internetworking with tcp ip volume one

... header contains IP ad- dresses whereas the frame header contains physical addresses Figure 7.2 shows the general form of a datagram: Figure 7.2 General form of an IP datagram, the TCP/IP analogy to ... shipped across the underlying network in a single frame In addition, because IP represents the offset of the data in multiples of eight octets, the fragment size must be chosen to be a multiple ... corrupted data go undetected Fields SOURCE IP ADDRESS and DESTINATION IP ADDRESS contain the 32-bit IP addresses of the datagram's sender and intended recipient Although the datagram may be routed

Ngày tải lên: 04/07/2014, 22:21

... basic unit of transfer in a TCP/IP internet is the IP da- tagram This chapter adds to the description of connectionless service by describing how routers forward IP datagrams and deliver them ... is to make IP routing decisions What about multi-homed hosts? Any computer with multiple network connections can act as a router, and as we will see, multi-homed hosts running TCPJIP have all ... to have routers record their IP addresses along with timestamps because the record route option already provides that capability However, recording IP addresses with timestamps eliminates Universal

Ngày tải lên: 04/07/2014, 22:21

... always specify the IP address of the original source and the IP address of the ultimate destination? When IP executes the routing algorithm, it selects a new IP address, the IP address of the ... an IP datagram has reached its final destination is not quite as trivial as it seems Remember that even a host may have multiple physical connec- tions, each with its own IP address When an IP ... monitoring IP traffic on a local area network for 10 minutes one even- ing, someone notices that all frames destined for machine A carry IP datagrams that have destination equal to A's IP address,

Ngày tải lên: 04/07/2014, 22:21

... message mechanism to the TCP/IP protocols The mechanism, known as the Internet Control Message Protocol (ICMP), is considered a required part of IP and must be included in every IP implemen- tation ... ICMP messages are encapsulated and sent using IP, ICMP is not considered a higher level protocol - it is a required part of IP The reason for using IP to deliver ICMP messages is that they may ... Testing Destination Reachability And Status (Ping) TCP/IP protocols provide facilities to help network managers or users identlfy net- work problems One of the most frequently used debugging tools

Ngày tải lên: 04/07/2014, 22:21

... cycle, it will pass around the cycle endlessly As mentioned previously, to prevent datagrams from circling forever in a TCP/IP internet, each IP datagram contains a time-to-live counter, sometimes ... operate indepen- dently, with each machine maintaining its own notion of the current time Clocks that differ widely can confuse users of distributed systems software The TCPJIP protocol suite includes ... estimation of round-trip delay can be difficult and substantial- ly restricts the utility of ICMP timestamp messages Of course, to obtain an accurate estimate of round trip delay, one must take many

Ngày tải lên: 04/07/2014, 22:21

... dividing an IP address into two parts arises from the size of the routing tables required in routers. Instead of keeping one routing entry per destination host, a router can keep one routing ... after TCP/IP was designed. Growth has been most apparent in the connected Internet, where the size has been doubling every nine to fifteen months. The large population of networks with trivial ... idea of sharing one network address among multiple physical networks is not new and has taken several forms. We will examine three: transparent routers, proxy ARP, and standard IP subnets.

Ngày tải lên: 04/07/2014, 22:21

... they encounter when traversing a TCP/IP internet 11.2 The Need For Multiple Protocols We have said that protocols allow one to specify or understand communication without knowing the details of ... multiple internet addresses map to the same hardware ad- dress The third technique, a TCPnP standard called subnet addressing, allows a site to share a single IP network address among multiple ... prohibits proxy ARP? One vendor decided to add subnet addressing to its IP software by allocating a single subnet mask used for all IP network addresses The vendor modified its standard IP routing software

Ngày tải lên: 04/07/2014, 22:21

... layer The realistic diagram in Figure 11.2b shows that the IP software may communicate with multiple high-level protocol modules and with multiple network interfaces Although a diagram of conceptual ... 11.5.1 The TCPAP 5-Layer Reference Model The second major layering model did not arise from a standards committee, but came instead from research that led to the TCPIIP protocol suite With a little ... located in the TCP/IP transport layer uses checksums, acknowledgements, and timeouts to con- trol transmission Thus, unlike the connection-oriented X.25 protocol layering, the TCP/IP software focuses

