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Networking Basics

Networking Basics 37
Networking Networking Networking Networking Basics Basics Basics Basics Raj Jain 1 JainCIS.Ohio-State.Edu Columbus, OH 43210 The Ohio State University Raj JainOverview Overview q q q q q q q Raj Jain 2 Domain Name System TCP Internet Protocol (IP), IPv6 Ethernet, HDLC, PPP Flow and Error Control ISO/OSI and TCP/IP Reference Model Standards OrganizationsInternational Standards Organizations International Standards Organizations q q m m m m q Raj Jain 3 IEC: International Electrotechnical Commission Example Standards: G.724, X.25, Q.931 Radio (CCIR) ITU-R: Consultative Committee on International Telephone and Telegraph (CCITT) ITU-T: Consultative Committee on International ITU: International Telecommunications Union Chartered by United Nations ISO: International Standards OrganizationNational Standards Organizations National Standards Organizations q m m m m Raj Jain 4 Represents USA in ITU, IEC, and ISO ANSI X3.131-1994 SCSI-2 ANSI T1.105-1995 SONET Non-governmental, nonprofit, over 300 committees ANSI: American National Standards InstituteProfessional Associations Professional Associations q m m ⇒ ISO (via ANSI) m ⇒ ⇒ q m q m q q Raj Jain 5 www.frforum.comFrame Relay Forum, www.atmforum.comATM Forum, TIA: Telecommunications Industries Association, Example: EIA-232 (RS-232) www.eia.orgEIA: Electronic Industries Association, ISO 8802-3:1998 IEEE 802.3 Ethernet IEEE IEEE: Inst of Electrical and Electronic Engineers,Professional Communities Professional Communities q m m m m m q q Raj Jain 6 draft-bhani-mpls-te-eval-00.txt draft-ietf-diffserv-framework-02.txt Drafts: =, Request for Comments (RFC), Now chartered by Internet Society development Originated by DARPA for TCP/IP protocol www.ietf.orgInternet Engineering Task Force, IETF:ISO/OSI Reference Model ISO/OSI Reference Model 3 ASCII Text, Sound Session 2 Transport Network 1 Physical Raj Jain 7 How to transmit signal: Coding Two party communication: Ethernet Datalink Routing, Addressing: IP End-to-end communication: TCP Establish/manage connection Presentation File transfer, Email, Remote Login ApplicationTCP/IP Reference Model TCP/IP Reference Model q q TCP/IP ProtocolsOSI Ref Model HTTP Session TransportUDP Transport IPNetwork Host to NetworkRadio Physical Raj Jain 8 Pointnet Point-to-PacketEther Datalink Internetwork TCP Presentation TelnetFTPApplication Application TCP/IP Ref Model IP = Internet Protocol (Routing) TCP = Transport Control ProtocolLayered Packet Format Layered Packet Format q FTP Raj Jain 9 TrailerHeader Ethernet Data EthernetEthernet Header IP Data IP Header TCP Data TCP Header FTP Data data. passed as N-1th layer Nth layer control info isFlow Control Flow Control q q q SenderSender DataDataData Ack Ack Data Data Ack Ack Raj Jain 10 ReceiverReceiver Methods: Stop and wait, Sliding window Sender throttled until receiver grants permission receiver, but maximizes throughput Flow Control = Sender does not flood theError Control Error Control q q q 11 1 Ack 2 Ack 3 233 2Ack 5 Ack 5 Raj Jain 11 Timeout Srej 3 Stop and Wait, Go back n Selective Reject Error Recovery: Automatic Repeat Request (ARQ) Numbers, Ack/Nak, Time-out Error Detection: Cyclic Redundancy Check, Sequence error, in the proper order to network layer Error Control = Deliver frames withoutConnection-Oriented vs Connection-Oriented vs Connectionless Connectionless q m m q m m Raj Jain 12 The address decides the next hop at each router Complete address on each packet Connectionless: Postal System. sufficient. Data need not have address. Circuit number is Path setup before data is sent Connection-Oriented: Telephone SystemMultiple Access Protocols Multiple Access Protocols q q q q Raj Jain 14 Standardized by IEEE 802.3 committee. Ethernet uses CSMA/CD. Stop if you hear someone else. Listen while transmitting. CSMA/CD: CSMA with Collision Detection Listen before you transmit CSMA: Carrier Sense Multiple Access Worst case utilization = 1/(2e) =18% Transmit whenever you like Aloha at University of Hawaii:Ethernet Standards Ethernet Standards q q q q q q q Raj Jain 15 repeaters). Also, known as synchronous Ethernet. 