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TCP/IP Networking

TCP/IP Networking. Chapter 13. Introduction. TCP/IP is the networking protocol suite most commonly used with most operating systems, and it is the native language of the Internet. IP – Internet Protocol TCP – Transmission Control Protocol

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TCP/IP Networking

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  1. TCP/IP Networking Chapter 13

  2. Introduction • TCP/IP is the networking protocol suite most commonly used with most operating systems, and it is the native language of the Internet. • IP – Internet Protocol • TCP – Transmission Control Protocol • TCP/IP defines a uniform programming interface to different types of network hardware • IP is the suite’s underlying delivery protocol • TCP and UDP are transport protocols built on top of IP to deliver packets to specific applications. Chapter 13 - TCP/IP Networking

  3. Introduction • TCP is a connection-oriented protocol that facilitates conversation between two programs. • It works a lot like a phone call: the words you speak are delivered to the person you called, and vice versa. • The connection persists even when neither party is speaking. • TCP provides reliable delivery, flow control, and congestion control. Chapter 13 - TCP/IP Networking

  4. Introduction • This chapter introduces the TCP/IP protocols in the political and technical context of the Internet. • Other network-related chapters in this book include: • Chapter 14 Routing • Chapter 16 Domain Name System • Chapter 20 Network Management and Debugging Chapter 13 - TCP/IP Networking

  5. 1. TCP/IP and the Internet • Introduction: • TCP/IP and the Internet share a history that goes back several decades. • The technical success of the Internet is due largely to the elegant and flexible design of TCP/IP. • In turn the Internet has helped TCP/IP prevail over several competing protocol suites that were favored at one time or another for political or commercial reasons. Chapter 13 - TCP/IP Networking

  6. 1. TCP/IP and the Internet • A brief History Lesson • Contrary to popular belief, the Internet is not a Microsoft product that debuted in 1995, nor is it the creation of a U.S. vice president. • The progenitor of the modern Internet was a network called ARPANET that was established in 1969 by DARPA. • ARPANET eventually became the NSFNET backbone, which was connected to supercomputer sites and regional networks. Chapter 13 - TCP/IP Networking

  7. 1. TCP/IP and the Internet • A brief History Lesson (cont) • By the end of the 1980s the network was no longer a research project and NSF extracted itself from the networking business. • This led to a transition to a commercial Internet over a period of several years. • NSFNET was turned off in April 1994 Chapter 13 - TCP/IP Networking

  8. 1. TCP/IP and the Internet • A brief History Lesson (cont) • In the Mid 1980s the Internet was essentially • the original ARPANET sites and • a handful of universities with DEC VAX computers running Berkeley UNIX on 10 Mb/s Ethernets connected by 56 Kb/s leased telephone lines. Chapter 13 - TCP/IP Networking

  9. 1. TCP/IP and the Internet • A brief History Lesson (cont) • Every September (when students came back to school) the net would suffer a congestion collapse. • This led to algorithms for collision avoidance and retransmissions coming out of the Lawrence Berkeley Labs. Chapter 13 - TCP/IP Networking

  10. 1. TCP/IP and the Internet • A brief History Lesson (cont) • Moore’s law (hardware speeds double every 18 months) and market pressure have greatly accelerated the development of the net. • Network interfaces have increased by a factor of 1,000 • Speed of leased circuits by a factor of 12,000 • Total number of hosts by a factor of 50,000 Chapter 13 - TCP/IP Networking

  11. 1. TCP/IP and the Internet • A brief History Lesson (cont) • Anyone who has designed software and seen it obsoleted by the next generation of hardware or the next operating system release knows how amazing it is that our Internet is still alive and kicking, running basically the same TCP/IP protocol suite that was designed 25 years ago for a very different Internet. Chapter 13 - TCP/IP Networking

  12. 1. TCP/IP and the Internet • How the Internet is managed today • The development of the Internet has always been a cooperative and open effort. • Several organizations are involved • ICANN – the Internet Corporation for Assigned Names • IEFT – the Internet Engineering Task Force • Development and Standardization of the technical aspects • ISOC – the Internet Society Chapter 13 - TCP/IP Networking

