Chapter 9 Panko and Panko Business Data Networks and Security, 9 th Edition © 2013 Pearson Revised August 2013.

Chapter (s)CoverageLayers 1–41–4Core concepts and principlesAll 5Single switched networks1–21–2 6–76–7Single wireless networks1–21–2 8–98–9Internets3–43–4 10Wide Area Networks1-4 11Applications5 © 2013 Pearson 2

 Companies are given host parts by their ISP or an Internet number authority.  They divide the remaining bits between a subnet part and a host part.  Larger subnet parts mean more subnets, but this results in smaller host parts, which means fewer hosts per subnet.  The reverse is also true. © 2013 Pearson 5

 If a part has N bits, it can represent 2 N - 2 subnets or hosts per subnet. ◦ 2 N because if you have N bits, you can represent 2 N possibilities. ◦ Minus 2 is because you cannot have a part that is all zeros or all ones. © 2013 Pearson 6 Part Size (bits) 2N2N 2 N -2 42 4 = 1616-2 = 14 8?? 124,0964,094 65,53665,53416 10??

© 2013 Pearson 7 DescriptionStep 32 Total size of IP address (bits) 1 Size of network part assigned to firm (bits) 216 Remaining bits for firm to assign 316 Selected subnet/host part sizes (bits) 48 / 8 Number of possible subnets (2 N - 2) 254 (2 8 - 2) Number of possible hosts per subnet (2 N - 2) 254 (2 8 - 2) By definition Assigned to the firm Bits for the firm to assign The firm’s decision

© 2013 Pearson 8 DescriptionStep 32 Total size of IP address (bits) 1 Size of network part assigned to firm (bits) 216 Remaining bits for firm to assign 316 Selected subnet/host part sizes (bits) 46/10 Number of possible subnets (2 N - 2) 62 (2 6 - 2) Number of possible hosts per subnet (2 N - 2) 1,022 (2 10 - 2) By definition Assigned to the firm Bits for the firm to assign The firm’s decision

© 2013 Pearson 9 DescriptionStep 32 Total size of IP address (bits) 1 Size of network part assigned to firm (bits) 28 Remaining bits for firm to assign 324 Selected subnet/host part sizes (bits) 412/12 Number of possible subnets (2 N - 2) 4,094 (2 12 - 2) Number of possible hosts per subnet (2 N - 2) 4,094 (2 12 - 2) By definition Assigned to the firm Bits for the firm to assign The firm’s decision

© 2013 Pearson 10 DescriptionStep 32 Total size of IP address (bits) 1 Size of network part assigned to firm (bits) 28 Remaining bits for firm to assign 324 Selected subnet/host part sizes (bits) 48/16 Number of possible subnets (2 N - 2) 254 (2 8 - 2) Number of possible hosts per subnet (2 N - 2) 65,534 (2 16 - 2) By definition Assigned to the firm Bits for the firm to assign The firm’s decision

© 2013 Pearson 11 DescriptionStep Size of network part assigned to firm (bits) 220 Remaining bits for firm to assign 312 Host part size (bits)4? Number of possible subnets (2 N - 2) ? Number of possible hosts per subnet (2 N - 2) ? Selected subnet part size (bits) Added4 Exercise Size of IP address232

© 2013 Pearson 12 DescriptionStep Size of network part assigned to firm (bits) 220 Remaining bits for firm to assign 312 Host part size (bits)4? Number of possible subnets (2 N - 2) ? Number of possible hosts per subnet (2 N - 2) ? Selected subnet part size (bits) Added6 Exercise Size of IP address232

 NAT ◦ Sends false external source IP addresses and port numbers that are different from internal source IP addresses and port numbers. ◦ For security purposes. ◦ To have many more internal IP addresses than your ISP gives you external IP addresses. © 2013 Pearson 14

© 2013 Pearson 16 NAT Firewall replaces the source IP address and port number of the packet with a false source IP address and port number. Adds to table. NAT Firewall replaces the source IP address and port number of the packet with a false source IP address and port number. Adds to table.

