Web Server Administration Chapter 2 Preparing For Server

Web Server Administration Chapter 2 Preparing For Server Installation 1

Overview n n n Identify server categories Evaluate server components Plan for system disasters and reduce their effects Evaluate network components Set up IP addressing 2

Identifying Server Categories. File Servers n n File servers emphasize sending and receiving files A fast disk subsystem is more important than the processor type File servers are useful in a Web environment when you have a large number of static HTML pages File servers are also appropriate for an FTP server 3

Identifying Server Categories. Application Servers n n Server applications can process requests from many users at a time Requires extensive processing power A DBMS is a typical example Exchange Server does more than send e-mail messages n n Its complexity puts more burden on the processor Servers may also combine the need for fast processors and fast disk subsystems 4

Evaluating Server Components n Processor is usually the main focus n n n Speed Cores – 8 to 16 core processors Cache RAM Secondary storage n n Hard disk RAID – redundant array of independent disks 5

Processor n CPU n n n “Brains” of a computer An integrated circuit Arithmetic logic unit (ALU) n n Responsible for mathematical and logical ops Control unit (CU) n Regulates instructions 6

Processors (continued) n Clock speed n n n Number of pulses per second generated by the motherboard Sets processor’s tempo Measured in MHz (millions of cycles per second) or GHz (billions of cycles per second) 7

Processors (continued) n Cache n n RAM built into the CPU that’s used to store frequently accessed data and instructions L 1 cache - Level 1 (L 1) cache L 2 cache - Level 2 (L 2) cache L 3 cache- Level 3 (L 3) cache 8

Processors (continued) n n CPU performs calculations with binary digits (bits) 32 -bit processor can store 32 -bit numbers n n Correlates with the amount of data a CPU can process per clock cycle 64 -bit processor can theoretically double the amount of data the CPU can process 9

Physical Memory: RAM & ROM n n n Memory chips installed on a computer Two major categories RAM: random access memory n n Volatile- needs constant source of power ROM: read-only memory n n Nonvolatile firmware 10

RAM n n Dynamic RAM (DRAM) Static RAM (SRAM) n n Much faster and more expensive than DRAM Used in L 2 and L 3 caches, and other memory chips Synchronous DRAM (SDRAM) Double Data Rate SDRAM (DDR SDRAM) 11

ROM n n Programmable ROM (PROM) Erasable programmable ROM (EPROM) Electrically erasable PROM (EEPROM) Flash memory 12

Storage Devices 13

Hard Disk Drives (HDD) n Integrated Drive Electronics (IDE) & Extended IDE (EIDE) Small computer systems interface (SCSI) Fibre Channel (FC) Serial Attached SCSI (SAS) Serial ATA (SATA) n Redundant Array of Inexp/Indep Disks (RAID) n n 14

Selecting a HDD n n n Capacity Data Transfer Rate Buffer Size Average Seek Time/Access Time Rotational Speed 15

Network Interface Card (NIC) NIC Type Speed Media Use Standard Ethernet 10 Mbps Twisted pair (sometimes fiber) Home computers Fast Ethernet 100 Mbps Twisted pair (sometimes fiber) Home computers Gigabit Ethernet 1, 000 Mbps Fiber (sometimes twisted pair) Servers and LANS 10 -Gigabit Ethernet 10, 000 Mbps Fiber Backbone Connections and High-end servers ATM 25 Mbps – 622+ Mbps Fiber Rare due to IP dominance 16

Evaluating Server Components n Intel Processors http: //ark. intel. com/ GT/s stands for gigatransfers per second n AMD Processors http: //www. amd. com/en-us/products/server 17

Break n Complete EX 2 -1 18

Ex 2 -1 1. What are the two most popular server chip manufactures? 2. Create a comparison table to compare two servers, one from each of the popular manufactures and identify the following: Processor Name/Server name Processor chip set Processor Speed Processor Cores Cache size Word size RAM type Cost Other interesting items 19

Disaster Planning n n n “Insurance plan” for server A challenge to balance costs with benefits fault tolerance is the objective n The ability of a system to keep running even when a component fails 20

Disaster Assessment and Recovery n Determine n n what can go wrong what effects it will have on the org what it will take to fix Hardware Failure n n n How to replace failed hardware How to restore software (if applicable) Who will diagnose hardware problems 21

