain the basics of FTP and telnetd server configuration

–Discuss the options for resolver configuration

–List some of the most common client applications

Networking basics


Key Terms

TCP/IP Profile

Send buffer size

Otelnetd

ASCII

Datagram Forwarding

Window Size

Inetd

Trace Route

Receive buffer size

FTPD

EBCDIC

netstat

Networking basics


The heart of the matter

The TCP/IP daemon implements the IP protocol tack and runs a huge number of IP applications to the same specifications as any other operating system might do.

Control issues and the stack

–A TCP/IP started task when started as a program using JCL uses a level of configurability that can’t be matched in a daemon environment.

–Example: You can support more than one instance of a TCP/IP started task.

An IPv6 apology

–This book uses IPv4, but System z fully supports IPv6.

Networking basics


The TCP/IP Profile

Sample JCL for TCP/IP task

//TCPIP PROC

//TCPIP EXEC PGM=EZBTCPIP,

//PROFILE DD DISP=SHR,DSN=SYS1.PARMLIB(PROFILE)

//SYSTCPD DD DISP=SHR,DSN=SYS1.PARMLIB(TCPDATA)

Networking basics


The TCP/IP Profile Profile Statements

–Link Configuration

Defining links, LPAR 1

DEVICE OSAEDEV1 MPCIPA PRIROUTER

LINK OSAELNK1 IPAQENET OSAEDEV1

DEVICE OSAEDEV2 MPCIPA PRIROUTER

LINK OSAELNK2 IPAQENET OSAEDEV2

DEVICE VIPADEV1 VIRTUAL 1

LINK VIPALNK1 VIRTUAL 1 VIPADEV1

HOME

201.2.11.9 VIPALNK1

201.2.11.1 OSAELNK1

201.2.11.2 OSAELNK2

Networking basics


The TCP/IP Profile

– IP Configuration

– TCP Configuration• TCPMAXRCVBUFRSIZE• TCPRCVBUFRSIZE• TCPSENDBFRSIZE

– Static Routing Information

– Automated IP Application Monitoring

Networking basics


The FTP Server

Information that can be controlled in the FTP.DATA set.

–Banner Page

–Anonymous Configuration

–Data Set Defaults

–Tracing and Logging

–File System

–SSL/TLS

–JES and DB2 environments

Character Sets

MVS and its UNIX subset

Networking basics


The telnet daemon

Two telnet Servers available in the z/OS environment:

–TN3270 – supports line mode telnet, but is primarily used to support the TN3270 Enhanced Protocol

–Z/OS UNIX Telnet server is a line mode server only.

–What is inetd?

Character sets

Networking basics


A good resolver is hard to find The resolver configuration file defines the operating characteristics of IP

applications.– Sample resolver configuration file

DOMAIN XYZ.COM HOSTNAME MAINFRAME

NAMESERVER 200.1.1.1 200.1.1.2

TCPIPJOBNAME TCPIP

Searching for resolver configuration information

–Resolver configuration parameters can be placed in the obvious location: /etc/resolv.conf

–Resolver configuration parameter can be placed in a file allocated to STSTCPD

–Resolver address space

The multi-stock environment

Networking basics


TCP/IP clients

IP applications supported by z/OS

–FTP

–telnet

–Ping

–Tracerte or traceroute

–Snmp

–Netstat

Character sets

Networking basics


Summary

The TCP/IP started task is the engine that drives all IP based activity on z/OS.

The TCP/IP profile data set controls the configuration of the TCP/IP environment.

The FTP server implements the FTP standard and can communicate with any FTP clients on the network.

IP applications running on z/OS use a resolver configuration file for environmental values.

TCP/IP on z/OS support all of the well known server and client applications

Networking basics


Chapter 6

TCP/IP in a sysplex

Networking basics


Objectives

After completing this chapter, you will learn:

–The key features of a z/OS sysplex

–How dynamic VIPA functions in a sysplex

–How dynamic XCF functions in a sysplex

–How sysplex distributor functions in a sysplex

–How the sysplex performs problem detection and recovery

–What are the routing needs of a sysplex

Networking basics


Key Terms

SYSPLEX

Multiple application-instance DVIPA

Sysplex distributor

RFC

Unique application-instance DVIPA

WLM

OSPF

Dynamic XCF

Stub area

XCF

Networking basics


Clustering in z/OS Computer cluster

–A cluster is a group of computers coupled together so they are working as one unit.

• Loosely coupled: Computers that are running with a minimum amount of communication and cooperation. Efficient use of the individual computer but limits the amount of coordination and sharing of workloads

• Tightly coupled: Very effective workload sharing and communication.