  13. 1. TCP/IP and the Internet • Network standards and documentation • The technical activities of the Internet community are summarized in documents known as RFCs • An RFC is a Request For Comments • Protocol standards, proposed changes, and informational bulletins all usually end up as RFCs • RFCs are numbered sequentially (currently there are a little more than 3,000) and they also have descriptive titles. Chapter 13 - TCP/IP Networking

  14. 1. TCP/IP and the Internet • Network standards and documentation (cont) • There are also subsets of RFCs • FYI – For Your Information • BCP – Best Current Practice • STD – Standard Numbers • RFCs are available from numerous sources. • There is a list of actively maintained RFC mirrors at www.rfc-editor.org Chapter 13 - TCP/IP Networking

  15. 2. Networking Road Map • Introduction • Now that we have provided a bit of context, let’s take a look at the TCP/IP protocols themselves. • TCP/IP is a “protocol suite.” It includes several components, each defined by a standards-track RFC or series of RFCs • IP – RFC 791 – routes packets • ICMP – RFC 792 – low level support for IP (errors, routing, and debugging) • ARP – RFC 823 – translate hardware to IP • UDP and TCP – RFC 768 and 793 Chapter 13 - TCP/IP Networking

  16. 2. Networking Road Map • Introduction (cont) • TCP/IP is designed around the layering scheme Chapter 13 - TCP/IP Networking

  17. 2. Networking Road Map • Introduction (cont) • Here is how the various components and clients of TCP/IP fit into its general architecture and layering Chapter 13 - TCP/IP Networking

  18. 3. Packets and Encapsulation • Introduction • UNIX can support a variety of physical networks • Ethernet, FDDI, Token Ring, ATM, wireless Ethernet • Hardware is managed within the Link layer of the TCP/IP architecture, and higher-level protocols do not know or care about the specific hardware being used Chapter 13 - TCP/IP Networking

  19. 3. Packets and Encapsulation • Introduction (cont) • Data travels on networks in the form of packets • Maximum length is imposed by each layer. • Each packet consists of a header and a payload • Header • Tells where it came from and where its going • Can also include checksums protocol-specific information, or other handling instructions • Payload • The data being transferred Chapter 13 - TCP/IP Networking

  20. 3. Packets and Encapsulation • Introduction (cont) • As a packet travels down the protocol stack, each protocol adds its own header information. • Each protocol’s finished packet becomes the payload part of the packet generated by the next protocol. • For example: • A UDP packet being transmitted over Ethernet contains three different wrappers or envelopes • UDP, IP, and Ethernet Chapter 13 - TCP/IP Networking

  21. 3. Packets and Encapsulation • Introduction (cont) Chapter 13 - TCP/IP Networking

  22. 3. Packets and Encapsulation • The link layer • Introduction • In this section, we cover several topics that bridge the gap between the lowest layers of the networking software and the network hardware itself Chapter 13 - TCP/IP Networking

  23. 3. Packets and Encapsulation • The link layer (cont) • Ethernet framing standards • One of the main chores of the link layer is to add headers to packets and to put separators between them • The headers contain the packets’ link-layer addressing information and checksums • The separators ensure that receivers can tell where one packet stops and the next one begins. • The process of adding these extra bits is known generically as framing. Chapter 13 - TCP/IP Networking

  24. 3. Packets and Encapsulation • The link layer (cont) • Ethernet framing standards (cont) • Two different standards for 10 Mb/s Ethernet are in common use: • DIX Ethernet II • Used by UNIX hosts and CISCO routers • IEEE 802.2 LLC SNAP • Novell and IPX • UNIX machines can talk to both, Windows can use either but can only talk to machines using the one selected. Chapter 13 - TCP/IP Networking

  25. 3. Packets and Encapsulation • The link layer (cont) • Ethernet cabling and signaling standards • The cabling options for 10 Mb/s Ethernet are fairly straightforward, but things got complicated when 100 Mb/s came out. There were 3 basic standards at first. • VG – 4 pair CAT 5 – initially pushed by HP (ignored by others) • TX – two pair CAT 5 • FX – fiber multimode • Refer to Chapter 15 – Network Hardware – for more information about the various Ethernet standards Chapter 13 - TCP/IP Networking

  26. 3. Packets and Encapsulation • The link layer (cont) • Wireless networking • The IEEE 802.11 standard attempts to define framing and signaling standards for wireless links. • Unfortunately, it was originally vague and included several parameters and options that were not fully specified. • One interoperability issue you may need to pay attention to is that of “translation” vs. “encapsulation” • Another is power-saving modes in laptops. Chapter 13 - TCP/IP Networking

