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Notes on TCP/IP (cont.)
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Previous notes on TCP/IP. References:
Delivering the Data
IP AddressingIP addresses, which uniquely identify every host on the Internet, deliver data to the correct host. Apply to Network Information Center (NIC) for IP addresses. Addresses used to be class-based (based on Hunt, Fig. 2.2): Class A:
+--------+--------+--------+--------+
|0 | | | |
+--------+--------+--------+--------+
|<------>|<------------------------>|
8 network bits 24 host bits
Class B:
+--------+--------+--------+--------+
|10 | | | |
+--------+--------+--------+--------+
|<--------------->|<--------------->|
16 network bits 16 host bits
Class C:
+--------+--------+--------+--------+
|110 | | | |
+--------+--------+--------+--------+
|<------------------------>|<------>|
24 network bits 8 host bits
Class A: 1-126 = 126 networks of 2^24 ~~ 16M hosts each Address space is depleted. Not enough Class B addresses. Blocks of Class C addresses swells router tables. NIC used to give Class A, B, or C network address. Local network administrator assigns host addresses within that network address.
MU is 134.48 More recently, use RFC 1518 and RFC 1519 Classless Inter-Domain Routing (CIDR), a combination of addresses and subnet masks.
Submitted by Zachary Lund:
RoutingGateways deliver data to the correct network on a hop-by-hop basis. Routing domains are co-equal collections of autonomous systems. They exchange routing information using Border Gateway Protocol (BGP). Each routing domain makes routing decisions for itself, based on routing tables. Pascal routing table: cmd > netstat -nr | more Routing Table: IPv4 Destination Gateway Flags Ref Use Interface -------------------- -------------------- ----- ----- ------ --------- 134.48.4.0 134.48.4.38 U 1 7262 bge0 224.0.0.0 134.48.4.38 U 1 0 bge0 default 134.48.4.1 UG 1 4598 127.0.0.1 127.0.0.1 UH 44355576 lo0 Routing Table: IPv6 Destination/Mask Gateway Flags Ref Use If --------------------------- --------------------------- ----- --- ------ ----- fe80::/10 fe80::203:baff:fe2e:328 U 1 0 bge0 ff00::/8 fe80::203:baff:fe2e:328 U 1 0 bge0 default fe80::203:baff:fe2e:328 U 1 0 bge0 ::1 ::1 UH 3 12986445 lo0 Flags:
Use: Number of packet transmitted since ? 127.0.0.1 is a special "loopback" address Each gateway looks in its routing table to see where to send the packet, but how does it translate the name into the IP address? Domain Name Service (DNS)Host TableOn pascal: cmd > more /etc/hosts # # Internet host table # 127.0.0.1 localhost 134.48.4.7 rescue 134.48.4.19 euclid euclid.mscs.mu.edu 134.48.4.30 neumann.mscs.mu.edu 134.48.4.22 fourier fourier.mscs.mu.edu 134.48.4.34 turing turing.mscs.mu.edu 134.48.4.38 pascal pascal.mscs.mu.edu loghost 134.48.4.230 offlp1 134.48.4.231 faclp1 134.48.4.233 colorlp1 134.48.4.234 proglp1 134.48.4.235 classlp1 134.48.4.237 studlp1 134.48.4.239 faccolorlp1 134.48.87.92 copier 134.48.13.142 usa2 usa2.lab.mscs.mu.edu Problems:
Enter DNS:
Root domain
Non-recursive query:
Example of traceroute: cmd > traceroute www.pku.edu.cn traceroute to sun1000e.pku.edu.cn (202.112.7.12), 30 hops max, 40 byte packets 1 gate4 (134.48.4.100) 7 ms 3 ms 3 ms 2 wisgw.mu.edu (134.48.1.250) 6 ms 4 ms 4 ms 3 milwaukee-marquette.wiscnet.net (140.189.32.1) 27 ms 73 ms 65 ms 4 Kathakt.nap.net (207.112.247.14) 76 ms * 211 ms 5 sl-chi-19-H11/0-T3.sprintlink.net (144.228.159.17) 87 ms 145 ms * 6 sl-chi-6-F0/0.sprintlink.net (144.228.50.6) 91 ms 104 ms 130 ms 7 144.228.10.54 (144.228.10.54) 161 ms 136 ms 86 ms 8 sl-stk-6-F/T.sprintlink.net (198.67.6.6) 96 ms 182 ms 183 ms 9 gsl-stock-3-Fddi0/0.gsl.net (204.59.128.197) 197 ms * 415 ms 10 204.59.160.246 (204.59.160.246) 655 ms 634 ms 708 ms 11 202.112.1.205 (202.112.1.205) 737 ms 601 ms 626 ms 12 202.112.1.197 (202.112.1.197) 755 ms 843 ms 679 ms 13 beijing-rgw.net.edu.cn (202.112.1.66) 742 ms 672 ms 640 ms 14 202.112.5.6 (202.112.5.6) 604 ms 726 ms 688 ms 15 sun1000e.pku.edu.cn (202.112.7.12) 674 ms 692 ms 751 ms MultiplexingProtocol and port numbers deliver data to the correct software module within the host. Network layer receives information for many applications Protocol numbers identify Transport Layer protocols. On pascal: cmd > cat /etc/protocols #ident "@(#)protocols 1.6 01/09/04 SMI" /* SVr4.0 1.1 */ # # Internet (IP) protocols # ip 0 IP # internet protocol, pseudo protocol number icmp 1 ICMP # internet control message protocol igmp 2 IGMP # Internet Group Management ggp 3 GGP # gateway-gateway protocol ipip 4 IP-IP # IP in IP (encapsulation) tcp 6 TCP # transmission control protocol cbt 7 CBT # Core Based Trees egp 8 EGP # exterior gateway protocol igp 9 IGP # any private interior gateway pup 12 PUP # PARC universal packet protocol udp 17 UDP # user datagram protocol mux 18 MUX # Multiplexing hmp 20 HMP # host monitoring protocol xns-idp 22 XNS-IDP # Xerox NS IDP rdp 27 RDP # "reliable datagram" protocol idpr 35 IDPR # Inter-Domain Policy Routing Protocol idpr-cmtp 38 IDPR-CMTP # IDPR Control Message Transport Protocol sdrp 42 SDRP # Source Demand Routing Protocol idrp 45 IDRP # Inter-Domain Routing Protocol rsvp 46 RSVP # Resource Reservation Protocol gre 47 GRE # Generic Routing Encapsulation mobile 55 MOBILE # IP Mobility ospf 89 OSPFIGP # Open Shortest Path First pim 103 PIM # Protocol Independent Multicast ipcomp 108 IPComp # IP Payload Compression Protocol vrrp 112 VRRP # Virtual Router Redundancy Protocol sctp 132 SCTP # Stream Control Transmission Protocol # # Internet (IPv6) extension headers # hopopt 0 HOPOPT # Hop-by-hop options for IPv6 ipv6 41 IPv6 # IPv6 in IP encapsulation ipv6-route 43 IPv6-Route # Routing header for IPv6 ipv6-frag 44 IPv6-Frag # Fragment header for IPv6 esp 50 ESP # Encap Security Payload for IPv6 ah 51 AH # Authentication Header for IPv6 ipv6-icmp 58 IPv6-ICMP # IPv6 internet control message protocol ipv6-nonxt 59 IPv6-NoNxt # No next header extension header for IPv6 ipv6-opts 60 IPv6-Opts # Destination Options for IPv6 Transport protocols use port numbers to identify applications. On pascal: cmd > more /etc/services # # # Copyright (c) 1999-2001 by Sun Microsystems, Inc. # All rights reserved. # # Network services, Internet style # tcpmux 1/tcp echo 7/tcp echo 7/udp discard 9/tcp sink null discard 9/udp sink null systat 11/tcp users daytime 13/tcp daytime 13/udp netstat 15/tcp chargen 19/tcp ttytst source chargen 19/udp ttytst source ftp-data 20/tcp ftp 21/tcp ssh 22/tcp # Secure Shell telnet 23/tcp smtp 25/tcp mail time 37/tcp timserver time 37/udp timserver name 42/udp nameserver whois 43/tcp nicname # usually to sri-nic domain 53/udp domain 53/tcp bootps 67/udp # BOOTP/DHCP server bootpc 68/udp # BOOTP/DHCP client kerberos 88/udp kdc # Kerberos V5 KDC kerberos 88/tcp kdc # Kerberos V5 KDC hostnames 101/tcp hostname # usually to sri-nic pop2 109/tcp pop-2 # Post Office Protocol - V2 pop3 110/tcp # Post Office Protocol - Version 3 sunrpc 111/udp rpcbind sunrpc 111/tcp rpcbind imap 143/tcp imap2 # Internet Mail Access Protocol v2 ldap 389/tcp # Lightweight Directory Access Protocol ldap 389/udp # Lightweight Directory Access Protocol submission 587/tcp # Mail Message Submission submission 587/udp # see RFC 2476 ldaps 636/tcp # LDAP protocol over TLS/SSL (was sldap) ldaps 636/udp # LDAP protocol over TLS/SSL (was sldap) . . . Port numbers:
E.g. TELNET:
Combination of IP address + port number = socket
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