networking
DESCRIPTION
TRANSCRIPT
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Networking
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
1 / 43
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Networking and Operating Systems
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
2 / 43
■ Many different pieces■ Some pieces are in the kernel; others are in
user space■ Apart from the division, we need appropriate
interfaces
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Kinds of Networking
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
3 / 43
■ Different protocols; different protocol suites■ User versus kernel consumption■ Synchronous versus asynchronous
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Applications
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
4 / 43
■ Service■ Servers■ Clients■ Peer-to-peer■ Which are part of the OS?
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The Stack
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
5 / 43
■ Seven layers: physical, link, network, transport,session, presentation, application
■ Well, not really, on the Internet■ Link layer — device drivers■ Network: IP (Internet Protocol)■ Transport (and a bit of session): TCP, UDP■ Presentation, application: applications■ All but the last are in the kernel
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Protocol Suites
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
6 / 43
■ TCP/IP — The Internet■ Subclass: IPv6■ OSI■ Novell IPX■ Appletalk■ NetBIOS■ Many others that have faded from the scene
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Connection-Oriented or
Connectionless?Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
7 / 43
■ Some protocols are connection-oriented —once things are set up, you always talk to asingle endpoint
■ Example: TCP■ Others are connectionless — each packet can
go to or come from a different place■ Example: UDP, as used in the DNS
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Mux/Demux
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
8 / 43
■ Many layers of multiplex/demultiplex■ Link layer selects different network layers (and
maybe different protocol suites)■ Network layer selects different transports■ Transport layer selects different applications■ User space can read all layers
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Layers
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
9 / 43
Link
Network Network
TransportTransport
Application
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Application Access
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
10 / 43
■ Why do applications have access to all layers?■ Debugging■ Implement layer at user level
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Example: tcpdump at Link Layer
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
11 / 43
# tcpdump -v -v -s 1500 not ip and not
arp
tcpdump: listening on bge0, link-type
EN10MB (Ethernet), capture size 1500
bytes 23:05:57.642505 00:48:54:71:ce:32
> Broadcast null I (s=0,r=0,C) len=42
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Example: DHCP
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
12 / 43
■ DHCP is used to assign IP addresses to hosts■ At the time a host issues a DHCP request, it
has no IP address, so it can’t speak IP■ Both the DHCP client and the DHCP server
have to listen – and speak – at link level
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Example: OSPF
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
13 / 43
■ The OSPF routing protocol runs directly ontop of IP
■ To implement this at user level, the programhas to read IP packets
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Example: ping
Networking
Networking andOperating Systems
Kinds of Networking
Applications
The Stack
Protocol SuitesConnection-Orientedor Connectionless?
Mux/Demux
Layers
Application Access
Example: tcpdumpat Link Layer
Example: DHCP
Example: OSPF
Example: ping
Interfaces
Applications
Middleware
The Global Grid
14 / 43
■ ping uses ICMP messages■ ICMP lives directly on top of IP■ In other words, ICMP packets have to be
available both in the kernel and at user level
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Interfaces
Networking
Interfaces
InterfacesNetworkConnections Aren’tFiles
The Socket Interface
Sockets and Layers
ConnectionlessNetworksCouldn’t We JustOpen /dev/tcp?
Interfaces —Summary
Applications
Middleware
The Global Grid
15 / 43
■ What is the interface to the networking stack?■ Is it file-like? Something special?■ The answer, of course, is “it depends”
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Network Connections Aren’t Files
Networking
Interfaces
InterfacesNetworkConnections Aren’tFiles
The Socket Interface
Sockets and Layers
ConnectionlessNetworksCouldn’t We JustOpen /dev/tcp?
Interfaces —Summary
Applications
Middleware
The Global Grid
16 / 43
■ We always do much more than just read orwrite
■ We often have to pass extra information, suchas source or destination address forconnectionless protocols
■ But sometimes, we do just read and write. . .
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The Socket Interface
Networking
Interfaces
InterfacesNetworkConnections Aren’tFiles
The Socket Interface
Sockets and Layers
ConnectionlessNetworksCouldn’t We JustOpen /dev/tcp?