The z/OS sysplex

–Coupling facility• Handles the communication between the LPARs.• Information exchanged: Workload, status, and data transmissions.

–Workload Manager (WLM)• Can be used to define performance goals for different applications and different types of work.

• Can configure z/OS to direct traffic to the LPAR with the lightest workload.

Networking basics


Dynamic virtual addressing

DVIPA is activated in one of the two different ways;–An application explicitly issuing a bind() function call to the IP address. This is called unique application-instance DVPIPA

–A TCP/IP stack dynamically activating the address. This is called multiple application-instance DVIPA.

Unique application-instance DVPIPA–Bind()function call can do two services.

• Associate a socket with a specific IP address• Associate a socket with a specific port number

–Enabling DVIPA on a TCP/IP Stack

–Moving the DVIPA

Multiple application-instance DVIPA

Networking basics


Dynamic cross system coupling

VTAM and XCF

Establishing the links

–When a TCP/IP stack becomes active in the sysplex and this stack has DYNAMICXCF coded, the following sequence of events occurs internally within the TCP/IP stack:

• A DEVIC statement for this stack’s XCF device is automatically generated• A corresponding LINK statement is automatically generated• A HOME statement entry using the DYNAMICXCF IP address is added to the active HOME list for the stack.

• The device is started.

More than just XCF

Networking basics


Sysplex distributor

What is a tightly coupled host to do?

–Terminology• Distributing Host• Target Host• Backup Host• Combinations

Sysplex distributor in action

–TCP/IP definitions

–Walking through distributed connections

–Controlling distribution

Moving distribution to the network

Problem detection and recovery in the cluster

Networking basics


Routing in a sysplex

Routing in a sysplex

–Open Shortest Path First (OSPF)• OSPF requirements in a cluster• Rejoining an active sysplex

–Network Interface Card

Summary–Sysplex is a cluster of tightly coupled independently functioning z/OS systems

–Internal communications are handled by the coupling facility

–TCP/IP uses the coupling facility and workload manager to optimize availability and load balancing in the sysplex

–With a sysplex environment, OSPF is used to handle routing changes dynamically.

Networking basics


Summary

A sysplex is a cluster of tightly-coupled independent instances of the z/OS operating system. The internal communications within a sysplex are facilitated by the Coupling Facility. TCP/IP takes advantage of the Coupling Facility and Workload Manager to optimize availability and load balancing in a sysplex.

Networking basics


Chapter 7

Systems Network Architecture (SNA) basics and implementation

Networking basics


Objectives


–The basic concepts of SNA subarea networking

–The major components in an SNA network

–Routing and addressing in an SNA subarea

–SNA flow control

–VTAM definitions for subarea nodes

Networking basics


Key Terms

SNA

Subarea Network

Logical Unit (LU)

Virtual route

Hierarchical Network

APPN network

Systems services control point (SSCP)

Transmission group

Peer network

Physical unit (PU)

Explicit route

VTAM

Networking basics


Why you need to know about SNA today

What is SNA?

–Systems Network Architecture is a data communication architecture established by IBM.

–Different implementations of SNA can occur from product to product.

–Recognize and recover from loss of data during transmission

History

–Introduced in 1974

–IBM needed to address the issues with the errors in data transmission, and design a protocol to guarantee data integrity

Future

–TCP/IP is the dominant protocol today, but it will take a long time for SNA to disappear

–Many companies do not want to spend the money to convert from SNA…”If it ain’t broke, don’t fix it”IBM introduced new technologies to preserve the SNA and integrate it into IP. (SNA over IP)

Networking basics


SNA basics

3 Major Implementations of SNA:

–Subarea Networking

–Advanced Peer to Peer (APPN)

–High Performance Routing and SNA/IP (HPR)

Hierarchical Network structure

–Aware of all activity on the network

–Sub networks have a central point of control

Difference between TCP/IP and SNA

–TCP/IP – Connectivity with computers and data sharing

–SNA – Developed for central control

Networking basics


Subarea Networking - 1

SNA Nodes

–Send data and receive data from the network

–Processors, controllers, and workstations

–Node “types” – categorization of nodes by hardware and capabilities

–Nodes fall into two broad categories

• Hierarchical Roles (Subarea Networking)• Peer-oriented roles (APPN

–Control point – manages the network resources

System Services Control Point

–Activates, controls, and deactivates network resources in a subarea network.

–Manages resources on a subarea network level

–Coordinates the initiation and termination of sessions between applications.

–Coordinates the testing and status monitoring of resources.

Networking basics


Subarea Networking - 2

Subareas and domains

–Every z/OS system with VTAM that implements SNA is referred to as a domain.

