On 11/11/2015 5:25 p.m., Fatah Mumtaz wrote: > Hi everyone, > Currently i'm building lab for my thesis on the topic Multicast WCCPv2 with > Squid. I'm trying to config WCCPv2 to work with single proxy server (Squid > 3.3.8) and multiple Cisco 2821 routers. WCCPv2 works well with one proxy > server and one router configuration. It's been 2 months since I'm trying to > implement multicast WCCPv2 and actually I don't know how to config Squid to > be able to communicate with multiple routers using multicast to announce > itself presence. Because I've read the documentation from Cisco and I've > concluded into something like this "the routers are somehow the "clients" > but not by sending IGMP messages, just by listening for multicast packets > send by the "sources", the cache engines, on a specific multicast group > address. " . So the proxy server (or Squid) acted as the multicast server > that sends multicast packets. Been look over the net and still have no clue. The three IP protocol modes: unicast, anycast, broadcast, multicast. This is a bit simplified, but basically how they operate: unicast - 1:1 IPs, client has an IP used to contact server IP. Messages flow between these two IPs. anycast - N:1 IPs. client has one IP, server has two IPs, one of the server IPs is shared by multiple servers. client contacts shared server IP, server responds from its unique IP, and packets flow as per unicast using the non-shared IPs. broadcast - N:N IPs. there are no servers and no clients. Just broadcasters each with a unique IP, and network-wide broadcast IP. An endpoint sends packet to the network broadcast IP. All devices on the network receive it. If there is any two-way communication the recipient can switch to unicast and communicate with the broadcasters unique IP. multicast - 1:N IPs. client has one IP, server has two IPs. clients register for listening to output from the server multicast IP. any router receiving a registration creates a "group" of clients wanting to receive that servers output (any other clients will just be added to the group), then registers itself to receive instead of the client it saw. Server sends its data packets to all the IPs that register directly with it. If they are routers they relay the packets to all the clients that registered with them, and so on until the actual client(s) receive. multicast is a most efficient way to distribute live streaming data, or cyclical repeated copies of an item sent to recipients in distinct chunks where the starting position does not matter. Like old fashioned radio or TV channels, or torrent downloads. But not at all good for TV-on-demand style services where clients need to fetch a fixed distinct thing from the beginning to end in full. Also, IPv4 requires admin to explicitly turn on multicast support and many have not. Making it very diffucult to use in most of the world. With IPv6 it is a native part of the protocol and enabled by default. > > And my question is simple : > 1. Is it possible to config squid to announce itself presence to the > routers using multicast? And if it is possible, please kindly provide any > detail. > Squid is not specifically coded to support it IIRC. It would be interesting to see if a multicast address configured in the usual wccp2_router directive worked with multiple responding routers (or to make it work). One thing to be aware of though is that Squid WCCP support is incomplete, only coded to a slightly older Draft version of WCCP predating recent IPv6 additions to WCCPv2, and contains some custom changes to fix issues in the published Draft specification that was followed. If you are going to be doing any coding in Squid I suggest you sign up with squid-dev mailing list and discuss your proposed changes there where all the dev can provided input. Most of the dev do no read this users list. Amos _______________________________________________ squid-users mailing list squid-users@xxxxxxxxxxxxxxxxxxxxx http://lists.squid-cache.org/listinfo/squid-users
