Routing architecture - Revision history

Jnc: /* Classification of Distributed Routing Architectures */ link nimrod

2022-07-05T18:46:33Z

‎Classification of Distributed Routing Architectures: link nimrod

Jnc: Add PV

2018-11-17T15:25:21Z

Add PV

Jnc: A good intro

2018-11-15T23:47:41Z

A good intro

New page

A '''routing architecture''' is the system of how paths across [[communication network]]s are decided.

There are 3 basic approaches:

* Manual - a human configures the switching nodes
* Centralized - an algorithm running on a central computer in the network control center selects paths for all source-destination pairs, and installs them in the switching nodes
* Distributed - the switching nodes cooperate to select paths

Generally, especially in a large network, the latter is the only one which will [[scale]], and it is now used everywhere (although the telephone network started with manual [[path selection]]).

==Characterization of Distributed Routing Architectures==

There are two orthogonal fundamental axes which can be used to characterize distributed routing architectures.

The first is 'path selection', which describes how paths are selected; this is actually a spectrum, along which are a large number of more complex alternatives to the approaches on each
end. Paths can be selected either:

* Fully distributed - each node along the path makes a completely independent decision as to which node user traffic will go through next; this is sometimes called hop-by-hop (HbH) path selection.
* Explicit: one node selects the entire path.

The term 'source routing' is sometimes used for one form of the latter, in which the host sending the packet computes the entire route, which is then included in every packet.

The second major axis is 'data types', which described what kind of data is being passed between the nodes:

* Destination Vector (DV) - nodes pass sets of (destination, information) n-tuples (i.e. basically, [[routing table]]s) to immediate neighbours.
* Map Distribution (MD) - nodes distribute information about their immediate surroundings through the network; this information is used to construct maps of the network.

==Classification of Distributed Routing Architectures==

These two orthagonal axes define a 4-way classification of routing architectures, one which is not, however, fully populated. The three main classes of routing architecture (along with examples of each), are:

DV-HbH - the classic initial routing architecture; used in:
* the original ARPAnet dynamic routing
* [[RIP]]
* [[BGP]]

MD-HbH - a newer routing architecture, used in:
* the new ARPAnet dynamic routing
* [[IS-IS]]
* [[OSPF ]]

MD-E - the direction of past research in advanced routing, and the likely future direction of routing work. Some examples include:
* IDPR (RFC-1478, 1993) - The first MD-E routing architecture, mostly for Inter-AS (EGP) applications.
* Nimrod (RFC-1992, 1996) - A follow-on to IDPR, enhanced to take over both the [[EGP]] and [[IGP ]]functionality, and with better tools for doing and managing abstraction.
* PNNI - For [[ATM]], based on Nimrod.

==External links==

* [http://www.chiappa.net/~jnc/tech/routing_slides.html Map-Distribution/Explicit Routing Architectures]

[[Category: Networking]]

@@ Line 30: / Line 30: @@
 ==Classification of Distributed Routing Architectures==
-These two orthagonal axes define a 4-way classification of routing architectures, one which is not, however, fully populated. The three main classes of routing architecture (along with examples of each), are:
+These two orthogonal axes define a 4-way classification of routing architectures, one which is not, however, fully populated. The three main classes of routing architecture (along with examples of each), are:
 DV-HbH - the classic initial routing architecture; used in:
@@ Line 44: / Line 44: @@
 MD-E - the direction of past research in advanced routing, and the likely future direction of routing work. Some examples include:
 * IDPR (RFC-1478, 1993) - The first MD-E routing architecture, mostly for Inter-AS (EGP) applications.
-* Nimrod (RFC-1992, 1996) - A follow-on to IDPR, enhanced to take over both the [[EGP]] and [[IGP ]]functionality, and with better tools for doing and managing abstraction.
+* [[Nimrod]] (RFC-1992, 1996) - A follow-on to IDPR, enhanced to take over both the [[EGP]] and [[IGP]] functionality, and with better tools for doing and managing abstraction.
 * PNNI - For [[ATM]], based on Nimrod.

@@ Line 3: / Line 3: @@
 There are 3 basic approaches:
-* Manual - a human configures the switching nodes
+* Manual - a human configures the [[switching node]]s
-* Centralized - an algorithm running on a central computer in the network control center selects paths for all source-destination pairs, and installs them in the switching nodes
+* Centralized - an algorithm running on a central computer in the network control center does [[path selection]] for all source-destination pairs, and installs them in the switching nodes
 * Distributed - the switching nodes cooperate to select paths
@@ Line 16: / Line 16: @@
 end. Paths can be selected either:
-* Fully distributed - each node along the path makes a completely independent decision as to which node user traffic will go through next; this is sometimes called hop-by-hop (HbH) path selection.
+* Fully distributed - each node along the path makes a completely independent decision as to which node user traffic will go through next; this is sometimes called '''hop-by-hop''' (HbH) path selection.
 * Explicit: one node selects the entire path.
-The term 'source routing' is sometimes used for one form of the latter, in which the host sending the packet computes the entire route, which is then included in every packet.
+The term '''source routing''' is sometimes used for one form of the latter, in which the [[host]] sending the [[packet]] computes the entire route, which is then included in every packet.
 The second major axis is 'data types', which described what kind of data is being passed between the nodes:
@@ Line 25: / Line 25: @@
 * Destination Vector (DV) - nodes pass sets of (destination, information) n-tuples (i.e. basically, [[routing table]]s) to immediate neighbours.
 * Map Distribution (MD) - nodes distribute information about their immediate surroundings through the network; this information is used to construct maps of the network.
 ==Classification of Distributed Routing Architectures==