Interfaces —Summary
Applications
Middleware
The Global Grid
17 / 43
■ Due originally to Berkeley, circa 1983■ Network access is initiated by the socket()
system call■ On Unix, socket() returns an ordinary file
descriptor; you can (eventually) doread()/write()/close()
■ On Windows, it returns a special type of filedescriptor; you can only do special socketoperations, such as send()/recv()
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Sockets and Layers
Networking
Interfaces
InterfacesNetworkConnections Aren’tFiles
The Socket Interface
Sockets and Layers
ConnectionlessNetworksCouldn’t We JustOpen /dev/tcp?
Interfaces —Summary
Applications
Middleware
The Global Grid
18 / 43
■ Sockets are used at all layers — parameters onthe socket() call specify the layer andprotocol
■ The semantics of the returned file descriptorare layer-dependent
■ A variety of options can be set withsetsockopt() and ioctl()
■ Sockets are also used for configuration control,such as assigning IP addresses to interfaces
■ You control the routing tables by writing to aspecial socket
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Connectionless Networks
Networking
Interfaces
InterfacesNetworkConnections Aren’tFiles
The Socket Interface
Sockets and Layers
ConnectionlessNetworksCouldn’t We JustOpen /dev/tcp?
Interfaces —Summary
Applications
Middleware
The Global Grid
19 / 43
■ Every packet written needs a destinationaddress as well as data
■ Every packet read contains a source address aswell as data
■ Use sendto()/recvfrom()■ (Address format will vary, depending on the
type of network; some networks even usevariable-length addresses
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Couldn’t We Just Open /dev/tcp?
Networking
Interfaces
InterfacesNetworkConnections Aren’tFiles
The Socket Interface
Sockets and Layers
ConnectionlessNetworksCouldn’t We JustOpen /dev/tcp?
Interfaces —Summary
Applications
Middleware
The Global Grid
20 / 43
■ On some systems, such as Solaris, you can!■ But — we still need special operations■ setsockopt() could just be an ioctl, but
accept() returns a new file descriptor■ Connectionless networks use special data
format
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Interfaces — Summary
Networking
Interfaces
InterfacesNetworkConnections Aren’tFiles
The Socket Interface
Sockets and Layers
ConnectionlessNetworksCouldn’t We JustOpen /dev/tcp?
Interfaces —Summary
Applications
Middleware
The Global Grid
21 / 43
■ Network connections aren’t really files■ Given all the special stuff that has to go on
anyway, there’s little advantage to using thefile system instead of sockets
■ There may be some advantage, though, togetting a normal file descriptor
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Applications
Networking
Interfaces
Applications
Applications
Service Applications
Service Dispatchers
The Port Mapper
The Port Mapper
Other Applications?
Telnet and SSH
Anonymous FTP
Middleware
The Global Grid
22 / 43
■ Service■ Servers■ Clients■ Peer-to-peer
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Service Applications
Networking
Interfaces
Applications
Applications
Service Applications
Service Dispatchers
The Port Mapper
The Port Mapper
Other Applications?
Telnet and SSH
Anonymous FTP
Middleware
The Global Grid
23 / 43
■ Service applications function as an extension ofthe OS
■ Example: with NFS, the client and server arein the kernel, but other pieces are at user level:mounting and unmount the file system,locking, etc.
■ Example: Routing — IP is pretty uselesswithout it
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Service Dispatchers
Networking
Interfaces
Applications
Applications
Service Applications
Service Dispatchers
The Port Mapper
The Port Mapper
Other Applications?
Telnet and SSH
Anonymous FTP
Middleware
The Global Grid
24 / 43
■ Certain applications exist just to run otherapplications
■ ineted — Runs most TCP and UDPapplications
■ (Original idea was to keep the process tablesmall, to improve performance. Now, itpermits (some) servers to just usestdin/stdout)
■ Example: portmapper — dispatches inboundRPC requests
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The Port Mapper
Networking
Interfaces
Applications
Applications
Service Applications
Service Dispatchers
The Port Mapper
The Port Mapper
Other Applications?
