An%20Overview%20of%20Selected%20Protocols%20(Courtesy:%20Dr.%20Waheed)

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An Overview of Selected Protocols(Courtesy Dr.
Waheed)

• Channel access protocols
• Network layer level protocols
• Transport layer level protocols
• Application layer level protocols
• Recent work
• Objective of this review
• To help you select one protocol for your term
  project

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Channel Access Protocols

• ALOHA
• Carrier sense multiple access (CSMA) protocols
• Collision-free protocols
• Limited contention protocols
• Channel access protocol standards
• IEEE 802.x standards
• All of these protocols deal with channel access
  problem
• Allocation of a shared channel among multiple
  stations
• All of these protocols are implemented at medium
  access sublayer level
• MAC layer is part of data link layer

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Network Layer Level Protocols

• IPv4
• IPv6
• Mobile IP
• RSVP
• Internet control protocols
• ICMP
• ARP
• RARP
• OSPF
• BGP

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IP Protocol

• Along with the Transmission Control Protocol
  (TCP), IP represents the heart of the Internet
  protocols
• IP is a network-layer protocol that contains
• Addressing information and
• Some control information that enables packets to
  be routed
• Documented in RFC 791
• IP has two primary responsibilities
• Providing connectionless, best-effort delivery of
  datagrams through an internetwork and
• Providing fragmentation and reassembly of
  datagrams to support data links with different
  maximum-transmission unit (MTU) sizes
• IP is a stateless protocol

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RSVP Resource Reservation Protocol

• RSVP allows
• Multiple senders to transmit to multiple groups
  of receivers
• Individual receivers to switch channels (groups)
  freely
• Optimize BW use while eliminating congestion
• RSVP uses multicast routing through spanning
  trees
• Each group is assigned a group address
• Sender puts groups address in packets
• Routing algorithm builds a spanning tree of all
  members of a group
• Difference from normal multicast
• Some extra information that is multicast to the
  group periodically to tell routers along the way
  to maintain certain data structures

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Internet Control Message Protocol (ICMP)

• ICMP is used to report unusual events or to test
  the internet
• Several types of ICMP messages
• Destination unreachable
• Time exceeded
• Parameter problem
• Source quench choke packet
• Redirect teach the router about geography
• Echo request ask a machine if it is alive
• Echo reply yes, Im alive
• Timestamp request same as echo request but with
  timestamp
• Timestamp reply echo reply with timestamp
• Each ICMP message type is encapsulated in an IP
  packet

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Address Resolution Protocol (ARP)

• Data link layer hardware does not understand IP
  addresses
• Mostly hosts are connected through Ethernet LANs
• All Ethernet cards have a unique 48-bit (data
  link layer) address
• How to map an IP address to data link address?
• One solution use of a configuration file
• Other solution Address Resolution Protocol (ARP)
• ARP
• Host that needs to map IP address to Ethernet
  address broadcasts a packet on the Ethernet,
  asking Who owns IP address w.x.y.z?
• Each machine on Ethernet receives this broadcast
  and checks its IP address
• Machine with matching IP address will respond
  with its Ethernet address to the sender
• Almost every machine on internet runs ARP
• ARP is defined in RFC 826

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Reverse ARP (RARP)

• ARP finds Ethernet address corresponding to an IP
  address
• Sometime reverse problem has to be solved
  mapping an Ethernet address to IP address
• This problem occurs while booting a diskless
  workstation, which gets its OS binary image from
  a remote file server
• How does it learn its IP address?
• This problem is solved by RARP
• A newly booted workstation broadcasts its 48-bit
  Ethernet address and asks for corresponding IP
  address
• RARP server sees this request, looks up Ethernet
  address in its configuration files, and sends
  back corresponding IP address
• RFC 903
• Advantage IP address is not needed in memory
  image
• Disadvantage RARP uses broadcast to reach RARP
  server therefore, all networks are required to
  have one RARP server as it cannot go through
  routers
• Solution Use BOOTP

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Bootstrap Protocol (BOOTP)

• It is a UDP/IP based protocol that allows a
  network user to
• Automatically receive an IP address or
• Have a diskless workstation boot automatically by
  
• Discovering its own IP address
• Discovering the IP address of a server and
• Obtain the name of a boot file that should be
  loaded into memory
• It uses UDP messages that are forwarded over
  routers
• Bootstrap process has two phases
• IP address discovery and boot file selection
  phase (BOOTP)
• File transfer phase
• BOOTP server managed by a network administrator
  automatically assigns the IP address form a pool
  of IP addresses
• It is a basis for an advanced network manager
  protocol, Dynamic Host Configuration Protocol
  (DHCP)

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Interior Gateway Routing Protocol OSPF

• Internet consists of autonomous systems (ASes)
• Each AS operated by a different organization
• Each AS can use any routing algorithm within its
  network
• Still standards help
• Simplify boundary between ASes
• Reuse of code
• A routing algorithm within an AS is called
  Interior Gateway Protocol
• Open Shortest Path First (OSPF) routing algorithm
• Successor of link state routing algorithm, which
  was a successor of Bellman-Ford distance vector
  routing algorithm
• It became a standard in 1990 and many router
  vendors support it

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Exterior Gateway Routing Protocol BGP

• A routing algorithm between ASes is called an
  Exterior Gateway protocol
• Border Gateway Protocol (BGP) is used for routing
  between ASes
• Different from OSPF as routing goals are also
  different
• Gateway routers often need to enforce certain
  policies
• Send and receive all packets to and from the
  Internet
• Do not carry transit packets from foreign ASes
• Carry transit traffic from specific ASes, etc.
• Example traffic starting or ending at SUN should
  not transit Microsoft
• Policies are manually configured into each BGP
  router
• BGP router handles transit traffic with three
  categories of networks
• Stub networks
• Have one connection to BGP graph and cannot be
  used for transit
• Multiconnected networks
• Have multiple connections but some may refuse
  transit traffic
• Transit networks
• These are backbones willing to handle third-party
  packets