–Explicit route• Forward explicit route• Reverse explicit route

–Logical Paths• Virtual Route (VR)• Transmission Priority (TP)• Route Extension

Connecting subarea nodes

–Transmission groups

Networking basics


Architectural components of the SNA network - 1

Physical Units

–Receives and acts upon request from the system services control point

–Manages links and link stations, while accounting for the unique aspects of different link types.

Logical Units

–Ports through which users access the SNA network.

–Logical Unit types• LU type 1• LU type 2• LU type 3• LU type 6.2

Networking basics


Architectural components of the SNA network - 2

SNA messages

– Message units that contain:• End-User data, called data requests• Network commands, called command requests

– Path information unit (PIU)• Transmission Header, Request Header, Request Unit, Response Header,

Response Unit

Initiating LU-to-LU sessions

– Class of service (COS)

Networking basics


VTAM subarea definitions - 1

Where are VTAM definitions stored?

–Stored in two data sets

–One data set stores text definitions of the SNA network and is reference by the VTAMLST DDNAME

–The second data set stores load modules and is reference by the VTAMLIB DDNAME.

Start Options

–Required Start Options• SSCPID• SSCPNAME• NETID• HOSTSA• HOSTPU

Networking basics


VTAM subarea definitions - 2

Configuration lists

– Specifies the resources that are to be activated when VTAM is started.

Defining resources to VTAM

Dynamic reconfiguration

– Dynamic definition

– Sift-down effect

Sample Network

Networking basics


Summary

An SNA network implements the IBM proprietary networking architecture.

In TCP/IP, the unit that is transferred through the network is called a packet. In SNA the unit that flows in the network is called a path information unit (PIU). It carries the data, the SNA headers, the transmission header (TH), and request header (RH).

SNA has robust data flow control that permits constant flow of data to and from the network and prevents congestion in network resources.

Although today TCP/IP is the dominant networking protocol in almost all organizations, SNA applications will exist for the foreseeable future due to the massive investment made in SNA applications.

Networking basics


Chapter 8

SNA Advanced Peer-to-Peer Networking (APPN)

Networking basics


Objectives


–What are the APPN node types

–How APPN routes SNA data

–The role of an APPN control point

–What is a boarder node

–APPN support for dependent LUs

–How to define VTAM APPN networks

–How to define a combined VTAM and APPN network

Networking basics


Introduction

APPN Comprises a group or groups of connected type 2.1 nodes

APPN allows for direct communication between any network-attached devices without the need for SSCP intervention.

Salient functions of APPN:

–Distributed directory searches

–Topology and route selection services

–Adaptive pacing and transmission priority

–Intermediate session routing

Networking basics


APPN node types - 1 Types:

–Low-entry networking (LEN) end node

–APPN end node

–APPN network node

–Interchange node

–Border node

Low entry networking node

APPN network node

–Network node server

–Provides the following:• LU-LU session services for its locally resident LUs• Intermediate session routing for LU-LU sessions of all types• Network server functions for attached APPN or LEN end nodes.• Management services focal point or relay services for network problem management

Networking basics


APPN node types - 2

APPN end node

Interchange Node

Migration data host

Networking basics


Directory Services - 1 Central directory server

–APPN network node extensions to the directory, maintained in every network node

–Central Directory Server acts as a focal point for origination broadcast searches in an APPN topology sub network.

–Number can be from 0 to several on a network

Directed Search

–Uses information stored in the directory services database of a network node server to direct the search to the location of the requested LU.

–Sending Units:• To a network node server from an end node and to an end node from a network node server

• From a network node to a central directory server when the network node does not have information on the location of the destination logical unit.

Networking basics


Directory Services - 2

– Who originates a search?• Network node server for the LUs it serves• Central Directory server

– A directed search is needed when a network node server or a central directory server receives a request of an LU that stored in its database

Broadcast search

– Each node receiving the search request sends the search to each of its network nodes.

Networking basics


Topology and route selection

Each node has a copy of the network topology

A network node uses the network topology database to computer routes for sessions that originate at LUs in its domain.

Topology database

–Created and maintained by the topology database manager.

–Consists of:• Local topology database, unique to a node• Network topology database (replicated across the network nodes)

Networking basics


Control point sessions - 1

CP-CP Session

–Established between type 2.1 nodes.

–Network node to other network nodes

–Used to perform searches for resources

–After a session is activated the topology database manager sends updates that contain the node’ topology database to the other note.

Route Selection

–Network node control point services performed• Located the destination LU • Calculate the best route

Dependent LU support

–Dependent LU Requester/Server

Networking basics


Control point sessions - 2

Border Node

–Two APPN networks can be interconnected by a border node, either extended or peripheral.