Telnet and SSH
Anonymous FTP
Middleware
The Global Grid
25 / 43
■ Subprocedures — or rather, their stubs —register with the portmapper
■ The caller’s stubs contact the port mapper tofind out the actual port number for thesubprocedure
■ This is not quite invisible to the applicationprogrammer; at the least, the registration hasto be set up
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The Port Mapper
Networking
Interfaces
Applications
Applications
Service Applications
Service Dispatchers
The Port Mapper
The Port Mapper
Other Applications?
Telnet and SSH
Anonymous FTP
Middleware
The Global Grid
26 / 43
$ rpcinfo -p cluster.cs.columbia.edu
program vers proto port service
100000 4 tcp 111 portmapper
100000 3 tcp 111 portmapper
100005 3 tcp 32782 mountd
100003 2 udp 2049 nfs
and many more besides
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Other Applications?
Networking
Interfaces
Applications
Applications
Service Applications
Service Dispatchers
The Port Mapper
The Port Mapper
Other Applications?
Telnet and SSH
Anonymous FTP
Middleware
The Global Grid
27 / 43
■ Most applications have nothing to do with theOS
■ A Web server could run, almost unchanged,just as well on Windows as on Unix
■ (Minor differences in a few system calls)■ But some do authentication
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Telnet and SSH
Networking
Interfaces
Applications
Applications
Service Applications
Service Dispatchers
The Port Mapper
The Port Mapper
Other Applications?
Telnet and SSH
Anonymous FTP
Middleware
The Global Grid
28 / 43
■ Telnet and SSH permit remote logins■ They have to authenticate users, using
OS-specific mechanisms■ Telnet can invoke login; SSH, which can do
its own authentication, cannot
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Anonymous FTP
Networking
Interfaces
Applications
Applications
Service Applications
Service Dispatchers
The Port Mapper
The Port Mapper
Other Applications?
Telnet and SSH
Anonymous FTP
Middleware
The Global Grid
29 / 43
■ Ordinary FTP has to authenticate users; seeabove
■ Anonymous FTP has a different problem:confining the remote user
■ Must use OS-specific sandbox mechanism
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Middleware
Networking
Interfaces
Applications
Middleware
Middleware
Goals of Middleware
Types of Middleware
CORBA
Publish-Subscribe
The Global Grid
30 / 43
■ Common middle layer between applicationsand the stack
■ I.e., common middle ground betweenapplications and the OS
■ Arguably as much a part of the OS as the Cruntime library
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Goals of Middleware
Networking
Interfaces
Applications
Middleware
Middleware
Goals of Middleware
Types of Middleware
CORBA
Publish-Subscribe
The Global Grid
31 / 43
■ Common interface■ Naming■ Replication■ Access
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Types of Middleware
Networking
Interfaces
Applications
Middleware
Middleware
Goals of Middleware
Types of Middleware
CORBA
Publish-Subscribe
The Global Grid
32 / 43
■ Document-based: the Web■ File-based: distributed file system■ Object-based: CORBA■ Publish-subscribe■ More. . .
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CORBA
Networking
Interfaces
Applications
Middleware
Middleware
Goals of Middleware
Types of Middleware
CORBA
Publish-Subscribe
The Global Grid
33 / 43
■ CORBA: Common Object Request Broker
Architecture
■ RPC extended procedure calls to the net■ CORBA extends objected-oriented
programming to the net■ Instead of referencing files or web pages, you
invoke methods■ The CORBA Object Broker handles naming,
location, access method, etc.