Disaster Assessment and Recovery n n n Software disasters are more complex than hardware disasters Could be a combination of application software and the operating system You may be directed to install software that may not work correctly n n Document installation and problems in detail Make sure that support is available 22

System Redundancy n Multiple power supplies n n UPS – uninterruptible power supply Spare hardware n n on hand as appropriate for the number of devices, reliability, and cost Also useful are warrantees that allow for replacement within 24 hours 23

Disk Redundancy through RAID n RAID 1 n n Data is duplicated across two drives Also called mirroring If there are two adapters, it is called duplexing RAID 5 (most common) n n n Distributes data across a minimum of 3 drives If any one of the drives fails, data can be recovered from the remaining drives Hot Swap – replace drive while server is running 24

Achieving High Availability with Multiple Servers n Clustering - Many computers act as one n n n Combines for computing power Fault tolerant High server availability IBM – assigns different tasks to each Microsoft – uses load balancing cluster n distribute work 25

Setting Up Backup Systems n n You should maintain a series of backups so you can restore data from a specific date Types of backup methods n n Full – all data is backed up Differential – backs up all files that are new or changed since last full backup Incremental – backs up all files that are new or changed since the last incremental backup Test your backup system 26

Backup Considerations n Back up the operating system n n Back up special application files n n DBMSs and Exchange keep files open, which cannot be backed up without special backup software modules Back up data files n n On Windows systems, you have to make sure that the Registry is backed up Easy and straightforward unless user has files open Can set up separate network just for backups 27

Evaluating Network Components n Servers/users need to be connected n n Hubs Switches (switching hubs) Routers WAN connection n T-carrier DSL Cable 28

Hubs n n n Connects segments of a LAN Contains multiple ports Processes frames of data Received frame is amplified to transmit Broadcasts frame to all ports Splits bandwidth between ports transmitting 29

Switches (switching hubs) n n n Connects segments of a LAN Contains multiple ports Processes frames of data Received frame is amplified to transmit Uses MAC address to determine recipient of frame Uses full bandwidth for each transmission 30

Routers n n n Connects LAN to WAN (or other LAN) Routes packets to other network Often integrates n n n 4 -8 port switch Network Address Translator (NAT) Dynamic Host Configuration Protocol (DHCP) Domain Name Server (DNS) Firewall 31

IP Addressing n IPv 4 n 32 bits – binary, 8 bits separated by period 197. 64. 242. 100 1100010101000000111100100 11000101 - 01000000 - 11110010 - 01100100 n IPv 6 (IPng IP next generation) n 128 bits – hexadecimal, 16 bits separated by colon (8 hex numbers) 3 ffe: 1900: 4545: 3: 200: f 8 ff: fe 21: 67 cf 32

IP v 4 n 32 bits =>232 = n n Early decisions wasted lots of addresses n n n 4, 294, 967, 296 addresses Those starting with 127 used for loopback 16, 277, 216 addresses, no longer available Internal structure of bits n n Network Id Host Id 33

IP Address n Network Identifier (Network ID): n n left-most bits used to identify the network Host Identifier (Host ID): n remainder of the bits are used to identify the host on that network. 34

Network vs Host ID n 227. 82. 157. 177 n network id: 227. 82. 0. 0 host id: 0. 0. 157. 177 OR n n network id: 227. 0. 0. 0 host id: 0. 82. 157. 177 35

Network vs Host ID Could be split anywhere… 227. 82. 157. 177 … 20 bits for network id and 12 bits for host id 36

IP Addressing n n Must know where the IP address is divided IP addressing schemes n n n Convention (Classful) Addressing Subnetted Classful Addressing Classless Addressing 37

IP “Classful” Addressing n Divide the IP addresses into 5 classes n n Class A, B, C, D, E IP address will have a network id and host id divided on an octet boundary 38

Class Value of w Network ID Host ID Number of networks Number of hosts per network A 1 -126 w x. y. z 126 16, 777, 214 B 128 -191 w. x y. z 16, 384 65, 534 C 192 -223 w. x. y z 2, 097, 152 254 N/A N/A N/A D 224 -239 E 240 -254 Reserved for multicast addressing Reserved for experimental use 39