–Peripheral subnetwork boundaries

–Extended subnetwork boundaries

Connection Network

–Representation of a shares access medium enabling dynamic direct connectivity between a pair of link stations attaching to the facility.

Networking basics


Summary

APPN is the IBM strategic SNA protocol in the mainframe. It is required for sysplex, Enterprise Extender implementation, and many other technologies.

APPN is dynamic in nature and reduces the amount of predefinition required in an SNA subarea network.

In contrast to subarea networking, where special hardware and software are required for intermediate session routing, every node that can act as network node can perform routing of SNA packets.

Networking basics


Chapter 9

SNA/IP Implementation

Networking basics


Objectives Be able to learn:

–The background and motivation behind integrating SNA and TCP/IP networks.

–Technologies and solutions applied within System z based organizations, for integrating SNA and TCP/IP networks.

–The features and benefits of each of these technologies and why you might use one method over the other.

–How a z/OS network administrator would implement these technologies.

Networking basics


Key Terms

DLSW

DLSW+

HPR

802.2

LLC2

Wan

EITF

AIW

Token Ring

SDLC

Spoofing

Networking basics


Background

Organizations have a heavy investment in SNA based transaction programs, applications and networking infrastructure.

In many cases they provide the core to an organizations business. Based on figures in 1997, over twenty trillion have been invested in SNA applications in over 40,000 organizations worldwide.

Surveys indicated SNA accounts for 61% or wide area network traffic, and 66% of WAN budgets

With the pervasiveness of the internet and IP networks being the de facto standard, organizations are standardizing on TCP/IP for intranet and external partner connectivity

Networking basics


Background

A transaction oriented program is dependent on the underlying protocol it uses. The API (application Programming Interface) is different if one uses SNA or TCP/IP as the transport in the network

Changing a transaction oriented program from one protocol (i.e. SNA) to another protocol (i.e. TCP/IP) requires a re-design of the communication part in the program, replacing the code that handles error recovery, exception processing, and many other tasks

Conversion of existing SNA applications to TCP/IP-enabled applications can be economically impractical

So, how can we enable IP applications and preserve SNA-application and endpoint investment, while converging on a single network protocol?

Networking basics


Commonly used SNA over IP integration technologies

There are several different ways of running SNA and TCP/IP mixed protocol communication over single IP protocol transport networks.

The following System z Communications Server solutions are common place at organizations.

– Data link switching (DLSw). SNA traffic is encapsulated in TCP packets.

– Enterprise Extender. SNA (HPR) packets are carried as User Datagram Protocol (UDP) packets over an IP network

–Telnet/3270 (TN3270). 3270 data streams are carried over TCP connections to a server that replaces the TCP transport with SNA transport

Networking basics


Data Link Switching (DLSw) DLSw was first developed by IBM and made available in 1993, to

provide SNA support within multi-protocol routers Cisco’s implementation of DLSw is known as DLSw+ , and

contains additional enhancements to the original DLSw flavor There are two types of DLSw:

–Local: Local DLSw does not use TCP/IP, instead it enables communication between Lan-attached SNA devices and an SDLC device that is link-attached to the same DLSw route

–Remote: Remote DLSw requires at least two routers (with DLSw feature loaded) connected to each other over an TCP/IP network. DLSw performs an encapsulation, decapsulation function, wrapping the SNA frames into TCP/IP packets for transportation across the IP network

Networking basics


Data Link Switching (DLSw)

The following points summarize some of the DLSw attributes:

–DLSw is a forwarding mechanism, and supports SNA device types, PU2, PU2.1 and PU4.

–DLSw provides switching at the Data Link Layer (Layer 2), and encapsulates SNA data into TCP/IP packets for transport.

–DLSw does not provide full routing capabilities, instead DLSw is implemented within routers, the SNA end points remain the same, no change is required.

–DLSw, like any other TCP connection, utilizes the dynamic and rerouting capabilities of the IP network.

Networking basics


Enterprise Extender

What is an Enterprise Extender?

EE is an extension of SNA HPR that provides encapsulation of SNA application traffic within UDP frames by EE-capable devices at the edges of an IP network.

Enterprise Extender capable devices would include:

–z/OS EE configured Communications Server running on an z/Series Host.

–Cisco Routers with SNASw defined

–Microsoft Host Integration Server or Communications Server for Windows

Networking basics


Enterprise Extender - advantages

Ability to consolidate onto a single transport network.

Eliminates parallel networks, reduces equipment, lowers data circuit cost, simplifies network management.

No Changes required to SNA applications.

SNA can exploit the OSA Gigabit Ethernet interface cards.

Takes advantage of the re-routing capabilities of the IP router network.

Enterprise Extender solutions preserve session priority.

