Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                
SlideShare a Scribd company logo

Routers and planes

•
•
A
Abhishek Kesharwani

This document provides an introduction to networking and network routing. It discusses routing from the perspective of getting from point A to point B as efficiently as possible. Addressing schemes like postal addresses and IP addresses are hierarchical, with the least specific information like city or network prefix first, allowing more efficient routing. IP addresses use hierarchical addressing schemes like CIDR and flat addressing. Network architectures have layers like the protocol stack and service models. Routing protocols operate at different layers and communicate routing information between routers. Standards bodies like IETF and ITU standardize network protocols and functions.

1 of 33
Download to read offline
1 Chapter-1: Networking and Network Routing: an introduction
2 What’s routing • Simply stated, how to go from point-A to point-B – There might be multiple ways to go: Which one to choose? •Take the perspective from the user (reach there as fast as possible) •From the perspective of the network (not letting some suffer by giving benefit to others) – Addressing •How addressing might be useful in routing
3 Postal System • Address has essentially three parts: – Name (‚User‛) – Street Address (‚House address‛) – City/Zip code (‚City‛) • If we consider routing to a person, the origination point doesn’t really need all three pieces of information, just the destination zip code is sufficient • Re-arranging, we look at address as follows: – City | House Address | User – Least specific part at the beginning, and more specific at the end • Note: for postal address, the postman doesn’t need to know the Name at all: her job is to drop at the House address, and let the residents of the house ‚route‛ to the actual person
4 Network-based System • Addressing is important as it can be useful in routing, and routing efficiently – Routers do not need to store detailed address information (means: less memory) • Two ways to look at address: – Hierarchical – Flat (also, a mixed mode is possible)
5 Hierarchical addressing • Postal code (in most countries) US zip code: five digit number The first two digits represent a geographical area, such as ‚64‛ in ‚64110‛ which signifies the Kansas City area Secondly, there’s a bit of structure to it, going from East cost to the west coast as the first two digits change from ‚01‛ to ‚94‛ • Telephone number in most countries: – Geographic code (area/city code) followed by a local number
6 Flat addressing • Doesn’t say anything about address proximity – IP address prefix (‚net-id‛) •134.193.0.0 identifies the address block assigned to the University of Missouri-Kansas City •134.192.0.0 identifies the University of Maryland at Baltimore •<address doesn’t show any geographic proximity>
7 Why structure of addressing matter? • In network routing, structure of the addressing can influence what can be accomplished (and what might be hard to do)
8 IP addressing: overview • 32-bit addressing originally defined (known as IPv4 address) – Originally classful: based on bit boundary (class A: 27, Class-B: 214, Class-C: 221)
9 IP address • It is used for identifying devices – Common terminology: ‚host‛ – Computers, routers <
10 IPv6 addressing • 128-bit address scheme – Divided by provider and country
11 Subnetting/Mask in IPv4 • The idea is identify if an IP address below to a ‚network‛ (subnet) – Classful: easy, because of bit boundary: for example 10.0.0.0 belongs to class-A and so on – Classless: not implicitly defined by a class boundary •Known as CIDR (classless inter-domain routing) notation
12 CIDR notation: illustration • Bit-wise AND operation of an address with its subnet mask 255.255.255.0, also written as /24 since (first 24-bits of the mask are all 1’s) • Bit-wise AND operation with mask /21: • While the outcome looks the same, clear they represent different subnets, one with /24 and the other with /21. – Explicitly mention the mask • 192.168.40.0/24, 192.168.40.0/21 – Note the difference with implicit mask as with classful address
