TCP/IP Explored Jun Wu 11/11/2018

Contents 1. Introduction 2. IP explored 3. TCP explored 4. Other common protocols in TCP/IP 5. TCP/IP programming 6. Summary 11/11/2018

Introduction TCP/IP – A suite of internet protocols named after Transmission Control Protocol/Internet Protocol, the de facto standard protocol for today’s internet. TCP/IP over OSI (Open Systems Interconnection) - OSI layers : Application, Presentation, Session, Network, Data Link, Physical - Included Protocols: FTP,SNMP, Telnet,TFTP, Finger, NFS, SMTP,DNS, POP,BOOTP,TCP, UDP, IP - TCP/IP layers: Application, Host-to-Host transport, Internet, Network interface 11/11/2018

IP – Internet Protocol Where does it work? Network layer, connectionless Functions - Receiving data bits from lower layer - Assembling them into packets - Selecting the “best” route to send packets to destinations. 11/11/2018

IP header format Version IHL Type of Service Total Length Identification DF MF Fragment offset Time to leave Protocol Header checksum Source address Destination address Options 11/11/2018

IP address (IPv4) 32 bits ( 4 groups of 8 bits ) Example: 204.163.25.37 5 classes: A (0, 0~127), B(10, 128~191), C(110, 192~223), D(1110, 224~254), E(11110, reserved) Two parts: Network ID & Host ID, different classes of IP address support different number of networks and hosts 11/11/2018

IP Subnet Partition a network address into separate subnetworks. Why? Expanding limited IPv4 address space Example: consider 1 class C IP address, it supports 1 network & 256 hosts (actually 254). Now if “steal” 1 higher-bit of host ID and used as part of network ID -> 2 subnets; “steal” 2 bits -> 4 subnets, and so on. Another solution: 128 bits IP address (IPv6) 11/11/2018

IP masking How to subnet? Masking! Rule: if a bit in an IPv4 address is used as part of network ID, then set the corresponding mask bit to 1; if used as host ID, set mask to 0. Example: IP address 192.203.97.0 with mask 255.255.255.0 -> Network ID is 192.203.97, host ID is 0~254. Now borrowing two leftmost bits of host ID, 4 subnets form ( 192.203.97.0, 64, 128, 192). Subnet mask 255.255.255.192, given 192.203.97.143, first routed to subnet 192.203.97.128, then to the host 15 on this subnet. 11/11/2018

Summary IP is a connectionless protocol on Network layer. IP packs data bits from lower layer into packets with a header and routes these packets between nodes. It also fragments & resembles datagrams when necessary. IPv4 address has only 32 bits – limited space! Different classes of IP address supports different number of networks & hosts. IPv4 address space can be expanded through subset and mask technique. 11/11/2018