Networking basics


Summary

Consolidating SNA onto IP is not a simple task. Each set of SNA components and applications should be evaluated on its own merits, and a solution should be found that best suits the requirements. In some cases a solution is to replace an application or device; in other cases it is to use DLSw, SNASw, BEX, Enterprise Extender, or a combination of these.

Networking basics


Chapter 10

Telnet/3270

Networking basics


Introduction

During the last several decades, before the Internet became popular, hundreds of companies established their own SNA networks. As a result, thousands of mainframe applications were written to communicate with 3270-type terminals

During the last decade, corporate networks started implementing IP as the transport protocol on their backbone. Because so many SNA and 3270 applications existed, they looked at integrating the SNA protocol into their IP backbone.

The technology used to move from SNA 3270 applications to TCP/IP is called TN3270.

Networking basics


3270 data stream

The 3270 data stream operations are designed primarily for transmitting data between an application program and a 3270 display with keyboard or 3270 printer

The 3270 data stream is implemented using a mapped character buffer in the device.

Data received from the application program and data to be transmitted to the application program are stored in a device buffer and displayed on the screen in the form of alphanumeric characters and symbols

The mode of operation used by 3270 terminals is called full screen. Full screen means that the buffer or parts of the buffer are transferred from the application program to the 3270 device and from the 3270 device to the application program.

Networking basics


3270 data stream

Field Attributes

The field attribute defines the start of a field and the characteristics of the field. Field attribute defines the following field characteristics:

–Protected or unprotected

–Autoskip

–Nondisplay or display

–Intensified display

–Alphanumeric or numeric.

Networking basics


TN3270 description

Telnet/3270 is an enhancement of the old Telnet protocol where Telnet clients can use this protocol to access the resources on a Telnet server as if the client was directly attached to the server

The Telnet protocol is based on three principles:

–The Network Virtual Terminal (NVT) concept

–A symmetric view of terminals and processes

–Negotiation of terminal options

Networking basics


TN3270 description

TN3270 client and server must negotiate certain additional options if they are to succeed in communication. The most important of these are:

–Binary Transmission

–End of Record

–Terminal Type

Networking basics


Positioning the TN3270E server

One of the dilemmas for many mainframe installations was where to place the TN3270E server. Should it be implemented outside the mainframe on one of the following boxes?

–AIX with IBM's Communications server

–WINDOWS with IBM's communications server

–WINDOWS with Microsoft's host integration server

–One of the other many TN3270E software packages that are available

If all your 3270 applications are in the same place (same host or same Parallel Sysplex) then it probably makes sense to implement TN3270E in CS for z/OS

If your 3270 applications are in the same location but not quite as closely coupled, you can still implement TN3270 in the mainframe and use the channel to channel connection between the LPARs to connect the TN3270 server to the target application

Networking basics


TN3270 functions supported in z/OS communications server

TN3270 functions that the Communications Server supports:

–Secure Sockets Support

–Multiple Ports Support

–IP Address to LU Name Mapping (IP Filtering)

Networking basics


Implementing TN3270 server in z/OS communications server

You can implement TN3270 in z/OS communications server either within the TCP/IP stack (the TN3270 definition are imbedded in the TCP/IP profile) or in a dedicated address space

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Summary

The TN3270E protocol represents the evolution of SNA as it converged into the world of TCP/IP. It is the primary method of connecting end users to mainframe computers. It consists of a character-based data stream. TN3270E connectivity is handled on the mainframe by the TN3270E server. The TN3270E server converts a TN3270E TCP/IP connection to an SNA session. The terminal LU of the SNA session is emulated so that the SNA application functions as though it were connected to a non-

programmable 3270 terminal.

Networking basics


Chapter 11

Operations Procedures

Networking basics


Objectives

Provide an overview of the types of operational tasks a z/OS network administrator would perform or assign to another group.

List network control products that are used for controlling and displaying z/OS network component status.

List z/OS network component commands and displays that are commonly used to monitor and control the network.

Networking basics


Operational tasks

Within z/OS networking components on the mainframe, some common tasks you will be you will be expected to fulfill include:

–Fix z/OS network related faults

–Change and configure the network components

–Monitor and control the network components.

–Provide performance and usage network statistics. Work with other groups on projects, tasks and faults.

Networking basics


Description

Where to start?