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BGP (Contd)

• Pairs of BGP routers communicated using TCP
• BGP is a distance vector protocol but differ from
  most others, such as RIP
• Instead of maintaining just the cost to each
  destination, each BGP router keeps track of the
  exact path used
• Instead of periodically providing distance info
  to each neighbor, each BGP router provides exact
  paths it uses to all other routers

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Transport Layer Level Protocols

• TCP
• UDP
• AATM AAL protocols

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TCP Protocol

• TCP entities exchange data in variable sized
  segments
• Consists of 20-byte header with 32-bit seq. ,
  followed by data
• It can accumulate data from several writes or
  split data from one write over multiple segments
• Two restrictions on the size of a TCP segment
• Segment, including 20-byte header should fit in
  65,535 byte IP payload
• Segment must fit in maximum transfer unit (MTU)
  of a network to avoid fragmentation/reassembly
• Each fragment adds 20 byte segment header
• Basic protocol used by TCP entities sliding
  window protocol
• When sender transmits a segment, it also starts a
  timer
• After receiving segment, the receiver sends an
  ack segment with an ack that is equal to next
  sequence it expects to receive
• If sender timesout before receiving ack, it
  retransmits the segment

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TCP Protocol (Contd)

• TCP need to handle following problems
• Bits and pieces of delayed, duplicate segments
  that may be fragmented differently
• Require special attention to extract the correct
  segments at receiver
• Example bytes 3072-4095 arrive but cannot be
  acknowledged until 2048-3071 bytes are received
• Retransmitted segments can take different routes
  resulting in different fragmentations
• TCP entity at receiving end is responsible for
  reliably extracting the original segment even
  though sporadic delayed duplicate fragments may
  turn up
• Segments may occasionally hit a congested network
• A number of algorithms have been implemented in
  TCP to solve these problems

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UDP

• This is a connectionless protocol
• Encapsulated IP datagram
• Useful for applications that need one request and
  one response
• A UDP segment consists of 8 byte header
• UDP length includes 8 byte header and data
• UDP checksum is optional
• 0 if not computed
• 1s complement of the sum of UDP header, data
  (padded to even number of bytes), and pseudo
  header

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ATM AAL Protocols

• If ATM layers functionality is similar to
  network layer, AAL is similar to transport layer
• AAL 5 protocol is similar to UDP
• Four protocols to handle four classes of service
• AAL1 AAL4
• Requirements for classes C and D were so similar
  that AAL3 and AAL4 are combined into AAL ¾
• AAL5 proposed by computer industry in contrast to
  telecommunication industry that proposed AAL1
  AAL3/4

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Application Layer Level Protocols

• Authentication protocols
• DNS
• SNMP
• E-mail related protocols
• NNTP
• HTTP
• Multimedia related protocols
• RTP
• RTSP

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Recent Protocols

• Active IETF working groups in following areas
• Applications
• Internet
• Operations and management
• Routing
• Security
• Sub-IP
• Transport

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Applications Area Protocols

• Cross Registry Information Service Protocol
  (CRISP)
• Instant Messaging and Presence Protocol (IMPP)
• Lightweight Directory Access Protocol (LDAP)
• Message Tracking Protocol (MsgTrk)
• SIP for Instant Messaging and Presence Leveraging
  Extension (SIMPLE)

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Internet Area

• Dynamic Host Configuration Protocol (DHCP)
• Extensible Authentication Protocol (EAP)
• IP over Cable Data Network (IPCDN)
• IP over InfiniBand (IPoIB)
• IP Routing for Wireless/Mobile Hosts (MobileIP)
• Protocol for Carrying Authentication for Network
  Access (PANA)
• IPv6

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Operations and Management Area

• IP Flow Information Export (IPFIX)
• Resource Allocation Protocol (RAP)
• Remote Network Monitoring (RMONMIB)
• Configuration Management with SNMP (SNMPConf)
• SNMP version 3 (SNMPv3)

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Routing Area

• Border Gateway Multicast Protocol (BGMP)
• Inter-Domain Multicast Routing (IDMR)
• Inter-Domain Routing (IDR)
• Multicast Source Discovery Protocol (MSDP)
• Routing Information Protocol (RIP)
• Virtual Router Redundancy Protocol (VRRP)

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Security Area

• Authenticated Firewall Traversal (AFT)
• IP Security Protocol (IPSec)
• Kerberized Internet Negotiation of Keys (KINK)
• Multicast Security (Msec)
• An Open Specification for Pretty Good Privacy
  (OpenPGP)
• Public-Key Infrastructure (PKIX)
• Secure Network Time Protocol (STIME)
• Transport Layer Security (TLS)

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Sub-IP Area

• General Switch Management Protocol (GSMP)
• IP Over Optical (IPO)
• Multiprotocol Label Switching (MPLS)
• Provider Provisioned Virtual Networks (PPVPN)

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Transport Area

• Audio/Video Transport (AVT)
• Datagram Congestion Control Protocol (DCCP)
• Differentiated Services (DiffServ)
• Telephone Number Mapping (ENUM)
• IP Telephony (IPTel)
• Media Gateway Control (MEGACO)
• Multiparty Multimedia Session Control (MMUSIC)
• Network File System Version 4 (NFSv4)
• Robust Header Compression (ROHC)
• Session Initiation Protocol (SIP)
• Speech Services Control (SpeechSC)

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Other References

• http//www.iol.unh.edu/
• http//www.ietf.org/rfc/rfcxx00.txt