IP Address Classes Network ID Bits Number of Host ID Number of hosts per Bits network Intended Use A 8 24 126 16, 777, 214 very large organizations B 16 16 16, 384 65, 534 medium-to-large organizations C 24 8 2, 097, 152 254 smaller organizations D n/a N/A IP multicasting E n/a N/A Reserved for “experimental use” 40

IP Address Classes Class First Octet in IP address Usable # of Network bits Number of Networks Number of Hosts Class A 1 – 127 0 xxx xxxx 8 -1 = 7 27 -2 = 126** >16, 000* Class B 128 – 191 10 xx xxxx 16 -2 = 14 214 > 16, 000 >65, 000* Class C 192 – 223 110 x xxxx 24 -3 = 21 221> 2, 000 254* ** Class A num networks less 2 (all 0’s and all 1’s have spl meaning) * Host Id of all 0’s or 1’s has special meaning 41

Class A: 109. 197. 63. 205 109 = 0110 1101 Class B: 152… 152 = 1001 1000 0000 to 1011 1111 128 to 191 Class C: 198…. 1100 0110 42

IP Address 43

IP Addressing – IPv 4 n IP “Classful” Addressing n Set up for organizations of different sizes 44

Rationale for Classful Addressing n n Simplicity and Clarity Reasonably Flexible Routing Ease Reserved Addresses 45

Problems with Classful Addressing n Lack of internal Address Flexibility n n n Inefficient use of Address Space n n Large org given big block – doesn’t match underlying structure No way to create internal structure Some waste – host size > 254… >65, 00 Proliferation of router table entries n 20 class c tables or 1 class B tables… 46

Break n Complete EX 2 -2 47

Ex 2 -2 1. What are the IP classes and give a notable fact about each. 48

Ex 2 -2 (continued) 2. Given the following addresses determine the IP class, the network id and the host id. n n n 192. 56 204. 63. 100. 103 92. 34. 240. 175 252. 102. 66. 105 147. 64. 242. 100 63. 230. 34. 2 49

Ex 2 -2 (continued) 3. What are the advantages and disadvantages of the class IP addressing system? 50

IP Subnet Addressing n n n IP address uses 3 level structure Network id, subnet id, host id Network id remains fixed to the class Host id is now divided into 2 parts A subnet mask is provided to identify the host id and the subnet 51

Subnetting a class B network Division is based on number of sub networks and effects the max number of host in a given subnetwork. 52

Subnet mask n n n Because the subnet/host division could be anywhere – must have a bit mask to find the subnet. Subnet mask bits correspond to bits in IP address Bits used for the network & subnet are 1’s and the rest are zero’s (removes the host bits) 53

Subnet mask 54

Subnet mask Component Octet 1 Octet 2 Octet 3 Octet 4 IP Address 10011010 (154) 01000111 (71) 10010110 (150) 00101010 (42) Subnet Mask 11111111 (255) 11111000 (248) 0000 (0) Result of AND Masking 10011010 (154) 01000111 (71) 10010000 (144) 0000 (0) 154. 71. 144. 0, is the IP address of the subnet to which 154. 71. 150. 42 belongs 55

Setting Up IP Addressing n n Subnetting the original classes (1 subnet per class) For each class, 0 bits are used for the subnet. 56

How many bits for subnet n Dividing the host portion into 2 Each bit taken for the subnet doubles the subnets n Each bit taken for the subnet halves the number of hosts 1 n 16 bits – 1 bit for subnet = 2 subnets or 2 15 bits for hosts = 215 -2 or 32, 766 or 2 bits for subnet = 22 or 4 subnets 14 bits for hosts = 214 -2 or 16, 382 n 57

Advantages of Subnetting n n n Better match to physical Network struct Flexibility Invisible to public Internet “internet within the Internet” No need to request new IP addresses No routing table proliferation 58

Disadvantages or Subnetting n n Largest subnet determines mask All subnets must be the same size n Unless Variable Level Subnet masking is used 59

VLSM Traditional subnet masking Variable Length subnet masking 60

Break n Complete EX 2 -3 61

Ex 2 -3 (continued) 1. Given the following addresses and number of bits used for subnet, determine the subnet mask, the number of subnets and the number of hosts. 192. 56, subnet - 3 bits 204. 63. 100. 103, subnet – 4 bits 92. 34. 240. 175, subnet – 14 bits 252. 102. 66. 105, subnet – 6 bits 147. 64. 242. 100, subnet - 10 bits 63. 230. 34. 2, subnet - 8 bits 62