10BASE-FB: 10 Mb/s fiber optic backbone (between 10BASE-FL: 10 Mb/s fiber optic point-to-point link 10BASE-T: 10 Mb/s over 2 pairs of UTP (ThinWire), 185 m max segments 10BASE2: 10 Mb/s over thin RG58 coaxial cable 1BASE5: 1 Mb/s over 2 pairs of UTP max segments 10BROAD36: 10 Mb/s over broadband cable, 3600 m 10BASE5: 10 Mb/s over coaxial cable (ThickWire)HDLC Family HDLC Family q q q q ISDN q q q q q q Raj Jain 16 V.120 and Frame relay also use HDLC Advanced Data Comm Control Proc (ADCCP): ANSI Logical Link Control (LLC): IEEE Point-to-Point Protocol (PPP): Internet Teletex Link Access Procedure for half-duplex links (LAPX): Link Access Procedure for modems (LAPM): V.42 Link Access Procedure for the D channel (LAPD): Link Access Procedure-Balanced (LAPB): X.25 High-Level Data Link Control (HDLC): ISO Synchronous Data Link Control (SDLC): IBMHDLC HDLC q q q q q q q q Raj Jain 17 may respond before command Asynchronous Response Mode (ARM): Secondary Station Asynchronous Balanced Mode (ABM): Combined secondary Normal Response Mode (NRM): Response from Balanced Configuration: Two combined station Unbalanced Configuration: One or more secondary Combined Station: Both primary and secondary Secondary Station:Issue responses Primary station: Issue commandsHDLC Framing: Bit Stuffing HDLC Framing: Bit Stuffing q q q 0 11111 11111 11111 10010 01111110 0 111110 111110 111110 10010 01111110 0 11111 11111 11111 10010 Raj Jain 18 Receiver Flag Transmitter Remove stuffed bits at destination Stuff bits if pattern appears in data HDLC frames are delimited by flags: 01111110HDLC Frames HDLC Frames q m m q m m ⇒ q m m m m Raj Jain 19 Miscellaneous commands and responses Recovery commands and responses Information transfer commands and responses Mode setting commands and responses Unnumbered Frames: Control No more data to sendFinal Go back N and Selective Reject Supervisory Frames: Flow and error control Poll/Final = Command/Response Piggybacked Acks: Next frame expected Information Frames: User dataPPP: Introduction PPP: Introduction q q q q q q q Raj Jain 20 Uses byte stuffing in stead of bit stuffing Uses flags like HDLC PPP is a variation of HDLC provider (ISP) via modem PPP is used when you connect to an internet service Now being used for router-router connection also Originally for User-network connection Point-to-point ProtocolPPP in HDLC-Like PPP in HDLC-Like Framing Framing Info q q 7E ⇒ 7D ⇒ Raj Jain 21 7D 5D 7D 5E Byte Stuffing: Flag = 0111 1110 = 7E FlagCRCPadding 000000111111111101111110 ProtocolControlAddressFlagInternet Protocol (IP) Internet Protocol (IP) q q q q q Raj Jain 22 IP address: 32-bit = 4 decimal s, e.g., Internet Control Message Protocol (ICMP) Error and control messages generated by Provides only “Send” and “Delivery” services Routing Information Protocol (RIP) Open Shortest Path First (OSPF), Uses routing tables prepared by other protocols, e.g., Handles only data forwarding and loss possible. Higher layers should handle these. Best-effort delivery: Delay, out-of-order, corruption, Connectionless service. Variable size datagramsIP Addressing: An Example IP Addressing: An Example 10 10 q Raj Jain 23 Fig 14.6 All hosts on a network have the same network prefix 192.5.48 Router 192.5.48 Router Router Router 128.211128.10 Router 128.211128.10 RouterSubnetwork Subnetwork q q q q q Network RRR Subnet 1 Subnet 2Subnet n Raj Jain 24 10010100 10101000 00010000 00000000.AND. 11111111 11111111 11111110 00000000Mask: 10010100 10101000 00010000 11110001Address: Example: First 23 bits = subnet Mask .AND. Address = Prefix All hosts on the subnet have the same address prefix Generally each subnet is one Ethernet Network = Multiple subnets connected via routersForwarding an IP Datagram Forwarding an IP