13 Why CIDR • Routing in IP is based on flat addressing, i.e., need an entry for each netid at the core of the Internet • Classful address for Class C creates a large number of addresses (2^21): CIDE allows aggregation • CIDR is used for routing purpose in the Internet (started with BGP version 4) • (More as we discuss routing later)
14 On Architectures • Used in many different ways: – Service Architecture – Protocol Stack Architecture – Router Architecture – Network Topology Architecture – Network Management Architecture
15 Service Architecture • A service model gives the basic framework for the type of services a network offers – IP networks • Best-Effort Services • Integrated Services • Differentiated Serivces • Note: a service architecture can be supplemented by proper traffic engineering to provide a high quality of service
16 Protocol Stack Architecture • OSI Reference Model • TCP/IP Protocol Stack Model
17 Where do routing protocols fit in? • It’s a mixed bag: OSPF: directly over IP; BGP & RIP: transport layer
18 • Important to note: – To do network layer function, upper layer mechanisms are needed to communicate routing information – Important to distinguish between routing information and the function of a network layer
19 Router Architecture • Routers provider several important functions – Packet Forwarding – Routing protocol message processing – Specialized services (for example, for monitoring and management)
20 Network Topology Architecture • Encompasses how a network is to be architected in an operational environment – Topology of the network – Bandwidth for carrying traffic volume – Operational considerations • Sometimes, simply referred to as ‘Network Architecture’
21 Network Management Architecture • Functional architecture for being able to monitor and manage the network • Different planes: – Management plane • Routing configuration, collection of various statistics – Control plane • Control information between routers for management of various functions, such as setup a virtual link – Data plane • User application traffic • Note that at IP layer, no distinction between packets due to these three planes
22 NM Architecture: Pictorial View
23 Public Switched Telephone Network • In short, PSTN; also known as GSTN (Global Switched Telephone Network) • Architecturally and technologically different than IP networks – Unit of information: a call – Uses circuit switching to set up a call on demand – End device (‚phone‛) is dumb, intelligence starts from the end office switch – Control information carried on a separate signaling network (known as SS7) – Its own addressing mechanism, known as E.164 (More details in later chapter)
24 Communication Technologies • Different technologies, link speeds are used for communicating information
25 Standards: a few words • Standards are important – Allows a common way to do something – Different vendors can build product which can ‚talk‛ in the language specified through standards – Market competition, drives to cost down
26 IETF • Internet Engineering Task Force (http://www.ietf.org) – Standardizes anything related to Internet • Published as Request for Comments (RFC) – Not all RFCs are standards document – They aren’t ‘request’ any more; name is historical, stuck on – Traditionally, didn’t do much below layer-3 – In recent years, Layer-2.5 and below functions such as Multi-protocol label switching (MPLS) – Note: anything related to web is standarded by WWW consortium (http://www.w3.org/) • Assignment: study how IETF works
27 ITU-T • International Telecommunications Union- Telecommunication Standardization Sector (http://www.itu.int) – A United Nations specialized agency – Develops standards referred to as Recommendations
28 Summary • An overview of addressing and routing – Comparison to other ‚routing‛ systems such as the postal system, the road transportation network • Overview of TCP/IP protocol architecture • A walk through the notion of architecture • Standards
29 Extras • Packet formats for IPv4, IPv6, TCP, and UDP enclosed
30 IPv4 packet format
31 IPv6 packet format
32 TCP packet format
33 UDP packet format

