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Networking: Packet Loss, TCP Flow Control, UDP, CIDR, OSPF and IP Routing, Slides of Fundamentals of E-Commerce

Aligarh Muslim UniversityFundamentals of E-Commerce

Various aspects of networking, including packet loss and error detection, tcp flow control, user datagram protocol (udp), classless inter-domain routing (cidr), open shortest-path first (ospf) routing, and ip routing. It covers topics such as packet loss rates, tcp connection reaction to congestion, window-based flow control, udp traffic growth, and ip packet transmission.

Typology: Slides

2012/2013

Uploaded on 07/29/2013

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Lost and Corrupted Packets
• Detecting corrupted and lost packets
– Error detection via checksum on header and data
– Sender sends packet, sets timeout, and waits for ACK
– Receiver sends ACKs for received packets
• Retransmission from sender
– Sender retransmits lost/corrupted packets
– Receiver reassembles and reorders packets
– Receiver discards corrupted and duplicated packets
Packet loss rates are high (e.g., 10%), causing
significant delay (especially for short Web transfers)!
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Download Networking: Packet Loss, TCP Flow Control, UDP, CIDR, OSPF and IP Routing and more Slides Fundamentals of E-Commerce in PDF only on Docsity!

Lost and Corrupted Packets

  • Detecting corrupted and lost packets
  • Receiver sends ACKs for received packets– Sender sends packet, sets timeout, and waits for ACK– Error detection via checksum on header and data
  • Retransmission from sender
  • Receiver discards corrupted and duplicated packets– Receiver reassembles and reorders packets– Sender retransmits lost/corrupted packets Packet loss rates are high (e.g., 10%), causing

significant delay (especially for short Web transfers)!

TCP Flow Control

  • Packet loss used to indicate network congestion
  • Affected TCP connection reacts by backing-off– Router drop packets when buffers are (nearly) full
  • Window-based flow control
  • Initial slow-start phase to learn a good window size– Sender reduces window size when packets are lost– Sender limits number of outstanding bytes
  • TCP flow-control header fields
  • Acknowledgement number (cumulative bytes)– Sequence number (byte offset from starting #)– Window size (maximum # of outstanding bytes)

Classless Inter-Domain Routing

(CIDR)

  • IP addresses are all 32 bits in length
  • IP address has “network” part and “host” part– “Dotted-decimal” notation: 113.34.96.
  • Addresses used to have a natural network length
  • Class C: 24-bit network and 8-bit host part– Class B: 16-bit network and 16-bit host part– Class A: 8-bit network and 24-bit host part
  • Now any division of the 32 bits is fine
  • E.g.: 113.34.96.0/24 for mask of 255.255.255.0– Arbitrary division into prefix and mask

Getting an IP Packet From A to B

  • Host must know at least three IP addresses
  • Default router to reach other hosts (e.g., gateway)– Domain Name Service (to map names to addresses)– Host IP address (to use as its own source address)
  • Simple customer/company
  • Does not run an Internet routing protocol– Has a set of IP addresses allocated in advance– Has just one router connecting to the provider– Connected to a single service provider

Example Network and Shortest

Path

3

2

2

1

1

3 1

4

3 5

routerlink

OSPF domain

12.34.0.0/

1.2.3.0/24, 4.5.0.0/

6.8.9.0/24, 7.0.0.0/ 5.5.5.0/

IP Routing in OSPF

  • Each router has a complete view of the topology
  • Updates periodically or on link failure/installation– Reliable flooding to all routers in the domain– Each router transmits information about its links
  • Each router computes shortest path(s)
  • Execution of Dijkstra’s shortest-path algorithm– Maintenance of a complete link-state database
  • Each router constructs a forwarding table
  • Hop-by-hop routing independently by each router– Forwarding table with next hop for each destination

Connecting to Other Networks

AOL

System (AS)Autonomous

EarthLink

System (AS)Autonomous

WorldNet

Autonomous System: A collection of IP subnets and routersAutonomous System: A collection of IP subnets and routers

under the same administrative authority.under the same administrative authority.

Exterior Routing Protocol (e.g., Border Gateway Protocol)Exterior Routing Protocol (e.g., Border Gateway Protocol)Interior Routing Protocol (e.g., Open Shortest Path First)Interior Routing Protocol (e.g., Open Shortest Path First)