Datagram q q q Raj Jain 25 Fig 16.2 Forward to R3Net 4 Deliver DirectNet 3 Deliver DirectNet 2 Forward to R1Net 1 Next HopDestination Table at R2: Net 4R3Net 3R2Net 2R1Net 1 Net 4R3Net 3R2Net 2R1Net 1 Next Hop field does not appear in the datagram Routers maintain a “routing table” of “next hops” Delivers datagrams to destination network (subnet)IPv6: How Many Addresses? IPv6: How Many Addresses? q q 12 q ⇒ q m m 6 8 q 15 q ⇒ 12 9 q ⇒ 1215 Raj Jain 26 networks to 10networks. Desirable 10 end systems and 10 10IPng Requirements addresses 10Safety margin addresses per host to 2Some believe 2 Multiple addresses per interface Multiple interfaces per node More addresses may be required since computers 10Assuming 100 computers per person Each person will be served by more than one computer 10 Billion people by 2020IPv6 Addresses IPv6 Addresses q 12838 q 2 21 ⇒ 6 q / μ 1733 q 17 ⇒ q q q q q Raj Jain 27 85% of the space is unassigned Allows provider based, site-local, link-local Allows unicast, multicast, anycast Allows multiple addresses per interface Allows multiple interfaces per host. 1,564 address per sq. m8×10 addresses to 2×10Expected to support 8×10 s, it would take 20 yearsIf assigned at the rate of 10 addresses per sq. m of earth surface 665×10 addresses = 3.4×10 128-bit long. Fixed sizeColon-Hex Notation Colon-Hex Notation q Dot-Decimal q Colon-Hex: m m m m Raj Jain 28 2345:BA23:7::/40 Can specify a prefix by /length, e.g., :: Can leave the last 32 bits in dot-decimal, e.g., ::3243:0000:0000:ABCD FEDC::3243:0000:0000:ABCD sequence of zero words, e.g.,oneCan skip Can skip leading zeros of each word FEDC:0000:0000:0000:3243:0000:0000:ABCD : vs IPv4 IPv6 vs IPv4 q q q q q q q Raj Jain 29 assignment Allows “Plug and Play” as well as “Secure” address No optional fields. Replaced by extension headers. All fixed size fields. Added: Priority and flow label meaning as in IPv4 Only version number has the same position and IPv6 only twice the size of IPv4 header 1995 vs 1975Dentist’s Office Dentist’s Office Dentist Raj Jain 301000 Computers on the Dock 1000 Computers on the Dock Raj Jain 31TCP: Key Features TCP: Key Features q q q q q q q Raj Jain 32 closing a connection is not lost. Graceful connection shutdown: Data sent before does not confuse new connections Reliable connection startup: Data on old connection Stream interface: Continuous sequence of octets Full duplex communication Reliable transfer: Data is delivered in order Point-to-point communication: Two end-points Connection orientedTCP Header TCP Header NoNo 16163232 4 6 616 1616 x y q q q Raj Jain 33 Window = Number bytes allowed to send Ack number (32 bits): Next byte expected 20 = FTP, 23 = Telnet, 53 = DNS, 80 = HTTP, ... Port (16 bits): Identifies source user process Size in bits sum DataPadOptionsUrgent Check- OffsetPortPort WindowControlResvd DataAckSeqDestSourceDomain Name System: Hierarchy Domain Name System: Hierarchy nsf cobra q Raj Jain 34 Example: cnri reston eenetlabcis vacoohio-state dec ... usaugoveducom Unnamed rootName Resolution Name Resolution Query Response Raj Jain 35 CacheCache base Data- ResponseResponse ServerResolver User NameName QueryQuery basebase Data-Data- Response ServerServer NameName Query CacheCacheSummary Summary q q q q q q q Raj Jain 36 DNS allows name to address resolution TCP is a connection-oriented reliable stream protocol IPv6 extends addresses to 128 bits addresses IP is a connectionless forwarding protocol with 32-bit Ethernet uses CSMA/CD HDLC uses 01111110 flag and requires bit-stuffing developments IETF’s RFCs and I-Ds are key sources for recentNetworking Basics: Key References Networking Basics: Key References q q q Raj Jain 37 Prentice Hall, 1996 A. S. Tanenbaum, “Computer Networks,” 3rd Ed, Technical Overview,” 6th Ed, Prentice Hall, 1998 M. W. Murhammer, et al, “TCP/IP Tutorial and 5th Ed, Prentice Hall, 1997 W. Stallings, “Data and Computer Communications,”
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