IPv4 REVIEW AND IPv6 ETI 2506 TELECOMMUNICATION SYSTEMS Monday, - - PowerPoint PPT Presentation

IPv4 REVIEW AND IPv6

ETI 2506 – TELECOMMUNICATION SYSTEMS Monday, 07 NOVEMBER 2016

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TELECOMMUNICATION SYLLABUS

Principles of Telecom (IP Telephony and IP TV) - Key Issues to remember 1. IPv4 Header and how it is used for routing packets 2. Subneting 3. CIDR 4. NAT 5. IPv6 Header and its use for routing packets

WHAT IS IPV4?

• 1. IPv4 is a connectionless protocol for use on packet-switched Link

Layer networks (e.g., Ethernet).

• 2. It operates on a best effort delivery model, i.e

a) It does not guarantee delivery, b) It does it assure proper sequencing, c) It does not avoid duplicate delivery of packets.

• 3. These aspects, including data integrity, are addressed by an upper

layer transport protocol , such as the Transmission Control Protocol (TCP).

IPV4 HEADER

• The IPv4 packet header consists of 14 fields, of which 13 are

required.

• The 14th field (labelled Options) is optional.

Version Four-bit field 0100 indicates version 4 (IPv4) 0110 indicates version 6 (IPv6). Header Length (HL) The number of 32-bit words in header. 5 ≤ HL ≤ 15 Type of Service (DiffServ) Carries QoS information, i.e precedence, throughput, delay, reliability, and monetary cost Total Length The entire datagram size, including header and data, in bytes Identifier Identifies fragments of an original IP datagram Flags Used to control or identify fragments. Bit 0: Reserved; must be zero. Bit 1: Don’t Fragment (DF) Bit 2: More Fragments (MF) Fragment offset Specifies the offset of a particular fragment relative to the beginning of the original unfragmented IP datagram.

Time to Live Maximum time the datagram is allowed to remain in the internet system. Zero means the datagram must be destroyed Header checksum 16-bit checksum field is used for error-checking. Destination Address specifies a custom IP address to be used as destination. May be changed in transit by a network address translator. Options Additional header fields that may follow the destination address. Value included in Total Length (TL) Not commonly used. Protocol Defines the protocol used in the data portion of the IP datagram, e.g TCP, UDP, etc. Source Address Specifies the IP address to be used as source IP address in sent packets. Can be used illegitimately for spoofing

TYPE OF SERVICE (DIFFSERV)

TOS allows the selection of a delivery service in terms of precedence, throughput, delay, reliability, and monetary cost.

REVIEW – IPV4

• The IP was first standardized in Sep 1981 as IPv4.
• Each host attached to the IP based Internet had to be assigned a

unique 32-bit address

• The 32-bit IP addressing scheme involves a two level addressing

hierarchy:

Network Number/Prefix Host Number

IPv4 REVIEW – CLASSFUL ADDRESSING

• 1. In classful addressing, each IP address is divided into 5 classes
• 2. Class A 8 bits N/W id and 24 bits host id and so on B,C.
• 3. There was wastage of IP addresses by assigning blocks of addresses

which fall along octet boundaries

TECHNIQUES USED TO REDUCE ADDRESS SHORTAGE IN IPV4

Three techniques are used to increase IPv4 address space, i.e

• 1. Subnetting
• 2. Classless Inter Domain Routing (CIDR)
• 3. Network Address Translation (NAT)

SUBNETTING

• 1. Subnetting uses three-level hierarchy, i.e network, subnet, and

host.

• 2. The network-prefix is extended to accommodate classful network-

prefix and the subnet-number

• 3. The extended-network-prefix is identified by the subnet mask

Network-Prefix Subnet-Number Host-Number

ILLUSTRATION OF SUBNETTING

Internet G H1 H2 H3 H4

Subnet mask 255.255.255.0

All traffic to 128.10.0.0 128.10.1.1 128.10.1.2 128.10.2.1 128.10.2.2 Sub-network 128.10.1.0 Sub-network 128.10.2.0

Net mask 255.255.0.0

CLASSLESS INTER-DOMAIN ROUTING (CIDR) - 1

• 1. Eliminates traditional classful IP routing.
• 2. Supports the deployment of arbitrarily sized networks
• 3. Routing information is advertised with a bit mask/prefix length.
• 4. The mask/prefix length specifies the number of leftmost

contiguous bits in the network portion of each routing table entry

• 5. Example: 192.168.0.0/21

• Extract the destination IP address.
• Boolean AND the IP address with the subnet mask for each entry in

the routing table.

