Direct Systems share a point to point link or Systems share a multi-point link Data can pass without intervening active agent Indirect Switched networks or Internetworks or internets Data transfer depend on other entities | William Stallings Data and Computer Communications Chapter 2 Protocols and Architecture Characteristics Direct or indirect Monolithic or structured Symmetric or asymmetric Standard or nonstandard * Direct or Indirect Direct Systems share a point to point link or Systems share a multi-point link Data can pass without intervening active agent Indirect Switched networks or Internetworks or internets Data transfer depend on other entities * Monolithic or Structured Communications is a complex task To complex for single unit Structured design breaks down problem into smaller units Layered structure * Symmetric or Asymmetric Symmetric Communication between peer entities Asymmetric Client/server * Standard or Nonstandard Nonstandard protocols built for specific computers and tasks K sources and L receivers leads to K*L protocols and 2*K*L implementations If common protocol used, K + L implementations needed * Use of Standard Protocols * Functions Encapsulation Segmentation and reassmebly . | William Stallings Data and Computer Communications Chapter 2 Protocols and Architecture Characteristics Direct or indirect Monolithic or structured Symmetric or asymmetric Standard or nonstandard * Direct or Indirect Direct Systems share a point to point link or Systems share a multi-point link Data can pass without intervening active agent Indirect Switched networks or Internetworks or internets Data transfer depend on other entities * Monolithic or Structured Communications is a complex task To complex for single unit Structured design breaks down problem into smaller units Layered structure * Symmetric or Asymmetric Symmetric Communication between peer entities Asymmetric Client/server * Standard or Nonstandard Nonstandard protocols built for specific computers and tasks K sources and L receivers leads to K*L protocols and 2*K*L implementations If common protocol used, K + L implementations needed * Use of Standard Protocols * Functions Encapsulation Segmentation and reassmebly Connection control Ordered delivery Flow control Error control Addressing Multiplexing Transmission services * Encapsulation Addition of control information to data Address information Error-detecting code Protocol control * Segmentation (Fragmentation) Data blocks are of bounded size Application layer messages may be large Network packets may be smaller Splitting larger blocks into smaller ones is segmentation (or fragmentation in TCP/IP) ATM blocks (cells) are 53 octets long Ethernet blocks (frames) are up to 1526 octets long Checkpoints and restart/recovery * Why Fragment? Advantages More efficient error control More equitable access to network facilities Shorter delays Smaller buffers needed Disadvantages Overheads Increased interrupts at receiver More processing time * Connection Control Connection Establishment Data transfer Connection termination May be connection interruption and recovery Sequence numbers used for Ordered delivery Flow control Error control * Connection Oriented .