Networking basics


Network startup, shutdown

The network subsystems such as VTAM and TCP/IP, and related components are normally started as part of the IPL startup sequence under z/OS

There is normally an automation software product that controls the startup, and this will have dependency checks or parent child relationships built into it, where VTAM would have to start prior to TCP/IP, and that FTP (an application daemon under TCP/IP) cannot start prior to TCP/IP is active

VTAM startup

TCP/IP startup

Networking basics



Example dependencies

–The network cannot start before the z/OS operating system and JES2 is up and going

–The network devices also need to be varied online by the operating system

–The network will startup before any applications, there is no point in starting these before the underlying network is available

–Some of the VTAM subsystem and major nodes must startup prior to TCP/IP starting

–EE cannot be enabled until both VTAM and TCP/IP are up

–Omproute is started after TCP/IP is available

Networking basics



Stopping the network

Taking VTAM down, effectively means that communication can no longer occur between end users, devices and VTAM applications, including EE. There are features and processes that organizations deploy to manage, a network takeover or movement of control when an outage occurs

The order in which the network is shutdown, is in reverse to that of a startup. Generally it would be:

–TCP/IP and VTAM Applications are stoppedEach application will have its own shutdown command.

–TCP/IP is stoppedvia: P TCPIP

–VTAM is then stoppedvia: Z NET,QUICK command

Networking basics


z/OS administrator tasks

The network administrator tasks are usually derived from:

–The Customer or organizations problem management or request system. Problems or requests might get called into a central helpdesk, then be assigned to your group for action. They will normally have a severity classification

–Project work. You may be assigned to a specific project that introduces a new function or upgrades a network software component

Networking basics


VTAM

The following commands provide examples of some of the VTAM commands that you might use in a z/OS network administration role

Displaying VTAM resources

Controlling VTAM resources

Changing VTAM resources

–Vary command

–Modify command

Networking basics


TCP/IP

TCP/IP, like VTAM, has a number of commands available to monitor, change and verify the environment.

TCP/IP provides two methods of issuing commands, either via z/OS console or SDSF log commands or TSO commands

Monitoring TCP/IP on z/OS

Changing the TCP/IP configuration

–You can alter the TCP/IP configuration with the Obeyfile command

Verifying the TCP/IP configuration

Networking basics


TCP/IP

This command displays the status of all known TCP/IP stack(s) within the z/OS LPAR

Networking basics


Documenting the network environment

Good documentation is worth its weight in gold. It is a great tool for learning about your network environment and helps reduce the time it takes for you to resolve a problem or find out information

The type of information you might expect to find in this type of documentation includes:

–Network component overview diagram

–Network component description

–External connections

–Network naming conventions

–Network processes

–Network related products, tools, exits, and automation

–Change log

–Problem log

–Contact details

Networking basics


Chapter 12

Problem Determination

Networking basics


Objectives

Be able to learn:

•The different system dumps

•The different VTAM traces

•The z/OS commands to display or modify data and settings

•The messages associated with each component

Networking basics


Key Terms

Dump

Command

Component

CSM

GF

NETSTAT

Trace

Symptoms

Tools

Storage

VIT

Buffer

Networking basics


Houston, we have a problem

Keeping the network problem free and responsive is a priority, so determining where a problem lies and fixing it quickly is imperative

Your first sign that there is a network problem likely will come from users or operators. Users might complain about:

–An unusual message received

–The system behavior being different than the past

–Slow response time on the network

–No response from the system

–System operators might report:

• Poor performance• A TCP/IP or VTAM abend• A loop or wait on the sub-system (TCP/IP, VTAM)

Networking basics


Houston, we have a problem

To begin, determine the general cause of the problem:

Read messages in the system log. Each z/OS component has a unique message prefix that identifies the component:–VTAM messages are prefixed with “IST”–TCP/IP messages are prefixed with “EZZ”–CSM messages are prefixed with “IVT”–TSO messages are prefixed by “IKT”

Look for suffix “E,” which stands for “Error.” Check the messages manual for an explanation of the error.

Check to see if the system created a dump at error time.

Find out if the system has changed; for example, whether the procedures for any components have changed:–VTAM start–TCP/IP start–TCP/IP profile–BUFFERS

Networking basics


Tools and diagnostic aids

VTAM tools and diagnostic aids

–Abnormal end (Abend) Dump

–Stand-Alone Dump

–SVC Dump

–First Failure Support Technology (FFST) Dump

–Network Traces

–Sense Codes

–VTAM Internal Trace

–Other VTAM Traces

–VTAM DISPLAY Commands

Networking basics



From SDSF, you can issue the commands to display aspects of VTAM. For output of the command view the “LOG” (System Log) panel. Examples include:–D NET,APPLS

