http://www.flickr.com/photos/rofi/2097239111/!
Nate Foster
Cornell University
Spring 2013
Based on lecture notes by Jennifer Rexford and Michael Freedman
CS 5114
Network Programming Languages
End Hosts
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Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
CS 5114 Network Programming Languages End Hosts, Lecture notes of Network Technologies and TCP/IP
A set of lecture notes from a course on Network Programming Languages at Cornell University in Spring 2013. The notes cover topics such as IP Suite, Identifiers, DHCP, ARP, DNS, Transport Layers, and more. The document also includes announcements about reviews and projects. It is a useful resource for students studying computer science, networking, or related fields.
Typology: Lecture notes
2012/2013
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http://www.flickr.com/photos/rofi/2097239111/!
Nate Foster
Cornell University
Spring 2013
Based on lecture notes by Jennifer Rexford and Michael Freedman
CS 5114
Network Programming Languages
End Hosts
Announcements
Signup Sheet: breakfast pickup and presentations
Reviews: start next week!
- Only review one paper but please read them all!
- Structure: summary, strengths, weaknesses, discussion
- Aim to write about half a page to one page
- Submit by email or hand in at the start of class
Projects
- Groups and initial proposal by Feb 19 th
- Full proposals due March 14 th
- Final reports and presentations due on May 2 nd
Host-Network Division of Labor Network
§ Best-effort packet delivery
§ Between two (or more) end-point addresses
Hosts
§ Everything else
host
host
network
IP Suite: End Hosts vs. Routers HTTP TCP IP Ethernet interface HTTP TCP IP Ethernet interface IP IP Ethernet interface Ethernet interface SONET interface SONET interface host host router (^) router HTTP message TCP segment IP packet (^) IP packet IP packet
The “Narrow Waist” of the Internet UDP TCP Data Link Physical Applications
The Hourglass Model
Waist
The narrow waist facilitates interoperability
FTP HTTP NV TFTP
TCP UDP
IP
NET 1 NET 2 … NETn
The Role of the End Host Network discovery and bootstrapping
§ How does the host join the network?
§ How does the host get an address?
Interface to networked applications
§ What interface to higher-level applications?
§ How does the host realize that abstraction?
Distributed resource sharing
§ What roles does the host play in network resource
allocation decisions?
Three Kinds of Identifiers Host Name IP Address MAC Address Example www.cs.cornell.edu 132.236.204.10 00-15-C5-49-04-A Size Hierarchical, human readable, variable length Hierarchical, machine readable, 32 bits Flat, machine readable, 48 bits Read by Humans, hosts IP routers Switches in LAN Allocation, top-level Domain, assigned by registrar (e.g., for .edu) Variable-length prefixes, assigned by ICANN, RIR, or ISP Fixed-sized blocks, assigned by IEEE to vendors (e.g., Dell) Allocation, low-level Host name, local administrator Interface, by admin or DHCP Interface, by vendor
Mapping Between Identifiers
Dynamic Host Configuration Protocol (DHCP)
§ Given a MAC address, assigns a unique IP address § … and gives host other information about the local network (e.g., gateway) § Automates the boot-strapping process
Address Resolution Protocol (ARP)
§ Given an IP address, provides the MAC address § Enables communication within the local network
Domain Name System (DNS)
§ Given a host name, provides the IP address § Given an IP address, provides the host name
Dynamic Host Configuration Protocol new client (^) DHCP server DHCP discover (broadcast) DHCP o ffer DHCP request DHCP ACK (broadcast) Host learns IP address, Subnet mask, Gateway address, DNS server(s), and a lease time.
Address Resolution Protocol (ARP)
Every host maintains an ARP table
§ (IP address, MAC address) pair
Consult the table when sending a packet
§ Map destination IP address to destination MAC address § Encapsulate and transmit the data packet
But, what if the IP address is not in the table?
§ Sender broadcasts: “Who has IP address 1.2.3.156?” § Receiver responds: “MAC address 58-23-D7-FA-20-B0” § Sender caches the result in its ARP table
Questions
Should addresses correspond to the interface (point of
attachment) or to the host?
Why have three identifiers? Do we need them all?
What should be done to prevent address spoofing?
Interface to Applications
Two Basic Transport Features
Demultiplexing: port numbers
Error detection: checksums
Web server (port 80) Client host Server host 128.2.194. Echo server (port 7) Service request for 128.2.194.242: 80 (i.e., the Web server) Client OS IP payload detect corruption
Two Main Transport Layers
User Datagram Protocol (UDP)
§ Just provides demultiplexing and error detection § Header fields: port numbers, checksum, and length § Low overhead, good for query/response and multimedia
Transmission Control Protocol (TCP)
§ Provides a “stream of bytes” abstraction § Retransmits lost or corrupted data § Puts out-of-order data back in order § Adapts the sending rate to alleviate congestion § Higher overhead, good for most stateful applications