Network Hardware

Network Hardware Chapter 15

Introduction • Nothing is influencing our culture today more than the ability to move large amounts of data from one place to another very quickly. • We now have world-wide connectivity at a level that only die-hard sci-fi fanatics would have dreamed of just a few years ago. • Behind all of this craziness is fancy network hardware and - you guessed it - a whole bunch of stuff that originated in the deep dark caves of UNIX Chapter 15 - Network Hardware

Introduction • Keeping up with these fast-moving bits is a challenge. • The speed and reliability of your network has a direct effect on your organization’s productivity. • A poorly designed network is a personal and professional embarrassment. • It can be very expensive to fix Chapter 15 - Network Hardware

Introduction • At least three major factors contribute to a successful installation: • Development of a reasonable network design • Selection of high-quality hardware • Proper installation and documentation. Chapter 15 - Network Hardware

1. LAN, WAN, or MAN? • Introduction: • We’re lucky, in a sense, that TCP/IP can be easily transported over a variety of media. • In reality, however, the network market is split into a variety of confusing classifications • LAN - within a building (or group of) • WAN - geographically dispersed • MAN - Metropolitan Area Network Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Introduction: • Having captured over 80% of the worldwide LAN market, Ethernet can be found just about everywhere in its many forms. • It started as Bob Metcalf’s Ph.D. at MIT • He graduated, and went to Xerox PARC • Xerox, together with DEC and Intel, eventually developed Ethernet into a product. Chapter 15 - Network Hardware

2. Ethernet: The Common LAN Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • How Ethernet works • Ethernet can be described as a polite dinner party at which guests don’t interrupt each other but rather wait for a lull in the conversation before speaking. • If two guests start to talk at once (a collision) they both stop, excuse themselves, wait a bit, and then one of them starts talking again. Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • How Ethernet works • The technical term for this scheme is CSMA/CD • Carrier Sense - you can tell whether anyone is talking • Multiple Access - everyone can talk • Collision Detect - you know when you interrupt someone Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Ethernet topology • The Ethernet topology is a branching bus with no loops (acyclic graph) • Ethernet provides a mechanism to exchange three types of packets on a segment • unicast • multicast • broadcast Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Unshielded twisted pair • UTP is the preferred cable medium for Ethernet • It s based upon a star topology and has several advantages over other media: • It uses inexpensive, readily available copper wire • UTP is much easier to install and debug than coax or fiber • Custom lengths are easily made. • UTP uses RJ-45 connectors which are cheap, reliable, and easy to install. • The link to each machine is independent (and private!) Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Unshielded twisted pair Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Unshielded twisted pair • Category of wires • Category 1 - (and 2) cables are suitable only for voice applications (if that) • Category 3 - the standard for 10 Mb/s (and voice) • Category 4 - 16 Mb/s token ring • Category 5 - support 100 Mb/s • Category 5E (and 6) support 1 Gb/s Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Connecting and expanding Ethernets • Ethernets can be logically connected at several points in the seven layer ISO network • Layer 1 - physical layer - repeaters (hubs) • Layer 2 - data link layer - switches • Layer 3 - network layer - routers Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Connecting and expanding Ethernets • Hubs and Concentrators • Hubs are active devices that connect physical segments in UTP Ethernet networks. (They require external power) • Acting as a repeater, a hub retimes and reconstitutes Ethernet frames but does not interpret them • The two farthest points ona network must never be more than 4 hubs apart (10 Mb/s) • 100 Mb/s allows 2 • 1000BaseT allows 1 Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Connecting and expanding Ethernets • Switches • Their purpose is to join two different physical networks in a way that makes them seem like one big physical network. • They do not require software, but rather receive, regenerate, and retransmit packets in hardware (therefore do not have the repeater limits) Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Connecting and expanding Ethernets • Switches (cont) • Most switches use a dynamic learning algorithm to determine where to forward packets. • The goal is only to those that need it. • Switches keep getting smarter as more functionality is built into their firmware. • Some can be used to monitor security by recording any foreign Ethernet address they receive. Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Connecting and expanding Ethernets • Switches (cont) • Large sites can benefit from switches that can partition their ports (through software) into subgroups called Virtual Local Area Networks (VLANs) • A VLAN is a group of ports that belong to the same logical segment. • Such partitioning increases the ability of the switch to isolate traffic -- which helps security and performance. Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Connecting and expanding Ethernets • Routers • Routers are dedicated computers-in-a-box that contain two or more network interfaces and direct traffic at the network layer (layer 3) • They shuttle packets based upon the information in the TCP/IP protocol headers. • They also packet filter. • Hardware interfaces of many types (FDDI, Ethernet, ATM, …) can be found in a single router Chapter 15 - Network Hardware