Status of application program major and minor nodes

–D NET,BFRUSE

VTAM buffer usage

–D NET,CSM

Communications storage manager buffer pools

–D NET,MAJNODES

Status of major nodes

Networking basics



Examples of the DISPLAY command

Networking basics


TCP/IP tools and diagnostic aids

Abend Dump

Stand-Alone Dump

SVC Dump

TCP/IP component trace

TCP/IP DISPLAY Commands for Problem Determination

PING command

TRACERTE command

Networking basics


TCP/IP tools and diagnostic aids

Example of a DISPLAY command

Networking basics


VTAM problems Abend message

Activating network nodes takes too long

Application program reports an unexpected return or sense code

Deactivating network nodes takes too long

Error message

Hung session, LU, or terminal

Hung system

IST error message

LOGON takes too long to complete

Performance is degraded after a network outage

Response time is slow

Storage message IST154I or IST561I-IST566I

Networking basics


VTAM Problems

Determining VTAM problems on the Network

PTF Number

Device Type

Terminal Action

VTAM Application Program

Hardware Error Condition

Coding Change

Networking basics


TCP/IP Problem Determination

Various messages appearing in the console log or in the SYSPRINT, SYSERR, SYSERROR, and SYSDEBUG data sets, together with alerts and diagnostic aids provide information that helps you to find the source of a problem

To find the SYSPRINT, SYSERR, SYSERROR, and SYSDEBUG data sets, check the DDNAMEs specified in the startup procedure for TCPIP.

Networking basics


TCP/IP Problem Determination Recommended Documentation for TCP/IP Problems

PTF Number

–If the problem appears after you apply a PTF (program temporary fix).

MCL Number

–If the problem appears after IBM has applied microcode level.

Profile TCP/IP

–If the problem appears after a modification or an addition of a device.

Network Topology

–If the problem is associated at a NETWORK modification (equipment change, configuration change).

Hardware Error

–Sometimes it is immediately apparent that a problem is related to a specific hardware error condition.

–If a hardware error occurred, note the failure condition that accompanied it, such as UNIT CHECK or CHANNEL-END/DEVICE-END.

Networking basics


CSM

CSM is a component of VTAM that enables host applications to share data with VTAM and other CSM users without having to physically copy the data. CSM reduces CPU utilization and optimizes system performance during the transfer of bulk data by enabling applications to share buffers

The code for CSM comes with VTAM, but once CSM is started it runs independently of VTAM and can be used by other MVS tasks and subsystems

CSM is started automatically when it is first invoked, and continues to run even if VTAM terminates. While CSM is not in use it retains a minimum amount of storage. It terminates only when MVS itself terminates

Networking basics


SNIFFER

When the problem seems to be outside the mainframe, we need to take a SNIFFER trace on different LAN segments to determine what is the problem root cause (station, fiber, protocol, router)

There are a lot of tools utilizing packet sniffers, network monitors, and protocol analyzers designed for LAN administrators, security professionals and network programmers.

The most used SNIFFER Tool is from NAI or ETHEREAL which is an Open Source Software released under the GNU General Public License.

An example of a Sniffer is the Distinct Network Monitor, which is a packet capture and network protocol analyzer software that translates complex protocol negotiation into natural language, pinpointing where errors occurred.

Networking basics


SNIFFER

This example shows traffic distribution by MAC address

Networking basics


Chapter 13

Performance tuning and capacity planning

Networking basics


Objectives

Be able to:

–Understand network tuning and capacity planning concepts

–Monitor the network for performance problems

–Determine network performance bottlenecks

–Use tools to fix performance problems

Networking basics


Key Terms

Performance

Bottleneck

Capacity Planning

Tuning

Monitor

RMF

Networking basics


Tuning and capacity planning overview

In a computer system, performance tuning is the skill of allocating existing resources to meet business objectives; these are often specified by the business in a service level agreement or SLA. In contrast, capacity planning is the means by which an IT professional predicts the resources that will be needed to meet future service objectives.

Similar approaches can be used for both performance tuning and capacity planning:

–Comparison with other systems

–Creating a transaction profile

–Assessing the costs of implementing new functions

–Using a performance modeling system

–Testing the system with industry standard benchmarks, such as the Teleprocessing Network Simulator (TPNS)

Networking basics


Tuning and Capacity Planning Overview

Networking basics


Defining performance management

Performance management means monitoring and allocating data processing resources to an application, according to a service level agreement (SLA) or informal objectives

The SLA is a contract that objectively describes such measurables as:

–Average transaction response time for network, I/O, CPU, or total

–The distribution of these response times (for example, 90% TSO trivial at less than 0.2 of a second)

–Transaction volumes

–System availability

Networking basics


Defining capacity planning

Capacity planning is a process of planning for sufficient computer capacity in a cost-effective manner to meet the service needs for all users.

Capacity planning involves asking the following questions:

–How much of your computer resources are being used?

–CPU, Processor Storage, I/O, Network

–Which workloads are consuming the resources (workload distribution)?

–What are the expected growth rates?

–When will the demands on current resources impact service levels?