 NAT is Transparent to Internal and External Hosts. ◦ The NAT firewall does all the work. ◦ Neither host knows that NAT is taking place. ◦ So there is no need to modify how hosts work. © 2013 Pearson 18

 Security Reasons for Using NAT ◦ External attackers can put sniffers outside the corporation. ◦ Sniffers read IP addresses and port numbers. ◦ Attackers can send attacks to these addresses and port numbers. ◦ With NAT, attackers learn only false external IP addresses. Cannot use this information to attack internal hosts. © 2013 Pearson 19

 Expanding the Number of Available IP Addresses ◦ Companies may receive a limited number of IP addresses from their ISPs. ◦ There are roughly 4,000 possible ephemeral port numbers for each client IP address. ◦ So for each IP address, there can be up to about 4,000 external connections. ◦ If a firm is given 248 IP addresses, there can be roughly one million external connections. © 2013 Pearson 20

 Expanding the Number of Available IP Addresses ◦ If each internal device averages several simultaneous external connections, each one will require a different port number. ◦ However, there should not be a problem with this many possible external IP addresses and port numbers. © 2013 Pearson 21

 Companies often use private IP addresses internally.  These can be used only within companies— never on the Internet.  There are three Private IP address ranges. ◦ 10.x.x.x ◦ 172.16.x.x through 172.31.x.x ◦ 192.168.x.x (most popular) © 2013 Pearson 22

 There Are Protocol Problems Caused by NAT ◦ IPsec, VoIP, and other applications have a difficult time with NAT firewall traversal. ◦ They must know the real IP address and port number of the host on the other side of the NAT firewall. ◦ There are NAT firewall traversal techniques, but they must be managed carefully. © 2013 Pearson 23

© 2013 Pearson 26 Originating host needs the IP address of host dakine.pukanui.com. Asks its local DNS server at Hawaii.edu. Originating host needs the IP address of host dakine.pukanui.com. Asks its local DNS server at Hawaii.edu.

© 2013 Pearson 30 The DNS really is a general naming system for the Internet. A domain is a set of resources under the control of an organization. There is a hierarchy of domains. The DNS really is a general naming system for the Internet. A domain is a set of resources under the control of an organization. There is a hierarchy of domains.

© 2013 Pearson 32 There are two kinds of top-level domains. Generic top-level domains indicate organization type (.com,.edu,.gov, etc.). Country top-level domains are specific to a country (.UK,.CA,.CH, etc.). There are two kinds of top-level domains. Generic top-level domains indicate organization type (.com,.edu,.gov, etc.). Country top-level domains are specific to a country (.UK,.CA,.CH, etc.).

 Traditionally, generic top-level domains were strongly limited in number.  There have been a few additions over the year, such as.museum,.name, and.co.  As of 2013, any individual or company can propose to administer a generic top-level domain. © 2013 Pearson 33

© 2013 Pearson 34 Companies want second-level domain names. (Microsoft.com, apple.com, panko.com, etc.). Competition for these names is fierce. Companies want second-level domain names. (Microsoft.com, apple.com, panko.com, etc.). Competition for these names is fierce.

 Typical configuration information: ◦ IP address for the DHCP client to use ◦ The subnet mask for the client’s subnets ◦ The IP address of the client’s default router ◦ The IP addresses of the firm’s multiple DNS servers © 2013 Pearson 41

 The two are often confused because both give a client PC an IP address. ◦ DHCP gives a client PC its own dynamic IP address. ◦ DNS gives a client PC the IP address of a host the client wishes to send packets to. © 2013 Pearson 42

 Core Elements (from Chapter 4) ◦ Management information base (MIB). ◦ Stores the retrieved information. ◦ “MIB” can refer to either the database on the manager or to the database schema. © 2013 Pearson 45 Manager MIB