More Related Content

Routers and planes

  • 2. 2 What’s routing • Simply stated, how to go from point-A to point-B – There might be multiple ways to go: Which one to choose? •Take the perspective from the user (reach there as fast as possible) •From the perspective of the network (not letting some suffer by giving benefit to others) – Addressing •How addressing might be useful in routing
  • 3. 3 Postal System • Address has essentially three parts: – Name (‚User‛) – Street Address (‚House address‛) – City/Zip code (‚City‛) • If we consider routing to a person, the origination point doesn’t really need all three pieces of information, just the destination zip code is sufficient • Re-arranging, we look at address as follows: – City | House Address | User – Least specific part at the beginning, and more specific at the end • Note: for postal address, the postman doesn’t need to know the Name at all: her job is to drop at the House address, and let the residents of the house ‚route‛ to the actual person
  • 4. 4 Network-based System • Addressing is important as it can be useful in routing, and routing efficiently – Routers do not need to store detailed address information (means: less memory) • Two ways to look at address: – Hierarchical – Flat (also, a mixed mode is possible)
  • 5. 5 Hierarchical addressing • Postal code (in most countries) US zip code: five digit number The first two digits represent a geographical area, such as ‚64‛ in ‚64110‛ which signifies the Kansas City area Secondly, there’s a bit of structure to it, going from East cost to the west coast as the first two digits change from ‚01‛ to ‚94‛ • Telephone number in most countries: – Geographic code (area/city code) followed by a local number
  • 6. 6 Flat addressing • Doesn’t say anything about address proximity – IP address prefix (‚net-id‛) •134.193.0.0 identifies the address block assigned to the University of Missouri-Kansas City •134.192.0.0 identifies the University of Maryland at Baltimore •<address doesn’t show any geographic proximity>
  • 7. 7 Why structure of addressing matter? • In network routing, structure of the addressing can influence what can be accomplished (and what might be hard to do)
  • 8. 8 IP addressing: overview • 32-bit addressing originally defined (known as IPv4 address) – Originally classful: based on bit boundary (class A: 27, Class-B: 214, Class-C: 221)
  • 9. 9 IP address • It is used for identifying devices – Common terminology: ‚host‛ – Computers, routers <
  • 10. 10 IPv6 addressing • 128-bit address scheme – Divided by provider and country
  • 11. 11 Subnetting/Mask in IPv4 • The idea is identify if an IP address below to a ‚network‛ (subnet) – Classful: easy, because of bit boundary: for example 10.0.0.0 belongs to class-A and so on – Classless: not implicitly defined by a class boundary •Known as CIDR (classless inter-domain routing) notation
  • 12. 12 CIDR notation: illustration • Bit-wise AND operation of an address with its subnet mask 255.255.255.0, also written as /24 since (first 24-bits of the mask are all 1’s) • Bit-wise AND operation with mask /21: • While the outcome looks the same, clear they represent different subnets, one with /24 and the other with /21. – Explicitly mention the mask • 192.168.40.0/24, 192.168.40.0/21 – Note the difference with implicit mask as with classful address
  • 13. 13 Why CIDR • Routing in IP is based on flat addressing, i.e., need an entry for each netid at the core of the Internet • Classful address for Class C creates a large number of addresses (2^21): CIDE allows aggregation • CIDR is used for routing purpose in the Internet (started with BGP version 4) • (More as we discuss routing later)
  • 14. 14 On Architectures • Used in many different ways: – Service Architecture – Protocol Stack Architecture – Router Architecture – Network Topology Architecture – Network Management Architecture
  • 15. 15 Service Architecture • A service model gives the basic framework for the type of services a network offers – IP networks • Best-Effort Services • Integrated Services • Differentiated Serivces • Note: a service architecture can be supplemented by proper traffic engineering to provide a high quality of service
  • 16. 16 Protocol Stack Architecture • OSI Reference Model • TCP/IP Protocol Stack Model
  • 17. 17 Where do routing protocols fit in? • It’s a mixed bag: OSPF: directly over IP; BGP & RIP: transport layer
  • 18. 18 • Important to note: – To do network layer function, upper layer mechanisms are needed to communicate routing information – Important to distinguish between routing information and the function of a network layer
  • 19. 19 Router Architecture • Routers provider several important functions – Packet Forwarding – Routing protocol message processing – Specialized services (for example, for monitoring and management)
  • 20. 20 Network Topology Architecture • Encompasses how a network is to be architected in an operational environment – Topology of the network – Bandwidth for carrying traffic volume – Operational considerations • Sometimes, simply referred to as ‘Network Architecture’
  • 21. 21 Network Management Architecture • Functional architecture for being able to monitor and manage the network • Different planes: – Management plane • Routing configuration, collection of various statistics – Control plane • Control information between routers for management of various functions, such as setup a virtual link – Data plane • User application traffic • Note that at IP layer, no distinction between packets due to these three planes
  • 23. 23 Public Switched Telephone Network • In short, PSTN; also known as GSTN (Global Switched Telephone Network) • Architecturally and technologically different than IP networks – Unit of information: a call – Uses circuit switching to set up a call on demand – End device (‚phone‛) is dumb, intelligence starts from the end office switch – Control information carried on a separate signaling network (known as SS7) – Its own addressing mechanism, known as E.164 (More details in later chapter)
  • 24. 24 Communication Technologies • Different technologies, link speeds are used for communicating information
  • 25. 25 Standards: a few words • Standards are important – Allows a common way to do something – Different vendors can build product which can ‚talk‛ in the language specified through standards – Market competition, drives to cost down
  • 26. 26 IETF • Internet Engineering Task Force (http://www.ietf.org) – Standardizes anything related to Internet • Published as Request for Comments (RFC) – Not all RFCs are standards document – They aren’t ‘request’ any more; name is historical, stuck on – Traditionally, didn’t do much below layer-3 – In recent years, Layer-2.5 and below functions such as Multi-protocol label switching (MPLS) – Note: anything related to web is standarded by WWW consortium (http://www.w3.org/) • Assignment: study how IETF works
  • 27. 27 ITU-T • International Telecommunications Union- Telecommunication Standardization Sector (http://www.itu.int) – A United Nations specialized agency – Develops standards referred to as Recommendations
  • 28. 28 Summary • An overview of addressing and routing – Comparison to other ‚routing‛ systems such as the postal system, the road transportation network • Overview of TCP/IP protocol architecture • A walk through the notion of architecture • Standards
  • 29. 29 Extras • Packet formats for IPv4, IPv6, TCP, and UDP enclosed