  27. 3. Packets and Encapsulation • The link layer (cont) • Maximum transfer units • The size of packets on a network may be limited both by hardware specifications and protocol conventions. Chapter 13 - TCP/IP Networking

  28. 3. Packets and Encapsulation • The link layer (cont) • Maximum transfer units (cont) • In the TCP/IP suite, the IP layer splits packets to conform to the MTU of a particular network link. • Fragmentation problems can be insidious. Particularly with VPNs adding their own headers. • Consult the ifconfig manpage to see how to set an interface’s MTU Chapter 13 - TCP/IP Networking

  29. 3. Packets and Encapsulation • Packet addressing • Introduction: • Like letters or email messages, network packets must be properly addressed in order to reach their destinations. • Several addressing schemes are used in combination: • MAC – for hardware • IP – for software • Hostname – for people Chapter 13 - TCP/IP Networking

  30. 3. Packets and Encapsulation • Packet addressing (cont) • MAC Addressing – Hardware • Ethernet devices are assigned a unique 6-byte hardware address at the time of manufacture • The first 3 bytes identify the manufacturer • www.iana.org/assignments/ethernet-numbers • The last 3 are a serial number • Some hardware and some OS’s let you change the hardware addresses – Don’t Do That! Chapter 13 - TCP/IP Networking

  31. 3. Packets and Encapsulation • Packet addressing (cont) • IP addresses – Software Numbers • One 4 byte IP address is assigned to each network interface. • IP addresses are globally unique and hardware independent • This is a small lie – see NAT discussions • IP addresses are discussed in the next section • Mapping of IP to MAC is handled at the link layer Chapter 13 - TCP/IP Networking

  32. 3. Packets and Encapsulation • Packet addressing (cont) • Hostname • Since IP addresses are long, seemingly random numbers, they are hard for people to remember. • UNIX allows one or more hostnames to be associated with an IP address. • This mapping can be set up in several ways • Static (/etc/hosts) • NIS, NIS+ • DNS – Domain Name System Chapter 13 - TCP/IP Networking

  33. 3. Packets and Encapsulation • Ports • IP addresses identify machines, or more precisely network interfaces on a machine. • They are not specific enough to address particular processes or services • TCP and UDP extend IP addresses with the concept know as a “port” • A port is a 16 bit number that supplements an IP address. Chapter 13 - TCP/IP Networking

  34. 3. Packets and Encapsulation • Ports (cont) • Standard UNIX services such as email, FTP, and the remote login server all associate themselves with “well-known” ports defined in the file /etc/services. • To help prevent impersonation of these services, UNIX systems restrict access to port numbers under 1,024 to root. Chapter 13 - TCP/IP Networking

  35. 3. Packets and Encapsulation • Address types • At both the IP layer and the link layer, there are several different types of addresses: • Unicast - addresses that refer to a single host (network interface, really) • Multicast - addresses that identify a group of hosts • Broadcast - addresses that include all hosts on the local network Chapter 13 - TCP/IP Networking

  36. 3. Packets and Encapsulation • Address types (cont) • Multicast addressing facilitates applications such as video conferencing in which the same set of packets must be sent to all participants. • At the IP layer, • Multicast addresses begin with a byte in the range 224 to 239. • Broadcast addresses have a host part that is all 1s Chapter 13 - TCP/IP Networking

  37. 4. IP Addresses: The Gory Details • Introduction • An IP address, also called an Internet Address, is four bytes long and is divided into a network part and a host part. • By convention, IP addresses are written as decimal numbers, one for each byte, separated by periods. • 134.197.40.1 Chapter 13 - TCP/IP Networking

  38. 4. IP Addresses: The Gory Details • Introduction (cont) • When 127 is the first byte of an address, it denotes the “loopback network,” a fictitious network that has no real hardware and only one host • The loopback address 127.0.0.1 always refers to the current host. Its symbolic name is “localhost” • An interface’s IP address and other parameters are set with the ifconfig command. Chapter 13 - TCP/IP Networking