 Messages ◦ Commands (sent by a manager to an agent)  Get (to get information from the agent)  Set (to tell the agent to change how the managed devices is operating) ◦ Responses (sent from agent to manager) © 2013 Pearson 46 Get or Set Command Response

 Set Commands ◦ Dangerous if used by attackers. ◦ Many firms disable Set to thwart such attacks. ◦ However, they give up the ability to manage remote resources without travel. ◦ SNMPv1: community string shared by the manager and all devices (poor). ◦ SNMPv3: each manager–agent pair has a different password (good). © 2013 Pearson 48

 Objects (Figure 9-8) ◦ Specific pieces of information ◦ Number of rows in the routing table ◦ Number of discards caused by lack of resources (indicates a need for an upgrade) © 2013 Pearson 49 Objects are NOT managed devices! Objects are specific pieces of data about a managed device. Objects are NOT managed devices! Objects are specific pieces of data about a managed device.

 Categories of Objects ◦ IP objects (one set per managed device)  Forwarding (for routers), Yes if forwarding (routing), No if not  Cause of resource limitations  Number of rows in routing table  Rows discarded because of lack of space  Individual row data © 2013 Pearson 51

 Categories of Objects ◦ TCP objects (one set per managed device)  Retransmission time  Maximum number of TCP connections allowed  Opens/failed connections/resets  Segments sent  Segments retransmitted  Errors in incoming segments  Data on individual connections (sockets, states) © 2013 Pearson 52

 Categories of Objects ◦ Interface objects (one set per interface)  Type (e.g., 69 is 100Base-FX; 71 is 802.11)  Status: up/down/testing  Speed  Errors: discards, unknown protocols, and so on © 2013 Pearson 55

 SNMP Manager program collects data. ◦ Places it in the MIB.  Visualization Program. ◦ The administrator’s interface to the MIB. ◦ Helps the administrator visualize patterns in the MIB data. ◦ Can order the SNMP Manager to collect certain data or to send set commands to change the configurations of managed devices. © 2013 Pearson 56

 User Functionality ◦ Reports, diagnostics tools, and so on, are very important. ◦ They are not built into the standard. ◦ They are added by network visualization program vendors. ◦ Critical in selection of a network management vendor. © 2013 Pearson 57

 Routers route each packet individually, going through the three steps we saw in the last chapter. ◦ Even if the next packet is going to the same destination IP address, the router will go through all three steps. ◦ This consumes a great deal of processing power per packet. ◦ This makes traditional routing expensive. © 2013 Pearson 59

 MPLS addresses this issue. ◦ Routers identify the best route for a range of IP addresses before sending data. ◦ That route is given a label number. ◦ Each packet in a stream gets a label with this label number. ◦ Routers do only a quick table lookup per packet. ◦ Table lookups require little processing power. ◦ So multiprotocol label switching is much less expensive than traditional routing. © 2013 Pearson 60

 Implementing MPLS is difficult.  Many individual ISPs and corporations do it.  Some individual ISPs have “peering” arrangements with other individual ISPs to do it.  There is no general way to move MPLS out to all ISPs and organizations. © 2013 Pearson 67

 Security was not addressed in the initial design of TCP/IP.  Jon Postel, who edited the main Internet RFCs, explained to the first author, “It just wasn’t a problem then, and we were stretched thin.”  Today, firms are adding security to their transmissions through IPsec VPNs. © 2013 Pearson 69

 A virtual private network (VPN) is a cryptographically secured transmission path through an untrusted environment. ◦ The Internet ◦ A wireless network ◦ Communication in a foreign country  Like having your own private network in terms of security. ◦ However, not a real private network. © 2013 Pearson 70

© 2013 Pearson 72 There are two types of VPN: Remote access VPNs connect a remote user to a corporate site. The user connects to a VPN gateway at the site. There are two types of VPN: Remote access VPNs connect a remote user to a corporate site. The user connects to a VPN gateway at the site.