Ex 2 -3 (continued) 2. What are the advantages and disadvantages of the IP subnet addressing system? 63

IP Classless Addressing - CIDR n n n Classless Inter-Domain Routing (CIDR) "Supernetting“ Eliminating the notion of address classes entirely Extend the life of IP version 4 the Internet becomes just one giant network that is “subnetted” into a number of large blocks 64

CIDR n n Some of these large blocks are then broken down into smaller blocks Which can in turn be broken down further. This breaking down can occur multiple times. Allows the “pie” of Internet addresses to be split into slices of many different sizes, to suit the needs of organizations. 65

CIDR n How to determine the network id and host id: n n Use mask – just like subnetting Use slash notation 184. 13. 152. 0/22 Network id – first 22 bits Host id – last 10 bits 66

CIDR - example CIDR (“Slash”) Notation and Its Subnet Mask Equivalent 67

Assigning IP Addresses n n IANA/ICANN divides addresses into large blocks Distributes to the four regional Internet registries (RIRs): n n APNIC, ARIN, LACNIC and RIPE NCC. They further divide and distribute them to n n n lower-level national Internet registries (NIRs) local Internet registries (LIRs) Internet Service Providers (ISPs) 68

Assignment example 69

Private Network n n IP Addresses used within a LAN that has no direct connection to the Internet IP address must be unique within its network Special IP addresses are used for Private networks NAT is needed to translate the Private Network IP address if connecting to the Internet 70

Private Networks Range Start Address Range End Address “Classful” Address Equivalent Classless Address Equivalent Description 10. 0 10. 255 Class A network 10. x. x. x 10/8 Class A private address block. 172. 31. 255 16 contiguous Class B networks from 172. 16. x. x through 172. 31. x. x 172. 16/12 Class B private address blocks. 192. 168. 255 256 contiguous Class C networks from 192. 168. 0. x through 192. 168. 255. x 192. 168/16 Class C private address blocks. 172. 16. 0. 0 192. 168. 0. 0 71

Network Address Translation (NAT) n n n Extend the life of IP version 4 Allows a small number of public IP addresses to be shared by a large number of hosts using private addresses Growing Concerns Over Security – indirect access to servers etc 72

Network Address Translation (NAT) n n NAT allows an IP address from one network to be translated into another address on an internal network You can also use NAT to translate a single IP address valid on the Internet into multiple internal addresses n Useful if your ISP gives you a single IP address, yet you have multiple servers and users on the internal network 73

Port-Based NAT n n n Ports - The port number in a message helps identify individual connections between two addresses (like an phone extension) The combination of an address and port uniquely identifies a connection The inside address and port can be mapped to an outside address and port by the NAT device. 74

Port numbers n n Port number assignments Choose a port number usually >1024 75

76

Advantages of NAT n n n Public IP Address Sharing Easier Expansion - easy to add new clients Greater Local Control – Mostly private LAN Greater Flexibility In ISP Service - Changing the organization's Internet Service Provider (ISP) is easier because only the public addresses change Increased Security – Automatic firewall (Mostly) Transparent - changes take place in one or perhaps a few routers. 77

Disadvantages of NAT n n Complexity Problems Due to Lack of Public Addresses - Certain functions won't work properly due to lack of a “real” IP address in the client host machines. Compatibility Problems With Certain Applications – some applications like FTP require more work with the mapping. Problems With Security Protocols – tinkering with the header… 78

Disadvantages of NAT n n Poor Support for Client Access- “Peer-to-peer” applications are harder to set up Performance Reduction n Each time a datagram transitions between the private network and the Internet, an address translation is required. In addition, other work must be done as well, such as recalculating header checksums. Each individual translation takes little effort but when you add it up, you are giving up some performance. 79

Summary n n n File servers and application servers are the two basic types of servers Various families of processors are available from Intel, AMD, and others There are many techniques for minimizing loss due to hardware and software failures Routers and switches allow servers to communicate IP addresses are divided into the network and host portions 80