Transcript Communication Network Protocols

Communication Network
Protocols
Brent R. Hafner
CSC 8320
Agenda
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OSI Protocols
Blade Center Technology
Virtual Machines
References
OSI Protocol Suite
Application
Presentation
Session
Transport
Network
Data Link
Physical
Two Sets of Layers
Application
Data
Transport
Application
• The application layer is the OSI layer closest to the end user, which
means that both the OSI application layer and the user interact
directly with the software application.
• This layer interacts with software applications that implement a
communicating component. Such application programs fall outside
the scope of the OSI model. Application layer functions typically
include identifying communication partners, determining resource
availability, and synchronizing communication. .
• Some examples of application layer implementations include Telnet,
File Transfer Protocol (FTP), and Simple Mail Transfer Protocol
(SMTP), DNS, Web/Http.
Application (cont.)
Client - Server
Peer-to-Peer
Presentation
• The presentation layer provides a variety of coding and conversion
functions that are applied to application layer data. These functions
ensure that information sent from the application layer of one system
would be readable by the application layer of another system. Some
examples of presentation layer coding and conversion schemes
include common data representation formats, conversion of
character representation formats, common data compression
schemes, and common data encryption schemes.
Presentation Layer (cont.)
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AFP, AppleShare File Protocol
GIF, GIF
ICA Citrix Systems Core Protocol][1]
JPEG, Joint Photographic Experts Group
LPP, Lightweight Presentation Protocol
NCP, NetWare Core Protocol
NDR, Network Data Representation
PNG, Portable Network Graphics
TIFF, Tagged Image File Format
XDR, eXternal Data Representation
X.25 PAD, Packet Assembler/Disassembler Protocol
Retrieved from "http://en.wikipedia.org/wiki/Presentation_layer"
Session
• The session layer implementation of the OSI protocol suite consists
of a session protocol and a session service. The session protocol
allows session-service users (SS-users) to communicate with the
session service. An SS-user is an entity that requests the services of
the session layer. Such requests are made at session-service
access points (SSAPs), and SS-users are uniquely identified by
using an SSAP address. Figure 30-4 shows the relationship
between the SS-user, the SSAP, the session protocol, and the
session service.
Session (cont.)
Session service provides four basic services to SS-users.
1. Establishes and terminates connections between SS-users and
synchronizes the data exchange between them.
2. Performs various negotiations for the use of session layer tokens,
which the SS-user must possess to begin communicating.
3. Inserts synchronization points in transmitted data that allow the
session to be recovered in the event of errors or interruptions.
4. Enables SS-users to interrupt a session and resume it later at a
specific point.
Transport
• The OSI protocol suite implements two types of services at the
transport layer: connection-oriented transport service and
connectionless transport service.
Five connection-oriented transport layer protocols exist in the OSI
suite, ranging from Transport Protocol Class 0 through Transport
Protocol Class 4. Connectionless transport service is supported only
by Transport Protocol Class 4.
Transport (cont.)
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Transport Protocol Class 0 (TP0), the simplest OSI transport protocol, performs segmentation and
reassembly functions. TP0 requires connection-oriented network service.
Transport Protocol Class 1 (TP1) performs segmentation and reassembly, and offers basic error
recovery. TP1 sequences protocol data units (PDUs) and will retransmit PDUs or reinitiate the
connection if an excessive number of PDUs are unacknowledged. TP1 requires connectionoriented network service.
Transport Protocol Class 2 (TP2) performs segmentation and reassembly, as well as multiplexing
and demultiplexing of data streams over a single virtual circuit. TP2 requires connection-oriented
network service.
Transport Protocol Class 3 (TP3) offers basic error recovery and performs segmentation and
reassembly, in addition to multiplexing and demultiplexing of data streams over a single virtual
circuit. TP3 also sequences PDUs and retransmits them or reinitiates the connection if an
excessive number are unacknowledged. TP3 requires connection-oriented network service.
Transport Protocol Class 4 (TP4) offers basic error recovery, performs segmentation and
reassembly, and supplies multiplexing and demultiplexing of data streams over a single virtual
circuit. TP4 sequences PDUs and retransmits them or reinitiates the connection if an excessive
number are unacknowledged. TP4 provides reliable transport service and functions with either
connection-oriented or connectionless network service. It is based on the Transmission Control
Protocol (TCP) in the Internet Protocols suite and is the only OSI protocol class that supports
connectionless network service.