© 2013 Pearson 73 There are two types of VPNs: Site-to-site VPNs protect all traffic traveling between two sites. Each site has a gateway to encrypt outgoing traffic and decrypt incoming traffic. There are two types of VPNs: Site-to-site VPNs protect all traffic traveling between two sites. Each site has a gateway to encrypt outgoing traffic and decrypt incoming traffic.

CriterionTransport ModeTunnel Mode SecurityBetter because it provides host-to- host protection. But firewalls cannot read encrypted traffic. Not as good because it only provides security over the Internet or another trusted network (a wireless network, etc.). CostHigher because of configuration work on each host. Lower because IPsec operates only on the IPsec gateway. © 2013 Pearson 79

 Origin ◦ Created by Netscape as SSL. ◦ IETF took over the standard. ◦ IETF changed the standard’s name to Transport Layer Security (TLS). ◦ We refer to the standard, generically, as SSL/TLS. © 2013 Pearson 84

 Attraction of SSL/TLS ◦ Universally supported by browsers and webserver applications. ◦ So no added cost on the client to use it! ◦ No extra software on the server is needed, but SSL/TLS must be configured, which usually is simple. © 2013 Pearson 85

 Limitations of SSL/TLS ◦ Operates at transport layer so no protection for IP or transport headers ◦ Limited to applications written to work with SSL/TLS: HTTP and e-mail, primarily ◦ Cryptographically weaker than IPsec  Has been partially cracked ◦ No policy servers for centralized management © 2013 Pearson 86

 Overall ◦ Decent quality, cheap, and easy security ◦ Limited in how it can be used and managed  Comparison with IPsec ◦ IPsec is more complex and so more expensive. ◦ Can be used for all types of VPNs. ◦ Can be managed well. ◦ Gold standard in TCP/IP security. © 2013 Pearson 87

 Must transition all clients, routers, firewalls, and so on  The IETF’s plan ◦ No backward compatibility ◦ Instead, add both IPv4 and IPv6 protocol stacks at the internet layer to all new devices ◦ As soon as most devices have IPv6 protocol stacks, configure the devices and add IPv6 support to IPv4 support ◦ Eventually, turn off IPv4 support © 2013 Pearson 90

 Problems and reactions ◦ IPv6 offered few benefits, so most companies ignored IPv6. ◦ The shortage of IPv4 addresses was handled (intelligently) through NAT. ◦ But now, IPv4 addresses are gone. ◦ Now some clients, such as mobile phones, only have IPv6 stacks at the protocol layer. ◦ To serve them, companies are rushing to turn on and configure IPv6 support. © 2013 Pearson 91

 Must deal with global IPv6 unicast addresses ◦ Like public IPv6 addresses ◦ Have 3 parts but different names © 2013 Pearson 92 IPv6 Address PartCorresponding IPv4 Address Part Length of IPv6 part Routing PrefixNetwork PartVariable Subnet IDSubnet PartVariable Interface IDHost Part64 bits Total32 bits128 bits

© 2013 Pearson 94 Global Routing Prefix (network part in IPv4) Subnet ID (subnet part in IPv4) Interface ID (host part in IPv4) (Almost) Always 64 bits Interface ID is not of variable length like IPv4 host parts. “Waste” 64 bits, but have plenty to lose.

 An IP address registrar gives you a 32-bit global routing prefix.  How long is your subnet ID?  How many subnets can you have (approximately)?  Many companies have a two-layer hierarchy of subnets, using some bits for the main subnet and remaining bits for sub-subnets. © 2013 Pearson 96

 Modified 64-bit Extended Unique Identifier (EUI) Format  First, display the MAC address in hexadecimal notation (48 bits) ◦ Remove dashes ◦ Convert text to lower case © 2013 Pearson 97 AD-B1-C2-D3-E5-F5 adb1c2d3e5f5

 1. Begin with MAC in hexadecimal notation  2. Divide the 48 bits into 2 halves of 24 bits  3. Insert fffe between the two halves  4. Place into four-hex groups separated by colons  5. Flip the second-least significant bit in the first octet © 2013 Pearson 100