  39. 4. IP Addresses: The Gory Details • IP Address classes • Historically IP addresses were grouped into “classes” depending upon the leftmost byte. • These classes determined which bytes of the addresses were in the network portion and which were in the host portion. • Classes A, B, and C denote regular IP addresses. • Classes D and E are used for multicasting and research purposes. Chapter 13 - TCP/IP Networking

  40. 4. IP Addresses: The Gory Details • IP Address classes (cont) Chapter 13 - TCP/IP Networking

  41. 4. IP Addresses: The Gory Details • Subnetting and netmasks • It is rare for a single physical network to have more than 100 computers attached to it. • Therefor the Class A and Class B networks which allow 16,777,214 and 65,534 hosts per network are really quite silly and wasteful. • Most sites that have these addresses use a refinement of the addressing scheme called subnetting • Here a portion of the host portion is “borrowed” to extend the network portion. Chapter 13 - TCP/IP Networking

  42. 4. IP Addresses: The Gory Details • Subnetting and netmasks (cont) • For example, the four bytes of a class B address would normally be interpreted as N.N.H.H • Subnetting would move the third byte to the network side - N.N.N.H • The use of subnetting turns a single class B network address into 246 distinct class-C-like networks, each capable of supporting 254 hosts. • 134.197.40.1 - ponderosa.cs.unr.edu Chapter 13 - TCP/IP Networking

  43. 4. IP Addresses: The Gory Details • Subnetting and netmasks (cont) • This reassignment is effected by using the ifconfig command to associate an explicit “subnet mask” with a network interface. • Each bit of the netmask that corresponds to the network portion of an IP address is set to 1, and the host bits are set to 0. • For example, the netmask for the N.N.N.H configuration would be • 255.255.255.0 in decimal • 0xFFFFFF00 in hex Chapter 13 - TCP/IP Networking

  44. 4. IP Addresses: The Gory Details • The IP address crisis • The Internet community realized in about 1992 that there were three fundamental problems with the original address allocation scheme. • First - we were going to run out of class B addresses by mid 1995 • At the same time the routing tables were growing so large they would not fit in memory of the routers. • Finally IP addresses were assigned on a first-come first-served basis • The next number could be next door or across the world. Chapter 13 - TCP/IP Networking

  45. 4. IP Addresses: The Gory Details • The IP address crisis (cont) • To solve these problems, two solutions were advanced in tandem: one for the immediate future, and one for the long term. • Short Term - CIDR Classless Inter-Domain Routing • A different way of managing the existing four-byte addresses • Long Term - IP v 6 • Address space is 16 bytes (basically one address per square meter of the earth’s surface) Chapter 13 - TCP/IP Networking

  46. 4. IP Addresses: The Gory Details • The IP address crisis (cont) • The complexity of IPv6, the efficiency of CIDR and NAT, and the inertia of an Internet that already works pretty well all combine to suggest that it may be a long time before we move to IPv6 • Other countries may push it (China and Japan) if they can’t get the IPv4 address space they want. • Voice over IP systems would also benefit from IPv6 Chapter 13 - TCP/IP Networking

  47. 4. IP Addresses: The Gory Details • CIDR: Classless Inter-Domain Routing • CIDR eliminates the class system that formerly determined the network portion of an IP mask. • With CIDR, several class C networks can be allocated to the same site without requiring the Internet to have separate routing table entries for each one. • The site could also be allocated a subspace of a class A or B address Chapter 13 - TCP/IP Networking

  48. 4. IP Addresses: The Gory Details • Address Allocation • In the early days, individual sites applied to the Internet Network Information Center (InterNIC) for address space • ARIN has replaced InterNIC in North America • Only network numbers are assigned, host numbers are the responsibility of the site. Chapter 13 - TCP/IP Networking

  49. 4. IP Addresses: The Gory Details • Address Allocation (cont) • Administratively ICANN (the Internet Corporation for Assigned Names and Numbers) has delegated blocks of addresses to three regional Internet Registries Chapter 13 - TCP/IP Networking

  50. 4. IP Addresses: The Gory Details • Private addresses and NAT • Another temporary solution to address space depletion is the use of private IP address spaces • RFC1918 sets aside 1 class A, 16 class B and 256 class C networks that will never be used and can be used internally by any site • The catch is that packets bearing those addresses must never be allowed to sneak out onto the Internet. Chapter 13 - TCP/IP Networking

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