Network Layer
The network layer provides the functional and procedural means of
transferring variable length data sequences from a source to a
destination via one or more networks while maintaining the quality of
service requested by the transport layer. The Network layer
performs network routing, flow control, network
segmentation/desegmentation, and error control functions
i.e. P (IPv4 • IPv6) • ARP • RARP • ICMP • IGMP • RSVP • IPSec •
• datagram network provides network-layer connectionless service
• VC network provides network-layer connection service
• analogous to the transport-layer services, but:
– service: host-to-host
– no choice: network provides one or the other
– implementation: in network core
Network Layer (cont.)
Virtual Networks
• used to setup, maintain
teardown VC
• used in ATM, frame-relay,
X.25
• not used in today’s
Internet
Datagram Networks
• no call setup at network
layer
• routers: no state about
end-to-end connections
– no network-level concept of
“connection”
• packets forwarded using
destination host address
– packets between same
source-dest pair may take
different paths
Data Link
• The data link layer provides reliable transit of data across a physical
network link. Different data link layer specifications define different
network and protocol characteristics, including physical addressing,
network topology, error notification, sequencing of frames, and flow
control. Physical addressing (as opposed to network addressing)
defines how devices are addressed at the data link layer. Network
topology consists of the data link layer specifications that often
define how devices are to be physically connected, such as in a bus
or a ring topology. Error notification alerts upper-layer protocols that
a transmission error has occurred, and the sequencing of data
frames reorders frames that are transmitted out of sequence.
Finally, flow control moderates the transmission of data so that the
receiving device is not overwhelmed with more traffic than it can
handle at one time.
Data Link (cont.)
“link”
Data Link (cont.)
The Logical Link Control (LLC) sublayer of the data link layer manages
communications between devices over a single link of a network. LLC is
defined in the IEEE 802.2 specification and supports both connectionless and
connection-oriented services used by higher-layer protocols. IEEE 802.2
defines a number of fields in data link layer frames that enable multiple
higher-layer protocols to share a single physical data link. The Media Access
Control (MAC) sublayer of the data link layer manages protocol access to the
physical network medium. The IEEE MAC specification defines MAC
addresses, which enable multiple devices to uniquely identify one another at
the data link layer.
Physical
The physical layer defines the electrical, mechanical, procedural,
and functional specifications for activating, maintaining, and
deactivating the physical link between communicating network
systems. Physical layer specifications define characteristics such as
voltage levels, timing of voltage changes, physical data rates,
maximum transmission distances, and physical connectors.
Physical layer implementations can be categorized as either LAN or
WAN specifications. Figure 1-7 illustrates some common LAN and
WAN physical layer implementations.
Physical Layer
OSI-Data Flow
IBM BladeCenter Networking
Load Balancing
Architecture
Workload management is often deployed to
proactively shift workload on the basis of the
current state of the system, server, and/or
networking metrics. This can be done at Level 4
or Level 7 in the OSI model.
For example, consider a service whose Domain
Name Server (DNS) name is Service_A.com.
Normally, there would be a server set up
somewhere with that host name and IP address.
With Layer 4 switching, the switch module itself
takes ownership of the IP address as a VIP
and has multiple ‘‘real’’ server blades behind it
capable of delivering the service Service_A.com,
whose addresses can be arbitrarily assigned,
since they are of only local significance.
Virtual Servers –
VMWare ESX
ESX Server installs on the “bare
metal” and allows multiple
unmodified operating systems and
their applications to run in virtual
machines that share physical
resources.
Each virtual machine represents a
complete system, with processors,
memory, networking, storage and
BIOS.
Advanced resource allocation
policies for virtual machines allow
you to guarantee resources to even
your most resource-intensive
applications.
Virtual Machines (cont.)
As shown in Figure 8, each of the server blades can
support virtual machine (VM) technology, such as
VMware** virtual infrastructure [34–36], in order to share
the blade physical resources by hosting multiple instances
of OS images. In addition to the blade being shared, the
networking infrastructure can also be shared with the use
of VLAN technology, and security can be maintained
between VMs. For example, each VM shown in Figure 8
can be logically associated with an independent VLAN
configured on the switch, so that with three VMs per
blade, there could be a total of 3 3 m total VLANs
configured internally and trunked out to the uplinks of
the switch.
References
1. S. W. Hunter, N.C. Strole, D.W. Crosby, and D.M Greene
‘‘BladeCenter Networking’’, IBM J Res & Dev,
November 2005; see
http://www.research.ibm.com/journal/rd/496/hunter.pdf
2. Jim Kurose, Keith Ross, Computer Networking: A Top
Down Approach Featuring the Internet, 3rd edition.
Addison-Wesley, July 2004.
3. Cisco Systems, OSI Network Protocols, October 2006;
see
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_
doc/osi_prot.htm#wp1022221
4. VMWare, ESX Server 3.0; see
http://www.vmware.com/products/vi/esx/