JUNOS High Availability

How to Use This Book

We are assuming a certain level of knowledge from the reader. This is important. If you are not familiar with any of the assumptions in the following list, this book will occasionally veer over your head. The JUNOS documentation site is a great place to start. It’s thorough, well written, and free.

OSI model

The Open Systems Interconnection (OSI) model defines seven different layers of technology: Physical, Data Link, Network, Transport, Session, Presentation, and Application. This model allows network engineers and network vendors to easily discuss and apply technology to a specific OSI level. This segmentation allows engineers to divide the overall problem of getting one application to talk to another into discrete parts and more manageable sections. Each level has certain attributes that describe it, and each level interacts with its neighboring levels in a very well-defined manner.

Switches

These devices operate at Layer 2 of the OSI model and use logical local addressing to move frames across a network. Devices in this category include Ethernet, ATM, and Frame Relay switches.

Routers

These devices operate at Layer 3 of the OSI model and connect IP subnets to each other. Routers move packets across a network in a hop-by-hop fashion.

Ethernet

These broadcast domains connect multiple hosts together on a common infrastructure. Hosts communicate with each other using Layer 2 Media Access Control (MAC) addresses.

Point-to-point links

These network segments are often thought of as wide area network (WAN) links in that they do not contain any end users. Often these links are used to connect routers together in disparate geographical areas. Possible encapsulations used on these links include ATM, Frame Relay, Point to Point Protocol (PPP), and HDLC.

IP addressing and subnetting

Hosts using IP to communicate with each other use 32-bit addresses. Humans often use a dotted decimal format to represent this address. This address notation includes a network portion and a host portion that is normally displayed as 192.168.1.1/24.

TCP and UDP

These Layer 4 protocols define methods for communicating between hosts. TCP provides for connection-oriented communications while UDP uses a connectionless paradigm. Other benefits of using TCP include flow control, windowing/buffering, and explicit acknowledgments.

ICMP

This protocol is used by network engineers to troubleshoot and operate a network, as it is the core protocol used by the ping and traceroute (on some platforms) programs. In addition, ICMP is used to signal error and other messages between hosts in an IP-based network.

JUNOS CLI

This is the command-line interface used by Juniper Networks routers, and is the primary method for configuring, managing, and troubleshooting the router. JUNOS documentation covers the CLI in detail and is freely available on the Juniper Networks website.