Ngày tải lên: 04/07/2014, 22:21

... while the TCPIIP protocols provide an example of a different layering scheme. In practice, protocol software uses multiplexing and demultiplexing to distinguish among multiple protocols within ... connections avoids assign- ing multiple IP addresses to the physical wires. Instead, it treats all the connections col- lectively as a single, independent IP network with its own frame format, hardware ... divided into multiple software modules that each control one network. We need to add one network interface for the new point-to-point network, but the new inter- face must control multiple hardware

Ngày tải lên: 04/07/2014, 22:21

... obtain the destination IP address without interacting with the IP layer However, the source IP ad- dress depends on the route IP chooses for the datagram, because the IP source address identifies ... from IP 12.8 UDP Multiplexing, Demultiplexing, And Ports We have seen in Chapter 11 that software throughout the layers of a protocol hierarchy must multiplex or demultiplex among multiple objects ... UDP cannot know a source IP address unless it interacts with the IP layer We assume that UDP software asks the IP layer to compute the source and (possi- bly) destination IP addresses, uses them

Ngày tải lên: 04/07/2014, 22:21

... here as part of the TCP/IP Internet protocol suite, it is an independent, general purpose protocol that can be adapted for use with other delivery systems For example, because TCP makes very few ... single specification for TCP that can be used to build software for a variety of machines Because TCP assumes little about the underlying communication system, TCP can be used with a variety of packet ... delivery systems TCP can use is one of its strengths 13.7 Ports, Connections, And Endpoints Like the User Datagram Protocol (UDP) presented in Chapter 12, TCP resides above IP in the protocol

Ngày tải lên: 04/07/2014, 22:21

... times, TCP computes an elapsed time known as a sample round trip time or round trip sample. Whenever it obtains a new round trip sample, TCP adjusts its notion of the average round trip ... checksum computation. As with other checksums, TCP uses 16-bit ar- ithmetic and takes the one's complement of the one's complement sum. At the receiv- ing site, TCP software performs ... segment they will transfer. TCP software uses the OPTIONS field to negotiate with the TCP software at the other end of the connection; one of the options allows TCP software to specify the

Ngày tải lên: 04/07/2014, 22:21

... exponentially if loss continues. In other words, if congestion is likely, TCP reduces the volume of traffic exponentially and the rate of retransmission exponentially. If loss continues, TCP ... round trip time is slightly longer than some multiple of T. Implementations of TCP that associate acknowledgements with the most recent re- transmission have been observed in a stable state with ... round trip time, RTT. Unfortunately, lowering the estimated round trip time guarantees that TCP will set the timeout too small for the next segment. Ultimately, the estimated round trip time

Ngày tải lên: 04/07/2014, 22:21

... 13.27 TCP State Machine Like most protocols, the operation of TCP can best be explained with a theoretical model called afinite state machine Figure 13.15 shows the TCP finite state machine, with ... UDP and TCP For example, a domain name server can be accessed either with TCP or with UDP In ei- ther protocol, port number 53 has been reserved for servers in the domain name system 13.30 TCP Performance ... application program instructs TCP to shut down the connection completely, TCP sends the second FIN segment and the original site replies with the third message, an ACK Trang 413.26 TCP Connection Reset

Ngày tải lên: 04/07/2014, 22:21

... current TCP standard specifies exponential backoff for retransmission timers and congestion avoidance algorithms like slow-start, multiplicative decrease, and addi- tive increase. In addition, TCP ... packet loss will TCP retransmit significant volumes of data unnecessarily? Lost TCP acknowledgements do not necessarily force retransmissions. Explain why. Experiment with local machines ... derived from experience with the global Internet. When TCPDP was first developed, participating research sites were connected to the ARPANET, which served as the Inter- net backbone. During initial

Ngày tải lên: 04/07/2014, 22:21

... About The Fourth Edition Of Internetworking With TCPIIP "This is the book I go to for clear explanantions of the basic principles and la- test developments in TCPAP technologies. It's ... Of The Next IP 602 33.7 Features Of IPv6 602 33.8 General Form Of An IPv6 Datagram 603 33.9 IPv6 Base Header Format 603 33.10 IPv6 Extension Headers 605 33.11 Parsing An IPv6 Datagram ... introduction to TCP/ IP for the uninitiated is a very difficult task. While combining the explanation of the general principles of computer communication with the specific examples from the TCP/ IP protocol...

Ngày tải lên: 19/03/2014, 13:35