Networking basics


What is a performance problem?

Most performance problems revolve around unacceptably high response times or resource usage, which we can collectively refer to as “pain”.

Some network bottlenecks can be caused by the following:

–Client-network interface

–Network bandwidth

–Network topology

–Server network interface

–Server CPU load

–Server memory usage

–Server bandwidth

–Inefficient configuration

Networking basics


Monitoring using RMF

RMF issues reports about performance problems as they occur, so that the mainframe IT staff can take action before the problems become critical.

Your installation can use RMF to:

–Determine that your system is running smoothly

–Detect system bottlenecks caused by contention for resources

–Evaluate the service your installation provides to different groups of users

–Identify the workload delayed and the reason for the delay

–Monitor system failures, system stalls, and failures of selected applications

Networking basics


Monitoring using RMF

Processor Problems

I/O Problems

Storage Problems

Sysplex Problems

Networking basics


Network performance and capacity planning

Performance and capacity management

–Resolving performance problems

–Extending the life of hardware

–Maintaining service levels in the face of application growth

–Exploiting technology

–Supporting software and hardware changes

–Ensuring new applications perform well

–Managing with scarcer skills

Examine the performance data in depth and focus on the essence of the questions you want to solve

Networking basics


Performance tools

NetView(R) Performance Monitor

Tivoli Monitoring for Network Performance

ASG-TMON for TCP/IP

OMEGAMON

zPCR

Networking basics


Performance Tools

TCP/IP performance checklist

Networking basics


Summary

The network administrator should first determine the general cause of the problem by reading error messages, checking for system memory dumps, checking to see if software or hardware has changed, and reading the system log. After determining the general cause of the problem, the network administrator should use the tools and diagnostic aids at hand to determine the specific cause of the problem. Lastly, tuning tasks should be carried out to ensure good network performance.

z/OS has diagnostic aids that the network administrator can use: abend dumps, stand-alone dumps, and supervisor call (SVC) dumps, which the Interactive Problem Control System can format for easier reading. Additionally, VTAM has specific aids, such as First Failure Support Technology, CSDUMPs, network traces, sense codes, VTAM traces, and commands that display the state of VTAM components and resources. TCP/IP has component traces and diagnostic commands (such as the NETSTAT command) that help determine problems in the IP network. Communications Storage Manager (CSM) problems generally manifest themselves as central storage problems. The network administrator can display CSM’s use of storage, activate CSM VTAM traces, and dump CSM storage for analysis.

Networking basics


Chapter 14

Change Control Procedures

Networking basics


Objectives

Be able to learn:

–Why Change Control is important from a z/OS networking perspective

–IT related Groups and areas that the z/OS networking administrator interacts with you will need to interact with during Changes

–Examples of types of changes and process that should be followed

–Some good practice and habits to use

Networking basics


Importance of change control

Change Control has become increasingly important as organizations focus on availability to their clients and revenue.

The z/Series platform should be treated with respect, the z/OS platform normally provides the core to an organizations business applications. If any of the components are unavailable on the z/OS environment, it can have a severe impact on revenue and client satisfaction

Implementing change is probably the greatest cause of component failure on z/OS, whether it be a coding error, incorrect command issued, unknown relationship with another component, the list goes on

The Change Control process is all about reducing risk and implementing change successfully.

Networking basics


Remember, this is not a single user system

Do not forget, that z/OS systems are used by many users and applications. Some systems may have in access of 30,000 interactive users. Any network change should be treated with respect, be well planned, and have processes in place for implementation and back out.

Networking basics


Change control process and relationships

All IT organizations will have a change control application or process, that you will be required to use and follow. There are a lot of different applications available, and are sometimes not that intuitive

In general the process might look like:

–Research component change, problem or request.

–Establish what needs to be done.

–How will you test the change ?

–Build and submit your change plan

–Test your change

–Change gets approved and scheduled

–Are there any other groups that need to know about your change ?

–Implement your change

–Complete and close change control form

Networking basics


Groups you will interact with

Change Control

Security

Operations

System Programmers

business users

Testers

Team leader

WAN group

Networking basics


Good habits

Log your changes, the How Why and When

Take a backup, take a backup, take a backup

Document your naming convention

Add comments to your configuration members

Take regular snapshots

Networking basics


Change Interaction

Change control

WAN group

Server group

z/OS group

Customer

Networking basics


Example changes and process

Telnet server update, dynamic vs. static changes

Networking basics


Good practice and habits

Telnet server Test=yes

Backup members , libraries

Always have back out, contingency plan in place

Create repeatable change templates, or refine process

Document, document, document

Understand impact of change

Networking basics © 2006 IBM Corporation Introduction to the Mainframe: Networking basics.

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