2. Ethernet: The Common LAN • Connecting and expanding Ethernets • Routers (cont) • Depending on your reliability needs and expected traffic load, a dedicated router may or may not be cheaper than a UNIX system configured to at as a router. • However a dedicated router will usually provide superior performance and reliability. • Spend the extra money and avoid the headaches if you are growing… Chapter 15 - Network Hardware

3. FDDI: The Disappointing and Expensive LAN • Introduction • Fiber Distributed Data Interface (FDDI) was marketed as a 100Mb/s token ring. • It once looked like it would be the easy solution to may organization’s bandwidth needs. • FDDI has been a disappointment • Cost - interfaces were around $10,000 • Performance was terrible. Chapter 15 - Network Hardware

3. FDDI: The Disappointing and Expensive LAN • Introduction (cont) • The FDDI standard specifies a 100 Mb/s token passing dual ring Chapter 15 - Network Hardware

4: ATM: The Promised (but sorely defeated) LAN • Introduction • ATM stands for Asynchronous Transfer Mode • or Another Technical Mistake • ATM is mostly dead - except in the WAN environment where large telco corporations are still trying to leverage their misguided investments in ATM hardware. Chapter 15 - Network Hardware

5. FRAME Relay: The Sacrificial WAN • Introduction • Frame relay is a WAN technology that offers packet-switched data service, usually for a reasonable cost. • Frame relay connections have some packet switching overhead, and link speed may degrade during periods of heavy use. Chapter 15 - Network Hardware

6. ISDN: The Indigenous WAN • Introduction • Integrated Services Digital Network (ISDN) is a phone company offering that takes many forms. • In its most common form, ISDN is essentially an all digital phone line that provides two dial up (64Kb/s) channels and one (16Kb/s) signaling channel. • You need interfaces (like modems) at each end. Chapter 15 - Network Hardware

7. DSL: The People’s WAN • Introduction • Digital Subscriber Line (DSL) uses ordinary copper telephone wire to transmit data at speeds of up to 7 Mb/s (256 Kb/s to 768 Kb/s is more typical) • This is the preferred technology for homes. • It is a dedicated network service that is always connected. • The race for “last mile” connectivity to hundreds of millions of homes is a hot one • The other option is cable. Chapter 15 - Network Hardware

8. Where is the Network going? • Introduction • The simple inexpensive technologies are succeeding and the complex expensive ones are dying. • Ethernet has pummeled its rivals because it is incredibly inexpensive. • Another exciting area of development is wireless networking. • Debugging a wireless network is something of a black art. • And TCP/IP runs on it all…. Chapter 15 - Network Hardware

9. Network Testing and Debugging • Introduction • One major advantage of the large scale migration to Ethernet is the ease of network debugging. • Since these networks can be analyzed link by link, hardware problems can often be isolated in seconds rather than days. • Having the right tools for the job is a big part of being able to get the job one. • The first is a hand-held cable analyzer. • The second is a network sniffer. Chapter 15 - Network Hardware

10. Building Wiring • Introduction • Whether you’re running gigabit Ethernet or just serial cables, we recommend that you use the highest possible quality of wire. • It will increase the chances that you can still use the same wire 10 years down the road Chapter 15 - Network Hardware

11. Network Design Issues • Introduction: • Most of network design consists of the specification of: • The types of media that will be used. • The topology and routing of cables • The use of repeaters, bridges, and routers. • Another key issue in network design is congestion control. Chapter 15 - Network Hardware

12. Management Issues • Introduction: • If the network is to work correctly, some things need to be centralized, some distributed, some local. • A typical environment includes • A backbone network among buildings • Departmental subnets connected to the backbone • Group subnets within a department • Connections to the outside world Chapter 15 - Network Hardware

12. Management Issues • Introduction: • Prime targets for central control are: • The network design, including the use of subnets, routers, switches, etc. • The backbone cable itself, including connections to it. • Host IP addresses, hostnames, and subdomain names. • Protocols • Routing policy to the internet. Chapter 15 - Network Hardware

14. Recommended Reading • Groth, David and Jim McBee. Cabling: The Complete Guide to Network Wiring. Sybex 2000. • Seifert, Rich. Gigabit Ethernet. Reading, MA: Addison-Wesley. 1998. Chapter 15 - Network Hardware

Chapter 15 - Network Hardware

Network Hardware