1 Problems with IPv4: Header Limitations Problems with IPv4: Header - PDF document

Outline Outline IPv6: An Introduction IPv6: An Introduction � Problems with IPv4 Problems with IPv4 � � Basic IPv6 Protocol Basic IPv6 Protocol � � IPv6 features IPv6 features Dheeraj Sanghi � Dheeraj Sanghi – – Auto Auto- -configuration, QoS, Security, Mobility configuration, QoS, Security, Mobility Department of Computer Science and Engineering Department of Computer Science and Engineering � Transition Plans Transition Plans � Indian Institute of Technology Kanpur Indian Institute of Technology Kanpur dheeraj@iitk.ac.in dheeraj@iitk.ac.in http://www.cse.iitk.ac.in/users/dheeraj http://www.cse.iitk.ac.in/users/dheeraj May 2005 May 2005 IIT Kanpur IIT Kanpur 1 1 Internet Protocol Internet Protocol IP Datagram Header IP Datagram Header 31 0 4 8 16 19 Transports a datagram from source host to destination, Transports a datagram from source host to destination, HLEN TOS TOTAL LENGTH possibly via several intermediate nodes (“routers”) possibly via several intermediate nodes (“routers”) VERS IDENTIFICATION FRAGMENT OFFSET FLAG Service is: Service is: � Unreliable: Unreliable: Losses, duplicates, out Losses, duplicates, out- -of of- -order delivery order delivery � TTL PROTOCOL CHECKSUM � Best effort: Best effort: Packets not discarded capriciously, delivery Packets not discarded capriciously, delivery � failure not necessarily reported failure not necessarily reported SOURCE ADDRESS � Connectionless: Connectionless: Each packet is treated independently Each packet is treated independently � DESTINATION ADDRESS OPTIONS (if any) + PADDING May 2005 May 2005 IIT Kanpur IIT Kanpur 2 2 May 2005 May 2005 IIT Kanpur IIT Kanpur 3 3 Problems with IPv4: Limited Address Space Problems with IPv4: Routing Table Explosion Problems with IPv4: Routing Table Explosion Problems with IPv4: Limited Address Space � IP does not permit route aggregation IP does not permit route aggregation � (limited supernetting possible with new routers) (limited supernetting possible with new routers) � IPv4 has 32 bit addresses. IPv4 has 32 bit addresses. � � Mostly only class C addresses remain Mostly only class C addresses remain � � Flat addressing (only netid + hostid with “fixed” Flat addressing (only netid + hostid with “fixed” � � Number of networks is increasing very fast Number of networks is increasing very fast � boundaries) boundaries) (number of routes to be advertised goes up) (number of routes to be advertised goes up) � Results in inefficient use of address space. Results in inefficient use of address space. � � Very high routing overhead Very high routing overhead � � Class B addresses are almost over. Class B addresses are almost over. � – lot more memory needed for routing table lot more memory needed for routing table – � Addresses will exhaust in the next 5 years. Addresses will exhaust in the next 5 years. � – lot more bandwidth to pass routing information – lot more bandwidth to pass routing information � IPv4 is victim of its own success. IPv4 is victim of its own success. � – lot more processing needed to compute routes – lot more processing needed to compute routes May 2005 May 2005 IIT Kanpur IIT Kanpur 4 4 May 2005 May 2005 IIT Kanpur IIT Kanpur 5 5 1

Problems with IPv4: Header Limitations Problems with IPv4: Header Limitations Problems with IPv4: Other Limitations Problems with IPv4: Other Limitations � Maximum header length is 60 octets. Maximum header length is 60 octets. � (Restricts options) (Restricts options) � Lack of quality Lack of quality- -of of- -service support. service support. � � Maximum packet length is 64K octets. Maximum packet length is 64K octets. � – Only an 8 Only an 8- -bit ToS field, which is hardly used. bit ToS field, which is hardly used. – (Do we need more than that ?) (Do we need more than that ?) – Problem for multimedia services. – Problem for multimedia services. � ID for fragments is 16 bits. Repeats every 65537th packet. ID for fragments is 16 bits. Repeats every 65537th packet. � � No support for security at IP layer. No support for security at IP layer. � (Will two packets in the network have same ID?) (Will two packets in the network have same ID?) � Mobility support is limited. Mobility support is limited. � � Variable size header. Variable size header. � (Slower processing at routers.) (Slower processing at routers.) � No ordering of options. No ordering of options. � (All routers need to look at all options.) (All routers need to look at all options.) May 2005 May 2005 IIT Kanpur IIT Kanpur 6 6 May 2005 May 2005 IIT Kanpur IIT Kanpur 7 7 IP Address Extension IP Address Extension IPng Criteria IPng Criteria � Strict monitoring of IP address assignment Strict monitoring of IP address assignment � 9 networks, 10 12 end � Private IP addresses for intranets Private IP addresses for intranets � At least 10 At least 10 9 networks, 10 12 end- -systems systems � � – – Only class C or a part of class C to an organization Only class C or a part of class C to an organization � Datagram service (best effort delivery) Datagram service (best effort delivery) � – Encourage use of proxy services – Encourage use of proxy services � Independent of physical layer technologies Independent of physical layer technologies � � Application level proxies � Application level proxies � Robust (routing) in presence of failures Robust (routing) in presence of failures � � Network Address Translation (NAT) Network Address Translation (NAT) � � Flexible topology (e.g., dual Flexible topology (e.g., dual- -homed nets) homed nets) � � Remaining class A addresses may use CIDR Remaining class A addresses may use CIDR � � Better routing structures (e.g., aggregation) Better routing structures (e.g., aggregation) � � Reserved addresses may be assigned Reserved addresses may be assigned � � High performance (fast switching) High performance (fast switching) � � Support for multicasting Support for multicasting � But these will only postpone address exhaustion. But these will only postpone address exhaustion. They do not address problems like QoS, mobility, security. They do not address problems like QoS, mobility, security. May 2005 May 2005 IIT Kanpur IIT Kanpur 8 8 May 2005 May 2005 IIT Kanpur IIT Kanpur 9 9 IPng IPng Criteria Criteria IPv6: Distinctive Features IPv6: Distinctive Features � Support for mobile nodes Support for mobile nodes � Header format simplification Header format simplification � � � Support for quality Support for quality- -of of- -service service � Expanded routing and addressing capabilities Expanded routing and addressing capabilities � � � Provide security at IP layer Provide security at IP layer � Improved support for extensions and options Improved support for extensions and options � � � Extensible Extensible � Flow labeling (for QoS) capability Flow labeling (for QoS) capability � � � Auto Auto- -configuration (plug configuration (plug- -and and-- --play) play) � Auto Auto- -configuration and Neighbour discovery configuration and Neighbour discovery � � � Straight Straight- -forward transition plan from IPv4 forward transition plan from IPv4 � Authentication and privacy capabilities Authentication and privacy capabilities � � � Minimal changes to upper layer protocols Minimal changes to upper layer protocols � Simple transition from IPv4 Simple transition from IPv4 � � May 2005 May 2005 IIT Kanpur IIT Kanpur 10 10 May 2005 May 2005 IIT Kanpur IIT Kanpur 11 11 2