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Publish-Subscribe
Networking
Interfaces
Applications
Middleware
Middleware
Goals of Middleware
Types of Middleware
CORBA
Publish-Subscribe
The Global Grid
34 / 43
■ Processes that have information publish it■ On a LAN, implemented as a broadcast■ Information router forwards such broadcasts to
other interested LANs■ If a process subscribes to a topic, its local
information broker tells other LANs it wantssuch data
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The Global Grid
Networking
Interfaces
Applications
Middleware
The Global Grid
The Global Grid
It’s a Distributed OSActually, There AreMany Grids
Scenarios
Security Issues
Sandboxing
Storage Space
Accounting
Other EssentialComponents
35 / 43
■ Share computing resources around the world■ (The original goal of the ARPANET!)■ Built on high performance computers and high
performance networks
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It’s a Distributed OS
Networking
Interfaces
Applications
Middleware
The Global Grid
The Global Grid
It’s a Distributed OSActually, There AreMany Grids
Scenarios
Security Issues
Sandboxing
Storage Space
Accounting
Other EssentialComponents
36 / 43
■ The Grid functions like a large-scale distributedoperating system
■ It has to solve all the distributed OS problemswe talked about
■ These include security, scheduling, locking,communications, and more
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Actually, There Are Many Grids
Networking
Interfaces
Applications
Middleware
The Global Grid
The Global Grid
It’s a Distributed OSActually, There AreMany Grids
Scenarios
Security Issues
Sandboxing
Storage Space
Accounting
Other EssentialComponents
37 / 43
■ The Grid is a concept and a set of protocols,not a single Internet-wide virtual machine
■ You and your friends can pool your ownmachines
■ Each Grid sets up its own access control policy
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Scenarios
Networking
Interfaces
Applications
Middleware
The Global Grid
The Global Grid
It’s a Distributed OSActually, There AreMany Grids
Scenarios
Security Issues
Sandboxing
Storage Space
Accounting
Other EssentialComponents
38 / 43
■ Specific computer; local I/O only — simplyhave to authenticate to host computer
■ Specific computer; remote I/O — mustdelegate security credentials to host OS toallow file retrieval and update
■ Run on “best” computer — must talk toscheduler and delegate credentials; schedulermust verify acceptability of credentials on eachcandidate machine
■ Multiprocessing — each remote job needscredentials to talk to other pieces
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Security Issues
Networking
Interfaces
Applications
Middleware
The Global Grid
The Global Grid
It’s a Distributed OSActually, There AreMany Grids
Scenarios
Security Issues
Sandboxing
Storage Space
Accounting
Other EssentialComponents
39 / 43
■ User authentication — straight-forward■ Must protect grid computers from remote
users — standard operating system problem■ Must have large-scale, secure, distributed file
system■ Users want to protect their data from the
remote OS — hard!
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Sandboxing
Networking
Interfaces
Applications
Middleware
The Global Grid
The Global Grid
It’s a Distributed OSActually, There AreMany Grids
Scenarios
Security Issues
Sandboxing
Storage Space
Accounting
Other EssentialComponents
40 / 43
■ If untrusted users are running jobs on yourmachine, you may want to sandbox them
■ But each user needs different resources; youneed a flexible sandbox
■ You want to isolate each remote user fromevery other, and (if possible) from your localusers
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Storage Space
Networking
Interfaces
Applications
Middleware
The Global Grid
The Global Grid
It’s a Distributed OSActually, There AreMany Grids
Scenarios
Security Issues
Sandboxing
Storage Space
Accounting
Other EssentialComponents
41 / 43
■ The Grid is for big problems; these take a lotof storage space
■ How do we manage allocation?■ How do we transfer that much over the net?■ How do we encrypt that much data during
storage?
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Accounting
Networking
Interfaces
Applications
Middleware
The Global Grid
The Global Grid
It’s a Distributed OSActually, There AreMany Grids
Scenarios
Security Issues
Sandboxing
Storage Space
Accounting
Other EssentialComponents
42 / 43
■ Someone has to pay for resources used■ The Grid includes accounting standards —
record CPU, disk, and RAM usage (andperhaps bandwidth)
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Other Essential Components
Networking
Interfaces
Applications
Middleware
The Global Grid
The Global Grid
It’s a Distributed OSActually, There AreMany Grids
Scenarios
Security Issues
Sandboxing
Storage Space
Accounting
Other EssentialComponents
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■ Name space■ File I/O and format conversion■ File replication and cache engine■ Brokers, which talk to schedulers■ These are middleware