 Hosts must be configured with IP addresses  IPv4 uses DHCP  IPv6 offers two configuration mechanisms ◦ DHCPv6 (very similar to IPv4) ◦ Stateless autoconfiguration, which does not use a DHCPv6 server ◦ Not available in IPv4 © 2013 Pearson 101

 Stateless Autoconfiguration ◦ The client configures itself, without using a DHCPv6 server. ◦ First, the client creates a link-local IPv6 address. ◦ Second, the client creates a global unicast IPv6 address. © 2013 Pearson 102

 Creating the Link-Local IPv6 Addresses ◦ Link-local IPv6 addresses can be used only within a single network (wireless or switched wired). ◦ If the client does not need a global IP address, the autoconfiguration process can stop here. © 2013 Pearson 103

 Creating the Link-Local Address ◦ First create a 64-bit interface ID using the MAC address of the client. ◦ Add a routing prefix 111 1110 10 followed by 56 bits of zeroes. ◦ This is the link-local IP address: fe80::x, where x is the octets of the EUI-64. © 2013 Pearson 104

 Testing the Link-Local Address ◦ Another host may be using this address. ◦ So the client uses the ICMPv6 neighbor discovery protocol to ask if any other host in the single network is using this address. ◦ If none reply, the client may use this address within its single network. © 2013 Pearson 105

 Creating the Global Unicast IPv6 Address ◦ Needed for communication over the Internet. ◦ Begin with the link-local address. ◦ Keep the interface ID but get a new routing prefix and subnet ID. ◦ Client sends an ICMPv6 router solicitation message to the address FFF02::1, which all routers listen for. © 2013 Pearson 106

 Creating the Global Unicast IPv6 Address ◦ Routers respond with IPv6 router advertisement messages. ◦ The router advertisement message may state that autoconfiguration is not allowed. ◦ If this is not the case, the message gives the routing prefix and subnet ID. ◦ The client now has a global unicast IPv6 address. © 2013 Pearson 107

 Limits ◦ More limited than traditional DHCP autoconfiguration. ◦ At a minimum, router advertisement messages give only a routing prefix and subnet ID. ◦ Of course, the packet containing the router advertisement message gives the IPv6 address of the router, which becomes the default router. © 2013 Pearson 108

 Uses ◦ How can a client get other IPv6 configuration information? ◦ If a client is a dual-stack client, the IPv4 stack can obtain full configuration information, which the IPv6 stack can use. © 2013 Pearson 109

 Uses ◦ If the client is not a dual-stack client, it needs at least one more piece of configuration information—the IPv6 addresses of DNS servers. ◦ The IETF has extended router advertisement messages to provide the IPv6 addresses of DNS servers. ◦ However, this is only an option. © 2013 Pearson 110

 Known Security Weaknesses ◦ An attacker might create an address that does not use its proper EUI-64. ◦ An attacker may create an address that uses the EUI-64 of another host to impersonate it. ◦ Several operations can be used to create flooding denial-of-service attacks. © 2013 Pearson 111

 Domain Name System (DNS) ◦ The DNS information for a host is contained in several records. ◦ DNS A Record. The A record contains the IPv4 address for the target host. ◦ DNS AAAA Record. For IPv6 addresses, a new address record had to be added.  IPv6 addresses are four times as long as IPv4 addresses, so the added record is called the AAAA record. © 2013 Pearson 114

 Address Resolution Protocol (ARP) Messages ◦ In IPv6, handled by the ICMP neighbor discovery protocol, which has two message types. ◦ Neighbor solicitation messages ask host to respond. ◦ Neighbor advertisement messages give the host’s data link address. ◦ There is no ARPv6. © 2013 Pearson 115

Chapter 9 Panko and Panko Business Data Networks and Security, 9 th Edition © 2013 Pearson Revised August 2013.

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Chapter 9 Panko and Panko Business Data Networks and Security, 9 th Edition © 2013 Pearson Revised August 2013.

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