• The answer you get after ANDing is checked with the base address

entry corresponding to the subnet mask entry with which the destination entry was Boolean ANDed.

• If a match is obtained the packet is forwarded to the router with the

corresponding base address

CLASSLESS INTER-DOMAIN ROUTING (CIDR) - 2

NETWORK ADDRESS TRANSLATION (NAT)

• Each organization has single IP address
• Within organization, each host (workstation) also has IP unique to

the organization from reserved address ranges. Reserved ranges for NAT

• 10.0.0.0 – 10.255.255.255 (16,777,216 hosts)
• 172.16.0.0 – 172.31.255.255/12 (1,048,576 hosts)
• 192.168.0.0 – 192.168.255.255/16 (65,536 hosts)

NETWORK ADRESS TRANSLATION (NAT) ILLUTRATION

10.0.0.4 10.0.0.1

B C

Source Computer Source Computer's IP Address Source Computer's Port NAT Router's IP Address NAT Router's Assigned Port Number A 10.0.0.1 400 24.2.249.4 1 B 10.0.0.2 50 24.2.249.4 2 C 10.0.0.3 3750 24.2.249.4 3 D 10.0.0.4 206 24.2.249.4 4

FEATURES OF IPV6

• Introduced in 1995
• Has larger Address Space
• Uses aggregation-based address hierarchy

– Efficient backbone routing

• Uses efficient and Extensible IP datagram
• Provides stateless Address Autoconfiguration
• Has enhanced security (IPsec mandatory)
• Supports for Mobility

128 BIT IPV6 ADDRESS

3FFE:085B:1F1F:0000:0000:0000:00A9:1234

8 groups of 16-bit hexadecimal numbers separated by “:”

IPV6 HEADER

Version

• 4-bit Version number of Internet

Protocol = 6. Traffic Class

• 8-bit traffic class field.
• Sets different classes or different

priorities of IPv6 packets Flow Label

• 20-bit field
• Labels packets for which the source

requests special handling by the IPv6 routers.

• For example, a source can request non-

default quality of service or real-time service.

Source Address 128 bits. The address of the initial sender of the packet. Destination Address 128 bits. The address of the intended recipient of the packet. Hop Limit 8-bit unsigned integer. Decremented by

• ne by each node that forwards the

packet. The packet is discarded if Hop Limit is decremented to zero. Next Header 8-bit selector. Identifies the type of header that immediately follows the IPv6 header. Payload Length 16-bit unsigned integer Length of the ret of the packet that follows the IPv6 header, in octets.

20 bytes 15 16 31 vers hlen TOS total length identification flags flag-offset TTL protocol header checksum source address destination address

• ptions and padding
• 1. Removed (6)
• ID, flags, flag offset
• TOS, hlen
• header checksum
• 2. Changed (3)
• total length => payload
• protocol => next header
• TTL => hop limit
• 3. Added (2)
• Traffic class
• Flow label
• 4. Expanded
• address 32 to 128 bits

COMPARISON OF IPv4 AND IPv6 HEADERS

IPv4

40 bytes

IPv6

vers traffic class flow-label payload length next header hop limit source address destination address

MAJOR IMPROVEMENTS OF IPV6 HEADER

• 1. No option field: Replaced by extension header. Result in a

fixed length, 40-byte IP header.

• 2. No header checksum: Result in fast processing.
• 3. No fragmentation at intermediate nodes: Result in fast IP

forwarding.

EXTENSION HEADERS

• 1. Routing – Extended routing, like IPv4 loose list of routers to visit
• 2. Fragmentation – Fragmentation and reassembly
• 3. Authentication – Integrity and authentication, security
• 4. Encapsulation – Confidentiality
• 5. Hop-by-Hop Option – Special options that require hop-by-hop

processing

• 6. Destination Options – Optional information to be examined by

the destination node