CLI Jockey

Terminology;

• Behaviour Aggregate (BA): A collection of packets with the same DSCP crossing a link in a particular direction
• Differantiated Services Code Points (DSCP): A value in the IP header used to select a QoS treatment for a packet
• Per-hop behaviour (PHB): The externally observable forwarding behaviour (QoS traetment) applied at a DiffServ-compliant node to a DiffServ BA

Characteristics that QoS can effect;

• Bandwidth
• Delay
• Jitter (Delay Variation)
• Packet loss

QoS Tools that effect bandwidth;

• Compression
• CAC (Call Admission Control)
• Queuing

Types of delay;

• Serialisation (fixed)
• Propogation (fixed)
• Queuing (variable)
• Forwarding/Processing (variable)
• Shaping (variable)
• Network (variable)
• Codec (variable)
• Compression (variable)

QoS tools that affect delay;

• Queuing
• Link Fragmentation and interleaving
• Compression
• Traffic Shaping

QoS tools that effects Jitter;

• Queuing (CQ, MDRR, CBWFQ)
• Link Fragmentation and interleaving
• Compression
• Traffic Shaping

QoS tools that effect loss

• Queuing
• RED
• WRED

Occasionally, during bootup of Cisco hardware through Cisco IOS software, error messages similar to these are displayed:

• %Error opening tftp://255.255.255.255/network-confg (Socket error)
• %Error opening tftp://255.255.255.255/cisconet.cfg (Socket error)
• %Error opening tftp://255.255.255.255/3620-confg (Socket error)
• %Error opening tftp://255.255.255.255/3620.cfg (Socket error)

These error messages are related to the default service configuration option built into Cisco IOS software, which attempts to access the service configuration files from a network Trivial File Transfer Protocol (TFTP) server.

In order to disable this feature, issue the no service config global command.

Router#config terminal
Enter configuration commands, one per line.  

Router(config)#no service config

Router(config)#exit

Router#copy running-config startup-config

These error messages no longer appear at the next bootup of the router.

IP range is 224.0.0.0 – 239.255.255.255

Well known link local addresses assigned by IANA (reserved use of 224.0.0.0 – 224.0.0.255;

• 224.0.0.1 – All Multicast systems on a subnet
• 224.0.0.2 – All routers n subnet
• 224.0.0.4 – All DVMRP routers
• 224.0.0.13 – All PIMv2 routers
• 224.0.0.5 – OSPF routers
• 224.0.0.6 – All OSPF DR’s
• 224.0.0.9 –  RIPv2 routers
• 224.0.0.10 – EIGRP

First Hop router – closest to source

Last Hop router – closest to reciever

Multicast Sources

• Create a session or group and announce via session announcement
• Originate multicast data and send it to a multicast group
• Apply proper actions if feedback info is available

All routers auto learn RP address

• configuration necessary only on candidate RP & Mapping agent

Multicasts ae used to distribute RP information

• Cisco announce: 224.0.2.39
• Cisco discovery 224.0.1.40
• Fowarded in Dense Mode

GRE tunneling can be used to encapsulate Multicast traffic. This could be useful for;

• An advantage of GRE tunneling relative to IPsec tunneling is that GRE can offer finer-grained QoS because routers have visibility into the IP packet header
• Tunnel Multicast traffic over unicast only networks

GRE tunnel does not maintain state, when only on side is configured it will show up/up. You need to enable keepalive support under the tunnel interface to resolve.

Tunnel source and destination must be statically defined and not routed through the tunnel interface.

The unicast source still needs to be reachable out the tunnel or RPF check will fail. Might need a mroute entry to achieve.

Commands

interface tunnel 0
  ip address <IP & Mask>
  tunnel mode gre ip
  tunnel source <int>
  tunnel destination <remote end>

MSDP describes a mechanism to connect multiple PM-SM domains together.

Each PM-SM domains uses its own RP and does not have to depend on RP in other domains.

This topic has been boken down into the following;

• MSDP
• MSDP to an Anycast Rendezvous Point

Using Anycast RP within PIM-SM domains is an implementation strategy that provides RP redundancy, rapid RP failover and RP load sharing

Anycast RP allows two or more RPs to share the load for source registration and the ability to act as hot backup routers for each other

MSDP is the key protocol in making Anycast RP possible, with all connected via it. This allows each RP to learn which sources have been registered with the other Anycast RPs in the domain. Read more »

Multicast Source Discovery Protocol (MSDP);

• MSDP has been designed for interdomain usage
• Creates a web of communicating RPs to exchange information about active multicast sources
• Each RP knows about the sources that are registered to it and this information is flooded to all MDSP peers using source-active (SA) message
• MSDP can also be used inside a single domain if it has multiple RPs Read more »

LDP esstablishes a session in 2 steps;

• hello messages peridically sent on all MPLS-enabled interfaces
• MPLS enabled routers respond to received hello messages by attampting to esstablish a session with teh source of the hello message

LDP link hello is UDP sent to “all routers on this subnet” multicast address (224.0.0.2)

TCP is used in esstablishing the session

Both TCP and UDP use well-known LDP port number 646

A 6-byte LDP identifier (TLV) identifies the oruter  - 1st 4 bytes and label space last 2 bytes

LDP keepalive set by default every 60 sec

mpls ldp neighbor #! defines the neighbor to use, can be used for non-adjacent routers. Once neighbor discovered same mechanism to establish session is used

Applications of targetted LDP sessions;

• MPLS Fast ReRoute (FRR)
• MPLS NonStopForwarding (NSF)
• MPLS LDP session protection